Case Study

National Master Plan for Development of Waste-to-Energy in IndiaTechnical Memorandum on Waste-to-Energy Technologies

ES IMWH

Executive Summary

A. Preamble1. The driving forces behind the development of many distinct waste-to-energy conversion

technologies that are presently available worldwide was the realization, three decades ago,that the global petroleum-based energy supplies have a finite life span and are dwindling fast.This realisation is relevant today also and in fact, there are further other serious concerns forinvestigating renewable energy options including waste-to-energy options. These concernsinclude sustainability, reduction of greenhouse gas emissions, shift from landfilling of wastes,developing philosophical preference for “green” energy and the fundamental desire to dealeffectively with increasing quantities of organic wastes.

2. The most significant waste-to-energy technologies are based on biological or thermalmethods:

• Biomethanation involves the biodegradation of organic wastes under strict anaerobicconditions to yield methane-rich biogas.

• Incineration is based on the combustion of organic wastes as fuel with the evolutionof heat energy for recovery.

• Advanced thermal conversion involves destructive heating of organic materials underreducing conditions, with a limited supply of oxygen (gasification) or without any oxygen(pyrolysis), to produce a combustible gaseous product consisting of simple hydrocarbonsand hydrogen.

B. Technology High-Lights

Biomethanation3. Biomethanation of aqueous wastes involves hydrolysis, acidogenesis, acetogenesis and

methanogenesis reactions, which generates a mixture of methane, carbon dioxide and othergases. It is essential to establish a stable heterogeneous bacterial consortium under strictanaerobic conditions and to establish process parameters that influence biomethantion ratesand biogas yield for various types of organic waste.

4. Several designs of bioreactors were developed and commercialised during the past threedecades for handling diverse industrial wastewaters and municipal sewage. These include:

• Suspended growth reactor systemsCompletely Mixed Digesters, Contact Reactors, Anaerobic Lagoons (Covered) andUpflow Anaerobic Sludge Blanket (UASB) Reactors

• Attached growth reactor systemsAnaerobic Upflow/Downflow Filters, Fluidized Bed Bioreactors

• Hybrid reactors.

The suspended growth reactor systems are suitable for wastewaters containing a highconcentration of suspended solids and soluble biodegradable substrate.


MONTGOMERY WATSON ES II

Attached growth reactors utilize biomass grown as a film on an inert media immersed in thereactor. As the wastewater flows through the media filled reactor, in upflow or downflowmode, the attached anaerobic biomass converts both soluble and particulate organic matter inthe wastewater to biogas. The attached growth reactors are well suited for wastewaters thatcontain primarily soluble biodegradable substrates.

In the hybrid system, the concentration and level of the sludge blanket is easily monitored andmaintained. The media at the top of the reactor assists in the retention of biomass and alsoserves as a gas-liquid-solid separator. The hybrid processes are applied to wastewaters withintermediate levels of particulates, although their performance is usually better with solublebiodegradable substrates.

5. The low-solids (4-6% solids) anaerobic digesters such as standard-rate digester, two-stagedigester and high-rate digester are widely used for biomethanation of sludge produced inaerobic wastewater treatment plants.

6. Biomethanation of solid/semi solid wastes can be carried out either with medium-solids (8-15%) or high-solids (20-35 %) process in anaerobic digesters, using a variety of proprietaryfeatures.

The medium-solids process is suitable to generate methane gas from animal manure, poultrylitter and municipal solid waste (MSW). One of the disadvantages of this process is the largequantity of water required for dilution. The high-solids process is also used for energyrecovery from MSW. Two important advantages of the high-solids process are less waterrequirements for dilution and high gas production per unit volume of the reactor.

7. An extensive literature review of biomethanation technology indicated that several variationsof biomethanation plants, ranging from small farm digesters to large-scale waste treatmentplant with biogas recovery, has been built in many countries by private, government, researchand non-governmental organizations.

8. In India, the high rate biomethanation process for energy recovery has been successfully usedfor various industrial wastewaters and sewage. The highlights of some biomethanationprojects implemented in the country are presented in the report.

Incineration9. In Incineration, a series of oxidation reactions take place in the combustion of organic waste

in presence of oxygen. In this exothermic reaction, heat energy is liberated which may beutilised for different purposes. This technology is commercially well established and is fullyunderstood in terms of maximising efficiency and obtaining optimum energy yields. A criticalissue associated with incineration is the control of atmospheric emissions, to achieve stringentregulatory norms.

10. Two approaches are currently available for incineration of MSW-Mass Burn Systems andRefuse Derived Fuel (RDF) systems.

Mass-burn incinerators burn raw waste in the same physical form as it is generated andreceived.

Refuse-Derived Fuel (RDF) systems refer to solid waste that has been mechanically processedto produce a storable, transportable, and more homogeneous fuel for combustion. RDF can beco-fired with fossil fuels in existing large industrial or utility boilers or used as the primary fuelin specially designed ‘dedicated’ boilers.


MONTGOMERY WATSON ES III

Fluidized bed combustion (FBC) is a versatile novel design and can be operated on a widevariety of fuels, including MSW, sludge, coal, and industrial wastes.

11. Incineration of MSW is a well established WTE Technology and widely adopted in thedeveloped countries. The recent focus is on environmental compliance using elaborate airpollution control systems for flue gas clean-up which has made it a rather expensive option.

Gasification and Pyrolysis12. Gasification or pyrolysis forms a molecularly simple and high quality gaseous fuel (producer

gas) for which complete and efficient combustion is inherent. It can be combusted in a gasengine or gas turbine to generate electricity. These systems have low environmental emissionsand higher energy recovery potential.

13. Gasification and pyrolysis processes can have a higher level of acceptability due to theadvantages over incineration. Gasification technology is at a commercial uptake in developedcountries and has a high potential of adaptability in India.

Emerging Technologies14. Emerging technologies like plasma pyrolysis, microwave waste destruction and laser waste

destruction are at various stages of commercial uptake and merit a continuing review to assesstheir relevance for possible application to the treatment of certain waste types under Indianconditions.

15. The plasma arc pyrolysis for waste destruction apparently creates no gaseous emissions andthe flue gas produced and the inert solid slag can be beneficially used. The process is a totallyenclosed system that achieves waste volume reductions of the order of 200 to 1 against 10 to1 achieved in conventional incineration processes.

16. Some patented processes using microwave energy are available for the destruction ofhazardous, infectious or otherwise intractable wastes, without any energy recovery. However,it is clear that this technology has positive benefits for the treatment of two particularlydifficult waste types namely medical wastes and tyres. The net export of energy, which ispossible in the tyre processing configuration and the minimisation of emissions, are attractivefactors.

17. The laser waste destruction technology is relatively new and has not yet been applied forwaste treatment applications.

C. Assessment of Technologies18. WTE technology options have been analysed using a set of five main evaluation criteria:

System Configuration, System auxiliaries, Environmental Aspects, Resource Recovery andCommercial Aspects. A uniform and unbiased numerical ranking (0-30 points) is assigned toeach of these criteria for the initial analysis. A maximum of 150 points can be scored by anytechnology in terms of a judicious rating of the various input criteria. Each of these maincriteria are also analysed using a set of sub-criteria and represented by an appropriatenumerical assessment.

• System Configuration (0-30)


MONTGOMERY WATSON ES IV

Simplicity and operability (0-12), process flexibility (0-12) and scale-up potential (0-6).

• System auxiliaries (0-30)

Pre-treatment (0-20), post-treatment (0-10).

• Environmental Aspects (0-30)

• Resource Recovery (0-30)

• Commercial Aspects (0-30)

Capital Cost (0-12), Operational Cost (0-12), Track Record (0-6).

19. An evaluation checklist with the ratings for the different main and sub-criteria for the fivecompetitive technology options showed the following overall scores and rank

Technology Score Rank

(Max:150)

Biomethanation 107 1

Landfill with gas recovery 83 2

Gasification 80 3

Incineration 67 5

• Biomethanation has emerged as a mature and widely accepted WTE technology on aglobal basis. It ranks first.with a good track record and less environmental impacts.

• Landfill with gas recovery system ranks second due to system simplicity and long trackrecord with good control of atmospheric emissions and leachates. However, it has a lowenergy recovery potential.

• Gasification/pyrolysis processes have emerged as a distinct third choice with a higherenergy recovery potential and reduced environmental impacts. With an increasing numberof installations worldwide for handling MSW, gasification can also emerge as a maturetechnology.

• Incineration technologies with a long track record of several successful operatinginstallations in the developed countries, has slipped to the fifth position according to thisstudy, owing to the competing features of gasification technologies.

• Composting is also included in this analysis for the purpose of comparison. Compostingscored an overall rating of 67 out of 150 points.

• The average quality of Indian MSW is generally poor and variable with a high proportionof moisture and inerts. These together have a great relevance to the selection of suitableWTE technology for MSW in India. With a gradual adoption of various technologies on alarge scale in India, the relative weightage for the commercial factors could become evenmore important with most of the technical and operational inputs becoming routine issues.These aspects would not be potential deterrents to technology selection for a given WTEapplication. Technologies like landfill with gas recovery and composting can also becomeviable options for certain locations in India, as a short to medium term option.


MONTGOMERY WATSON ES V

Nevertheless, the global ranking of the WTE technologies developed in this study can beconsidered to be relevant to Indian MSW after a preliminary screening of the alternatives.

D. Mass and Energy Balance20. Process calculations for typical MSW biomethanation plant capacities of 150, 350, 500 and

1,000 TPD show an average power generation potential of 1 MW per 100 TPD of unsortedIndian MSW.

21. Energy calculations carried out for a 500 TPD MSW gasification system based on ‘SWERF’(Solid Waste Energy and Recycling Facility) process indicated power generation potential of2.0 MW per 100 TPD.

22. Similar calculations for a 500 TPD fluidized bed incineration system indicated the powergeneration potential of 1.24 MW per 100 TPD of MSW as RDF.

23. The power generation potential of a landfill serving a population of 2,00,000 (100TPD MSW)will be a modest 0.4 MW.

24. UASB plant handling 10 MLD domestic sewage has the potential to generate 150 kW power,while saving 53 kW power over a conventional activated sludge process.

E. Cost Analysis Upcoming/Proposed25. Costs of nine upcoming/proposed projects are used to indicate the current Indian scenario (six

based on biomethanation technology, two utilizing gasification technology and one on RDFincineration).

26. Costs and revenue income for high solids (dry) and medium solids (wet) anaerobic digestionprocesses for capacities of 300,500 and 1,000 TPD indicates the following trends:

• The cost of a biomethanation project varies between Rs. 10-14 lakhs per T of MSW

• The high solids anaerobic process will be relatively cheaper by 5 % than the mediumsolids anaerobic process

• The unit capital cost decreases for both the processes with an increase in plant capacity

• The revenue generation in the high solids process is more than the revenue generation inthe medium solids process

• The revenue generation increases with the increase in the plant capacity

• One-third of the revenue can be generated through sale of manure.

• The pay back period of biomehanation project will be 4 - 6 years depending upon theprocess and the capacity of the plant.

27. The commercial viability of a typical 1,000 TPD waste-to-energy project showed that thecapital cost of gasification plant is higher than biomethanation (Rs. 220 vs 90 Crores) and thepresent value of net revenue (Rs. 151 Crores ) will be similar for both.


MONTGOMERY WATSON ES VI

F. Conclusions28. A number of distinct Waste-to-Energy conversion technologies are now available worldwide.

These technologies are suitable for various waste such as - aqueous wastes, sludges, slurriesand municipal solid waste (MSW). While some technologies (e.g biomethanation, incineration,landfill) have been well known and widely used for many years, others such as gasification andpyrolysis, have been developed to a successful commercial stage recently.

29. Evaluation of the applicability of the technologies of biomethanation, gasification/pyrolysis,incineration and landfilling as Waste-to-Energy options, and their comparison againstcomposting as a competing technology for waste disposal, has shown the following:

• Biomethanation has emerged as a favoured technology for various urban and industrialwaste.

• Gasification/pyrolysis have a distinct promise, and although there are limitations to itsuptake, these can be overcome as the technology matures.

• Incineration is a mature technology for energy recovery from urban and industrial wastesand has been sucessfully commercialized in the developed countries. The recent focus hasbeen on environmental compliance due to which it will become an expensive option.

• The present trend is in favour of material recovery facilities and a shift away fromlandfills for MSW disposal in developed countries.

• Compositing is not a WTE option and does not come out as worthwhile waste treatmentprocess.

• Technologies like landfill with gas recovery and composting can become viable optionsfor certain locations in India, as a short to medium term option.


Chapter 8-1MWH

8 Waste-To-Energy Technologies – Overview8.1 IntroductionA number of waste-to-energy (WTE) options are available throughout the world to handle variouskinds of wastes. The selection of an appropriate technology to convert a specific waste in to energy isa crucial task that requires a detailed evaluation of the options that are available with respect to itslocation, and characteristics of the waste. This technical memorandum on “Waste to EnergyTechnologies” strives to identify a range of effective WTE technological options that can beapplicable for various waste streams.

8.2 Alternate Energy ResourcesWorld oil prices increased by more than 50% during the seventies, subsequent to the oil embargo byOPEC (Organisation of Petroleum Exporting Countries). This necessitated a global search foralternative energy resources. The Government of India recognised this potential and formulated aseparate ministry, Ministry of Non-Conventional Energy Sources (MNES) in the year 1992. Thefunctions of MNES is to co-ordinate, fund, manage and implement the projects in the non-conventional energy sector utilizing resources such as the wind, solar, biogas, hydro and geothermaland urban and industrial waste in the country. There is an exclusive group in MNES, which deals with"Energy Recovery from Wastes". The waste-to-energy projects are implemented through NationalProgramme on Energy Recovery from Urban and Industrial wastes and UNDP/GEF project on‘Development of High Rate Bio-methanation Processes.

Municipal Solid Waste (MSW) emerged as a potential energy source owing to several desirableattributes – high organic and low sulphur contents. Other wastes originating from animal andagricultural farms also has a high proposition of organic matter an also be utilized for energyrecovery. The former includes cattle farm and poultry wastes, while the latter consists of agro-residues (such as rice, wheat, sugar-cane), stalks, leaves, trees, stumps and saw dust. Industrialactivities also generate liquid and solid wastes with a significant proportion of organic constituents.Some examples of industrial wastewater in this category include black liquor (paper), spentwash(distillery), steep liquor (corn), milk processing (dairy products), food processing, and leather tanning.The typical characteristics and energy recovery potential of some urban and industrial wastesgenerated in India are given in Table 8-1 (liquid) and Table 8-2 (solid/ semi solid).

8.3 Technology OptionsSeveral technologies are now available for energy recovery from urban and industrial wastes that arebased on thermal or biological methods (Figure 8-1).

Landfill has been the most common and widely prevalent practice of MSW disposal in manycountries. Some of the issues that now tend to limit the practice of sanitary landfilling include landavailability, production of leachates and deleterious odorous gases, and public acceptability of landfillas a disposal method. Adverse public opinion has been a critical factor limiting the overall success ofrefuse disposal by landfilling, even though well-engineered landfills have overcome some of theoperational problems. A further issue has been the absence of a satisfactory waste collectioninfrastructure. Biomethanation of municipal sewage has also emerged as a proven WTE option(Figure 8-2) with energy recovery as biogas.

The thermal methods utilize the calorific value of the solid waste and release the energy potential. Thecarbon and hydrogen contents in the waste either combusted in the presence of oxygen to generateheat that can be used in boilers/turbines for the production of steam/power, or the waste is


Chapter 8-2MWH

decomposed in the absence of oxygen to generate carbon monoxide, hydrogen, traces of other gases,fuel oil and char.

Incineration systems have been widely adopted in North American and European communities for thesafe disposal of MSW and power generation to augment grid supply. Recent technologicaldevelopments have focussed on advanced thermal conversion (ATC) processes such as gasificationand pyrolysis (Figure 8-1) as viable waste-to-energy systems with increasing commercial uptake.Sugarcane bagasse, a solid waste from sugar industry, used as a conventional boiler fuel, has beenused for cogeneration with surplus power supplied to the state grid. Newer technologies beingdeveloped/ adopted in India include fluidised bed combustion (incineration) and gasification systemsfor handling distillery spentwash, and paper mill black liquor after concentration in multiple effectevaporators. (Figure 8-2).

Technology options available for energy recovery from industrial and farming sector wastes areshown in Figure 8-2. Several of the high strength (BOD, COD) industrial wastewaters listed in Table8-1 have been successfully utilised for energy recovery by biomethanation techniques through variousbioreactor configurations. Farm wastes (poultry, cattle, etc.) have been slurried and digested torecover energy as biogas or dewatered and dried for thermal processing. Abattoir, tannery fleshingsand sludge have also been used for bio-energy recovery through anaerobic digestion.

Bio-conversion of waste matter to biogas can provide the dual benefits of energy recovery and safewaste disposal. The potential for methane fermentation of various organic feedstocks is high and cansignificantly contribute to the ever-increasing energy needs of society. The anaerobic digestion of theorganic fraction of wastes such as proteins, fats and carbohydrates involves hydrolysis – acidogenesis,acetogenesis and methanogenesis reactions - to generate a mixture of methane, carbon dioxide andtraces of few other gases. Proprietary anaerobic digesters are available for handling MSW, animalwaste, farm waste and other organic solid residues. Crops such as seaweed and water hyacinth canalso be anaerobically digested.

A wide variety of systems have been developed and commercialised during the past two -threedecades to tap the energy potential of various solid wastes, and concurrently solve the problems ofwaste disposal. The use of solid waste for energy recovery has a great potential for full-scaleapplications. Newer energy recovery processes based on biological or thermal technologies can beimplemented to meet long-range energy needs of modern societies.

All of these processes are based on the use of several heavy-duty mechanical equipment for handlinga large quantity of MSW or other solid wastes for feed preparation. Both thermal systems(incineration and advanced thermal conversion) and anaerobic digesters incorporate unique processfeatures and skills in operation to meet performance stipulations.

Energy recovery as electric power is a feature of all waste-to-energy systems. Consequently, thesesystems generally involve significant capital and maintenance costs. In order to match the quality andamount of waste to be processed with an appropriate technology package diverse expertise and skillsin materials management, engineering skills, finance, judiciary, statutory regulatory aspects,ecological and socio-economic issues are required.

8.4 Assessment/ Selection of WTE TechnologiesA checklist of criteria, based on the nature of solid wastes, process technology features, system costs,environmental factors, socio-economic and other aspects for technology assessment/ selection ofWTE projects is given in Table 8.3. The significance of the different criteria is discussed below:

Nature & Characteristics of Feedstock


Chapter 8-3MWH

The quantum and characteristics of waste available for processing are important factors. The wastequantity will decide the capacity of the WTE plant, unless storage hoppers can be utilised to takeaccount of a waste stream that varies widely in daily quantities. The nature of the constituents makingup the organic fraction of the waste will determine its thermal or biochemical energy potential. Anadequate quantity of waste of a desirable quality must be available to sustain continuous operation ofthe system selected.

Successful implementation of such programmes also requires an efficient waste management system,specific for the type of waste considered for large-scale utilization in WTE projects. Many of theseapplication will also require elaborate pre-treatment via shredders, hydrapulpers, cyclones, airclassifiers, etc. for the removal of grits, ferrous/ non-ferrous metals, glass, etc, to obtain a suitablefeed-stock.

The scale of operations of an individual unit is rather too small in many sectors such as tannery, starch(sago), poultry and cattle farm. The utilisation of the wastes from these units will require anappropriate collection mechanism to obtain an adequate quantum of feedstock to sustain the operationof a viable full scale WTE facility. Clustering of the individual units in some locations can beconsidered to make the WTE facility a viable proposition. Industrial and urban wastes can also beblended for co-processing in a WTE facility.

Technology Features

Process technology plays a key role in the selection of appropriate process equipment and accessories,process instrumentation, layout, manpower, training, capital and recurring expenses for theimplementation of a waste-to-energy project on a turnkey basis. A major difference between thethermal and biological process is the operating temperature level viz.10000C vs. 350C – 600Crespectively. The large size equipment associated with the thermal systems will also entail highcapital investment.

The maturity of a particular technology indicates whether that technology is well proven and has a agood track record. It is also important to know whether a technology is available on a commercialscale with a reliable supplier and, if necessary, whether it can be scaled-up to meet specificrequirements. It is not always true that a small-scale successful WTE plant will perform well on acommercial scale. Experience has indicated that heat transfer characteristics may be one of thebarriers in scaling-up a WTE plant, especially in the case of Advanced Thermal Conversion (ATC)processes.

Effectiveness of a technology will be determined by its flexibility in responding to a variety of wastes,potential future improvements, and its adaptability to changing regulations. The ability of atechnology to treat waste effectively and to recover significant quantities of energy will help todetermine the efficiency of a WTE plant. Critical analysis of mass-balance and energy-balance datacan help in determining the efficiency of a system. Factors such as land requirements and other site-specific requirements are also important for the successful implementation of the selected scheme.

The success of a WTE technology will depend critically on its ease of operation and maintenance. It islikely that highly sophisticated technologies will require specialized manpower and processinstrumentation for their operation and maintenance. Training of operators may be a very significantand limiting issue in the case of such highly sophisticated technologies.

Economic Factors

There are two important economic aspects of waste-to-energy technology selection: the first is capitaland operating costs, and the second is the revenue generated from the sale of recovered energy.


Chapter 8-4MWH

Disposal of by-products in an efficient way can not only save disposal costs, but also produce someadditional revenue.

• Capital and Operating Costs

Several factors such as the size of a plant, the plant location, process type, technology developer, costof local labour, construction material proximity and pre-processing requirements will determine thecapital and operating costs. Initial costs and running costs can vary significantly due to localconditions. For example, high-pressure gasification systems are more efficient and cheaper atelectricity generation stages but require high capital, as compared to low-pressure gasification. Properconsideration of all of the above factors is required while selecting a particular technology.

• Revenue From By-Products

Electricity is the most common form of energy produced from WTE facilities constructed today.Assuming a uniform energy sale price the quantum of energy recovered will primarily determine theviability of the WTE technology.

By-products produced in waste-to-energy processes present two-fold economic considerations. Thefirst is the cost of residue disposal, and the second is possible revenue from the sale of variousresidues. For example, for biomethanation, the reactor residue has a potential value as a compost orsoil conditioner, and in gasification, the vitrified slag comprising of inert inorganic constituents can beused as road material.

Environmental Factors

Environmental issues are recognized as critical to the viability of WTE facilities. Most technologiesfor treatment and disposal of MSW have associated environmental issues and concerns seriouslylimiting their widespread adoption. Landfills have been the most popular disposal option in developedcountries in spite of problems of leachates contaminating groundwater and soil, odour, fire and otherlocal hazards. Composting also has limitations such as odour nuisance and poor off-take of compost.Thermal methods such as incineration require elaborate air pollution control system to comply withstrict regulatory requirements, besides problems of dioxins and furan emissions, which are highlytoxic. The technology that has lower pollution control costs as well as minimal general impacts on theenvironment will be the most favoured one on environmental grounds. For a given technology theimpact of emissions on air quality, water quality, land and other environmental consequences needs tobe resolved and addressed. Incineration, for example, is coming under intensive scrutiny in terms ofdeleterious emissions to air. Installation of air pollution control equipments is often exceedingly (andincreasingly) costly and an associated perception of emitting greenhouse gases is also a concern.

Socio-Economic/ Others

General public acceptance is critical in choosing a waste-to-energy technology. Issues such as trafficgeneration to and from the facility site, odour, noise, air pollution, and other perceived health risks ofwaste treatment, disposal and energy recovery options all play a role in public acceptance .Alternatives that are politically sensitive need special consideration. The system that is compatiblewith existing systems and which generates significant employment opportunities are more likely to befavoured by the local population. The potential effects of construction and operation on public safetyare important factors.

The hierarchy of integrated waste management focuses on waste minimization/ prevention, recyclingand reuse, waste transportation and disposal. The quantum of waste to be transported will be reducedsignificantly due to the waste to energy facility. In case of MSW it could be possible to reduce thefinal residues for landfilling to less than 25% of MSW after recycling (35%-50%).


Chapter 8-5MWH

8.5 SummaryThis chapter presents an overview of the nature of various urban and industrial wastes available in thecountry as renewable sources of energy. Thermal and biological processes available for energyrecovery from these wastes are indicated. The methodology adopted to gather details of WTEtechnologies and a checklist of critical factors for technology assessment/ selection of WTE Projectsare also highlighted.


MONTGOMERY WATSON Chapter 8-6

Table 8-1. Characteristics of Indian Urban and Industrial Liquid Wastes

Sr.No.

Waste Sector WasteGenerated

(m3/Ton)

pH SS(mg/L)

BOD(mg/L)

COD(mg/L)

Oil &Grease(mg/L)

TDS(mg/L)

Indicative Bio-chemical Energy

Potential(N m3 biogas/m3)

A. Urban Liquid Waste

1. Sewage 100+ 7-8.5 150-250 200-400 400-750 15-30 500-800 0.25

B. Industrial Liquid Wastes

2. Distillery 25* 4-4.5 4000-6000 45000-50000 90000-100000 Nil 70000-90000 25

3. Mini Paper (Black liquor) 15-30 10-11

1000-1500 4000-9000 12000-25000 Nil 10000-15000 5

4. Dairy

Chilling Plants 2 10-11

180-360 400-600 150-300 500-1200 -

Milk Plants 3 8-9 1250-1350 1800-2000 2500-3200 650-750 2000-2400 1.2

Integrated Dairy 4-4.5 6-8 150-350 1000-12000 1800-2500 70-150 600-900 0.8

5. Starch

a. Maize 15 4-5 560-1100 4000-12650 10000-20000 <20 4000-6000 6.0

b. Tapioca 30 5-6 550-650 4600-5200 5600-6400 <20 3500-4000 2.5

6. Tannery 30-40 7.5-8.5

3000-4500 1200-2500 3000-6000 <20 14000-20000 1.0

7. Abattoir 40-50 7.3-7.5

420-750 3500-4000 6000-8000 50-150 2500-3000 0.25

8. Sugar 0.3-0.5 4.5-6 250-300 1250-2000 2000-3000 60-100 1000-1200 1.0

9. Pharmaceuticals Variable 4-8 Variable>500

Variable >5000 Variable >12000 Nil Variable >4000 Variable

Source: Adapted from various sources* cum per cum of alcohol produced + lpcd



Table 8-2. Characteristics of Indian Urban and Industrial/ Farm Wastes

Sr.No

Waste Sector Moisture%

TotalSolids

%

Inerts%

Organics(Volatile)

% TS

Thermal EnergyPotential *Kcal / kg

(Dry basis)

A. Urban Solid Waste

1. MSW 30-40 60-80 35-50 50-65 1000-1200

B. Industrial/ Farm Solid Wastes

2. Poultry 75-80 20-25 25 75 1000-1400

3. Cattle Farm 80-90 10-20 20 80-85 3700

4. Sugar

a. Pressmud 75-80 20-25 10-20 75-80 4000

b. Bagasse 50 50 5-8 80-90 4000

5. Abattoir 75-80 20-25 NA 75-85 NA

6. Tannery fleshings 75-80 20-25 NA 75-85 NA

7. Starch

a. Corn cobs 10-15 85-90 <5 95 3500

b. Tapioca peelings 10-15 85-90 5-10 85-90 3000

c. Tapioca Tippi 80-90 10-20 2-5 90 3000

8. Rice husk 5-8 70-78 20-25 75-80 3000

9. Coal (Bituminous) 8-10 90 25-30 70-75 4500

10. Fuel Oil 0 - <2 > 98 10000

Note: Values of coal and fuel oil are included for the purpose of comparisons*Adapted from www.indiasolar.com


Chapter 9-1MWH

9 Biomethanation Processes9.1 IntroductionSolid and liquid wastes consist of both organic and inorganic constituents, and the degradation of theformer can take place in the presence or absence of oxygen (air). When microbial degradation oforganics takes place in the absence of air, the process is known as ‘anaerobic digestion’ or‘biomethanation’. This results in the production of biogas, which contains methane, carbon dioxideand traces of other gases. Anaerobic digestion occurs naturally in swamps, waterlogged soils and ricefields, deep-water bodies, and in the digestive systems of animals. Anaerobic processes can take placein a reactor such as digester vessel, covered lagoon or landfill in order to recover the methane gas (asbiogas), which can be used for power generation.

The purpose of this chapter is to provide a brief overview of various biomethanation processesdeveloped and adopted for handling diverse types of wastes, having significant bio-energy potential.

Biomethanation systems are amongst the most mature and proven processes, which converts waste into energy efficiently, and can be used to achieve the following goals:

• Pollution prevention/ reduction

• Reduction of uncontrolled GHG emissions and odour

• Recovery of bio-energy potential as biogas for fuel/ power generation

• Production of stabilized residue for use as fertilizers

Biomethanation processes can be used to recover energy from various municipal, agricultural andindustrial organic wastes, which are listed below:

• Municipal solid waste

• Municipal liquid waste (sewage, leachate)

• Animal farms and agricultural residues (cattle, poultry, bio-mass)

• Industrial wastes (sugar [pressmud], starch, distillery, paper, rayon, dairy, tannery, abattoir,etc.)

• Other industries producing organic wastes

Anaerobic digestion systems were constructed more than a century ago for the stabilisation of sludgesoriginating from sewage treatment plants. These sludge digestion systems merely acted as storagetanks with a long detention time (30 – 50 days). This practice was continued to benefit from theenergy produced as biogas and to use the stabilised sludge as soil conditioner/ manure.

With a better understanding of the mechanisms of the pathways of anaerobic digestion processes andthe experiences of operating installations, the conventional sludge digester design and configurationshave undergone major developments. Anaerobic digestion has evolved into a mature technology, andseveral innovative high-rate reactor designs are now available for the treatment of diverse municipal,industrial and farm sector wastes. Commercial systems available for anaerobic processing can beclassified on the basis of the nature of waste used as the substrate. These are listed below:

• Aqueous industrial and municipal (sewage) wastes


Chapter 9-2MWH

• Semi-solid/ slurry wastes from industrial, municipal (sewage sludge, municipal solid waste-MSW), and farms as well as biomass residuals

The feedstock generally undergoes pre-treatment prior to biomethanation. Pre-treatment of industrialprocess wastewater would generally include equalization of flow and composition, heat exchange fortemperature regulation, neutralization for pH adjustment, sedimentation for the removal of suspendedparticulate matter and oil/ grease, and other physical – chemical processes for detoxification. In thecase of municipal sewage, preliminary processing will include bar screen, detritor and primaryclarifier.

Municipal Solid Waste (MSW) consists of biodegradable organic fraction (volatile solids) up to 50%-70% (dry basis) and the rest is non-biodegradable matter such as grit, sand, metal, plastics, glass,wood, rubber, etc Pre-processing of MSW involves both dry and wet techniques for handling a largequantum of waste, and represents an elaborate preparatory stage prior to biomethanation.

Biomethanation processes have also been successfully applied to solid/ semisolid wastes from cattlefarm, poultry farm, food processing industries, etc. Water is added in all these applications to increasethe moisture content (20% – 40% solids) or prepare slurry (10% – 15% solids) depending upon theprocess requirements.

Anaerobic processes offer several benefits such as methane production (biogas as fuel), low capital,and operating costs, power savings with no aeration requirement and high treatment efficiency. Fullscale anaerobic treatment plants are in operation in many countries, including India, in industrial andurban sectors such as distilleries, breweries, chemical manufacturing, dairy, food processing, landfillleachate, pharmaceuticals, pulp and paper, slaughterhouse, sugar, sewage sludge and MSW.

9.2 Principles of BiomethanationThe anaerobic microbial conversion of organic substrates to methane is a complex biogenic processinvolving a number of microbial populations, linked by their individual substrate and productspecificities. The overall conversion process may be described as involving both direct and indirectsymbiotic associations between different groups of microorganisms present in the digester.

A simplified schematic diagram of the major biochemical transformations during anaerobicfermentation processes is given in Figure 9-1. These processes were developed for reducing solidcontent and improving the dewatering characteristics of sludge produced in wastewater treatmentplants. This has been accomplished by a consortium of anaerobic bacteria capable of convertinginsoluble particulate organic material to form biogas (consisting of methane and carbon dioxide),through a number of intermediate steps.

These conversion possibilities can serve as a convenient basis for emphasizing some importantbiochemical and environmental requirements of anaerobic microbial treatment of municipal,agricultural and industrial wastes, and for directing the development or selection of substrate-linkedprocess configurations. The methanogenic bacteria are crucial for the anaerobic stabilization ofvarious substrates, since they constitute the final step leading to the generation of biogas.

Waste composed of particulate organic material (waste sludge, MSW, etc.) must first be solubilizedby the action of extra cellular enzymes that are produced by hydrolytic bacteria. The solubilisation ofparticulate material is relatively slow and accomplished by providing a long contact time between thesubstrate and an anaerobic microbial consortium. Wastes containing soluble organics will requireshort retention times for achieving high treatment efficiency, since the kinetic rates of the acidogenicand methanogenic bacteria are relatively rapid.


Chapter 9-3MWH

9.3 Biomethanation Systems: Aqueous WastesVarious anaerobic reactor designs are currently in use for full-scale applications for treatment ofdomestic sewage and various industrial wastewaters to produce methane-enriched biogas as shown inFigure 9-2. In general, the suspended biomass growth processes are advantageous for the treatment ofwastewater containing low proportions of particulate biodegradable material. The attached growthprocesses are well suited to wastewater that primarily contains soluble organic substrates. The hybridprocesses can be applied to wastewaters with intermediate levels of particulates, althoughperformance is usually better with soluble wastewaters. A comparison of the salient process featuresof suspended growth and attached growth bioreactors are given in Table 9-1. Table 9.2 gives aconsolidated list of the major advantages and limitations of the different commercial reactors,classified on the basis of the retention of microbial biomass in suspension or attached in the system.Table 9.3 gives a comparative assessment of some important process design features of differentbioreactor configurations handling distillery spent wash, based on feedback from full-scale operatinginstallations in India. The information/ data contained in these tables will be valuable in preliminaryscreening and selection of an appropriate reactor configuration for a given application.

9.3.1 Suspended Growth SystemsA. Continuous Stirred Tank Reactor

The simplest form of suspended growth anaerobic digester is the completely mixed digester Figure9.3 Mechanical impeller-type or gas recirculation mixers are used to achieve the completely mixedconditions in these reactors. In a completely mixed digester, the concentration of suspended solidsremaining in the effluent after treatment will be a function of the influent composition and the degreeof treatment provided. Completely mixed digesters are particularly suitable for wastewaterscontaining high concentrations of suspended solids. The process is susceptible to toxics and shockloadings with relatively low biomass concentrations and short operating SRTs.

The system offers several process advantages as illustrated below:

• Process can provide uniform environment throughout the reactor

• Good mixing can minimize short circuiting, dead pockets and flow channeling

The main disadvantage of the process is large reactor volumes required to provide necessary SRTs

B. Anaerobic Contact Reactor

The anaerobic contact reactor configuration can overcome some of the disadvantages of theconventional digester by recycling the biomass enhancing the SRT in the digester. Figure 9-4. Thebiomass separation system used in the anaerobic contact process will retain active microorganismspromoting biodegradation of organic matter in the influent. The anaerobic contact process retainsmost of the advantages of a conventional digester with the extra benefits of increased SRTs andsmaller reactor volumes. Anaerobic contact systems that utilize gravity settling for anaerobic flocsusually entrain biogas. Solids settleability can often be problematic, and can be improved by gasstripping, or vacuum degasification, inclined plate or lamella settlers and the addition of coagulantsand flocculants to promote floc formation.

The treatment efficiency of an anaerobic contact process is usually much greater than that of acompletely mixed digester. Total COD reduction of 80-90% is possible for highly biodegradablewastewaters with COD concentration 2000 – 10000 mg/L.

Some of the major advantages of the contact system are listed below:


Chapter 9-4MWH

• Suitable for wastes with high concentration of organics

• Uniform substrate concentration in the uniform environment

• Relatively high quality effluent

• Aerobic post-treatment sludge can be wasted to the anaerobic reactor for stabilisation

• Can handle waste with low to medium concentration of suspended solids

Disadvantages

• Biomass settleability is critical

• Vacuum degasification to promote settlability

• Limited equalisation capacity for shock inputs

C. Covered Lagoons

A low-rate treatment process that has gained acceptance is an advanced version of anaerobic lagoon(shown in Figure 9-5). Feed is introduced at one end of the reactor through a distribution system tomaximize contact between the wastewater and a bed of anaerobic biosludge at the inlet zone of thetank. The biogas evolved at the inlet zone contributes significantly towards internal mixing, whichtakes place along the length of the tank. Near the outlet end of the lagoon, where biogas production isminimal, a relatively quiescent clarification zone is maintained to reduce the suspended solid contentof the treated effluent. In recent designs, internal mixers and sludge recycle are incorporated toimprove contact between the wastewater and the anaerobic sludge. The entire reactor is covered witha floating synthetic membrane that conserves process heat and permits the collection of the biogas.

D. Upflow Anaerobic Sludge Blanket (UASB) ReactorsThe UASB reactor incorporates multiple functions of a treatment system such as pre-sedimentation,anaerobic treatment, sludge/ biogas separation and stabilization in a single unit, making it the mostattractive high rate bioreactor system. It produces relatively high value by-products such as treatedwastewater for reuse; methane enriched biogas and mineralised sludge, which can be used as manure.

UASB reactors were developed initially for the anaerobic treatment of industrial wastewaters withmoderate to high COD concentration. The basic idea is to develop flocculant or granular sludge insituin the reactor, depending on the wastewater characteristics and operational parameters. The sludgewill tend to settle under gravity and will be retained when applying moderate upward velocities in thereactor and a separate sedimentation unit will not be necessary. Organic compounds present in thewastewater are absorbed or adsorbed on the sludge granules in the reaction zone during its passagethrough the sludge bed.

An integral three-phase Gas-Liquid - Solids separator (GLSS) is provided to dislodge the sludgeparticles from the entrapped biogas bubbles and separated in the settling zone. Wastewater enters thereactor from the bottom and travels through the reactor in the upward direction. The rising biogasbubbles, settling sludge particles and the differential density currents in the bulk of the reactor,achieve further mixing in the reaction zone.

Biogas contains methane (CH4), carbon dioxide (CO2), hydrogen gas (H2), hydrogen sulphide (H2S)traces of ammonia (NH3) and nitrogen (N). A cross-sectional view of the UASB reactor system isgiven in Figure 9-6


Chapter 9-5MWH

9.3.2 Attached Growth SystemsAttached growth or Biofilm reactors utilize a support medium for the development of a highconcentration of required biomass for efficient anaerobic treatment. An inert medium is placed in thevessel and the process is operated to favour the growth of microorganisms as a layer (biofilm) on thesurface. The media is fully submerged and wastewater flow can be in upflow or downflow mode. Theattached anaerobic biomass converts both soluble and particulate organic matter in the wastewater tobiogas. The most common designs of anaerobic attached growth systems are anaerobic filters andfluidised bed reactors.

A. Upflow Filters

Waste stream is passed upward through a bed of medium in an anaerobic filter. The highconcentration of biomass grown and retained as biofilm on the surface of the media contributes to theshort hydraulic retention time and high organic loading rates.

The earlier designs, with stone media having low voids, have largely been replaced by syntheticmedium with an open structure and high void volumes (95%). The large interfacial area availablepromotes the development of an attached biofilm. Figure 9-7 gives a schematic representation of anupflow anaerobic filter.

Random loose-fill packings such as plastic pall rings and stacked modular media, formed from plasticsheets, have both been used in full-scale applications. The specific surface-to-volume ratios of thesepackings provide interfacial area of 100 – 150 m2m-3 for biofilm development.

B. Downflow Filters

The downflow reactor utilizes stacked modular packing, which provides relatively straight verticalflow channels (Figure 9.7). By operating the reactor in a downflow mode, influent suspended solidsand sloughed biofilm solids are carried with the flow and require a downstream clarifier unit. Thismay result in lower effluent quality in some circumstances, particularly when the influent contains alarge proportion of insoluble material.

In general, fixed bed reactors offer a stable and simple anaerobic treatment process. The largeproportion of attached biomass in fixed bed reactors enhances biomass retention and improves thestability of the process under variable feed conditions. In comparison to suspended growth systems,the cost of the biofilm support medium could be prohibitive.

C. Fluidised Bed Bioreactors

A fluidised bed bioreactor utilizes an inert medium such as sand (0.4-0.6 mm) for the growth ofbiomass as an attached biofilm.

The higher upflow velocities produce 25% to 100% bed expansion and the media particles remainsuspended in the fluidised state. The high-energy requirement for bed expansion or fluidisationthrough effluent recycle is one of the major disadvantages of a fluidised bed bioreactor.

The inert medium increases the average density of the biomass particle and prevents washout of thebed even under very high flow rate conditions. The large upflow velocities increase turbulence at thebiofilm/ liquid interface and promote good mass transfer across the biofilm and exert sufficient shearto prevent the development of thick biofilms on the media. The high upflow velocities allow compactreactors to be designed with a relatively large height/ diameter ratio.


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Sand is the most common medium used in full-scale anaerobic fluidised bed systems. An absorptivemedium such as activated carbon could prove to be an advantage for the treatment of toxic orinhibitory wastewaters. In addition, the adsorbed toxicant may eventually undergo biodegradation ifan acclimated microbial population can be developed.

Fluidised beds have some design requirements that are comparable to those of the fixed bedprocesses. The need for influent equalization should be evaluated in both cases. Efficient influent flowdistribution is also critical in fluidised beds. The design of the influent distributor is one of theproprietary features of the fluidised bed. Maximum dilution of wastewater is provided at the reactorinlet by the very high effluent recirculation ratios required for media fluidisation. This enables thefluidised bed processes to accommodate a wide range of wastewater with a COD concentration of upto 100,000 mg/L. Organic loading rates of up to 20 kg COD/m3/d are typical of these systems.

9.3.3 Hybrid ReactorsThe recent trend in design is toward the use of a “hybrid” reactor. The removal of the lower 50% –75% of the media in anaerobic filters could produce a hybrid sludge blanket/ anaerobic filter. Theresulting hybrid design has the potential of substantially reducing media plugging and the associatedhydraulic and mass transfer problems found in fixed bed reactors, while realizing the advantages ofboth fixed film and upflow sludge blanket treatment.

In the hybrid process, non-attached biosolids are free to accumulate, and the concentration and levelof the sludge blanket is easily monitored. Wasting of excess biomass from the sludge blanket zone isalso relatively simple. The packed zone at the top of the reactor serves as a gas-solid-liquid separatorthat assists in the retention of the non-attached sludge flows. It further provides a zone of attachedbiomass that improves process stability under transient operating conditions. The most significantbenefit of the hybrid reactor concept is the reduced cost of the support media required.

9.3.4 Wastewater CharacteristicsThe general range of characteristics of various industrial wastewaters suitable for anaerobicprocessing is given in Table 9-4. Some factors to be considered for screening the suitability ofanaerobic treatment technology include the following:

• Source and nature of wastewater

• Flow rate

• Concentration of organic pollutants (BOD, COD) and suspended solids

• Temperature

• Presence of toxicants, and

• Biogas and sludge generation potentials

The rates of all biomethanation reactions are controlled by the biomass activity and biomassconcentration in the system. Suspended growth processes can be designed in such a way that biomassis separated from the treated effluent and returned to the reactor. In this manner, Solids RetentionTime (SRT) and Hydraulic Retention Time (HRT) of the process can be segregated and controlled/varied independently. Biofilm reactors utilize an inert medium or carrier to favour the growth ofmicroorganisms on the media surface as a fixed film. This physical attachment will prevent biomasswashout and enable the development of the high biomass concentrations.

Wastewaters containing particulate organic material are degraded relatively slowly, since hydrolysisbecomes the rate-limiting step. Minimum Solids Retention Time (SRT) of four to ten days may be


Chapter 9-7MWH

required at mesophilic temperatures to prevent the washout of hydrolytic anaerobic bacteria. Thegrowth rate of methanogenic bacteria will be the rate-limiting step for anaerobic fermentation ofsoluble wastewaters containing acetate as the primary organic contaminant. In this case, SRT of twoand a half to five days may be required to allow growth and retention of methanogenic bacteria.

9.3.5 Features of Bioreactor OperationThe rates of methanogenesis in anaerobic microbial conversion processes depend primarily uponsubstrate availability and viable microbial population besides environmental factors such as the pH,temperature, ionic strength or salinity, the presence of nutrients and toxic or inhibitory substances inthe reactor. Some of the features of bioreactor operation are as follows:

• Most anaerobic processes operate best at neutral pH and are maintained with sufficientalkalinity in the medium. Gas production and pH levels are good indicators of the satisfactoryperformance of biomethanation processes.

• Low pH, excessive acid production and accumulation are inhibitants to methanogens thanfermentative bacteria.

• Methanogenesis reactions are strongly temperature-dependent, with reaction rates generallyincreasing with temperature up to 600C. Optimal temperature ranges used are mesophilic(350C - 40°C) and thermophilic (550C to 600C), with decreased rates between these optima,due to lack of adaptation.

• The nutrient requirements are met with BOD : N : P ratio of 100 : 0.5 : 0.1. The organicconstituents of the waste usually supply the fundamental requirements for macronutrientssuch as carbon and nitrogen.

• Other trace elements necessary to sustain metabolic activities include iron, nickel,magnesium, calcium, sodium, barium, tungstate, molybdate, selenium, and cobalt.

• Toxicity or inhibition of methanogenic processes can be attributed to a variety ofcircumstances, including the generation of intermediary products such as the volatile fattyacids, hydrogen sulphide and ammonia, besides some heavy metals and cyanide present inprocess wastewaters.

• Several full-scale facilities have been constructed and operated successfully for dilutewastewaters such as municipal sewage and for very concentrated effluents such as rumspillage (distillery spentwash).

• Anaerobic treatment alone can give 70%-90% BOD and 50%-75% COD removal efficiencyleaving relatively high residue of un-degraded organics in treated effluents.

• Higher BOD (COD) concentration levels would entail the recovery of a higher quantum ofbiogas necessary for power generation.

• Wastewater characteristics suitable for efficient working of anaerobic system are shown inTable 9-4. For concentrated wastes containing a COD of more than 30,000 mg/L, or for highconcentrations of suspended solids, low-rate anaerobic digestion system will be moreappropriate.

• Anaerobic digestion is well known as a treatment process for sewage sludge and animalmanures that contain high levels of suspended solids. The high concentration of insolubleorganic material will lead to a long digestion periods (10 – 30 days) in order to allow for therelatively slow biological process of hydrolysis and solubilisation of the insoluble materials.

• High-rate anaerobic treatment technologies are intended for wastewaters in which the organicpollutants are soluble.


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9.4 Biomethanation Systems: Sludge/ Semi-solids/ MSW

9.4.1 Low Solids Digestion (4%-6% solids)Conventional (standard-rate) sludge digestion is carried out as a single stage process. Thefunctions of digestion, sludge thickening, and supernatant separations are carried out concurrently.Raw sludge (4%-6% solids) is added in the active digestion zone. (The sludge is heated by means ofan external heat exchanger to maintain mesophilic conditions). The biogas rises to the top domesection for collection, and it also lifts sludge particles and other materials, such as grease, oils, andfats, to form a scum layer.

Digested sludge is mineralised, and thickens due to gravitational force and he supernatant layer isformed above the digested sludge. As a result of the stratification and the lack of intimate mixing, notmore than 50 percent of the volume of a standard-rate single-stage digester is used. Because of theselimitations, the standard-rate process can be used only for small installations.

In the two-stage digestion process, the first tank is used for digestion. It is heated and equipped withmixing facilities consisting of one or more of the following:

(1) Sludge-recirculation pumps;(2) Gas recirculation using short mixing tubes, one or more deep-draft tubes, or bottom-mounted

diffusers;(3) Mechanical draft-tube mixers, and(4) Turbine and propeller mixers.

Figure 9-10 is a schematic diagram of a two-stage, high-rate anaerobic digester system. Due to thereason that anaerobically digested sludge does not settle readily, many secondary digesters have notperformed well. They produce dilute sludge and a high strength supernatant. The second tank is usedfor the storage and concentration of digested sludge and for the formation of a relatively clearsupernatant. Frequently, the tanks are made identical, in which case, either one may be the primary. Inother cases, the second tank may be an open tank, an unheated tank, or a sludge lagoon. Tanks mayhave fixed roofs or floating covers. Any or all of the floating covers may be of the gasholder type.Alternatively, gas may be stored in a separate gas holder or compressed and stored under pressure

Higher solids loading rates can be applied on the high-rate-digestion process compared to theconventional single-stage process. The sludge is intimately mixed by gas recirculation, pumping, ordraft-tube mixers (separation of scum and supernatant does not take place) and it is heated to achieveoptimum digestion rates. With the exception of higher loading rates and improved mixing, there areonly a few differences between the primary digester in a conventional two-stage process and a high-rate digester. The mixing equipment should have greater capacity and should reach the bottom of thetank, the gas piping should be somewhat larger, fewer multiple sludge draw offs replace thesupernatant draw offs, and the tank should be deeper to aid mixing.

Sludge should be pumped to the digester continuously or in cycles. The incoming sludge displacesdigested sludge either to a holding tank or to a second digester for supernatant separation andresidual-gas extraction. Because there is no supernatant separation in the high-rate digester, and thetotal solids are reduced by 45 to 50 percent and given off as gas, the digested sludge is about half asconcentrated as the untreated sludge feed.

Compared to operation at ambient temperatures, control of the temperature in the mesophilic rangespeeds up the process substantially. In temperate countries, medium to high solid wastes such assewage sludge and animal slurries are usually treated in fully mixed mesophilic digesters with arelatively long retention time and low volumetric and organic loading rates (1-5 kg COD/m3/d). This


Chapter 9-9MWH

is because a substantial percentage of the biodegradable portion of these wastes is cellulosic material,and the slow rate of hydrolysis of these compounds requires long retention times to achieve areasonable level of degradation. Retention times are typically 15-30 days for most of these wastes.

Mixing and heating together lead to a uniform reactor environment and maintain conditions for theoptimum growth of the microbes that drive the digestion process. Figure 9-11 is a schematic diagramof a single-stage high-rate, continuous stirred digester.

Mixing creates a homogeneous environment and allows newly introduced waste to come in contactwith the microorganisms. It also evenly distributes temperature and waste products. Mixing can beaccomplished by a variety of methods, either mechanically or by the use of compressed digestion gas.The three common methods of gas mixing include:

• injection of compressed gas through a series of small-diameter pipes suspended from thecover into the digesting sludge,

• the use of a draft tube in the centre of the tank with compressed gas injected into the tube tolift recirculating sludge from the bottom, and

• supplying compressed gas through a number of diffusers mounted in the centre at the bottomof the tank.

9.4.2 Medium Solids Anaerobic Digestion (10%-15% solids)The medium-solids anaerobic fermentation process is used in many parts of the world to generatemethane gas from sewage, animal waste, agricultural wastes and the organic fraction of MSW.Medium-solids anaerobic digestion is a biological process in which organic wastes are fermented atsolids concentration of 10-15 percent. One of the disadvantages of this process is the water requiredfor dilution, which must be dewatered prior to disposal. The disposal of this liquid stream resultingfrom the dewatering step is also an important consideration.

There are three basic steps involved in medium-solids anaerobic digestion process. They are:

1. Preparation of the organic fraction of the MSW involving sorting and separating.

2. Addition of water and nutrients, blending, pH adjustment (6.5-7) and heating of the slurry to55oC - 60oC (if necessary). Anaerobic digestion is carried out in a continuous flow stirredreactor. The required moisture content and nutrients can be added to the wastes to beprocessed, in the form of wastewater sludge or cow manure.

3. Collection of biogas (50%-60% CH4).

4. The dewatering and disposal of the digested sludge is an additional task.

One of the disadvantages of this process is the water required for dilution, which must be dewateredprior to disposal. The disposal of this liquid stream resulting from the dewatering step is also animportant consideration.

9.4.3 High Solids Anaerobic Digestion (25%-35% solids)High-solids anaerobic digestion is a biological process in which the fermentation occurs at a totalsolids content of 25–35 percent for energy recovery from the organic fraction of MSW. Twoimportant advantages of the high-solids anaerobic digestion process are lower water requirement andhigher gas production per unit volume of the reactor size.


Chapter 9-10MWH

The three steps described for the medium-solids anaerobic digestion are also relevant for high-solidsanaerobic digestion process. The principal difference is at the end of the process, where less effort isrequired to dewater and dispose of the digested sludge.

The effects of many environmental parameters on microbial populations are more severe in the caseof the high-solids concentration. For example, ammonia toxicity can affect the methanogenic bacteria,which will have an adverse effect on system stability and methane production. In most cases,ammonia toxicity can be prevented by a proper adjustment of the Carbon to nitrogen ratio of the inputfeedstock.

Process selection between anaerobic processes is typically between the medium-solids and the highsolids options. Selection of equipment and facilities for the medium-solids anaerobic digestionprocess usually involves the type of mixing equipment (internal mixers, internal gas mixing andexternal pump mixing), the general shape of the digester (e.g. circular or egg-shaped), the controlsystems, and the ancillary facilities needed for feeding the incoming wastes and dewatering thedigested sludge.

Table 9.5 gives some important process design consideration for medium and high solids anaerobicdigestion processes for handling the organic fraction of MSW.

9.5 Environmental and Regulatory AspectsBiomethanation processes have been very successfully adopted for handling both urban (MSW andsewage) and industrial process wastewaters. The primary driving force has been the significantsavings in energy requirements compared to conventional aerobic processes. The pollution load (BODor COD) on aerobic treatment can be reduced considerably by an anaerobic pre-treatment. The energyrequired to operate the latter is very low, and offers an opportunity for energy recovery correspondingto the bio-chemical energy potential of the waste. The sludge produced by anaerobic processing ofurban waste is also well stabilised for potential use as manure.

Downstream treatment of the post-anaerobic treated waste by aerobic or other suitable techniques willbe mandatory for compliance with regulatory stipulations. Consequently, environmental andregulatory considerations would apply for the pollution control facility as a whole.

This will be a matter of concern where stand-alone anaerobic (biomethanation) systems have beenwidely adopted for the treatment of some industrial wastes such as distillery spentwash. Theperformance of the down-stream pollution control facility must meet the stipulated norms asapplicable for the specific application.

9.6 Overview of Biomethanation Technology

9.6.1 International ScenarioSeveral variations of biomethanation plants have been built in many countries by private, government,research and non-governmental organizations. Unlike advanced thermal conversion (ATC)technologies, relatively few patented biomethanation technologies are in existence. However,biomethanation is a mature technology and there is extensive experience worldwide in all the aspectsof biomethanation. Thousands of biomethanation plants have been built, ranging from small farmdigesters to large-scale waste treatment and biogas recovery plants. Biomethanation technologies areamong the most promising options for waste-to-energy recovery, particularly for agriculture-basedcountries such as India. Around 135 commercial installations were available for anaerobic digestionof different feedstock (1999). Figure 9-12 shows the number of anaerobic technologies that are


Chapter 9-11MWH

available for waste-to-energy recovery. Source separated MSW has been used as a feedstock in theexisting plants. One-quarter of the plants are utilized for manure and industrial organic waste.

Other factors influencing success have been local environmental regulations and other policiesgoverning land use and waste disposal. Because of these environmental pressures, many nations haveimplemented, or are considering methods to reduce the environmental impacts of waste disposal. Thecountry with the greatest experience using large-scale digestion facilities has been Denmark, where 18large centralized plants are now in operation. In many cases, these facilities co-digest manure, cleanorganic industrial wastes, and source separated MSW.

The numbers of installations to the credit of individual system providers are shown in Figure 9-13.Commercially available technologies - Kruger (Denmark), Kompogas (Switzerland), Entec (Austria),Eco Tech (Finland), BTA (Germany), Dranco (Belgium) are some of the major players who haveinstalled most of the units around the globe, with more than six units adapting the individual processconfiguration.

An extensive literature search was carried out for representative case studies, projects and experiencein various regions of the world. The literature searched, and the available information are organizedin the following manner:

• Commercial Biomethanation Technologies and Technology Providers (Appendix 9-A)

• Status of Biomethanation in Representative countries (Appendix 9-B)

• List of Worldwide Representative Biomethanation Projects and Technologies (Appendix 9-C)

• Case Studies (Appendix 9-D)

9.6.1.1 Commercial Biomethanation Technologies

As mentioned above, there are not too many biomethanation technologies that have beenpatented. However, various distinctive processes and unique technologies have beendeveloped and are being used for biomethanation of organic waste. Some technologies arelisted below and further details are given in Appendix 9-A. Contact details of Indian andInternational technology providers is also included in Appendix 9-A

• High Solids Anaerobic Digestion (HSDA)

• CBI Walker/ Enning ESD™ System

• Biogas Induced Mixing Arrangement (BIMA)

• Valorga Process

• Smag Process

• Dranco Process

• Wabio Anaerobic Digestion Process

• Linde-KCA-Dresden GmbH

• TBW-biocomp Process

• BTA Process

• Kompogas Process

• PFMSW Methanization - WAASA® Process.


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9.6.1.2 Representative Countries Status of Biomethanation

Six to eight million family-sized, low technology digesters are used in the Far East with varyingdegrees of success. There are also over 600 farm-based digesters operating in Europe and NorthAmerica. More than 115 large-scale anaerobic digestion plants are in operation, or under constructionworldwide for treatment of municipal solid wastes. The total annual capacity is almost five milliontonnes, and another 40 digestion plants are in the planning phase with an annual capacity of nearlytwo million tonnes. More than 50 prime technology license holders have a proven system operating atthe pilot-or full-scale level.

Some information regarding the status of biomethanation in the following countries is available:• Austria

• Belgium

• Canada

• Denmark

• Germany

• Greece

• India (Section 9.7.2)

• Italy

• The Netherlands

• Norway

• Portugal

• Sweden

• Switzerland

• The United Kingdom

A brief status report for each of the above countries is given in Appendix 9-B.

Worldwide Representative Projects and Technologies

The use of anaerobic digestion for treating industrial wastewaters has grown tremendously duringthe past decade, to the point where there are now more than 1,000 vendor-supplied systems inoperation or under construction throughout the world. Over 30 types of industries have beenidentified, which have wastewater suitable for anaerobic digestion treatment, includingprocessors of beverages, chemicals, food, meat, milk, pulp and paper, and pharmaceuticals.Many of these industries use anaerobic digestion as a pre-treatment step to lower sludge disposalcosts, control odours, and to reduce final treatment costs at a municipal wastewater treatmentfacility. However, the most common use of anaerobic digestion is in farm-based manure and gasfacilities. A list of some of the biomethanation projects operating or constructed worldwide aresummarized in Appendix 9-C.Case Studies

A brief description of some of the biomethanation plants is given in Appendix 9–D.


Chapter 9-13MWH

Various methods of Power Generation from biogas and other applications of biogas are given inAppendix 9 E. Appendix 9 F provides a overview and cost appraisal of 10 operating plants innorthern Europe and recent UK. .

9.6.2 National ScenarioSeveral case studies of biomethanation installations in India are given in Appendix 9 G and Table9.6. A list of these case studies low:

Waste to Energy Projects

Distillery1. Waste-To-Energy Project at Kanoria Chemicals Ltd. Ankleshwar2. SMAT Process for Treatment of Distillery Effluent at the Brihan Maharashtra Sugar Syndicate

Ltd., Shreepur, Maharashtra.3. Power Generation based on Biogas at M/s Ugar Sugar Works Ltd., Belgaum, Karnataka

Starch and Sago4. Varalakshmi Company, Namakkal, Tamil Nadu.

MSW5. Municipal Solid Waste based Power Generation Programme in Uttar Pradesh6. MSW to Energy – Nagpur Project7. Wabio Anaerobic Digestion Process To Produce Energy From Garbage

Waste to Biogas Projects

Distillery8. BACARDI’S Anaerobic Treatment of Distillery Spentwash at Andhra Sugars Limited, Tanuku,

Andhra Pradesh9. Thermophillic Process for Treatment of Distillery Effluent at Rampur Distillery and Chemicals,

Rampur, Uttar Pradesh10. M/s. Som Distilleries, Dist. Raisen, Madhya Pradesh Power Generation Utilising Biogas at K.M.

Sugar Mills Ltd., (Distillery Unit, Faizabad, U.P.)

Pulp and Paper Biomethanation of Waste Liquor from Rayon Grade Pulp Mill

Starch and Sago11. Biogas Generation Plant based on Industrial Wastes from Starch and Glucose Manufacturing at

Vensa Bioteck, Samalkot, AP.12. UASB Process for Treatment of Starch Effluent at M/s. Universal Starch-Chem Allied Ltd.,

(USA) Dondaicha, Dhule, Maharashtra.13. Biogas Generation plant based on Industrial effluent from starch Industry, Ahmedabad, Gujarat

Dairy14. Biogas Generation Plant based on Industrial Wastes from Vasudhara Dairy at Alipur, Gujarat,

India

Slaughter House15. Biogas Generation Plant based on Industrial Wastes from Abattoir Unit, Alkabeer, Medak, A.P.

Poultry


Chapter 9-14MWH

16. Biogas From Poultry Waste at Western Hatcheries

Sewage17. Installation and Performance Evaluation of a Fixed Film Sewage Treatment Plant

MSW18. GENL’S Pilot Plant for Biogas from Municipal Solid Waste

Fruit and Vegetable Market Waste19. CFTRI Initiatives For Energy Generation From Fruit And Vegetable Processing Waste20. Biomethanation of Vegetable Market Waste

9.7 Summary and Recommendations

Biomethanation and Gasification have emerged as two major competing options for energyrecovery from MSW in developed countries.

High rate biomethanation processes at mesophilic and thermophilic temperatures can yield ahigher biogas production rate, and also provide a higher rate of waste stabilization for secondaryuse as manure. High rate biomethanation of municipal sludge, municipal solid waste, industrialwaste, and animal waste has a similar value for energy recovery and environmental pollutioncontrol. This process has multiple benefits to the community, and eventually to the country, forsolving its substantial energy shortfall and controlling its very significant environmental pollutionproblems.

High rate biomethanation processes must be considered for waste-to-energy and wastestabilization projects in India, for the following principal reasons:

• It is a proven and established technology.

• India has excellent in-house expertise in high rate biomethanation processes and is thereforeless dependent on foreign expertise.

• There is an established network of equipment suppliers and services during construction,maintenance and operation of high rate biomethanation systems.

• Stabilization of municipal waste (sewage, sludge and MSW), currently a major source ofenvironmental pollution and human health problems, will bring significant benefits to theenvironment and human health.

• Municipal sludge and MSW can be cost-effectively combined for high rate co-digestionprocesses.

• It allows for wide variations in size and capacity.


Chapter 9-15MWH

Table 9-1. Salient Features of Suspended and Attached Growth Anaerobic Bioreactors

Sr.No.

Feature Suspended GrowthBioreactor

Attached GrowthBioreactor

1. Biomass concentration (g/L) Low (5 – 10) High (15 – 50)

2. SRT (d) Low (15 – 25) High (20 – 50)

3 Wastewater

a) Suspended Solid (mg/L) < 5000 < 100

b) High BOD (COD) Suitable Suitable

c) Low BOD (COD) Suitable if thequantity is more

Suitable

4. Removal efficiency Low High

5. Resistance to toxics Low High

6. Hydraulic Integrity Simple withmechanical mixing

Flow channelling (biomassaccumulation)

7. Captive power Low Fluidised bed (very high)Filter (Low)


Chapter 9-16MWH

Table 9-2. Advantages/ Disadvantages of Anaerobic Bio-reactors for Wastewaters

S. No. ReactorConfiguration

Advantages Disadvantages

A. Suspended Growth Reactors

1 Contact reactor Suitable for wastes with highconcentration of soluble organics

Uniform substrate concentration,temperature and pH

Higher degree of treatment

Post-treatment sludge can also bestabilised

Can handle wastes with low to mediumconcentration of suspended solids

Biomass settlability is critical

Vacuum degasification topromote settlability

Limited equalisation capacityfor shock inputs

2 Lagoon (covered) Simple design of reactor

Suitable for wastes with highconcentrations of organic andsuspended solids

Toxicants and shocks can be equalizedin large reactor volume

Significance of sludge settlability isless

Relatively high quality effluent

Very long SRT reduces waste sludgeproduction

Plug Flow conditions lead toinefficient internal mixing andfeed distribution

Large land requirement

3 UASB Higher sludge concentration (granules)

Low energy requirements

Less stabilised sludge with gooddewatering characteristics

Production of biogas with highermethane content

High rate process with high volumetricloading

Low land requirement

High COD (BOD) removal efficiency

Slow process start-up

Requires skills to maintaingranular sludge blanket orzone


Chapter 9-17MWH

S. No. ReactorConfiguration

Advantages Disadvantages

B. Attached Growth Reactors

4 Upflow Filter/Downflow Filter

High biomass concentrations and longSRT

Smaller reactor volumes due to highorganic loading rates

Relatively stable operation undervariable feed conditions or toxicshocks

Suitable for wastes with lowsuspended solids concentrations

No mechanical mixing required

Effluent recycle gives uniformtemperature, pH and substrateconcentrations in reactor

Land area required is less

Suspended solidsaccumulation may adverselyaffect reactor hydraulics andinternal mass transfercharacteristics

Relatively short hydraulicretention time (HRT) results inreduced equalisation capacityfor shock inputs

High costs of packing materialand support.

5 Fluidised BedBioreactor

High biomass concentrations and longSRT

Excellent mass transfer characteristics

Compact reactor volumes due to highorganic loading rates

High degree of treatment

Relatively stable operation undervariable feed conditions or toxicshocks

Suitable for wastes with lowconcentration of suspended solids

No mechanical mixing

Effluent recycle gives uniformconcentration, temperature and pH

Small land area required.

Prolonged start-up duration

High power requirement forbed expansion or fluidisation

Control of media and biomassinventories can be difficult

Accidental washout of mediacan damage downstreamcomponents

Relatively short HRT results inreduced equalization capacityfor shock inputs

Hydraulic design of the systemis relatively complex

High cost of carrier medium


Chapter 9-18MWH

Table 9-3. Process Design Criteria for Bioreactors*

Type of Process OrganicLoading

Kg COD/m3

day

HRT(d)

BODRemoval

Efficiency%

CODRemoval

Efficiency%

A. Suspended Growth Systems

Covered Lagoon 1 – 2 30 – 50 85 – 90 75 – 80

Contact Reactor 3 – 5 15 – 20 70 – 75 60 –65

UASB 12 – 15 10 – 12 85 – 90 70 – 75

B. Attached Growth Systems

Downflow/ Upflow Filter 8 – 10 10 – 12 80 – 85 70 – 75

Fluidised Bed 15 – 20 10 - 12 85 - 90 75 - 80

* Based on feedback from operating distillery installations in India.


Chapter 9-19MWH

Table 9-4. Waste Characteristics Suitable for Anaerobic Treatment

Parameter Range

35 – 40 (Mesophilic)Temperature (0C)

55 – 60 (Thermophilic)

pH 7-8

BOD 250 – 50,000

COD 500 – 100,000

SS 100 – 5000

NH4+ - N < 1700

SO42- < 5000

Ca2+ < 2000

Cations < 4000

Formaldehyde < 50Note: Except pH all other units are in mg/L, unless otherwise it is mentioned next to the parameter


Chapter 9-20MWH

Table 9-5. Comparative Analysis of Medium and High Solids Anaerobic Digesters

Waste Feature Medium Solids High Solids

A. Process Characteristics

Size of material Shredded for efficientpumping and mixingoperations

Shredded for efficient feedingand discharging mechanisms

Mixing Mechanical Plug flow

Hydraulic Retention Time, days 10 - 20 20 - 30

Loading rate kg/m3.d 0.6 - 1.6 5 - 7

Solids concentration % 10 - 15 25 – 35

Temperature o-C (mesosphilic) (thermophilic)

35 - 40

55-60

35 - 40

55-60

VS Destruction % 60 - 80 90 – 95

TS destroyed % 40 – 50 50 - 60

Gas production,

m3/kg VS destroyed

0.6 - 0.75 0.8 - 1.0

Biogas % CH4 50 – 60 55 – 60

B. Design and Operational Parameters

Reactor Design Complete-mix reactors Plug-flow reactors

Water addition High Low

Mass removal rate Low High

Feed/ discharge arrangement Pumps Screw pumps and conveyors.

Toxicity Less severe Salts and heavy metal toxicityAmmonia toxicity for C/N <15

Sludge dewatering Expensive Less expensive

Technology status Proven (several installations) Proven (several installations)


Chapter 9-21MWH

Table 9-6. Highlights of Some Waste-to-Energy Industrial Projects

Sr. No. Description Kanoria Chemicals The Brihan SugarSyndicate

K. M. Sugar Mills

1. Type of Waste Spent wash Spent wash Spent wash

2. Location Ankaleshwar, Gujarat Shreepur, Maharashtra Faizabad, Uttar Pradesh

3. Project Objective Waste to energy Waste to energy Waste to energy

4. Project Description Biomethanation ofeffluent producing biogasto be utilised forgenerating electricity (2MW)

Biomethanation of spentwash producing biogas tobe utilized for generatingelectricity (1 MW)

Power generation plant of1MW capacity usingbiogas produced in theanaerobic treatment ofeffluent

5. Technology Anaerobic digesters(Degremont andBacardi)

UASB UASB

6. Capacity (Cum/day) NA 525 500

7. Hydraulic Retention Time(days)

NA NA NA

8. Organic Loading (kg COD/day) NA NA NA

9. COD Removal Efficiency NA NA NA

10. Biogas Production (cum/day) 21,000 10,800 12000

11. Specific Biogas Production(Cum/kg COD removed)

0.5 0.5 0.5

12. Mode of Energy Utilisation Produced biogas isutilised for generatingelectricity using pure gasengines

Produced biogas isutilised for generatingelectricity using pure gasengines

Generation of Electricityusing DFG engine

13. Energy Produced (kWh/month) 10,32,375 720,000 400,000

14. Project Capital cost (Rs. Inlakhs)

890 505.61 382

15. Revenue Generation (@Rs.3.87kWh/month)

3995291.25 2786400 1548000

16. Operation and MaintenanceCost (Rs./ Year)

NA NA NA

17. Present Status Commissioned in 1998 Commissioned inNovember 2000

Commissioned in May1997, WorkingSatisfactorily

18. Remarks The industry has alsoinstalled hydrogensulphide removalbiological process.

Plant is workingsatisfactorily.

Produced energy isutilised in-house in theplant and residentialcolony

19. Funding Assistance from NBB Assistance from NBB Assistance from NBB


Chapter 9-22MWH

Sr. No. Description Varalakshmi Company Andhra Sugars Rampur Distillery andChemicals

1. Type of Waste Sago waste Spent wash Spent wash

2. Location Namakkal, Tamil Nadu Tanuku, Andhra Pradesh Rampur, Uttar Pradesh

3. Project Objective Waste to energy Waste to energy (biogas) Waste to energy (biogas)

4. Project Description Power generation of 0.2MW capacity from 40TPD sago plant effluent

Biomethanation of spentwash producing biogas tobe utilized as fuel in theboiler.

Biomethanation of spentwash producing biogasto be utilized as fuel inthe boiler.

5. Technology UASB Bacardi Thermophilic

6. Capacity (Cum/day) 500 225 1000

7. Hydraulic Retention Time(days)

NA 14 9

8. Organic Loading (KgCOD/day)

3000 6750 100,000

9. COD Removal Efficiency 80% 70% 50%

10. Biogas Production (cum/day) 4700 6,800 20,000

11. Specific Biogas Production(Cum/Kg COD removed)

0.5 0.5 0.4

12. Mode of Energy Utilisation Generation of electricityusing DFG engine

Produced biogas isutilised directly as fuelfor generating steam inthe boiler.

Produced biogas isutilised directly as fuelfor generating steam inthe boiler.

13. Energy Produced(kWh/month)

111166 NA NA

14. Project Capital Cost (Rs. inlakhs)

360 NA 200

15. Revenue Generation(@Rs.3.87 kWh/month)

430215 1,200,000 NA

16. Operation and MaintenanceCost (Rs./ Year)

NA NA 4

17. Present Status Commissioned in 2002,Results awaited

Commissioned in 1989 Commissioned in 1987

18. Remarks All the performanceparameters are based onthe Feasibility Report

Plant is workingsatisfactorily

Payback period of theplant is calculated as 3.3years.

19. Funding Assistance from NBB Self funding Self funding


Chapter 9-23MWH

Sr. No. Description Vasundhara Dairy Universal Starch The Anil StarchProducts Ltd.

1. Type of Waste Dairy waste Maize starch waste Maize starch waste

2. Location Alipur, Gujarat Dhule, Maharashtra Ahmedabad, Gujarat

3. Project Objective Waste to energy (biogas) Waste to energy (biogas) Waste to energy (biogas)

4. Project Description Vasundhara Dairyprocesses 200,000 litresof milk per day tomanufacture processedmilk, buttermilk andghee. Wastewatertreatment

Biogas is fed to the boilerto save boiler fuelconsumption

Produced biogas is fed tothe boiler to save boilerfuel consumption

5. Technology UASB UASB UASB

6. Capacity (Cum/day) 400 1700 1600

7. Hydraulic Retention Time (days) NA NA NA

8. Organic Loading (kg COD/day) NA 28679 6816

9. COD Removal Efficiency 80% 70% 80%

10. Biogas Production (cum/day) 40 10000 4800


0.1 0.5 0.5

12. Mode of Energy Utilisation Produced biogas is flaredin to the atmosphere.

Biogas is burned in theboiler to save costs ofboiler fuel used for glutendrying

Biogas is burned in boilerto save costs of boilerfuel

13. Energy Produced (kWh/month) NA NA- NA

14. Project Capital cost (Rs. in lakhs) 45 200.58 301.64


NA NA NA

16. Operation and Maintenance Cost(Rs./ Year)

NA NA NA

17. Present Status Commissioned in 1993,the plant is functioningsatisfactorily.

Commissioned in March2002

Commissioned in April2001, Results awaited

18. Remarks Biogas produced is notutilised for any purpose.

Plant is workingsatisfactory. All theperformance parametersare based on theFeasibility Report

Plant is workingsatisfactory

19. Funding Assistance from NDDB Assistance from NBB Assistance from NBB


Chapter 9-24MWH

Sr. No. Description Vensa Bioteck Al Kabeer Exports Al Kabeer Exports

1. Type of Waste Starch and glucosemanufacturing

Sheep + Goat + Buffalofleshings

Effluent from Abattoirunit

2. Location Samalkot, Andhra Pradesh Medak, Andhra Pradesh Medak, Andhra Pradesh

3. Project Objective Waste to energy (biogas) Waste to energy (biogas) Waste to energy (biogas)

4. Project Description Industry processes 40,000MT of maize starch and25,000MT of Tapiocastarch to manufactureglucose and starch.Biomethanation of effluentproducing biogas to beutilized as fuel in the boiler.

Biomethanation offleshings and then afterproducing power.

The slaughterhouse hasa processing capacity toslaughter 600 buffaloesand 1500-2,000 sheepper day. To reduceoperation andmaintenance costs of thewastewater treatmentplant

5. Technology Adopted UASB BIMA UASB

6. Capacity (Cum/day) 1600 60 TPD 2,000

7. Hydraulic Retention Time (days) NA NA NA

8. Organic Loading (Kg COD/day) 19,200 9,000 14,000

9. COD Removal Efficiency 70% NA 80%

10. Biogas Production (cum/day) 8,000 2,500 4,000


0.6 0.59 (cum/Kg VS) 0.36

12. Mode of Energy Utilisation Produced biogas is utiliseddirectly as fuel forgenerating steam in theboiler.

NA Produced biogas is usedas fuel in the boiler.

13. Energy Produced (kWh/month) NA NA NA

14. Project Capital cost (Rs. in lakhs) 180 397.44 NA


48 lakhs by savings in fuel NA Rs. 30 lakhs worth offuel to boiler is savedper year

16. Operation and Maintenance Cost(Rs./ Year)

NA NA NA

17. Present Status Commissioned in 1999 Commissioned in 1999,Working satisfactorily.

Commissioned in 1999,Working satisfactorily.

18. Remarks Payback period is estimatedto be 4 years

Biogas produced is flaredin the atmosphere.

Along with utilisation ofbiogas, the benefits arealso derived from savingof power consumption inwastewater treatmentplant, and producedsludge is used as soilconditioner.

19. Funding Assistance from NBB Assistance from NBB Assistance from NBB


Chapter 9-25MWH

Figure 9-1. Anaerobic Pathways for Industrial, Agricultural, Municipal Wastes

Aceticacid

Butyric acidPropionic acid

H2, CO2

SOLUBLE ORGANICSSugars

Fatty acidsAmino acids

Hydrolysis(Extracellular

Enzymes)

Acid-formingBacteria

AcetogenicBacteria

AcetoclasticMethanogens

H2 – UtilizingMethanogens

CarbohydratesProteins, Fats

ORGANIC PARTICULATE

BIOGAS(CH4, CO2)


Chapter 9-26MWH

Figure 9-2. Anaerobic Bio-reactor Configurations

COVEREDLAGOONS

ANAEROBIC PROCESSES

SUSPENDED SYSTEMS HYBRIDSYSTEMS

ATTACHED GROWTHSYSTEMS

CONTACTREACTOR ANAEROBIC

FILTERFLUIDIZED

BED

UPFLOW ANAEROBICSLUDGE BLANKET

(UASB)

UPFLOW DOWNFLOW


Chapter 9-27MWH

Figure 9-3. Completely Mixed Suspended Growth Anaerobic Digester

Figure 9-4. Anaerobic Contact Reactor System

EFFLUENT

BIOGAS

INFLUENT

ANAEROBICREACTOR

SECONDARYCLARIFIER

VACUUMDEGASIFIER/ GAS

STRIPPER (OPTIONAL)

SLUDGE RECYCLE

INFLUENT

BIOGAS

EFFLUENT


Chapter 9-28MWH

Figure 9-5. Covered Anaerobic Lagoon (Bulk Volume Fermenter)

FLOATING INSULATED MEMBRANE COVER

SCUM LAYER

BAFFLE

BIOGAS

PRIMARYREACTION

ZONE

SECONDARYREACTIONZONE

CLARIFICATIONZONE

EFFLUENT

SLUDGE

SLUDGEMIXER

FEED

SLUDGE RECYCLE

WASTE


Chapter 9-29MWH

Figure 9-6. Typical Cross-Section of a UASB Reactor


Chapter 9-30MWH

Figure 9-7. Upflow Anaerobic Filter

GAS

EFFLUENT

INFLUENT

RECYCLE


Chapter 9-31MWH

Figure 9-8. Downflow Anaerobic Filter

GAS

INFLUENT

RECYCLE

EFFLUENT


Chapter 9-32MWH

Figure 9-9. Schematic Anaerobic Fluidised Bed Bio-Reactor

Gas/Solid/LiquidSeparation

Biogas

TreatedWastewater

UntreatedWastewater

Fluidizedbed

reactor


Chapter 9-33MWH

Figure 9-10. Two-Stage High-Rate Anaerobic Sludge Digester System


Chapter 9-34MWH

Figure 9-11. Single-Stage High-Rate Biomethanation


Chapter 9-35MWH

Figure 9-12. Commercial Installations with Different Feed Stock (1999)

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No.

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Chapter 9-36MWH

Figure 9-13. Technology-Wise Number of Commercial Installations (1999)

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National Master Plan for Development of Waste-to-Energy in India Technical Memorandum on Waste-to-Energy Technologies

Chapter 10-1

MWH

10 Incineration Processes

10.1 Introduction

Incineration, also known as combustion, has been a traditional technology for treating waste and recovering energy. Organic wastes can be directly incinerated in waste-to-energy facilities with minimal pre-processing. Incineration has been successfully used for the disposal of various wastes such as:

• Municipal solid waste (MSW)

• Sludge

• Liquid waste (organics/ solvents)

• Agricultural waste (biomass)

• Hospital waste

• Various industrial wastes (sugarcane bagasse, black liquor solids, distillery spentwash, etc.)

• Waste tyres

10.2 Principles of Incineration

Incineration is a series of oxidative chemical reactions in which carbon, hydrogen, and other elements in the waste combine with oxygen in the air in an exothermic reaction and liberate heat. Usually, excess air is supplied to the incinerator in order to ensure efficient mixing and achieve maximum combustion efficiency in terms of complete oxidation. The principal products of combustion include carbon dioxide, carbon monoxide, water, and oxides of nitrogen, oxides of sulphur, airborne particulates and ash. Figure 10-1 shows typical inputs and resulting products of incineration of waste material.

10.3 Incineration Systems

A typical incineration system consists of the following four steps: Drying

This is the first step, where heat is used to evaporate a substantial proportion of the moisture in the substrate to be combusted. Volatilisation

After moisture has been evaporated, the combustible volatiles are released between 175º C and 525º C Ignition

Combustion begins as the volatiles reach ignition temperature in the presence of oxygen. Combustion of Fixed Carbon

Combustion of the volatile matter is completed with the fixed carbon being oxidized to carbon dioxide. A schematic flow diagram of the incineration process is shown in Figure 10-2.


Chapter 10-2

MWH

Two approaches are currently available for waste incineration - Mass Burning Systems and Refuse Derived Fuel (RDF) systems.

10.3.1 Mass Burning Systems

Mass burning can be further classified into

• Field-Erected Mass burning Systems (FEMBS), and • Factory-Fabricated Modular Mass Burning Systems (FFMMBS).

Mass-burning incinerators burn raw waste in the physical form as it is fed. Incombustible materials such as metals are normally removed before or after combustion, by the use of various mechanical equipments. 10.3.1.1 Field-Erected Mass-Burning Systems (FEMBS)

Field-Erected Mass-Burning systems (FEMBS) are available in various capacities ranging from 200 to 3,000 tonnes/day. FEMBS include either waterwall furnaces with integral boilers or refractory-lined furnaces with waste-heat boilers. In waterwall incinerators, the furnace or combustion chamber and boiler are integral components, whereas refractory-lined furnaces consist of a convection-type waste heat boiler located downstream from the furnace. In most of the systems, combustion occurs in single-chamber furnaces, usually equipped with grates that move the MSW through the furnace and help control burning. Some systems use a refractory-lined or waterwall rotary kiln. A schematic of a typical field-erected mass burning system waterwall arrangement is given in Figure 10-3. The steam generated in FEMBS is passed through turbine generator to produce electricity or through an extraction turbine to generate electricity and provide process steam for heating or other purposes. Field-erected mass burning systems are usually equipped with a feed hopper and chute arrangement that continuously feed waste onto the first furnace grate by gravity. Most systems include a horizontal hydraulic ram at the bottom of the chute to push waste onto the grates, allowing more control over waste feeding and firing. The method of moving waste through the furnace and mixing it with air is the key element of the incineration process to achieve good combustion. In field-erected mass burning units, this process is usually accomplished by burning the waste on a grate system that slopes from the front to the rear of the furnace. The grates are also designed to agitate the waste and mix it with air. The action of the grates combined with gravity cause the waste to tumble slowly downward as it burns. Combustion air is supplied from below (underfire air) and above (overfire air) the grates. Underfire air is mixed with the refuse by the action of the grates, initiating combustion and supplying oxygen to the refuse burning on the grates. Overfire air is induced in to the furnace and gets mixed with the combustible gases released during volatilisation, ensuring proper combustion. A number of grate designs, including several patented designs, are used in mass burning facilities. A refractory-lined or waterwall rotary-kiln can be used for combustion instead of a grate system. In a refractory-lined furnace, the temperature of combustion is controlled by the amount of excess air provided. Refractory-lined combustion typically uses excess air in the range of 50% to 150%. Increasing the excess air inflow cools the furnace and reduces the energy recovery efficiency. The energy is recovered as steam, by either a waterwall or waste-heat boiler. The radiant or waterwall section is the combustion chamber lined with water-filled tubes that absorb the radiant energy released during combustion. In the convection section, the hot gases from combustion pass through banks of water tubes, and heat is transferred to the water in the tubes by convection.


Chapter 10-3

MWH

In refractory-lined systems, all heat transfer occur downstream of the furnace in a water-tube waste-heat boiler that is identical to the convection section of waterwall. In both waterwall and refractory-lined systems, additional convection sections can be included to superheat the steam (super-heater) and to preheat boiler feed-water. In both types of systems, the temperature of the gases leaving the boiler section is not permitted to fall below 230°C to 260°C to ensure that condensation of corrosive acids does not occur. The gas leaving the combustion chamber contains various air pollutants such as particulates, SO2, NOx, CO, HCl, metals, and various organics such as dioxins, furans, and polynuclear aromatic hydrocarbons. These emissions must be controlled before discharging into the atmosphere. (Environmental aspects of incineration systems are discussed later in Section 10.4.) Advantages of Mass-Burn Systems

• Mass-burn systems have larger capacities and higher thermal efficiencies

• Mass-burn systems, as compared to modular systems, generate a higher-quality steam, allowing for higher revenues per tonne of waste

• These facilities can accept refuse that has undergone little pre-processing other than the removal of oversized items

• Mass-burning avoids many of the refuse handling problems caused by the extreme heterogeneity and variability of MSW

• The net energy conversion can be equal to or better than that for RDF systems, since minimal energy is used for front-end processing and no burnable material is removed

• Since most of the burning occurs on the grate, less particulate matter is entrained in the gas stream and air pollution control costs are thus reduced

• The units are compact and therefore land requirements are less than for RDF Limitations of Mass-Burn Systems

• Higher costs than modular systems

• Controlling combustion is difficult where MSW is not processed prior to burning

• Requires more field erection time and costs as compared to modular systems 10.3.1.2 Factory-Fabricated Modular Mass Burn Systems (FFMMBS)

Factory-Fabricated Modular Mass Burn Systems (FFMMBS), also known as Modular Combustion Systems, are small mass burn facilities. Modular combustion systems consist of individual modules for waste feeding, primary and secondary combustion chambers, energy recovery, and ash handling. The modules are usually prefabricated and shipped fully assembled to the construction site, where they can be mounted on footings. The installation is housed usually in an inexpensive prefabricated building with sufficient additional space for waste storage and handling, usually in the form of a concrete tipping floor. The system configuration depends on the requirements of the particular installation. However, modular systems capacity ranges between 5 to 120 tonne/day and typically in the 15 to 100 tonne/day capacity range. The capacity of a existing plants can be increased by adding modules. Because of their small capacity, modular combustors are generally used in smaller communities or for commercial and industrial operations. A majority of modular units produce steam as the sole energy product. A typical schematic of a Factory-Fabricated Modular Mass Burn System is given in Figure 10-4.


Chapter 10-4

MWH

In modular systems, refuse vehicles deposit their loads onto a tipping floor. A front-end loader is used to segregate the combustible material from the unsorted waste. The segregated combustible material is then stored in a convenient area. This method is less effective than a pit in controlling odours and pests and in containing fires. Consequently, some of the larger modular systems are equipped with a pit and crane for storage and retrieval of MSW. In many modular systems, waste is charged to the furnace intermittently, using a horizontal hydraulic ram. A front-end loader fills a hopper, with the load size depending on the furnace temperature. The operator manually activates the feed cycle. However, some modular systems continuously feed waste using a chute similar to field-erected systems. Combustion in a modular system is typically achieved in two stages. The primary stage may be operated in “starved air”; i.e. with less than the theoretical amount of air necessary for complete combustion. The controlled air condition creates volatile gases, which are fed into the second chamber, mixed with additional combustion air, and burnt under controlled conditions. Combustion temperatures in the secondary chamber are regulated by controlling the air supply, and when necessary, through the use of an auxiliary fuel. In modular systems, the flow of combustion air in the primary chamber is limited to reduce turbulence, and thus reduce the amount of particulate matter that gets mixed with the gas stream. As a result, modular systems may not require extensive air pollution control system beyond the secondary chamber, which represents a major capital and operating cost savings compared to the FEMBS. The principal disadvantage of the two-stage combustor is that waste burnout is not as complete as with excess air field-erected systems, thereby reducing the efficiency of energy recovery and slightly increasing the quantity of residue to be landfilled. The majority of existing modular systems employ a step-hearth design in the primary chamber and use water-cooled hydraulic transfer rams to move waste through the chamber. The transfer rams are housed in the riser of the previous step, and when activated, push the waste down onto the next step. A few modular installations employ grate systems similar to those used in field-erected installations. Grates agitate the waste more thoroughly and allow more under fire air to reach it, thus promoting better burnout. Other primary combustion chamber designs, including rotary-kiln and rotary-hearth systems, are also used in modular systems. In modular systems, energy is usually recovered as steam in waste-heat boilers, although some manufacturers use a waterwall primary chamber to enhance energy recovery. Waste-heat boilers can be either fire-tube or water-tube systems, depending on the requirements of the energy user. In fire-tube boilers the hot combustion gases flow through tubes encased in a water-filled vessel, and heat is transferred to the water. Such boilers are generally used to produce low-pressure saturated steam in small-scale systems of 20 kg/cm2 and 50 tonne/day capacities. Where large boiler modules and/ or high-pressure steam is required, water-tube waste-heat boilers, similar to those used in field-erected systems, are generally more applicable. Most of the earlier modular systems required no additional emission control devices beyond the secondary chamber or afterburner, where combustion of volatile gases is completed. However emission standards are continually tightening, and this requires further and more expensive pollution control equipment. Advantages of FFMMBS

• Capital costs per tonne of capacity are lower – more cost-effective than other combustor alternatives


Chapter 10-5

MWH

• Modular combustors and waste heat boilers can be factory-assembled or fabricated and delivered, minimizing field erection time and cost

• Available for smaller capacities.

• Flexibility in addressing various potential energy markets with system sizing Limitations of FFMMBS

• Energy production is generally lower than for other incineration technologies.

10.3.2 Refuse Derived Fuel (RDF) Systems

Refuse-Derived Fuel commonly refers to solid waste that has been mechanically processed to produce a storable, transportable, and more homogeneous fuel for combustion. RDF can be co-fired with fossil fuels in existing large industrial or utility boilers, or it can be used as the sole or primary fuel in specially designed “dedicated” boilers. Co-firing of RDF has the obvious advantage of capital cost savings since a new boiler is not required. However, RDF as the primary fuel burning in a dedicated boiler has become more common, since the dedicated boiler can be designed to accommodate some of the characteristics of RDF that can otherwise cause operating problems in existing boilers designed for conventional fuels. When RDF plants were originally developed in the United States, the plan was to produce a fuel that could be co-fired in the existing boilers of electric utility power plants. However, operational and maintenance problems from some components of the RDF led to a change in strategy towards the creation of power plants designed specifically for the combustion of RDF alone. In the United States, these facilities tend to be quite large, with the capacity to process 2,000-3,000 tonnes per day and with electrical generation capacity of 50-75 MW. These plants typically employ water-tube boilers or fluidised-bed combustors to produce steam for power production. The waste is pre-processed to remove incombustible materials, thus increasing the calorific value of the fuel. The incombustible materials are removed using various mechanical methods for example, ferrous metals are removed using magnetic separators, glass, grit, and sand are be removed through screening. Some systems utilize air classifiers, trommel screens, or rotary drums to further refine the waste. This processing requires a substantial amount of electrical energy. The World Bank estimates that 70-90 kWh of electricity is required to process one tonne of MSW into RDF, with another 100-120 kWh required for the drying of the incoming fuel. RDF is characterized by a wide range of material densities, particle sizes, variable moisture contents, a high proportion of flake shape particles and the presence of heavy inert materials such as glass, sand, dirt, metals, etc. A typical RDF incinerator schematic is given in Figure 10-5. Generally three type of RDF combustors are in practice:

• Grate Burning Systems

• Suspension-Fired Boilers

• Fluidised Bed Combustors In RDF systems, the heat energy generated may be recovered in a similar manner to mass-burn and modular systems. Emission control is also similar to other combustion technologies discussed.


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10.3.2.1 Energy recovery from RDF Pellets

Refuse Devised Fuels (RDF) can be considered as one of the WTE options to obtain a valuable fuel by the up gradation of MSW. A RDF based power plant consist of two major stages, which are discussed below: RDF Pellets Over two years of development work has resulted in the establishment of a viable technology for pelletising the combustibles separated from MSW. The process of converting MSW to RDF pellets involves the following steps:

• Solar drying

• Size reduction

• Screening

• Pneumatic separation for the removal of non-combustibles

• Mixing with additives

• Pelletisation

Various grades of fuel pellets have been test marketed at different industries for establishing marketability. The characteristics of fuel pellets are summarised below: A. Physical Size (mm): dia 8/20/30, length 8-40

Calorific value (Kcal/kg - minimum): 4,000 Bulk density (MT per cu.m): 0.7 Density (gm per cc - minimum): 1.3 Ash content (%): < 15 Moisture (%): 10 (approx.)

B. Proximate Analysis (%)

Moisture: 3 - 8 Ash content: 12 - 20 Volatile matter: 50 - 65 Fixed carbon: 12 - 18

C. Ultimate Analysis (%)

Moisture: 3 - 8 Mineral matter: 15 - 25 Carbon: 35 - 40 Hydrogen: 5 - 8 Nitrogen: 1 - 1.5 Sulphur: 0.2 - 0.5 Oxygen: 25 - 30


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D. Gross Calorific value (Kcal/kg)

With binder: 4,000 – 45,000 Without binder: 3,500 – 3,700

RDF is a very useful substitute for coal because it is clean, energy efficient and eco-friendly. The RDF pellets produced from MSW combustibles are of cylindrical shape varying in diameters (up to 30 mm) as required by the end users. Pellets are hard enough to be transported and stored. Their several distinct advantages over coal are:

• Clean fuel, free from stones

• Lower ash content

• Uniform size (no size reduction required at the user end)

• Regular trouble free supply

RDF pellets are economical and have tremendous market potential in non-coal producing zones. The problem of coal in respect of availability, quality, higher prices etc. can be overcome by using the fuel pellets. RDF pellets can be used efficiently in a variety of boiler configurations-fixed or travelling grate, multiple fuel and fluidised bed incinerators. A study done at a testing and analytical laboratory in Mumbai, confirms the fact that thermal energy costs are reduced by 35% and boiler efficiency increased by 3.3% for plants employing RDF pellets instead of coal as shown below:

Factors RDF Coal Boiler Efficiency (%) 52.6 49.3 Evaporation Ratio (kg/kg) 3.68 3.30 Steam Cost (Rs./tonne) 326.00 500.00

Test analyses have further shown that there is a marginal drop in CO2 emission with the burning of RDF pellets as compared to coal, as indicated below:

Fuel Average kg. CO2 / kg. steam CO2 (%) Produced

Coal 8.30 0.40 RDF pellets 7.40 0.38

The Department of Science and Technology, Government of India had sponsored a Demonstration Pilot Plant Facility for producing 50 TPD RDF pellets using 150 – 160 TPD of MSW at Mumbai. A simple schematic of the plant for obtaining RDF pellets from unsorted MSW is shown in Figure 10.6. A pelletisation plant to convert 700 TPD MSW to 210 TPD of pellets was planned for Hyderabad in 2001 by a private entrepreneur in association with Hyderabad Municipal Corporation1, based on technology developed by the Department of Science and Technology. The pellets would be used as industrial fuel initially and for 6 MW power generation ultimately. 1 Source: Financial Resources and Private Sector Participation in Solid Waste Management in India, (FIRE Project Report May 2001).


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Power Generation Combustion systems for RDF with higher energy content can be smaller and more efficient than mass-fired incineration systems. Comparative data for the generation of 20 MW power using steam turbo generators showed MSW requirements of 800 and 600 TPD with mass-fired and RDF-fired arrangements respectively. Hot flue gases from the combustion of MSW can be converted to high-pressure steam and used for power generation using a steam turbine. A simplified schematic of an energy recovery system using a steam turbine with RDF combustion is shown in Figure 10.7. A typical RDF based power generation facility from MSW consists of the following steps:

• Drying

• Magnetic Separation

• Pneumatic Separation – Removal of non-combustibles

• Pelletisation of Combustibles

• RDF Pellets

• RDF Combustion/ Boiler/ HP steam

• Steam Turbine

• Power

The most common method for the production of electricity is the steam turbine system. Steam is produced in a boiler by combusting RDF. The steam is used to drive a steam turbine and then condensed back into boiler feed water. The steam turbine drives an electricity generator, which supplies onsite power and excess power for export. The system is essentially a scaled – down version of a coal-or gas-fired electricity utility plant. RDF pellets derived from MSW have the potential to generate up to 3 MW electricity per 100 Tonnes of RDF. RDF Power Projects Limited is in the process of establishing a power plant, based on municipal solid waste at Hyderabad, at a cost of Rs. 40 crores to process 700 metric tonnes of MSW per day and produce 9 MW of power. RDF Power Projects Limited has a technical and financial tie-up with M/s Power Therm Limited and M/s Lohning International Pvt. Ltd., Australia. (Source: Bio Energy News, December 1997) 10.3.2.2 Issues

In the United States, RDF commonly has a caloric value of 14 – 17 MJ/kg. As a comparison, sub-bituminous coal typically contains 19 – 26 MJ/kg. However, the production of RDF with a high calorific value is more problematic in locations where there is already fairly effective source separation of combustible, such as in India. In such circumstances, much of the volatile portions of the MSW with high-energy value are collected and recycled separately and never enter the MSW stream. One option can be to mix a lower energy value RDF with other waste streams, such as agricultural residues, and then combust the resulting mixture to produce process heat and possibly electricity. A large-scale experimental RDF based gasification plant has been successfully operated in Chianti,


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Italy, using sorghum bagasse and/ or RDF to provide low-calorific value gas to a large cement kiln. It is planned to reach the ultimate capacity of 40 MW thermal and 6.7 MW of electric power. 10.3.2.3 Advantages and Limitations of RDF Systems

Advantages

• One of the benefits of RDF is that it can be shredded into uniformly sized particles or densified into "briquets". Both of these possibilities facilitate handling, transportation and combustion. RDF can often be combusted or "co-fired" with another fuel such as wood or coal in an existing facility. RDF is thus valuable as a low cost additive that can reduce costs of generating heat or electricity in a variety of applications.

• Another benefit of burning RDF rather than raw MSW is that fewer non-combustibles such as heavy metals are incinerated. Although metals are inert and give off no energy when they are incinerated, the high temperature of a furnace causes metals to be partially volatised, resulting in the release of toxic fumes and fly ash. The composition of RDF is more uniform and well understood than that of MSW; therefore fewer combustion controls are required for RDF combustion facilities than for facilities combusting unsorted MSW.

• RDF boilers can be smaller than those for mass burning, since a considerable amount of incombustible material is removed from raw MSW.

• RDF can be burned in existing fossil fuel boilers, which can greatly reduce capital costs.

• RDF can be produced at a remote site and transported to the conversion facility - an important advantage if land is scare or expensive, if truck traffic is undesirable near the intended energy user, or if the energy user is far from the source of MSW.

• The recovery and sale of reusable materials from MSW can reduce landfill requirements. Limitations

• High combustible dust concentrations increase the risk of dust explosions within the enclosed RDF processing equipment.

• Storage/ retrieval problems may exist for the RDF fuels since they have to be prepared in the required physical form and in sufficient quantity to ensure a continuous fuel supply for the combustion equipment.

• Material handling problems can accompany the preparation, storage, transportation and usage steps of RDF.

• Higher capital costs are associated with the considerable pre-processing required.

10.3.3 Fluidised Bed Combustion

Fluidised bed combustion (FBC) is an alternative design to conventional combustion systems. In its simplest form, an FBC system consists of a vertical steel cylinder, usually refractory-lined, with a sand bed, a supporting grid plate and injection nozzles known as ‘tuyeres’ (Figure 10-8). When air is forced up through the tuyeres, the bed fluidises and expands up to twice its static volume. Solid fuels can be injected into the reactor below or above the level of the fluidised bed. The “boiling” action of the fluidised bed promotes turbulence and mixing, and transfers heat to the fuel. In operation, auxiliary fuel (natural gas or fuel oil) is used to bring the bed up to operating temperature (8000C to 9500C). After start-up, the auxiliary fuel is usually not needed, and the bed will remain hot up to 24 hours, allowing rapid restart without any auxiliary fuel.


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Fluid bed combustion systems are quite versatile and can be operated on a wide variety of fuels, including MSW, sludge, coal, and numerous chemical wastes. The bed material can be plain sand or limestone (CaCO3). When limestone is used, it reacts with oxygen and the sulphur dioxide (SO2) (formed by the combustion of organic-containing wastes) to release carbon dioxide, and calcium sulphate (CaSO4), a solid that can be removed with the ash. The use of limestone as the bed material allows the combustion of sulphur containing wastes with minimum emissions of sulphur dioxide. Several FBC systems are being used for solid waste combustion throughout the world. One of the first installations was a small (150 TPD ) fluidised bed unit in Lausanne, Switzerland. This unit was utilised for the disposal of MSW and sludge, produced in sewage treatment plant. A boiler is used to generate steam, which was further utilised for heating and electricity generation. A larger scale plant (700 TPD), was built in Duluth, Minnesota, to dispose 300 TPD of dewatered sludge and 400 TPD of MSW processed in a front-end system prior to combustion (Figure 10-9).

10.4 Environmental and Regulatory Aspects

10.4.1 Major Environmental Issues

There is growing worldwide public concern about the environmental aspects of the incineration process. Public health and environmental concerns (mainly failure to meet emission standards) have led to the closure of various incineration facilities worldwide, banning new incineration projects in some parts of the world, significant and costly retrofitting exercises at many others. The major environmental issues associated with incineration are as follows:

• Emissions of contaminants to air

• Hazardous constituents present in the ash pose challenges in terms of their safe and proper disposal

• Possible land use conflicts with adjacent land owners

• Use of large amounts of water for cooling purposes, and release of blow-downs

• Likely public opposition because of uncertainties over health, safety, odour, visual and traffic impacts, and emissions

• Possible conflict with waste reduction and recycling programmes Environmental issues are recognised as critical to the viability of an incineration facility. While air emissions often dominate the public and political assessments of a given process, problems with all effluents, and the related environmental consequences, must be resolved as part of the permitting process. The major air pollutant released by incineration facilities is particulate matter, and the same is effectively controlled by the use of devices such as electrostatic precipitators or fabric filters within bag-houses. Other pollutants include sulphur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), hydrogen chloride (HCl), metals, and lesser quantities of dioxins, furans, and polynuclear aromatic hydrocarbons, depending upon feedstock composition and combustion conditions. The concentrations of these contaminants in the exhaust air from an incineration facility depend on various factors, including waste composition, temperatures and residence time.

10.4.2 Prevailing International Standards

A compilation of International Standards for atmospheric emissions from municipal solid waste incinerators is given in Table 10-1, which includes the recent Indian Municipal Solid Wastes (Management & Handling) Rules 2000.


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Amongst the regulatory standards prevailing in various countries, the 1986 German TA Luft standard and the revised 1990 standard (17BIM Sch V90) are the most stringent norms for stack emissions from MSW incineration facilities. The latter specifies suspended particulate emission limit of 10 mg/Nm3 compared to the EC directive (76/2000 EEC) of 30 mg/ Nm3 and US EPA (1999) regulatory limit of 70 mg/ Nm3 versus 150 mg/ Nm3 stipulated by CPCB, India. Developed countries like UK, US, Sweden, etc. have specified a limit of 0.1 ng/ Nm3 for dioxin. Recent research seems to indicate that dioxin and furan production will not be a significant risk with an operating temperature of 8500C and 6% excess air in the freeboard at the top of the incinerator. The new EC Directive 2000/76/EC on the incineration of waste published on 28 December 2000 in the official journal of the European Communities covers the incineration of hazardous (formerly Directive 94/67/EC) and non-hazardous (89/369/EEC AND 89/429/EEC) wastes. Article 7 specifies that incineration plants shall be designed, equipped, built and operated in such a way that the emission limit values set out in Table 10.2 are not exceeded in the exhaust gas. (Annex V of the Directive has been reproduced as Table 10-2). USEPA 40 CFR (Code of Federal Regulations) PART 60, amended on August 25 1997, gives emission guidelines for Municipal Waste Combustors. The same are summarised in Table 10-3.

10.4.3 MSW Rules India

The Municipal Solid Wastes (Management and Handling) Rules 2000, Ministry of Environment and Forests Notification dated 25th September 2000 Schedule IV specifies the operation and emission standards for Composting, Treating Leachates and Incineration. The rule also states that the waste processing or disposal facilities shall include composting, incineration, pelletisation, energy recovery or any other facility based on state-of-the-art technology, duly approved by the Central Pollution Control Board. The incinerators shall meet the following operating and emission standards: A. Operating Standards

1. The combustion efficiency (CE) shall be at least 99.00%.

2. The combustion efficiency shall be computed as follows:

% CO2 C.E. = --------------------- X 100 %CO2 + %CO

B. Emission Standards

Parameters Concentration mg/ Nm3 at (12% CO2 correction)

1. Particulate matter 150

2. Nitrogen Oxides 450

3. HCl 50

4. Minimum stack height shall be 30 meters above ground.

5. Volatile organic compounds in ash shall not be more than 0.01%.

Note:

(i) Suitably designed pollution control devices shall be installed or retrofitted with the incinerator to achieve the above emission limits, if necessary.


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(ii) Wastes to be incinerated shall not be chemically treated with any chlorinated disinfectants.

(iii) Chlorinated plastics shall not be incinerated.

(iv) Toxic metals in incineration ash shall be limited within the regulatory quantities, as specified in the Hazardous Wastes (Management and Handling) Rules, 1989 as amended from time to time.

(v) Only low sulphur fuels like LDO, LSHS Diesel shall be used as fuel in the incinerator. 10.4.3.1 Cost Implications Due to Environmental Standards

The control of air emissions involves a considerable cost, and as individual country standards for the control of contaminants emitted to air becoming stringent, there is a immediate need for sophisticated emission control equipment, and inevitably, the costs will also increase. The costs of air emissions control are in fact dictating the European countries to move away from retrofitting of existing plants with control equipment. Even new incineration facilities with state-of-the-art pollution abatement hardware are receiving limited uptake in Europe.

10.5 Overview of Incineration Technology

Various companies and agencies worldwide have built waste-to-energy facilities based on the incineration process. Several companies and developers have extensive experience in constructing mass burning and RDF facilities, as well as in fabricating modular incineration systems. Some of these patented incineration technologies are discussed in Appendix 10-A. Appendix 10-B presents a partial list of municipal waste combustion and tyres-to-energy facilities in the U.S.

10.5.1 International Scenario

Even with all its negative connotations, incineration is still a traditional technology for treating waste and for recovering energy. Hundreds of incineration plants have been built in many countries, but many of these plants have since been shut down due to various environmental, economic, political and social reasons. However, incineration is likely to continue as a waste disposal and energy generation option, particularly where there is a lack of landfill sites. Appendix 10-C gives a general over view and status of incineration technology in representative regions of the world; namely, Africa, Asia - East /Pacific, Asia -South and West, Latin America and the Caribbean. However, it will be prudent to be aware of the current status of incineration technology in Europe and North America because these regions are at the forefront of technological development and have more stringent environmental standards. A specific discussion on these specific regions is therefore included below. Europe European countries vary widely in their reliance on incineration. Northern European countries are highly reliant on mass-burn incineration, coupled with energy generation. In Western European countries, around 35%, and in some cases as much as 80%, of the residential waste is disposed of through incineration. Until recently, these countries relied on mass-burn technology, but there is increasing interest in and growing positive experience with fluidised-bed technologies. Among other factors, the relative paucity of open land has resulted in a social consensus that incineration is necessary, as compared to North America, for example. At the same time this consensus has in general also extended to a strong commitment to pollution control, a commitment which is strengthened by the proximity of European nations to each other and by their awareness that they are all at risk from pollution.


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Another factor underlying the acceptance of incineration in Europe is that the energy generated by European waste-to-energy plants goes to supply steam for district heating loops. The heavy reliance on district heating, and the ready market for steam that this reliance provides, is part of what makes incineration so attractive in European cities. Producing steam is more energy-efficient and more profitable than generating electricity, and contributes to the robustness of the European waste-to-energy sector. The coupling of incineration with electricity generation, which contributes substantially to the capital costs of incineration, is quite rare in Europe, in part because most of the European countries do not, have utility rate structures that allow non-utility-generated electricity to be sold to the grid. Waste incineration is nevertheless often the subject of controversy in Europe, usually because of its air pollution potential. The emission of acid gases, including SOx and NOx, together with heavy metals, dioxins and mercury are the principal matters of concern. Pollution control equipment on more modern incinerators includes, in most cases, flue gas cleaners in the form of acid gas scrubbers, together with either electrostatic precipitators or bag house filters. Acid gases such as SOx and NOx are removed in the flue gas cleaning systems, which usually consist of either wet or dry scrubbers. In Sweden, a combination of the two is more often used. Heavy metals are more likely to be removed in post-scrubbing filters, or via the injection of sodium sulphate in an electrostatic precipitator. This type of pollution control equipment can also remove dioxins and furans. The cost of these pollution control devices is high. The European Union is moving to enforce severe emissions standards for all types of incinerators, along with rules for protecting the health and safety of workers. While accepting their long-term dependence on waste incineration as a disposal and energy recovery strategy, many European governments are phasing out the non-energy-generating incinerators. In some cases, these older incinerators are being upgraded and retrofitted with pollution control equipment. European countries tend to be well advanced in the utilization of by-products of incineration. Fly ash is often used in bonded asphalt and other road products. The use of bottom ash and slag as aggregates in road construction or in the production of brick materials is more common in some countries like The Netherlands than in others, but has had some setbacks, as awareness has grown of the presence and the leachability of the toxic constituents of these materials. In countries where these materials cannot be used, they are generally sent to the landfill. These byproducts are considered as a hazardous waste in North America. The production of RDF is another type of energy recovery system practised in Europe. The mixed waste sorting system started during early 1970s produced a number of recycling and RDF-producing installations, mostly of German or Italian design. Many of these facilities were initially designed to feed the wet and biodegradable wastes into composting systems. North America Most of the MSW combustion currently practised in North America incorporate energy recovery in the form of steam, which is used either to drive a turbine to generate electricity or directly for heating. In the process, the volume of solid waste is reduced by up to 90% and its weight by up to 75%. In past years it was common to simply burn MSW in incinerators to reduce its volume and weight, but energy recovery has become more prevalent since the 1980s. While about 30% of the MSW stream was incinerated without energy recovery in 1960, this has decreased to about 1% in 2000. Currently, waste-to-energy incineration systems are used to manage about 10%-15% of the MSW stream in North America. A partial list of existing waste and tyres-to-energy facilities in the United States is given in Appendix 10-B.


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It should be noted, however, that the recent development of regional landfills providing relatively inexpensive disposal options has made it more difficult for capital-intensive WTE plants to compete. The amount of solid waste processed in WTE facilities varies significantly by region. The north-eastern US currently incinerates and recovers energy from over 40% of its solid waste, while many states incinerate less than 2% of the solid waste they generate. There are currently about 160 WTE facilities in the US. In Canada, the number is lower. In fact, the province of Ontario was operating only three incinerator facilities in 1991 and has since placed a ban on any new facilities being constructed. The three most widely used and technically proven WTE technologies in North America are (a) mass-burn combustion, (b) modular combustion, and (c) RDF production and combustion. Over the last several years, local governments have largely favoured mass-burn systems that recover electricity, over other WTE technologies, such as modular units and steam-only processes. Several other emerging WTE technologies have been pilot-tested, but are not yet commercially proven. Mass-burn systems are the predominant form of WTE in North America. Operating mass-burn facilities process about 60% by weight of the solid waste from which energy is recovered. Mass-burn systems generally consist of either two or three combustion units ranging in capacity from 50 to 1,000 tonnes per day; thus, facility capacities range from about 100 to 3,000 tonnes per day. About 90% of operating mass-burn facilities generates electricity. These facilities can accept refuse that has undergone little pre-processing other than the removal of oversized items. Although this versatility makes mass-burn facilities convenient and flexible, local programmes to separate household hazardous wastes (e.g., cleaners and pesticides) and recover certain recyclables are necessary to help ensure environmentally responsible incineration and resource conservation. Modular combustors are usually prefabricated units with relatively small capacities of between 5 and 120 tonnes of solid waste per day. Typical facilities have between one to four modular units for a total plant capacity of about 15 to 400 tonnes per day. Because of their small size, only about 7% of solid waste that undergoes energy recovery in North America is processed through modular WTE facilities. The majority of modular units produce steam as the sole energy product. Because of their small capacity, modular combustors are generally used in smaller communities or for commercial and industrial operations. Their prefabricated design gives modular facilities the advantage of shorter construction time frames. On an average, capital costs per tonne of waste processed are lesser for modular units than for mass- burn and RDF plants. As of 1998, 22 facilities in the US processed RDF for off-site combustion; 17 facilities combusted RDF in dedicated boilers on-site; and 9 facilities combusted RDF with other fuel (i.e., co-fire RDF). The vast majority of RDF combustion facilities generate electricity. On an average, capital costs per tonne of waste processed are higher for RDF combustion units than for mass-burn and modular WTE units. In a fluidised-bed combustor, instead of a grate supporting a layer of solid fuel, the furnace contains a bed of sand or limestone supported by an air distribution system. Several facilities in the US use fluidised beds to co-fire RDF with other fuels (e.g., sewage sludge) and at least two facilities dedicated to fluidised-bed solid waste combustion are under development. They are large-scale plants that incorporate front-end processing with materials recovery. In North America, the major public concerns about the environmental risks of incineration facilities are the potential emission of contaminants into the air through exhaust stacks (i.e. particulates, nitrogen oxides, sulphur dioxide, carbon monoxide, metals, acid gases, and dioxins) and into water through ash leachate. US federal and most state and provincial air pollution control laws and regulations, however, have been strengthened in recent years to specifically address potential impacts


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from WTE air emissions. To meet these standards, modern pollution control equipment has been developed which effectively removes most of the emissions that are of concern. The major air emission control technologies employed in North American WTE facilities are fabric filters or bag houses, electrostatic precipitators, and scrubbers. However, these emission control technologies are expensive. Integration of WTE with the other elements of the solid waste management system, such as recycling and landfilling, is another important issue in North America.

10.5.2 Indian Scenario

Appendix 10-D gives an overview of the current status of incineration technology and systems in India. A list of some of the significant developments relevant to WTE in U&I sector is given below.

• The Delhi Incineration Experience

• MSW to RDF, UCAL RDF Limited, Chennai

• Hazardous Waste Incinerator, Sandoz (India) Limited

• MSW to RDF plant, SELCO International, Hyderabad

• Fluidised Bed Combustion of Municipal Solid Waste, RDF Power Projects Limited, Hyderabad

• DIEG Process, Vasantdada Sugar Institute, Pune

• Fluidised Bed Soda Recovery System at Shreyans Paper, Ahmedgarh, Punjab

• Energy Recovery from Bagasse by Co-generation


Incineration of MSW has been widely adopted in industrialised countries having limited space for landfill and high land costs. However, it has found only limited application in the developing world to date, because of the composition of urban wastes. For example, most WTE combustion systems are optimised for U.S. and European wastes, with their high fractions of paper, cardboard and plastic and their consequently relatively high-energy value. In contrast, much of these waste constituents are picked out of Indian MSW streams. Indian MSW contains a high fraction of inert matter - rocks, dust, ashes, and dirt. This material further reduces overall energy content of the waste; causes excessive wear on moving parts of WTE combustion systems, and still have to be disposed of with the incineration ashes. The inert matter can be screened out prior to combustion, but this is an additional processing step, requiring considerable labour and equipment. The typical low calorific value MSW streams in India are generally outside the design parameters of most commercially available MSW combustion technologies, which means that the waste stream would probably have to be "upgraded" by the removal of inert fractions, and incombustible material. Also, the high-moisture content of Indian urban MSW requires considerable drying prior to the combustion process, also the low-energy content of the MSW do not provide sufficient heat for substantial electric power generation. Environmental issues associated with incineration system mean that expensive exhaust gas cleaning systems are required. Ash disposal may also be a significant environmental issue. Major international bilateral and multilateral donors now require the inclusion of such pollution abatement systems, if a proposal is to qualify for either power sector or urban waste treatment loans.


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All of these factors have negative effect on the uptake of incineration technologies for waste-to-energy applications in India. However, it may be added that a particular MSW stream can overcome at least some of these constraints, and thus an approach of individual case assessment is warranted in the consideration of incineration as a waste-to-energy technological option in India.


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Table 10-1. International Standards for Atmospheric Emissions from MSW Incinerators Country Switzerland Germany France Sweden Norway Denmark Netherl

ands India *

USA (EPA) **

EC Directive 76/2000 EEC ***

Date of Issue

1986 TA Luft 1986

BIMSch GermanyV90 (1990), Daily mean

VH90 (1990), Half-hour max

1986 1986 2000 1999 2000

Gas Correction

11% O2 dry 11% O2 dry

11% O2 dry

11% O2 dry

7% CO2 wet

10% O2 dry

10% CO STP dry

10% CO2 STP dry

11% O2 STP dry

12% CO2 dry

7% O2 dry

11% O2 dry

Particulate (mg/Nm3)

50 30 10 60 50 20 30 40 5 150 70 30

HCl 30 50 10 60 100 100 100 100 10 50 62 10

HF 5 2 1 4 1 1

SO2 500 100 50 200 300 300 40 20 50

NOx (Calc as NO)

500 500 100 400 70 450 388 200

CO 100 50 80 1250 100 50 157 50

Total C 20 10 40 10 20

Dioxin (ng/Nm3)

0.1 NATCO equivalent

0.1toxic equivalent

0.1 toxic equivalent



Heavy metals (mg/Nm3)

Total Class I 0.2 0.2 2 0.3 0.05

Cd 0.2 0.1 0.1 0.1 0.1 0.004 (Cd + TI)

Hg 0.2 0.1 0.1 0.08 0.1 0.1 0.47 0.05

Total Class II

1 1 1 1 1

As

Ni

Total Class III 5 5 5 5 0.5

Pb Pb + Zn = 5 1.4 5 (Pb + Zn)

0.04 (Pb+Cr+Mn+Cu+Sb+As+Co+Ni + V)

Cr Source: Sewage and Industrial Effluent Treatment, J. Arundel (Blackwell Science, 1995) * MSW (Management and Handling) Rules, 2000 ** www.epa.gw/ttn/oarpg/t1/fr_notices/ciswi_fr.pdf *** http://europa.cu.int


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Table 10-2. EC Directive 2000 on Incineration of Waste: Air Emission Limit Values

(a) Daily Average Values

Total dust 10 mg/m3

Gaseous and vaporous organic substances expressed as total organic carbon

10 mg/m3

Hydrogen chloride (HCl) 10 mg/m3

Hydrogen fluoride (HF) 1 mg/m3

Sulphur dioxide (SO2) 50 mg/m3

Nitrogen monoxide (NO) and nitrogen dioxide (NO2) expressed as nitrogen dioxide for existing incineration plants with a nominal capacity exceeding 6 tonnes per hour for new incineration plants

200 mg/m3 (*)

Nitrogen monoxide (NO) and nitrogen dioxide (NO2) expressed as nitrogen dioxide for existing incineration plants with a nominal capacity of 6 tonnes per hour or less

400 mg/m3 (*)

(*) Until 1 January 2007 and without prejudice to relevant (Community) legislation the emission limit value for NOx does not apply to plants only incinerating hazardous waste. Exemptions for NOx may be authorised by the competent authority for existing incineration plants: • with a nominal capacity of 6 tonnes per hour, provided that the permit foresees the daily average values do not exceed

500 mg/m 3 and this until 1 January 2008, • with a nominal capacity of >6 tonnes per hour but equal or less than 16 tonnes per hour, provided the permit foresees

the daily average values do not exceed 400 mg/m 3 and this until 1 January 2010, • with a nominal capacity of >16 tonnes per hour but <25 tonnes per hour and which do not produce water discharges,

provided that the permit foresees the daily average values do not exceed 400 mg/m3 and this until 1 January 2008. Until 1 January 2008, exemptions for dust may be authorised by the competent authority for existing incinerating plants, provided that the permit foresees the daily average values do not exceed 20 mg/m3.

(b) Half- hourly Average Values Total dust 30 mg/m3 10 mg/m3

Gaseous and vaporous organic substances expressed as total organic carbon

20 mg/m3 10 mg/m3

Hydrogen chloride (HCl) 60 mg/m3 10 mg/m3

Hydrogen fluoride (HF) 4 mg/m3 2 mg/m3

Sulphur dioxide (SO2) 200 mg/m3 50 mg/m3 Nitrogen monoxide (NO) and nitrogen dioxide (NO2) expressed as nitrogen dioxide for existing incineration plants with a nominal capacity exceeding 6 tonnes per hour for new incineration plants

400 mg/m3 (*) 200 mg/m3 (*)

(*) Until 1 January 2007 and without prejudice to relevant Community legislation the emission limit value for NOx does not apply to plants only incinerating hazardous waste.


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Table 10-3. Summary of EPA Emission Guidelines for Municipal Waste Combustors2

Applicability According to section 60.32b of US EPA 40 CFR (Code of Federal Regulations) PART 60, the designated facility to which these guidelines apply is each municipal waste combustor unit with a combustion capacity greater than 250 tonnes per day of municipal solid waste for which construction was commenced on or before September 20, 1994. Any municipal waste combustion unit that is capable of combusting more than 250 tonnes per day of municipal solid waste and is subject to a federally enforceable permit limiting the maximum amount of municipal solid waste that may be combusted in the unit to less than or equal to 11 tonnes per day is not subject to this subpart if the owner or operator satisfies the conditions mentioned in section 60.32 Emission guidelines for Municipal Waste Combustor operating practices. Table A provides emission limits for the carbon monoxide concentration level for each type of designated facility. Table A.--Municipal Waste Combustor Operating Guidelines -------------------------------------------------------------------------------------------------- Carbon monoxide emissions Municipal waste combustor technology level (parts per Averaging million by volume)a time b -------------------------------------------------------------------------------------------------- Mass burn waterwall 100 4 Mass burn refractory 100 4 Mass burn rotary refractory 100 24 Mass burn rotary waterwall 250 24 Modular starved air 50 4 Modular excess air 50 4 Refuse-derived fuel stoker 200 24 Buddling fluidised bed combustor 100 4 Circulating fluidised bed combustor 100 4 Pulverized coal/refuse-derived fuel mixed fuel- fired combustor 150 4 Spreader stoker coal/refuse-derived mixed fuel-fired combustor 200 24 ------------------------------------------------------------------------------------------------ a Measured at the combustor outlet in conjunction with a measurement of oxygen concentration, corrected to 7 percent oxygen, dry basis. Calculated as an arithmetic average. b Averaging times are 4-hour or 24-hour block averages. MWC organic emissions (measured as total dioxins/furans) Emission limits for dioxins/furans contained in the gases discharged to the atmosphere from a designated facility at least as protective as the emission limit for dioxins/furans specified below:

2 US EPA 40 CFR (Code of Federal Regulations) PART 60 Amended on August 25 1997


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1. The emission limit for designated facilities that employ an electrostatic precipitator-based emission control system is 60 nanograms per dry standard cubic meter (total mass), corrected to 7% oxygen

2. The emission limit for designated facilities that do not employ an electrostatic precipitator based emission control system is 30 nanograms per dry standard cubic meter (total mass), corrected to 7% oxygen

MWC metal emissions The emission limits for municipal waste combustor metals are specified as follows: 1. The emission limit for particulate matter contained in the gases discharged to the atmosphere from

a designated facility is 27 milligrams per dry standard cubic meter, corrected to 7 percent oxygen. 2. The emission limit for opacity exhibited by the gases discharged to the atmosphere from a

designated facility is 10 percent (6-minute average). 3. The emission limit for cadmium contained in the gases discharged to the atmosphere from a

designated facility is 0.040 milligrams per dry standard cubic meter, corrected to 7 percent oxygen.

4. The emission limit for lead contained in the gases discharged to the atmosphere from a designated facility is 0.49 milligrams per dry standard cubic meter, corrected to 7 percent oxygen.

5. The emission limit for mercury contained in the gases discharged to the atmosphere from a designated facility is 0.080 milligrams per dry standard cubic meter or 15 percent of the potential mercury emission concentration (85-percent reduction by weight), corrected to 7 percent oxygen, whichever is less stringent.

MWC acid gas emissions (measured as SO2 and HCl) 1. The emission limit for sulphur dioxide contained in the gases discharged to the atmosphere from a

designated facility is 31 parts per million by volume or 25 percent of the potential sulphur dioxide emission concentration (75-percent reduction by weight or volume), corrected to 7 percent oxygen (dry basis), whichever is less stringent. Compliance with this emission limit is based on a 24-hour daily geometric mean.

2. The emission limit for hydrogen chloride contained in the gases discharged to the atmosphere

from a designated facility is 31 parts per million by volume or 5 percent of the potential hydrogen chloride emission concentration (95-percent reduction by weight or volume), corrected to 7 percent oxygen (dry basis), whichever is less stringent.

Nitrogen oxides emissions Table B provides emission limits for the nitrogen oxides concentration level for each type of designated facility. Table B--Nitrogen Oxides Guidelines for Designated Facilities ------------------------------------------------------------------------------------------------------------ Nitrogen oxides emission Municipal waste combustor technology limit (parts per million by volume)a ------------------------------------------------------------------------------------------------------------ Mass burn waterwall 205 Mass burn rotary waterwall 250 Refuse-derived fuel combustor 250 Fluidised bed combustor 240 Mass burn refractory combustors no limit ------------------------------------------------------------------------------------------------------------- a Corrected to 7 percent oxygen, dry basis.


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Figure 10-1. The Incineration Process

WASTE


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Figure 10-2. Incineration Process Flow Diagram


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Figure 10-3. Schematic of a Field Erected Mass Burning System with Waterwall Arrangement


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Figure 10-4. Typical Factory Fabricated (Modular) Incineration System


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Figure 10-5. Typical RDF Combustion Facility


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Figure 10-6. Schematic of RDF Pelletisation Plant

Unsorted MSW

Solar Drying (Dump-Yard)

Size Reduction

Screening Rejects,

(Inerts, Stones, etc.)

Fines

Cyclones Heavies

Homogenisation

Binders

Pelletisation

RDF Pellets


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Figure 10-7. Energy Recovery System for RDF Plant

~

MSW/RDF

AIR

HP Steam

Power

Condenser

Boiler Feed Pump

INCINERATOR/BOILER


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Figure 10-8. Typical Fluidised Bed Combustion System for Refuse Derived Fuel (RDF)

Source: Integrated solid waste management Tchobanoglous G, Theisen H and Vigil S.A.


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Figure 10-9. Schematic of Fluidised Bed System

National Master Plan for Development of Waste-to-Energy in India Technical Memorandum Waste-to-Energy Technologies

MWH Chapter 11-1

11 Advanced Thermal Conversion (ATC) Processes – Gasification and Pyrolysis

11.1 Introduction

Advanced Thermal Conversion (ATC) technologies, exemplified in particular by similar processes of gasification and pyrolysis, have undergone extensive development, refinement and commercialisation in recent years. While considered novel and “fringe” in nature until recently, there is now widespread and growing acceptance of these processes as legitimate and important choices as waste-to-energy technologies.

11.2 Principles of ATC

Pyrolysis (also known as thermolysis) and gasification have been used as process concepts for many years. Major development activity for gasification processes, mainly applied to coal, occurred in the 1970s and 1980s in response to the two oil shocks, in order to produce strategic fuel and energy alternatives to crude oil. The impetus to apply gasification technology to MSW grew out of concern for the mounting MSW problem, including diminishing landfill volumes, lack of suitable landfill sites, groundwater contamination by landfill leachates, and the technical problems associated with the early combustion technologies applied to the incineration of MSW. Conventional incineration uses air for combustion and oxidation reactions whereas pyrolysis and gasification operate either in absence of air (pyrolysis) or in a partial oxidation mode (gasification). The consequence of this is that flue gas streams from incinerators are at a high volume, requiring major investment for gas cleaning equipment, whereas pyrolysis and gasification produce more concentrated syngas streams which can be cleaned in significantly lower volume (and lower cost) equipment. Figure 11-1 shows four types of gasification and pyrolysis processes and their products. Pyrolysis and/or gasification can give rise to the following general outcomes:

• Produce syngas that is combusted. Steam is produced from the hot flue gases in a heat exchanger and then used in a turbine to generate electricity.

• Produce syngas that is cooled and cleaned prior to the direct generation of electricity via gas engines.

• Produce a transportable fuel, either as a solid char that is subsequently combusted to generate energy via a conventional steam cycle at some other location (or occasionally at the same site), or clean methanol/hydrogen for use as fuel, or bio-oil that can be used as a low-grade fuel.

Within the gasification process the majority of the carbon is converted into simple gaseous products, leaving the inert as residue. This process takes place via partial combustion of a portion of the fuel in the reactor with air (or oxygen), or with steam. Relatively high temperatures are employed, 900 – 1100 °C with air and 1000 – 1400 °C with oxygen. Air gasification is the most widely used technology, giving rise to a low heating value gas, containing up to 60% nitrogen, and with a heating value of 6 – 8 MJ/Nm3. Oxygen gasification gives a better quality gas, with a heating value of 11 – 18 MJ/Nm3. But, of course, oxygen supply is required with associated issues of cost and safety. Conventional pyrolysis is the thermal degradation of carbonaceous materials at temperatures between 400 and 800 °C, either in the complete absence of air or oxygen, or with such a limited supply that gasification does not occur to any appreciable extent. Such processes devolatilize and decompose solid organic materials by heat (Greek – thermos) and a number of developers refer to this pyrolysis


MWH Chapter 11-2

processes as thermolysis. The products of pyrolysis always include gas, liquid and solid char, with the relative proportions of each depending on the precise method of pyrolysis and the specific reaction parameters. Slow pyrolysis (carbonisation) requires a slow reaction at low temperatures to maximise the yield of solid char. Fast or flash pyrolysis is used to maximise the yield of either gas or liquid products. The gas produced through pyrolysis is of medium heating value (13 – 21 MJ/Nm3) and the liquids are complex mixtures of hydrocarbons that require refining and upgrading before they can be used as conventional fuel oils. Gasification and pyrolysis processes can use a wide variety of waste feedstocks. Sorted wastes or wastes which are homogeneous in nature are generally preferred. Some of the more common feed stocks include:

• Refuse-derived fuel (RDF) or sorted MSW

• Plastics, rubber, tyres

• Industrial wastes

• Wood waste, biomass

• Agricultural wastes

• Animal wastes

• Sewage sludge

Table 11-1summarises the products, energy content and uses of Thermal Conversion Processes.

11.3 System Description

In general these technologies offer both reduction in environmental emissions and high yield of energy.

11.3.1 Gasification System

The Gasification Technology Council of the USA has proposed the following three-part definition of “gasification”:

• A process technology that is designed and operated for the purpose of producing synthesis gas (a commodity which can be used to produce fuels, chemicals, intermediate products, or directly to produce power) through the chemical conversion of carbonaceous materials.

• A process that converts carbonaceous materials through a process involving partial oxidation of the feedstock in a reducing atmosphere in the presence of steam at temperatures sufficient to convert the feedstock to synthesis gas; to convert inorganic matter in the feedstock (when the feedstock is solid or semi-solid) to a glassy solid material known as vitreous frit or slag; and to convert halogens into the corresponding acid halides.

• A process that incorporates a modern, high temperature pressurised gasifier (which produces raw synthesis gas) with auxiliary gas and water treatment systems to produce a refined product synthesis gas which, when combusted, produces emissions in full compliance with the Clean Air Act.

The gasification process described by this definition operates by feeding carbonaceous materials into a preheated and pressurised chamber (the gasifier), along with a controlled and limited amount of oxygen (air) and steam. At the high operating temperatures and pressures created by conditions in the


MWH Chapter 11-3

gasifier, chemical bonds are broken by thermal energy (and not by oxidation), and inorganic mineral matter is fused or vitrified to form a molten glass-like substance called slag or vitreous frit. With insufficient oxygen, oxidation is severely limited and the thermodynamics and chemical equilibria of the system shift reactions and vapour species to a reduced rather than an oxidized state. Consequently the elements commonly found in fuels and other organic materials (C, H, N, O, S, Cl) end up in the syngas as CO, H2, H2O, CO2, N2, CH4, H2S, and HCl with trace amounts of other compounds such as NH3, HCN, elemental carbon and other hydrocarbons. Fuel can be fed to the gasifier in the form of aqueous slurry, as dry solids, or as a liquid. Slurry and liquids are fed using high-pressure, positive displacement charge pumps in an enclosed system. Dry solids are generally pneumatically conveyed with nitrogen and fed through an enclosed lock-hopper in the form of ground or shredded solids, pellets or briquettes. Solid support fuels can be crushed to the appropriate particle size before being gasified. For slurry-fed processes the ground solids are mixed with water (typically recycled from the process) in a mill to form aqueous slurry. Primary fuel handling systems such as storage piles, conveyors, crushing, grinding, etc are similar to systems used in conventional CHP systems. They include unit operations for the control of fugitive dust emissions. The chemical reactions of the gasification process take place in the presence of steam in an oxygen-lean, reducing atmosphere, in contrast to combustion where reactions occur in an oxygen-rich, excess air environment. In other words, the ratio of oxygen molecules to carbon molecules is significantly less than one in the gasification reactor. The following simplified chemical conversion equations describe the basic gasification process: C (fuel) + O2 → CO2 + heat reaction 1 (exothermic) C + H2O (steam) → CO + H2 reaction 2 (endothermic) C + CO2 → 2CO reaction 3 (endothermic) C + 2H2 → CH4 reaction 4 (exothermic) CO + H2O → CO2 + H2 reaction 5 (exothermic) CO + 3H2 → CH4 + H2O reaction 6 (exothermic) A portion of the fuel undergoes partial oxidation by precise control of the amount of oxygen fed to the gasifier (reaction 1). The heat released in the first reaction provides the necessary energy for the primary gasification reaction (reaction 2) to proceed very rapidly. Gasification temperatures and pressures within the refractory-lined reactor typically range from 1200 °C to 1950 °C and from near atmospheric to 1200 psig, respectively. At higher temperatures the endothermic reactions are favoured. A wide variety of carbonaceous feedstocks can be used in the gasification process. Low heat content wastes may be blended with high heat content supplementary fuels such as coal or petroleum coke to maintain the desired gasification temperatures in the reactor. However, unlike incineration, these supplementary fuels contribute primarily to the production of more syngas within the gasifier, and not to the production of carbon dioxide. The reducing atmosphere within the gasification reactor prevents the formation of oxidized species such as SO2 and NOx. Instead, sulphur and nitrogen (organic-derived) in the feedstocks are primarily converted to H2S, ammonia and nitrogen (N2). Trace amounts of hydrogen cyanide may also be present. Halogens in the feedstock are converted to inorganic acid halides (eg. HCl, HF, etc) in the gasification process. Acid halides are easily removed from the syngas in downstream gas cleaning operations.


MWH Chapter 11-4

The concentrations of H2S, HCl, N2 and NH3 in the raw syngas are almost entirely dependent on the levels of sulphur, chlorine and nitrogen present in the feedstock, whereas the proportions of CO, H2, CO2 and CH4 are indicators of gasifier temperatures and oxygen : carbon : hydrogen ratios. In fact, the methane concentration in the syngas is often used as an operational, control monitoring parameter. Glassy vitrified slag in the slag quench zone of the gasifier is discharged at the bottom of the gasifier vessel into a collection system where the solids are dewatered and the water is recycled to the process. The separated non-toxic slag can be stored on-site and subsequently sold or disposed of in a non-hazardous landfill. Syngas from gasification processes can be treated in a series of clean-up and by-product recovery operations. However, unlike incineration where combustion gases are treated at atmospheric pressure, the volume of syngas that must be treated in a gasification process is reduced significantly because of the elevated pressure of the syngas. As for incineration systems, wet scrubbers and dry filtration systems are typically used to remove particulate matter and acidic gases from the raw syngas stream. The clean product, syngas, exiting the clean-up process may be combusted in a gas turbine or gas turbine/combined cycle (i.e., gas turbine with a heat recovery steam generator) system to produce electricity and steam. There are two key reactor types in a gasification system.

• Entrained Bed Reactor, and

• Moving Bed Reactor Entrained Bed Reactor

A number of entrained-bed gasification reactors, equipped with either water quench or waste heat recovery systems, are currently in use. In entrained bed gasifiers, fuel and oxygen (air) enter the reactor in concurrent flow arrangements and in an appropriate ratio such that the gasifier is operating in a slagging mode (i.e., the operating temperature is above the melting point of the ash). In two-stage entrained gasifiers, additional fuel (in slurry form) is added to a second gasification stage to cool and enhance the heating value of the syngas from the first gasification stage. The molten ash flows into a water bath or spray at the exit of the gasifier. This process serves to solidify the molten ash, creating a glassy vitrified solid slag or frit material that is removed from the gasifier, either intermittently via a lock-hopper system or through a continuous pressure let-down system. In quench gasifiers, the syngas is extracted with the slag, and is cooled when it contacts the pool of water within the slag quench zone of the gasifier. Gasification units produce only a small amount of slag if the feedstock contains small amounts of inorganic mineral matter. Moving Bed Reactor

In the moving bed gasifier, sized fuel (eg. shredded MSW, pellets or briquettes) is fed to the top of the gasifier. At the bottom, oxygen (air) and steam enter and the slag is withdrawn. Liquid wastes can also be introduced into the gasifier at the bottom of the reactor vessel. As the solid fuel moves down through the bed, counter-current to the rising syngas, it proceeds through four zones drying, devolatilization, gasification and combustion. Drying occurs when the hot syngas contacts the feed at the top of the gasifier. Then after the fuel devolatilizes, forming tars and oils. These compounds exit with the raw syngas, and are captured in downstream clean-up processes and recycled to the gasifier. The devolatilized fuel then enters the higher temperature reaction zone where it reacts with steam and carbon dioxide. Near the bottom of the gasifier the resulting char and ash react with oxygen, creating temperatures high enough to melt the ash and form slag. The slag is then removed and quenched with water.


MWH Chapter 11-5

11.3.2 Pyrolysis System

Pyrolysis is a process in, which thermal degradation of organic wastes takes place in the absence of air or oxygen. The pyrolysis process takes place under low-pressure. However, it is extremely difficult to create completely anaerobic conditions, and therefore some oxidation inevitably occurs in pyrolysis. The pyrolysis process typically takes place in the 400 - 800 º C temperature range. Pyrolysis is often a precursor to gasification, under both anaerobic and partially aerobic conditions. Organic compounds have a tendency to dissociate when sufficient heat is applied and this process follows a steady path towards a series of simple and more stable end products. The three essential products of the pyrolysis process are gas, char and bio-oil. The exact nature and end uses of the products of pyrolysis depend on the characteristics of the feedstock, and precise conditions at which the process has occurred. Commercially, the pyrolysis process is divided into two types – fast pyrolysis and slow pyrolysis; these are discussed further below. A typical (and general) pyrolysis process consists of the following key elements:

• fuel preparation

• pyrolysis

• condensation and separation

• products and their uses In the fuel preparation step, the waste feedstock is sorted and homogenised, and the particle size is reduced to, typically, around 5 cm x 0.6 cm, by grinding or shredding. Magnetic separators recover residual ferrous matter. Any feedstock with moisture content of above 20 % requires drying. The prepared waste is then fed into the pyrolysis reactor. The waste can be charged to the pyrolysis reactor in various ways, such as by rotating screws, reciprocating rams, entrainment, or lock hoppers. The hopper discharge and the feed systems must be designed and operated with an airlock mechanism in place to prevent air or oxygen entering the reactor. Pyrolysis reactors can either be heated directly or indirectly. In direct heating, a strictly limited supply of oxygen or air is introduced to create a combustion zone inside the reactor. Supplementary fuel such as oil may also be used. Indirect heating requires a heater system to heat the reactor from the outside. This can take the form of a heater jacket, or heated tubes around the reactor. Some pyrolysis reactor designs allow sufficient air infiltration to provide some burning within the reactor. This is done in order to provide internal heat to sustain the process. A wide range of reactor types can be used in the pyrolysis process, such as ablative reactors, entrained flow reactors, rotating cone reactors, vacuum reactors and fluid-bed reactors. Fluid-bed reactors such as bubbling fluid-bed, and circulating fluid-bed, are the most commonly used reactor types. This is mainly because fluid-bed reactors can be readily scaled-up and they are also relatively easy to operate. On the basis of operating temperature and residence time, pyrolysis processes are typically categorised as:

• Slow pyrolysis, and

• Fast pyrolysis Slow Pyrolysis


MWH Chapter 11-6

In slow pyrolysis, relatively large particles are subjected to inherently slow heating rates and long residence times in the reactor. This process usually takes place between 550 – 800° C. The process produces gaseous products in high yields and with a high calorific value. This high calorific value is due to the presence of higher hydrocarbons and methane. Thermodynamic stability and heat of reaction are two very important factors in determining the products of pyrolysis processes. The thermodynamic stability of hydrocarbons can be measured by means of the free energy formation from the elements carbon and hydrogen. Above 500 °C, all hydrocarbons become unstable. Under thermal treatment, these organic compounds are converted into simpler compounds of increasing stability as shown in the order below. paraffins → olefins → diolefins → aromatics → polycyclic aromatics (tar) → carbon +hydrogen. At lower temperatures the olefins and diolefins tend to polymerise to tars with a highly complicated structure. The thermal decomposition of oxygenated compounds yields simpler and more stable compounds, such as formaldehyde, acetone, acetic acid, etc. and generally proceeds to ultimately yield CO, CO2, H2O, and CH4 as final products. Fast Pyrolysis

In fast pyrolysis, finely divided waste is heated rapidly in the absence of air and the products are rapidly cooled (quenched) after short residence times, to preserve high concentrations of non-equilibrium pyrolysis products. Fast pyrolysis takes place below 550 º C and usually at around 500 º C in the vapour phase. The main products of this process are oils or liquids, tars, and carbonised residue. To obtain high yields of liquid, careful control of the process is required. Fast pyrolysis can produce up to 80 % of oil from a dry feedstock. The char and gas produced is usually further utilised within the system, thus making the process free of a waste stream. The process thermal yield is high and heat losses are low. Pyrolysis Products and Uses

Pyrolysis results in the formation of a solid char, a fuel gas and a condensable matter consisting of tar, oil and so-called pyroligneous liquor (a mixture of a highly oxygenated aliphatic and aromatic compound). The quality and yield of these products from a specific reactor design are dependent on the chemical and physical characteristics of the feedstock, the heating rate, the reaction chamber temperature, the solids retention time and the quantity of air introduced into the reaction chamber. In slow pyrolysis, the main product is gas, whereas mainly liquid products result from the fast pyrolysis processes. Gas produced in the pyrolysis process mainly comprises methane, carbon monoxide, hydrogen and ethylene. The gas contains an approximately 35 % non-combustible fraction (eg. CO2, N2, etc). The product gas exiting the pyrolysis reactor is collected in a storage vessel, and condensation of organic acids and other compounds takes place in this vessel. Approximately 30-40 % of the product gas is utilised to heat the pyrolysis reactor and thus drive the process. The energy content of product gas decreases upon cooling of the gas, as condensable products (with supplementary calorific value) thereby leave the gas stream. Therefore the gas is kept in a heated state as long as possible (in fact, often utilised directly) so that maximum energy recovery takes place. For the same reason, storage of the product gas is minimised because the condensables will leave the gas stream relatively readily in any quiescent area. A range of pyrolysis gas compositions, obtained under different pyrolytic conditions, is given in Table 11-2.


MWH Chapter 11-7

Under optimised pyrolysis conditions in a generic reactor, more than 620 MJ/Nm³ of fuel gas with a heating value of approximately 11 – 12 MJ per ton of biomass is produced. The brown liquid produced in the fast pyrolysis process is known as bio-oil. Bio-oil also has several other names including pyrolysis liquid, pyrolysis oil, pyroligneous liquor, and wood oil. Bio-oil is typically dark brown in appearance, with a smoky acidic smell. It has a heating value nearly half that of a conventional fuel oil, typically in the range of 16- 18 MJ/ kg. Bio -oil is immiscible with hydrocarbons and is less stable than typical fossil fuels. Bio-oil can be used as a substitute for fuel oil or diesel in many static combustion applications, including boilers, furnaces, engines and turbines for electricity generation. Depending on the feed material and process, there are also a range of chemicals that can be extracted or derived from bio-oil. Char is one of the main by-products of pyrolysis. Char is generally low in volatility, sulphur and ash, with heating values ranging between 5.8 and 11.6 MJ/kg. Considerable quantities of char may be produced in a typical pyrolysis process. For example, approximately 150 to 300 kg of char per tonne of RDF is generated, when RDF is the feedstock in a pyrolysis process. The available markets and/or end-uses for char play an important role in the economics of pyrolysis of waste. Char can be used for various purposes such as activated carbon material for water purification, as a high-carbon fuel for boilers, etc. The specific use for char often depends on the composition of char and on the feedstock from which it was derived.

11.4 Overview of ATC Processes

Any development requires considerable quantum of resources, the development of ATC process also requires significant quantum of resources. Most of these technologies were developed during the mid 1980s. There are over sixty patented gasification technologies and processes in existence. These technologies generally use the basic gasification or pyrolysis processes. They include their own unique parameters of equipment elements and process variables, thereby existing as stand-alone technologies worthy of scrutiny as viable waste-to-energy processes.

11.4.1 International Scenario

“IEA Bioenergy” and “CADDET Renewable Energy Programmes” (1998) have identified around forty advanced thermal conversion plants for various waste feedstocks in their report, “Advanced Thermal Conversion Technologies of Energy from Solid Waste”. Similarly, in “Pyrolysis & Gasification of Waste - A Worldwide Technology & Business Review”, recently published by the environmental consulting company Juniper, there is a detailed discussion of over sixty processes and technologies. In 1996 “National Renewable Energy Laboratory” (NREL) undertook a detailed technology evaluation of thermal processes for the treatment of municipal solid waste. During the project over forty firms were initially contacted and subjected to set screening criteria. Finally, seven processes were investigated further, with two of these being novel thermal processes and five being gasification. In Appendix 11-A, sixteen projects have been selected to demonstrate variations in gasification and pyrolysis technologies. Partial lists of various technologies and gasifier manufacturers are given in Appendix 11-B and Appendix 11-C, respectively. Appendix 11-D gives a list of gasification related useful documents. EC/UK Perspectives in Advanced Thermal Processes for MSW is given in Appendix 11 E While Appendix 11-A provides an extensive summary of some sixteen different gasification and pyrolysis technologies these have been selected to illustrate the very broad range of process types and


MWH Chapter 11-8

fundamental parameters within the complete spectrum of these technologies. Thus, some of these sixteen examples have a very limited commercial history. It is considered important to present detailed information on some established illustrative technologies which show that gasification and pyrolysis have indeed passed from a classification of being novel and commercially unproven to a state, at least for certain examples, where technological uptake and commercial success are demonstrable. The three selected technologies are:

• The “GEM” Waste-to-Energy Gasification Converter,

• The Siemens Thermal Waste Recycling Process, and

• The Waste Gas Technology (WGT) Thermolysis Process “GEM” Waste-to-Energy Converter The GEM system has been developed and tested to convert standard Municipal Solid Waste (MSW) and selected commercial / industrial waste streams into useful energy. The system is a positive ‘closed circuit’ one, with no emissions to atmosphere from the actual conversion of waste to gas. The gas generated by the system is very clean in all respects and can be compared to natural gas. When the gas produced is used within a conventional steam boiler, the flue discharge to atmosphere is at least as clean as any other conventional gas fired boiler and, therefore, it can be used in any standard Combined Heat and Power (CHP) generator. At the end of the process, there is no residue produced which requires disposal to landfill as the small percentage of ash residue is inert and non-toxic. It can be utilised as a suitable material in the manufacture of concrete blocks or for use as a road or building aggregate. The overall energy conversion of the unit can be very high; up to 100% from dry feedstock to useful gas, and the system has a very low parasitic energy demand from 5%-20%, depending upon the particular feedstock and the front-end waste preparation process. The overall system produces virtually 100% re-cycling or re-use of materials with very little requirement for support from fossil fuel. Feed Stock The quality and quantity of energy within the produced gas is related to the energy and moisture content of the feedstock. The moisture content of MSW is usually around 35% (depending on the source). This moisture, being of no use, is removed prior to gasification by drying, using waste process heat. Ferrous and non-ferrous metals are also removed for re-cycling. Most of the glass bottles and ceramics, typically found within MSW, are removed via a ‘bottle bank’ or a similar process. A few bottle fragments are welcome as they pass straight through the gasifier, helping to maintain a clean and polished surface in the reaction chamber, and with no detrimental effect. The fuel that is required for the gasifier needs to be reduced into very small crumbs or flakes in order that it can be heat penetrated in about 100th of a second.


MWH Chapter 11-9

In order to achieve this GEM has developed an extremely powerful “flail” device. Raw MSW is fed straight from the collection vehicles onto a conveyor system, which carries the material into a large hopper mounted on the top of the main feed ram. The ram compresses the MSW in a way similar to that of a conventional compactor, but instead of just compressing the material into a smaller volume, it forces the bags into the path of two sets of knives which shred the waste into 100 mm wide strips. These strips of waste material are then ejected into the paths of high-speed flails. The effect of this is that the material is further reduced in size and is now of a satisfactory size to be fed into the gasifier. All the necessary engineering mechanisms are in place to ensure that no large items such as blocks of concrete, iron engine blocks, fence posts etc. are introduced into the main flail mechanism, thus ensuring maximum efficiency and minimal maintenance of the hardware. Before the shredded material is used in the gasifier, it is necessary to remove the metals. Material trajectory is used to aid this separation process. The material leaves the last flail within a chamber onto a flat conveyor at its base. The angle of discharge of the material is raised in order that the light materials fall short and land on the conveyor bed but the heavy materials such as particles of mild steel can ‘fly’ much further and land further along the conveyor. The ejection length is 12 metres and results in the waste material layering itself along the conveyor, the soft light plastic fragments lie on the bottom and the steel on the top. This allows the clean removal of the steel by means of a magnetic overband conveyor, followed by an eddy-current ejector at its end, for the next heaviest i.e. aluminium, and so on. The remaining material is now clean and fine, and is ready for feeding into a vacuum dryer, which indirectly uses the exhaust heat from the boilers and a vacuum pump to dry the material. This can now be referred to as a totally dry, high CV fuel since, with the removal of inert materials and the inclusion of a drying step, the original MSW feedstock has lost around 50% of its initial weight but has retained all of its energy potential in the form of a totally dry organic fuel. If, for example, the CV of the waste coming off the delivery truck was 9 MJ/kg, the CV of the prepared fuel would have been lifted to 18 MJ/kg. This is now a very useful input fuel for the gasifier to convert into so-called “green energy”. The prepared fuel is now odourless and can be stored in a dry condition for extended periods without any deterioration or degradation. The moisture content that is withdrawn from the material is removed in a completely sealed environment using waste heat extracted from the exhaust of the power generating equipment. A vacuum circuit which removes the generated steam or water vapour then passes that steam or vapour through a condenser, resulting in the condensate being collected and discharged to a foul sewer.


MWH Chapter 11-10

Conversion into High Calorific Value (CV) Gas The gasifier chamber is where the actual manufacture of the gas takes place. The chamber runs at a high temperature and is suspended inside an insulated oven, which is heated by conventional burners running on any fuel that is found to be convenient, including produced gas. Inside the gasifier chamber, a low pressure is maintained by the rapid expansion of the fuel material into gas. After start-up, where everything is purged with nitrogen for safety, together with the clearing of any air (oxygen), the fuel injection systems are started. Assuming that tractor or conveyor from the fuel store is filling the fuel reception hopper, the fuel is metered from the hopper onto a feed-speed controlled conveyor. The fuel is dropped onto an elevator, running at constant speed, which carries it up to a level above the gasifier. The fuel is discharged into a ‘roll feeder’, while the vibrating conveyor ensures a stable supply of material. This ‘roll feeder’ is a piece of equipment, which accomplishes three tasks: -

i) It forms a seal to stop the possibility of the produced gas escaping from the gasifier to the atmosphere.

ii) It ensures that all traces of free air (oxygen) are prevented from entering the gasifier.

iii) It transfers all of the new fuel from the vibro-conveyor into the mouth of the ‘finger-feeder’ and then finally into the gasifier itself.

The ‘finger-feeder’ is a piece of equipment which receives the material from the ‘roller-feeder’ and, by means of oscillating ratchet type plates, feeds the material into the gasifier at a uniform flow rate. Inside the gasifier the material from the finger-feeder holds onto the inner surface of the reaction chamber. The speed of conversion into gas depends upon the size of the fuel particles but generally, with dry fine material feed; conversion times of 100th of a second are achievable. This material is forced continually to the inner surface of the outer chamber while gradually dropping to the base of the gasifier chamber by gravity. When the carbon/ash reaches the bottom channel, the ash etc. is discharged via a rotary valve and augers, resulting in the production of very clean gas, totally free from any solid particles. In addition, liquid feedstocks such as waste oil can be introduced either singularly or as a mixture with dry fuel stocks in order to increase the CV of the input fuel. From the discharge ports, the gas is released out of the gasification chamber to the blast cooler. Syngas Conditioning and Uses The produced gas leaves the gasifier at a high temperature and in a large volume. The gas is immediately piped to a ‘blast cooler’. This consists of a cylindrical shell into which is fitted a series of manifolds which carry a considerable number of nozzle sprays. The fluid used is oil, which is circulated through a chilling exchanger and enters the blast cooler at approximately 20 °C. Due to the volume of oil in the spray and the fact that the oil is in direct contact with the gas, very rapid cooling takes place. The blast cooler is sized in order to allow the oil spray to continue “washing” the gas after it is cooled, but before the gas leaves the blast cooler. The oil removes practically all of the chlorinated and fluorinated compounds from the gas, with these compounds finishing up in the oil storage tank, which is connected to the blast cooler.


MWH Chapter 11-11

The majority of these chemicals are extracted as a gel, which can easily be drawn off and disposed via specialist disposal channels. The volume of gel to be discharged is very small and may only be equal to a single tanker load in every six months, depending on the waste throughput. The CV of the produced gas is related directly to the potential chemical energy within the original feedstock. The average CV of the gas generated from MSW is around 32-38 MJ/m³, depending upon characteristics. Because of the relatively high percentage of hydrogen within the final product it is generally better to use this gas as a prime fuel in a CHP unit. Environmental Benefits

• No discharges to atmosphere during the gasification process

• No requirement for landfill at all

• 100% re-cycling (water to water company – metals to foundry – ashes to building)

• Gasification allows the potential replacement of a considerable proportion of energy needs, thus saving fossil fuels.

Figure 11-2 presents a mass balance comparison of the GEM technology against incineration. The Siemens Thermal Waste Recycling Process The Thermal Waste Recycling Process is based on an original patented process invented by a German engineer, Karl Keiner. The Keiner pyrolysis process was developed during the 1970s on a small batch scale and has been further developed by Siemens to the commercial stage, starting in 1984. The technology is now referred to as the TWR process. In the further development of this system, Siemens sought to:

• Reduce the environmental impact of thermal waste disposal processes

• Emphasise recycling to maximise the recovery of useable by-products

• Maximise energy recovery from the process

• Combine certain technologies, already proven in industrial applications, to create a novel overall technical concept

To achieve these environmental objectives the process aims to:

• Minimise emissions to air

• Treat the ash residues within the process, to produce a minimal volume of glassified slag which can be reused as a construction material or landfill

• Minimise the quantity of residues requiring ultimate disposal to landfill Because Siemens has used a combustor within the process, various observers consider that the TWR process is really just incineration. However, although the process does employ a first pyrolysis stage, followed by high temperature combustion, the overall process is very different from conventional incineration in as much as the solid residues from the boiler and flue gas cleaning processes are sent to a high temperature combustion chamber where energy from the waste is used to melt the inorganic


MWH Chapter 11-12

fraction to produce a single glass-like inert material, rather than producing bottom ash and fly ash as in incineration. Process Description The process combines pyrolysis with high temperature combustion, as follows. Ist stage: pyrolysis Following pre-treatment of the solid waste to remove recyclable material and reduce the particle size of the solid feedstock to less than 200 mm, the waste is fed via a screw conveyor to the thermal conversion drum. There it is heated in an oxygen-deficient atmosphere to a temperature of 450 °C and retained for a residence time of approximately one hour. The conversion drum axis is tilted at 1.5 degrees from the horizontal and rotates at approximately 3 rpm. Internal heating tubes transfer heat to the waste material, which is thoroughly mixed in the pyrolysis stage. The syngas produced is supplied directly to the combustion chamber. Solid residues are removed, cooled to less than 150 °C and screened to separate fine and coarse recyclable fractions. The coarse fraction chiefly comprises ferrous and non-ferrous metals, and inert material. The fine fraction, which contains 99% of the solid carbon formed in the pyrolysis process, is mixed with recycled dust fractions from the boiler and flue gas cleaning processes. This dust mixture has an approximate carbon concentration of 30%, resulting in a minimum heating value of around 10 MJ/kg. 2nd stage: combustion The syngas and fine residues (containing carbon) are burned at approximately 1300 °C in the combustion chamber. This combustion temperature is 100 to 150 °C above the fusion point of ash compounds; consequently, the unrecyclable ash residues, which are injected into the high temperature combustion chamber, are converted into a molten slag, which flows downwards into the wet slag removal unit. The slag granulates to form a vitreous substance, which can be utilised as, for example, a road construction material without further treatment. The temperature, residence time and turbulence in the combustion stage ensure that all organic compounds are destroyed. High burnout and low NOx formation are ensured by uniform temperature distribution effected by flue gas recirculation. 3rd stage: steam production The thermal energy contained in the resulting flue gases is used to generate steam in a heat recovery boiler (400 °C and 40 bar), which is then used to generate electricity and/or heat. The flue gases are cooled to around 250 °C before passing to the flue gas cleaning/by-product recovery section of the plant. The flue gas is scrubbed to meet the requirements of air emissions legislation. Boiler ash, fly ash and spent active carbon from the bag filter are fed back to the melting furnace, and the ultimate residues requiring disposal are salts and sludges from the wastewater treatment plant. Mass and Energy Balance The process converts MSW to recyclable metals and inert inorganic substances, recyclable granular slag and HCl. Heavy metal-contaminated materials from the flue gas cleaning process can be produced (depending on the nature of the feedstock), and these will require careful disposal in a hazardous waste landfill. Scale-Up and Commercialisation


MWH Chapter 11-13

Since 1984 Siemens have developed the technology in various pilot plants and now in two full scale commercial operations, in Japan and Germany. The combination of individual process components, well proven in industrial and/or power generation applications, indicates good reliability and maintainability in commercial scale plants. The first commercial plant at Furth, Germany, converts MSW and sewage sludge, whereas the first commercial unit in Japan processes MSW. The feed material handling is critical to proving the required flexibility and operability of the TWR process. The Furth facility is designed for 150,000 tonnes per year and is constructed in two parallel process lines, each with a capacity of 5 tonne/hour. The Waste Gas Technology (WGT) Thermolysis Process Waste Gas Technology UK Ltd (WGT) was established in 1992 to conduct research for a waste-to-energy process, employing an advanced thermal treatment technique. The objective was to develop a simple low cost industrial process suitable for installation on a small scale, and with the flexibility to accept varied feedstocks such as those encountered in municipal solid waste. A pilot plant with the capacity to receive up to 80 kg/hour of waste feed was constructed by WGT in Hampshire, United Kingdom, to provide the focus for the research and development work. The WGT process utilises a novel thermal conversion technique for production of a clean, high calorific value, fuel gas stream from organic-based solid waste materials. The quality of the produced gas is suitable for direct supply to a prime mover for generation of electrical power. Alternatively the gas can provide a source of clean fuel for firing of heaters or boilers. The process, referred to as thermolysis, cannot be precisely described as pure pyrolysis nor gasification. The waste feed material is subjected to elevated temperatures within an oxygen-free environment. Application of a high temperature causes the carbonaceous waste material to gasify, with the resulting gas being cracked into lower molecular weight hydrocarbons and hydrogen. A solid residue is formed comprising ash and carbon. Prior to introduction into the thermolysis reactor the waste feedstock is purged with an inert gas such as nitrogen to displace entrained air and therefore eliminate gaseous oxygen from the process. Waste is delivered into a horizontal cylindrical rotary reactor, which is indirectly heated to a temperature between 750 and 800 °C. The reactor operating conditions are carefully controlled to ensure optimum gas production. The produced gas and solid char residue are separated in a hot cyclonic vessel mounted at the reactor outlet. The hot produced gas is cooled in a direct contact liquid quench, prior to treatment in a gas clean-up system. This downstream clean-up system employs conventional gas treatment technology to ensure efficient removal of contaminants such as acid gas species and particulates. Status of the Technology Over a seven year period the WGT pilot plant has demonstrated the successful performance of the process for a diverse range of wastes. In fact, the pilot facility has proven sufficiently robust to accept all organic-based solid waste materials encountered to date, provided that the material is prepared in a form that can be conveyed by a screw auger. In the case of MSW a degree of feed pre-preparation is required, involving size reduction and segregation to remove large inert objects. The main categories of wastes successfully treated in the pilot plant include:

• Dried sewage sludge

• Sewage screenings


MWH Chapter 11-14

• Wood wastes

• Straw

• Copier material

• Commercial waste

• Plastics

• Segregated MSW

• Poultry litter

• Meat and bone meal

• Tannery wastes

• Shredded tyres

• Drilling muds

• RDF An important feature of the pilot plant has been its capability to demonstrate the generation of electrical power in a gas engine, which is supplied directly by gas produced in the process. The flexibility of the equipment to process a variety of materials has been clearly determined and the pilot plant now serves as a useful tool to acquire operating data on specific wastes, as well as demonstrating the technology. The first industrial scale application of the WGT process is now in progress. OSC process Engineering, under licence from WGT, have constructed a plant for gasification of dried sewage sludge and sewage screenings for Welsh water. Data obtained from the WGT pilot plant provided the design basis. The plant, with a nominal feed rate capacity of 500 kg/hour, is installed at the Nash Water Treatment Works in South Wales. Centrifuged sewage sludge is dried in a thermal fluid heater to provide the plant feedstock. The function of the gasification plant is to provide a sustainable route for disposal of sewage sludge by supplying the upstream drier with a high calorific value fuel gas stream. Potential Application The application of the WGT process for disposal of sewage sludge is currently driven by EU legislation. Cessation of sludge disposal into the sea has generated an immediate requirement to seek alternative disposal methods including on-site treatment. The combination of sludge drying with thermal treatment offers a sustainable solution suited to the small-scale throughput required at many works. To date legislation has not, however, provided the same driving force for application of advanced thermal treatment technology to small-scale treatment of MSW. A number of authorities and waste operating companies have been endeavoring to develop such projects in advance of legislative constraints. However successful implementation is subject to current economic viability and can be considered to be opportunity-led. In the case of MSW, the feed preparation facility required for a small-scale plant can contribute significantly to the project cost. Another factor affecting project economics is the selection of electrical generating equipment. For example, with limited field experience on gas produced from gasification/thermolysis, engine suppliers are currently offering conservative performance guarantees


MWH Chapter 11-15

leading to the selection of de-rated equipment entailing higher cost of installation. It is anticipated that improved guarantees will be available after experience is gained on initial installations. Potential to process MSW using WGT technology on a relatively small scale has been well proven. A key factor in this application is the economic viability of preparing a suitable plant feedstock. The process itself has been proven at the pilot scale for prepared MSW and is currently undergoing commercialisation at the industrial scale for sewage sludge, sewage screenings and copping. The capability of the WGT pilot plant to process diverse materials provides confidence that the industrial scale experience can be translated successfully to MSW.

11.4.2 Indian Scenario

Ministry of Non-Conventional Energy Sources is the nodal agency in India, which is effective in the development of waste to energy sector. Gasification is one of the core areas promoted by the Ministry. The Programme on Biomass Gasification is being implemented with the main objective of development and promotion of conversion and utilisation technologies, such as biomass briquetting and gasification, for various end-use applications in rural and urban sectors and R&D on biomass production and gasification. Appendix 11-F gives an overview of application of gasification & pyrolysis techniques in India. Some major developments included in this compilation include the following applications

• National Programme on Biomass Gasification

• Proposed Power Plant from MSW in Chennai by EDL

• Indirect Gasification Process (Esvin Advanced Technologies Ltd., Chennai, Tamil Nadu)

• Power From Solid Wastes Using Cyclone Gasifier


Gasification or pyrolysis of MSW and other organic waste produces a gaseous product stream with substantial heat content. This gas can be readily cleaned of particulates, trace metals, acidic gases, ammonia, hydrogen sulphide, and other contaminants and burnt in a gas engine or gas turbine to generate electricity. A much more efficient combustion process takes place in gasification or pyrolysis involving molecularly simple, high quality gaseous fuels, for which complete and efficient combustion is inherent. In comparison, incineration involves combustion of partially sorted MSW or other organic feedstock. These materials generally contain some combustion-resistant constituents and produce a large number of highly undesirable by-products such as dioxins, acid gases, etc. in significant concentrations. These by-products require very costly flue gas clean-up processes. Moreover, the gas clean-up efforts in gasification or pyrolysis focus on a relatively low volume gas stream compared to the substantial volume of flue gases from incineration systems. Environmental emissions control is therefore significantly inexpensive in gasification or pyrolysis systems than in incineration system. According to a study conducted by NREL in 1996, the capital costs of many gasification and pyrolysis processes are comparable to typical contemporary mass-burn incineration systems. However some gasification and pyrolysis technologies have significantly higher capital costs, with royalty issues being a major factor. Most operating costs are quite comparable or slightly lower than those for incineration facilities. It is highly likely, according to a Juniper Consultancy Services report (1997), that capital costs will decrease in relative terms for gasification and pyrolysis technologies over time, with the growing implementation of these processes.


MWH Chapter 11-16

Comparisons between advanced thermal conversion technologies and mass-burn incineration technologies made by the IEA Bioenergy programme and the CADDET renewable energy programme, indicate that the advanced thermal conversion technologies typified by gasification and pyrolysis have:

• Similar costs to incineration,

• Lower environmental emissions and

• Higher levels of energy recovery. Gasification and pyrolysis technologies are moving swiftly from the developmental stage to a general accumulation of commercialised operating experience. While the initial history of scale-up and commercial application of various technologies was not particularly encouraging the lessons learnt have been valuable to succeeding commercialisation ventures. As a result, a chronicle of successes in gasification and pyrolysis technological applications is building up. There are now good examples of credible technologies that have the right parameters for adoption in India. Constraints exist in terms of issues such as royalties but these are certainly not serious enough to disqualify the careful selection and introduction of key technologies.


MWH Chapter 11-17

Table 11-1. Advanced Thermal Conversion Processes, Products and Uses

ATC Process Sub-

Classification Gas/ Main

Product Characteristics

Energy Content MJ/Nm3

Typical Use

Gasification

Air Gasification

Low Energy Gas (Generator Gas)

6 - 8 Close couple to gas/oil boilers, operation of diesel and spark engines, crops drying

Oxygen Gasification

Medium Energy Gas (Town Gas, Syngas)

11 - 18 Suitable for limited piped transportation

Pyrolysis

Pyrolysis Medium Energy Gas, fuel oil, and charcoal

11 - 20

Pyrolysis Gasification

Medium Energy Gas (known as Town Gas or Syngas)

13 - 21

Suitable for limited piped transportation, synthesis of fuels, resins, fertilisers and ammonia


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Table 11-2. Pyrolysis Processes – Range of Fuel Gas Characteristics

Gas composition,

Vol. % Pyrolysis temperature, °C

480 650 815 925

Carbon monoxide 33.6 30.5 34.1 35.3

Carbon dioxide 44.8 31.8 20.6 18.3

Hydrogen 5.6 16.5 28.6 32.4

Methane 12.5 15.9 13.7 10.5

Ethane 3.0 3.1 0.8 1.1

Ethylene 0.5 2.2 2.2 2.4

Heating Value,MJ/m3 11.6 15.0 14.6 14.4

Source: Handbook of Incineration Systems 1991.


MWH Chapter 11-19

Figure 11-1. Advanced Thermal Conversion Processes


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Figure 11-2. Mass Balance Comparison of the GEM Technology Against Incineration.


Chapter 12-1MWH

12 Options for Beneficial Waste UtilisationSuccessful implementation of the waste-to-energy projects requires adequate and assured supply ofwaste, generally with a predominantly organic matter. However, in India, a waste-to-energy proposalas a beneficial disposal process is still a new concept for wastes such as MSW. Therefore, in order tofacilitate its implementation on a national scale, it is essential that any waste-to-energy proposalcompete successfully with other beneficial waste utilisation options that are feasible for India’s wastestreams. Further, from this point of view, it becomes necessary to understand the pros and cons ofthese competing options properly so that waste-to-energy technologies can be put in the propercontext, in terms of their perceived advantages and viability against the other waste utilisationstrategies. This chapter reviews the following technological options: landfill with gas recovery,composting and fermentation to liquid fuels.

12.1 Landfill with Gas Recovery

12.1.1 IntroductionHistorically, landfills have been the most economical and environmentally acceptable means fordisposal of solid wastes throughout the world. Even with the initiation of concepts like wastereduction, recycling and transformation technologies, disposal of residual solid wastes in landfillsremains an important component of an integrated solid waste management system.

Over the past two-three decades, engineering features have been added to address the numerousenvironmental concerns of atmospheric contamination by landfill gases (LFG) and contamination ofground/ surface water resources by leachates and surface run-off. A schematic of a modern engineeredlandfill is shown in Figure 12-1.

12.1.2 Landfill Operations and DesignThe salient features of all the major stages of landfill such as operation, processes, engineering design,leachate, LFG management as well as environmental monitoring are listed below:

• Landfill Design

Foundation, liner, leachate collection, LFG collection, drainage and filling design, run-offcollection and closure design

• Landfill Operations

Waste inventory (load, type, etc.), cell layouts

• Biochemical transformations

Biodegradation of MSW organics, LFG generation

• Leachate Management

Monitoring, collection, treatment, reuse

• LFG Management

Monitoring, collection, quantity, quality and energy recovery (power)


Chapter 12-2MWH

• Environmental Monitoring

Atmospheric air quality (CH4, H2S, VOC, etc.) ground water quality, pests, etc.

Landfill Gas

LFG is primarily generated as a consequence of anaerobic decomposition of MSW, and can beexpressed by the following reaction:

Organic matter + H20 = CH4 + CO2 + Other gases + Biodegradable organic matter

The quantum of LFG generated from a landfill depends on the characteristics of the waste deposited.The amount of degradable materials in MSW is determined by the composition of waste and itsexposure to moisture in the landfill.

The rate of landfill gas generation is influenced by several environmental factors. These factorsdetermine the decomposition rate, which, in turn, affects the volatility and productive life of a landfill.Figure 12-2 illustrates the various factors that influence the gas production process.

An adequate prediction of landfill volume requirements can be made by projecting records of pastquantum of waste landfilled, waste weight. Knowledge of the composition of waste contained in thelandfill is very important for a preliminary assessment of the LFG generation potential. However,waste disposal records are often incomplete or non-existent, and specific studies may have to beconducted at a site to assess the waste composition and LFG production patterns.

The organic fraction of MSW is assumed to have an empirical formula - CaHbOcNd (carbon, hydrogen,oxygen and nitrogen). Rapidly decomposable organic material is represented by C68H111O50N. Thedecomposed chemicals combine with water molecules (H2O) to produce LFG, which comprises ofmethane, carbon dioxide and traces of other gases. Water is essential to provide the hydrogen (H)needed to combine with carbon (C) to form methane.


Chapter 12-3MWH

The transition from solid matter to gases that occurs through anaerobic digestion is illustrated below:

Particulars Degradablematter

+ Water -> Methane + Carbon dioxide + Other gases

Organiccompounds

C68H111O50N 16H20 -> 35 CH4 33 CO2 NH3

Weight 791 kg 131 kg -> 255 kg (27.6%) 660 kg (71.6%) 8 kg (0.8%)

Gas volume* 354 m3 (50.8%) 333 m3 (47.8%) 10 m3 (1.4%)

* At standard temperature and pressure (STP).

In this example, the LFG generated by anaerobic decomposition contains 51% of methane and 48% ofcarbon dioxide by volume. The total yield of landfill gas is 0.88 m3 per kg of decomposable material.

The US EPA issued final regulations for control of LFG at new and existing landfills in March 1996.The regulations specify a default value of 0.17 m3 LFG yield per kilogram of MSW, which landfilloperators can assume in the absence of site-specific data. While the volume of LFG assumed in USEPA models is very close to the amount calculated in the example, the LFG yield can vary betweenlandfills, and between different sections of one landfill. The composition of waste, filling practicesand exposure of waste to water are the major causes of varying LFG yields. The total yield of LFG isnot released as soon as decomposition commences. LFG is generated over time, and the degradationrate depends of the type of waste landfilled.

The time taken for the decomposition of half of the degradable content of MSW also varies, forexample, food waste takes 1 year, garden trimmings takes 5 years whereas card board takes almost 15years.

Generally, it takes almost two years, from the beginning of landfill, to generate maximum quantity ofLFG . During this time, anaerobic digestion of most of the organic content of food wastes occurs.LFG generation continues after this time but at slowly decreasing rates. While gas generation canextend for periods of up to fifty years, in most cases, LFG release occurs within five years, becausefood and garden waste typically comprise a large proportion of all organic materials in MSW.

The total yield of LFG and the annual rate of generation are key factors in the annual flow of LFGfrom a landfill. There are several other important factors such as the age of the materials in thelandfill. The annual flow comprises of LFG generated from waste of all ages.


Chapter 12-4MWH

The following are the five factors that influence the annual flow of LFG:

Sr Factor Units Label

1 Total LFG yield per kg of MSW m3/kg Lo

2 Filling rate kg/yr R

3 Time since landfill opened (years) number of years t

4 Time since landfill closure (years) number of years c*

5 Annual rate of LFG generation 1/years k

(* Note that if the landfill is still accepting waste, then the value of c is 0.)

The US EPA model (First-order decay model) to estimate the total amount of LFG generated in aparticular year (LFGt) is given by the equation: LFGt = LoR(e-kc - e-kt). According the final regulationsfor control of LFG at new and existing landfills, March 1996 published by USEPA, the maximumvalue for Lo is 0.17, therefore for a given value of R, t and c the annual rate of LFG generation (k) canbe calculated.

The annual rate of LFG generation (k) is expressed as an inverse proportion of the assumed number ofyears that LFG is released. For example, if LFG release is expected to occur over twenty years, then kis (1/20) = 0.05. The US EPA has set 0.05 as the default value for k in their model of LFG generation.

Although the gas is produced once anaerobic conditions are established within the landfill, it may takeseveral years to produce sufficient quantity of LFG, which intrun can be used o produce power. LFGproduction (and also the quality of the gas) declines along with the time to the extent at which powergeneration is no longer economical. Generally, for a typical well-engineered and well-operatedlandfill, the expected period of LFG production may be as long as 50 to 100 years. However, powergeneration may be economically feasible only for 15 to 20 years.

Composition of Landfill Gas

The microbial process and the reactions that take place within the landfill influence the compositionof landfill gas. For a landfill with gas recovery, proportion of methane present in the LFG is theconcern. The methane content typically ranges between 40 to 60 %. Other compounds that areproduced include carbon-di-oxide and traces of some gases. The typical composition of landfill gas isgiven Table 12.1. The oxygen and nitrogen produced in the LFG are due to the intrusion of air duringgas sampling or analysis. The annual rate of methane generation is higher if more of the MSW is foodwaste or exposed to optimal amounts of water. If a landfill comprises of a relatively high proportionof paperboard, or is located in a dry climate, then the annual rate of methane generation will tend to belower.

Table 12.2 Typical composition of landfill gas

Component Content (%)

Methane (CH4) 40-60

Carbon dioxide (CO2) 35-50

Nitrogen (N2) 2-5

Oxygen (O2) <1


Chapter 12-5MWH

Hydrogen Sulphide (H2S) 40-100 ppm

Heavier Hydrocarbons <1 ppm

Complex Organics 1,000-2,000 ppm

12.1.3 Landfill with Gas Recovery System and UsageA typical landfill gas collection system has three critical components:

• Collection wells

• Condensate collection and treatment system, and

• Compressor

In addition, most landfills with energy recovery systems have a flare for the combustion of excess gasand for use during times when the equipment is under maintenance.

Gas collection typically begins after a portion of a landfill (called a cell) is closed. There are twocollection system configurations - vertical wells and horizontal trenches. Vertical wells are the mostcommon type of well used for gas collection. Trenches are generally appropriate for deeper landfillsand are used in areas of active filling. The wells are normally of perforated HDPE or uPVC andbedded in 30 mm gravel rounds, which allow gas migration while preventing fine materials fromclogging the perforations. The wells are interconnected by horizontal pipes, and the gas is pumped outunder negative pressure from a blower to a main collection header. Ideally, the collection system isdesigned in such a manner that the operator can monitor and adjust the gas flow, if necessary.

An important part of any LFG collection system is the condensate collection and treatment system.Condensate forms when warm gas from the landfill cools as it travels through the collection system. Ifcondensate is not removed, it can block the collection system and disrupt the energy recovery process.Condensate control typically begins in the field collection system, where sloping pipes and headersare used to allow drainage into collecting tanks or traps. This system is typically augmented by post-collection condensate removal. Some of the methods for disposal of condensate are - discharge to thesewer system, on-site treatment, and recirculation onto the landfill.

A blower is necessary to draw the gas from the collection wells into the collection header, and acompressor may be required to compress the gas before it can enter the energy recovery system. Thesize, type and number of blowers and compressors needed depend on the gas flow rate and the desiredlevel of compression, which is typically determined by the energy conversion equipment.

A flare is simply a device for igniting and burning the landfill gas. Flares are considered as acomponent of each energy recovery option because they may be needed during system start-up anddowntime. In addition, it may be cost-effective to gradually increase the size of the energy recoverysystem, and flares are thus used to flare excess gas between system upgrades (e.g. before the additionof another engine).

A series of purification steps are necessary, including moisture removal and the removal ofundesirable gaseous contaminants using molecular sieves. With a properly designed collection systemit is possible to recover up to 80% of the LFG.

The cost of the collection and treatment system varies widely, based on a number of site-specificfactors. If the landfill is deep, collection costs tend to be higher due to the fact that well depths need tobe increased. Collection costs also increase with the number of wells installed.


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The calorific value of a representative landfill gas is around 4500 -5000 Kcal/m3 and dependsfundamentally on the methane content of the LFG. The high calorific value means that landfill gas hassignificant energy generation potential. This can be achieved by:

• Direct use of the gas on-site or at a neighbouring site, for electricity generation and/or as aheating fuel

• Blending with an existing gas distribution system

• Generation of electricity for general distribution and sale via the power grid

Direct use of LFG is the cheapest and simplest option. Costs can be substantially reduced if a singlepipeline to supply a single end user is possible. Typical applications include firing of boilers andinternal combustion engines.

Injection of purified LFG into an existing gas reticulation system may also often be viable, especiallyif no direct usage is possible. Pipeline injection requires that the gas be compressed to the pipelinepressure before introduction.

Electricity generation from LFG is normally accomplished by the use of internal combustion enginesor gas turbines. In cases where extremely large gas flows are available, steam turbines can be used forpower generation.

Of particular current interest worldwide is the development of fuel cell technology, where these cellsare powered by LFG. Such units can produce energy in the range of 1 to 2 MW, and are highlyefficient. They operate by converting chemical energy into useable electrical and thermal energy.

12.1.4 Environmental and Regulatory AspectsIf released directly into the atmosphere, methane is a potent greenhouse gas, with a global warmingpotential that is about 21 times higher than carbon dioxide. Landfill gas can be flared but using it togenerate energy encourages more efficient collection and thereby reduces atmospheric emissions.Control of LFG by flaring or, preferably, by use for energy generation also removes the significantexplosion risk posed by uncontrolled release of methane.

Thus, where it is economically viable, energy recovery from LFG offers significant environmentalbenefits. Such use may also reduce the reliance on conventional fuels for power generation, and thisoffers a further environmental advantage by reducing contaminant emissions.

Soil degradation from poorly managed landfill sites results in vegetation die off when LFG percolatesthrough the soil substrate to the surface, thus displacing oxygen within the plant root zone. Thepresence of LFG in the soil also prevents revegetation of landfill sites, and dispersion may take aslong as 70 years in some climates.

Further environmental problems posed by organic waste disposal at dumping sites (i.e. not atengineered landfills) comprise of:

• Groundwater contamination through leachate

• Surface water contamination through runoff

• Air contamination due to gases, litter, dust, bad odour

• Other problems including rodents, other pests, fire, bird menace, slope failure, erosion etc.


Chapter 12-7MWH

With respect to regulatory issues surrounding landfilling, many countries are seriously short ofsuitable space for new landfills. The EU Commission has proposed to mandate that raw MSW shouldundergo treatment prior to landfilling, and this initiative has already been accepted in several EUcountries. Under the EU proposition, waste with a total organic content greater than 10% may not belandfilled and co-disposal of wastes will be eliminated in five to ten years. Waste management incountries with a high dependency on landfilling, such as the UK, will be forced to shift towardsgreater recycling and greater use of thermal processing. Thermal treatment of waste, as discussed inChapters 10 and 11, is an alternative disposal solution that can deal adequately with the largequantities of variable composition waste such as MSW. In recent years, regulators have focussed onstricter control of atmospheric emissions from thermal treatment processes, cumulating in the German17 BimschV and EU Waste Incineration Directive. A great amount of effort and cost has beenincurred by a number of EU countries to upgrade their incineration facilities such that, after December1996, only state-of-the art facilities will be operating. With Germany, Denmark and Holland leadingthe way, the environmental focus has now shifted to reducing the impact of solid ash residues fromincinerators on environment, the goal being to increase the beneficial recycling of residues. Somehighlights of the landfill regulatory stipulations around the globe are discussed below:

EC Directive

The EC Directive 1999/31/EEC on the landfill of wastes was published on 26th April 1999 in theofficial journal of the European Communities. The directive covers various operational and technicalrequirements of the waste and landfills. It also covers procedures to prevent or reduce the possiblenegative effects on environment, in particular on surface water, groundwater, soil, and air and also onthe global environment, including the greenhouse effect. It also covers resulting risks from landfillingof waste to human health during the whole life cycle of the landfill. Highlights of this directive aregiven in Appendix 12 A.

EPA Standards

The Resource Conservation and Recovery Act (RCRA) Subtitle D approach uses a combination ofdesign and performance standards for regulating MSW landfills. USEPA’s Subtitle D rule, publishedOctober 9, 1991, also establishes facility design and operating standards, groundwater monitoring,corrective action measures, and conditions (including financial requirements) for closing municipallandfills and providing post-closure care for them. A phased implementation of the regulations beganon October 9, 1993. A current version of 40 CFR Parts 257 and 258 should be consulted to determinethe applicable deadline dates for each type and size of municipal landfill. Appendix 12 B gives detailsabout the USEPA – Landfill Regulation.

MSW Rules in India

The Municipal Solid Wastes (Management and Handling) Rules 2000, Ministry of Environment andForests Notification dated 25th September, 2000 Schedule III gives the specification for Land-filling.It covers the various aspects of Landfill from site selection to monitoring. The salient features of theIndian Landfill regulation are given in Appendix 12 C.

12.1.5 Summary and RecommendationsLandfill of MSW relies on methanogenic bacterial activity under anaerobic conditions in a preciselyanalogous way as conventional biomethanation. The difference lies in the relative efficiencies of thetwo processes and the fact that biomethanation of MSW has the primary purpose of producing biogasat maximum yields in a short time frame, and with an enhanced methane content. In contrast,landfilling of MSW is principally a waste disposal method, with incidental advantage of LFGproduction, recovery and use.


Chapter 12-8MWH

One would not therefore tend to place MSW in a landfill for the sole purpose of generating LFG,since the same can be much more efficiently and rapidly accomplished using biomethanationtechnologies. However landfills do exist and this method of waste disposal would continue to be usedin the future also, especially in developing countries. Thus, while MSW can be purposely diverted towaste-to-energy end uses, both existing and future landfills can also be utilised for energy extractionas a subsidiary element of their prime waste disposal purpose. In other words, LFG recovery and usecan co-exist alongside waste-to-energy utilisation of MSW, and essentially, the two options are not insignificant competition with each other, since the available MSW stream is large enough for bothtechnologies.

Maximising the success of LFG exploitation in India will, however, require development of properlyengineered landfills that receive a regular supply of waste with a considerable organic content. If, forexample, the landfill is not properly capped or laterally confined, LFG will be lost by diffusion to theatmosphere, and concurrent ingress of atmospheric oxygen in the landfill cell will destroy thenecessary anaerobic conditions for methanogenesis. Another significant requirement in landfillmanagement is the regular compaction of the waste as it is interred. This removes trapped air withinthe waste and hastens the development of the requisite anaerobic conditions. This, of course,presupposes that an effective waste collection system is in place to maintain a constant supply ofwaste in an appropriate volume.

Neverthelessthese constraints, it is feasible for India to develop an LFG recovery and use programmefrom its existing and proposed landfills. It is also possible to increase its efficiency and output withtime and by paying proper attention to its engineering details. Such a programme will becomplementary to the other waste-to-energy technologies and will not be in competition with thesewaste-to-energy technologies that rely on MSW.

12.2 Composting

12.2.1 IntroductionComposting is the controlled biological degradation of organic material. The presence of moisture andoxygen is essential to assist the aerobic bacterial decomposition process, which results in theevolution of carbon dioxide, and the generation of compost as a end product.

Compost has potential uses in a wide variety of contexts - as a soil additive and/or conditioner, and asa soil surface covering to stifle weed growth and aid moisture retention in soils. Compost can bebeneficially tilled into the soil to aid drainage and to assist the uptake of nutrients by plants. Rootgrowth is also enhanced and less fertiliser application is generally required. Compost can also preventtopsoil loss and thus reduce soil erosion. The use of compost can encompass both commercialagricultural use and in domestic gardens, as well as in municipal contexts such as parks, golf courses,gardens and the like.

On a national scale, the typical organic waste stream contains contributions from backyard domesticsources (grass, tree clippings, paper, etc) together with the more general municipal solid waste(MSW) stream that encompasses food waste, plastics, paper and packaging material, rubber wastes,metallic materials, and an inert component (e.g. soil, concrete, etc).

The analysis of a typical national MSW make-up is relevant to an assessment of the true extent of thatstream which can be diverted for composting. In the following discussion, MSW composting isconsidered, since this gives the most appropriate comparison with a waste-to-energy competingapplication for the same waste resource.


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Other types of composting that may be relevant and which could be usefully compared with waste-to-energy utilisation of the same waste include on-site institutional composting and residential source-separated composting. On-site institutional composting generally includes sewage sludge as acomponent. Residential source-segregated composting requires an intensive educational and physicalresourcing programme so that households separate recyclable non-compostable materials fromcompostables prior to collection.

12.2.2 Composting System and UsageComposting systems range from relatively simple windrows to capital-intensive digester drums.These technologies are necessary to provide more process control (particularly on odour), better-finished product quality and reduced composting time to maximise throughput in a facility.

Mixed waste MSW composting facilities separate MSW into component streams for composting,recycling and landfill disposal of intractables. Odour problems have been a major issue at MSWcomposting facilities and the necessary odour mitigation initiatives (e.g. construction of biofilters)have raised composting costs. Emissions of harmful fungi during the composting process have alsobeen reported. The compost produced by these facilities is often contaminated by metals and glass(even with pre-sorting of wastes), and this reduces the range of application of the compost, its value,and its acceptability in the marketplace.

Mixed waste MSW composting facilities in the United States once appeared to be the panacea forsolid waste disposal problems. The promise was that MSW could be transformed into high qualityproducts with no modification to waste collection systems while greatly decreasing the dependence onlandfilling. In practical terms, mixed waste MSW composting facilities require relatively high costpreprocessing equipment such as trommels, shredders and other size reduction equipment.

A significant prerequisite is to establish markets for the finished product compost. Education isneeded on a significant scale to encourage uptake of compost, both by domestic and commercialusers. There may be negative connotations associated with the presence of foreign matter in theproduct and a view that the material harbours biological health hazards.

In theory, a fully and properly implemented MSW composting programme could utilise the entireorganic waste component of MSW, given that it is appropriately and efficiently collected in acentralised manner via an existing (or latterly established) collection system. This assumes that readymarkets exist for such a large volume of product compost.

Composting programme costs that have been alluded to include a surprisingly high capital cost forequipment necessary for the composting process, land requirements to establish an economicallyviable composting facility, and a single product stream where the final value is rather uncertain andthe market uptake is difficult to predict in advance.

12.2.3 Environmental and Regulatory AspectsEnvironmental issues associated with composting are very significant. While odour is an obviousprimary problem, there are several health issues that are important, including generation of harmfulfungi and implications of infrequent collection of compostable materials that needs to be stored in themeantime. Direct environmental issues relevant for composting include the important realisation thatcomposting does not remove heavy metals and chlorinated compounds during the process, negatingthe use of the product in commercial agriculture.

Net greenhouse gas emissions for composting are lower than landfilling, since composting avoidsmethane emissions, but higher for green wastes where the CO2 emissions in composting are greaterthan the carbon storage credits which are ascribed because of the imperfect degradation of cellulosicmaterials under landfill conditions.


Chapter 12-10MWH

Mixed waste MSW composting, even allowing for pre-composting treatment to remove recyclablesand inert non-compostables, still produces a compost containing contaminants such as heavy metals,chlorinated compounds and dioxins (the latter arise from bleached paper). In the United States thisrealisation has resulted in the withdrawal of support for MSW composting by key environmentallobby groups, such as the Environmental Defense Fund, which were previously vigorous supporters ofMSW composting.

The contaminants inevitably present in MSW compost may, depending on the precise make-up of theoriginal wastes, make the product unsuitable for agricultural uses where crops are grown. This islikely to significantly limit the applications and marketability of MSW compost.

12.2.4 Composting vis-à-vis Energy Recovery from MSWThe composting process can be applied as a waste disposal option for MSW, and the biodegradableorganic material can be converted into compost as an end product that has a potential use as a soiladditive/ conditioner and as bio fertiliser. Both compost and WTE options of waste utilisation arebeneficial, given that desirable (and saleable) products are the end result, and there are also otherbenefits in each case in terms of waste volume reductions, pollution control, and other environmentalbenefits such as greenhouse gas reductions.

A detailed numerical cost/ benefit analysis cannot be readily applied in a general sense to comparecomposting and waste-to-energy applications as competing MSW disposal options because there aresimply too many regional and/or city-specific variables for virtually all the applicable process/ designparameters and considerations.

Compost is also valuable as a covering (“mulching”) agent to negate the growth of weeds and aid soilmoisture retention. Compost use can be widespread in terms of domestic and municipal garden andpark applications, and in commercial agricultural use if transport costs are not a significantimpediment to such use.

The most difficult task is to establish reliable, consistent and long-term markets for the finishedproduct compost. Major public education programmes are necessary (and can be expensive), and thenegative associations of foreign matter and biological health hazards with compost are difficult toovercome in the public mind.

There are direct economic benefits from composting in terms of the avoided costs of disposal ofMSW to landfill (for example). Composting greatly reduces volumes of MSW going to landfill andthis prolongs landfill life. Also, the negative environmental issues associated with landfills such asodour, leachate production, greenhouse gas emissions and vermin are all greatly overcome by thediversion of the biodegradable components of MSW to composting.

Thermal methods of MSW destruction in waste-to-energy facilities like incineration; gasification andpyrolysis have various practical and environmental problems as highlighted earlier. Costs aresubstantial and the sophistication of the technologies is also a significant impediment. Howeversubstantial and valuable energy outputs ensue from each of these technologies.

Biomethanation has much lower associated costs, a reduced degree of sophistication of equipment andis a well-understood technology that requires relatively simple training for operators. The solidresidues have application as compost and the biogas product stream has substantial value for energyproduction. Environmental effects are mostly positive, and in fact, the technology is often applied inthe first instance for pollution control, with utilisation of the product biogas for energy generationbeing a secondary consideration in developed countries.


Chapter 12-11MWH

Table 12-1 presents a summary of the comparable features of sanitary landfilling, composting andanaerobic digestion.

12.2.5 Summary and RecommendationsAdvantages in using compost are in terms of commercial, municipal and domestic applications. As faras composting itself is concerned, there are direct economic benefits in cases where landfilling orother disposal costs are high. These so-called “avoided costs" of disposal represent a significantcomparative reduction in the case of composting against landfilling or, say, incineration where tippingfees may exceed US$100 per tonne.

A composting programme also extends current landfill life and avoids the environmental costs oflandfilling such as for leachate control and methane recovery. In the case of residential source-reduction programmes, where compostables are separately collected, there is a further cost saving byeliminating the need to sort MSW at the composting facility.

Large scale composting of MSW, however, requires significant capital expenditure on equipment,considerable land area requirements and the development of a pre-sorting regime, either at source orat the facility. Operation and maintenance costs are also significant and are not usually comprehendedat first glance.

The saleable value of MSW compost is low. The utilisation possibilities are generally limited on theextent of product contamination. In general, the development of market for compost has proveddifficult in practice, even though pre-implementation surveys have suggested otherwise.

Today, MSW composting has fallen from favour to a very considerable extent in the United States,after a promising start two decades ago. In fact, a wide variety of economic, environmental andmarketability issues, which were largely not understood in the early years of MSW compostingdevelopment, have subsequently come to light and have tipped the balance very much away from thismethod of MSW disposal and utilization. This is an important observation and is of great significanceto any future considerations of composting as a waste resource use in India.

12.3 Fermentation to Liquid Fuels

12.3.1 IntroductionThe conversion of biomass to various alcohols via fermentation is a well-known process that has beenextensively researched and developed over many decades. The most widely produced alcohol isethanol. The predominant use of the product alcohols has been as a transport fuel (Henry Ford’soriginal version of the “Model T” motor car was initially powered by ethanol), although use as achemical feedstock is also important.

The conversion of organic substrates to ethanol and other alcohols requires, firstly, that the cellulosiccomponents be converted to sugars by a suitable process, most usually hydrolysis. The resultingsugars are then fermented by yeasts or fermentative bacteria, to produce ethanol (and sometimes otheralcohols).

The history of the development of fermentation processes to derive ethanol for transport fuel use hasfocussed on agricultural residues, woody wastes and specific crops as feedstocks with the requisitecellulosic content for primary conversion to fermentable sugars.

The fermentation process is now well defined and yields have been optimised in various primaryprocesses. However research and development activities, particularly in the United States, arefocussed on improved bioreactor development, better methods for processing lignin residues from


Chapter 12-12MWH

cellulosic feedstocks, advanced pre-treatments to enhance sugar yields, and product diversification toco-produce non-fuel products such as organic chemicals, as well as ethanol as the principal product.

12.3.2 Fermentation SystemsRecently, there has been increasing interest in the use of MSW (sometimes augmented by the additionof biosolids) as a feedstock for ethanol generation via fermentation. The first commercial facility toutilise this technology has recently been commissioned in Middletown, New York. The facility firstlyrecovers recyclables from the MSW input stream and then mixes the residual organic portion of theMSW with biosolids from the adjacent wastewater treatment plant as a combined feedstock in afermentation process to produce ethanol. The processing capacity is 230,000 tonnes/year of MSWtogether with 49,000 tonnes/year of dry biosolids. The process utilises a proprietary fermentationtechnology to convert the cellulose present in the MSW/ biosolids mixture into sugars and then toethanol.

Development of the project has eliminated the need to design and construct a new landfill for thecounty. The $52 million cost of this has thus been saved, and, although the ethanol facility will cost anestimated $150 million, the project is economically feasible, given the current market price anddemand for ethanol. The plant will have a capacity to produce 7.1 million gallons of ethanol perannum. The primary use of the product ethanol will be as a component of reformulated petrol.

Besides MSW, other non-agricultural feedstocks for ethanol production are under investigation on aworldwide basis. For example, the conversion of whey to ethanol is now well established as aneffective method for treating this difficult cheese production waste, whose BOD poses a major andexpensive disposal problem. The high lactose content of whey makes it a suitable substrate forfermentation to ethanol, or to a fuel alcohol blend of isopropanol, butanol and ethanol.

Synthesis gas fermentation technology is another new process, involving the gasification of waste toform CO/CO2/H2 as “synthesis gas”, and the anaerobic biological conversion of this gas byfermentative bacteria to ethanol. The process shows distinct promise but is currently in thedevelopment stage and is well short of commercial application.

12.3.3 Environmental and Regulatory AspectsFuel alcohols produced in waste fermentation processes can be used as petrol extenders or substitutes;they allow a reduction in vehicle emissions of carbon monoxide and NOx and also enhance the octanerating of the resulting fuel blend.

A further positive potential environmental benefit from alcohol substitution in transport fuels is thatthey remove the need to add methyl tertiary butyl ether (MTBE) as a so-called oxygenate toconventional petroleum-based fuels. MTBE is a suspected carcinogen and is also not readilybiodegraded in the event of leakage or spillage of fuel.

It should be noted, however, that the use of alcohols, particularly methanol or ethanol, as vehicle fuelsrequires a concerted national or at least regional strategy involving the conversion of vehicle engines,and an upgrading of various aspects of the fuel distribution system. There are very significant costsand infrastructural requirements, and the decision to move in this direction is fundamentally a politicalone. Currently the Government of India has not shown a readiness to contemplate such a step.

A further regulatory consideration is that bulk alcohol production facilities require a high level ofsecurity (often imposed via a licensing regime which places strict security demands on the facilitymanagement) because of the possibility of theft of the product.


Chapter 12-13MWH

12.3.4 Summary and RecommendationsApplications of fermentation technologies to waste treatment are in various stages of commercialuptake but these innovative technologies merit a careful and continuing overview to assess theirrelevance and possible application to the treatment of certain waste types under Indian conditions.


Chapter 12-14MWH

Table 12-1. Comparable Features of Sanitary landfill, Composting and Anaerobic digestion

Sr. No. Particulars SanitaryLandfill

AerobicComposting

AnaerobicDigestion

1 2 3

1) Capacity (TPD) 500 500 500

Area (Acres) 100

(for landfillheight of 10m)

13.5 10

Power Requirement (kW) 500 55000 750

2) Process, Whether open to Atmosphere Yes Yes No

3) Segregation of Organic and InorganicMatters Prior to Treatment

No No Yes

4) Process Susceptibility

a) Moisture Yes Yes No

b) Rainy Season Yes Yes No

5) Products

a) Biogas Yes (Up to 8 -10 years)

No Yes

b) Compost No Yes Yes

6) Quality of Product

a) Biogas Quality NA NA 50 - 60%methane

b) Compost Inferior Quality Inferior Quality withpathogens andmetals

Pathogens andmetal free

7) By-products and wastes

a) Recyclables No Yes Yes

b) Rejects No Yes Yes

c) Ashes No No No

d) Pyrolytic Oils No No No

8) Environmental Pollution

a) Green House Gas Emission toAtmosphere

Maximum Moderate Minimum

b) Dioxin and Furan to Atmosphere No No No

c) Odour Nuisance Maximum Moderate Minimal

d) Ground Water Pollution Maximum Moderate No


Chapter 12-15MWH

Sr. No. Particulars SanitaryLandfill

AerobicComposting

AnaerobicDigestion

1 2 3

e) Leachate Generation Yes Yes No

f) Liquid Waste Treatment Requirements Yes Yes Yes

g) Ash with heavy metals No No No

9) Energy Requirements Very low Low Moderate

10) Gas Collection System Complicated Not Required Easy

11) Operation Cost Low Moderate Moderate

12) Commercially Operating Plants on MixedMSW (Indian Types)

Yes (Onlydump yardswithout propergas and leachatecollectionfacilities)

Yes No ( Few Plantsare underexecution)

13) Compliance with Solid Handling Rules2000 of MoEF, GOI dated 25/09/2000

No Yes Yes

14) Environmental Friendliness No No Yes

15) Suitability of Technology for IndianMSW

Yes Yes Yes

16) Choice for Indian Environment in PresentScenario

Yes Yes Yes

(With all necessary precautions)


Chapter 12-16MWH

Figure 12-1. Schematic of a Modern Engineered Landfill


Chapter 12-17MWH

Figure 12-2. Factors Influencing Landfill Gas Production

Precipitation

Site Cover

Atmospheric Pressure

HydrogeologyTopographyAir

INFILTRATION

Ammonium Trace Elements

METHANOGENS

Moisture ContentTemperature Aeration

Concentrated Organic Acids

AcidicSulphate ReducersNitrate Reducers

SulphideChlorinated Carbons

Electron Donors


Chapter 13-1MWH

13 Emerging Technologies

13.1 Potential TechnologiesThere are mainly three emerging potential technologies for waste destruction. Each of thesetechnologies has an accompanying energy recovery capability. These technologies are:

• Plasma pyrolysis,

• Microwave waste destruction, and

• Laser waste destruction.

13.2 Plasma Pyrolysis

13.2.1 Process DescriptionPlasma pyrolysis (also known as plasma arc pyrolysis) is a variation on conventional pyrolysis. It isalso a feasible technology for converting waste in to energy.

While the application of plasma pyrolysis technology for an environmental purpose such as wastedestruction is a relatively new process, the technology itself has been used for decades in the metalsrefining industry. It is thus well proven and has a significant track record. For example, in the UnitedStates, plasma pyrolysis technology has been used for some time as the final step in the destruction ofcertain “special” wastes, including radioactive and hazardous wastes.

This process is distinctly different from combustion (incineration) in that it uses energy from theplasma to thermally convert organic waste from a solid (or liquid) to a gas through a process calledcontrolled pyrolysis or controlled gasification. The constant high operating temperature ensures thedestruction of all complex organic compounds, and the proprietary process controls minimizes thepossibility of reformation of complex pollutants. The escape of volatile metals and acid gases canalso be minimized to levels that can meet the most stringent air emission standards. In cases wherethe organic content of the waste stream is reasonably high, the pyrolysis product gas, composedmainly of hydrogen and carbon monoxide, can be used to safely recover much of the energy in thewaste.

Along with controlled pyrolysis of organic materials, the Plasma system can melt inorganic materialssuch as glass, soil, metals, and ash. These components, common in many waste streams, are meltedand typically recovered as a glassy slag. The glass layer serves as a medium for chemically bindingmany metals in a non-leachable manner through vitrification.

In this technology, the processing chamber is heated to the desired temperature (900 to 2,500 °C)before feeding the waste in to the processing chamber. A feed system is selected based on the wasteform and type, and the waste is fed into the processing chamber on a continuous basis. The plasma arctorch heat source produces a very high temperature plasma gas, with a temperature profile between3,000 and 8,000 °C. At these temperatures the organic materials within the waste rapidly dissociateinto simple molecular constituents, mainly hydrogen, carbon monoxide and hydrogen chloride. Theremaining carbon (a solid) continues in that state until a limited supply of oxygen (usually as steam) isintroduced, at this time it reacts to form carbon monoxide.

The result is a pyrolysis product gas composed of hydrogen, carbon monoxide and some acid gas suchas HCl from the halogen constituents of the waste. Small amounts of other gases are also present,including nitrogen, if air or nitrogen is being used as the plasma “carrier” gas. Some NOx is


Chapter 13-2MWH

consequently formed in the plasma arc of the torch but in the strongly reducing environment of thepyrolysis chamber, most of this NOx is rapidly reduced to gaseous elemental nitrogen.

The pyrolysis product gas formed from the organic waste is transferred to a quench and gas scrubbingsystem where the acid gas is neutralised, and the entrained particulate is removed. The resulting cleanfuel gas (comprising mostly hydrogen and carbon monoxide, with traces of methane, ethylene andacetylene) is available for use as a fuel for steam or electricity generation.

Inorganic constituents in the input waste melt in the processing chamber to form a glassy moltenliquid that also comprises any metals present in the input waste. This molten slag accumulates in thebottom of the processing chamber. It can be recovered, as a vitreous solid that is essentially doesn’tproduce leachate.

Different types of waste will generate different product gas and slag characteristics. Input wastes witha high carbon content and a high percentage of non-volatile material will produce gaseous and solidproduct streams, very similar to those from municipal solid waste. Other waste materials, such asbiomass, liquid wastes and organic wastes will produce hardly any slag since virtually all of the wasteis gasifiable.

Pyrolysis versus Incineration

The Plasma Thermal Conversion of Waste process achieves almost a total destruction of simple andcomplex organic materials in an eco-friendly manner. The comparison between the incineration andplasma process system is given in Table 13.1.

The waste is destroyed by the molecular dissociation of the feedstock through a reduced oxygenenvironment (i.e. pyrolysis), and the heat that causes the pyrolysis is provided by an electric arc.Within the processing chamber, where the waste is fed and destroyed, thermal oxidation (i.e.combustion) will not occur. The process is essentially endothermic. By comparison, "starved-air"incinerators, which some may claim to be similar “pyrolysis systems, require combustion of afeedstock and/or supplementary fossil fuel from which to derive the energy to drive the process.

The combustion process is an oxidizing process and thus there is a significant potential for freeChlorine to form dioxins and furans, while the pyrolysis process is chemically reducing, convertingvirtually all of the liberated chlorine to hydrogen chloride (HCl). The Plasma (chemical dissociation -pyrolysis) process achieves destruction and removal efficiencies that are far better than incineration,without the typical by-products of incineration (see Appendix for comparison of Plasma ThermalConversion emissions with other technologies). The Plasma system is also typically much smallerand generates a much smaller volume of process gases (that require cleaning) than a comparableincinerator.

Project Economics

The possible cost that can be incurred and revenue that can be generated while implementing a typical500 TPD plasma based combined cycle power plant is given in Table 13.2. This plant will produceapproximately 500 MM BTU/hr (126 million kcal/hr) of syn gas energy (when used in a combinedcycle power plant, this could generate approximately 55 MW).

13.2.2 ApplicationsThe following are examples of pilot-scale or commercial applications of plasma pyrolysis technologyfor waste-to-energy.


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Plasma based MSW to Energy Plant, UP, India

M/s Terrasafe Technologies Private Limited has proposed to implement of projects under Non-Conventional Energy development Agency (NEDA) of UP, a state body under the Ministry of Non-conventional Energy Sources (MNES), to dispose MSW at Agra and Allahabad.

MSW Destruction, Lumpkin County, Georgia, USA

A 50 tonnes/day plasma pyrolysis waste destruction system is now in operation. The operatingtemperature is 3,900 °C and the unit achieves a 98% reduction in waste volume. By-products areclaimed to be simple gaseous hydrocarbons (principally methane), steam and a vitreous slag. No pre-treatment or segregation of waste is required. Economic data are unavailable but this plasmapyrolysis option was selected as environmentally preferable to landfilling or conventionalincineration.Source: www.solidwaste.com

Startech Waste-to-Methanol Plants

The Startech plasma pyrolysis converter produces a vitreous solid slag and a synthesis gas which isconverted to methanol. The yield of methanol is claimed to be 600 litres per tonne of processed wastetyres. Other kinds of waste have also been disposed, including MSW. No cost information isavailable.Source: www.startech.net

Plasma Pyrolysis with Vitrification (PPV), Lubsko, Poland

Plasma pyrolysis with vitrification is applied to MSW at 2,000 °C, with the addition of steam toaccelerate the process. A highly energetic synthesis gas is formed, comprising 80% hydrogen/carbonmonoxide. The Lubsko facility treats 50,000 tonnes/year of MSW and produces 12 MW ofelectricity, 4 MW of heat and 45 tonnes/year of ethanol. No other details are available.Source: www.is.pw.edu.pl

Global Plasma Systems Group, Washington DC, USA

GPSG utilise plasma pyrolysis technology to treat a wide variety of wastes. The primary purpose isdestruction of special, particularly hazardous wastes.Of late emphasis has also been placed on energyrecovery via the synthesis gas produced in the pyrolysis process. The reactor size is claimed to be 30times smaller than for a similar through-put incineration system. No pre-processing or sorting isrequired.Source: www.globalplasmasystems.com

13.3 Microwave Waste Destruction

13.3.1 Process DescriptionMicrowave destruction of certain wastes is emerging as a novel waste-to-energy technology. Thepatented “Reverse Polymerization” process reduces organic waste to carbon residues in a combustion-free environment, along with the production of hydrocarbon gases and oils as useable by-productswith energy generating potential. “Reverse Polymerization”, conducted in the relatively lowtemperature range of 150 – 350 °C.

The general process involves the following stages:

• Oxygen purging via nitrogen flushing

• Microwave reduction


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• Environmental control of gaseous emissions

• Handling of discharged residue materials

In the “Reverse Polymerization” process oxygen is purged and the organic waste enters themicrowave reduction chamber. Microwave energy causes molecular excitation, which ultimatelybreaks chemical bonds to depolymerise long-chain hydrocarbons.

13.3.2 ApplicationsThe process has been applied to medical waste and waste tyres, as these are difficult-to-treatMicrowave treatment of tyres yields hydrocarbons as simple gaseous molecules and oils, high qualitycarbon black (amorphous carbon) and steel (from tyre reinforcing wire). The tyres are moved on aconveyor through the microwave reduction chamber where microwave energy is applied.Hydrocarbon gases are drawn off and passed through a condenser to remove the oil components. Theremaining hydrocarbons are directed to a scrubber to remove hydrogen sulphide, before beingrecovered as a gaseous fuel. The gas and oil can be used for power production via a steam or gasturbine, or by direct feed as a supplemental fuel into other combustion equipment.

A commercial system in operation in Canada processes 6,000 tyres per day and is capable of 5.5 MWof gross power generation. Approximately 50% of this power is used to run the plant, with the other50% available for sale.

In the case of microwave destruction of tyres there are up to five revenue components, which mayoffset the capital, operating, and maintenance costs of the technology. These are:

• Fees for landfill disposal of scrap tyres

• Generation of electric power from the simple gaseous hydrocarbons produced in themicrowave destruction process

• Sale of carbon black for use in printing ink or rubber manufacture

• Sale of scrap steel wire

• (Possibly) carbon credits because of the reduction of greenhouse gas emissions via thisdisposal method

13.4 Laser Waste Destruction

13.4.1 Process DescriptionLaser waste destruction (LWD) technology is an emerging technology, which can be used for treatingboth liquid and solid wastes. This technology causes the destruction of solid and liquid waste matterand converts the by-products into a pyroclastic material without discharging pollutants into theatmosphere. A CO2 laser is usually used and this emits coherent electromagnetic radiation, whichbreaks down the components of the waste at a molecular level. In this process energy and additionalcoherent electromagnetic radiation are derived. The resulting pyroclastic by-product material containssufficient hardness and inert, which can be used in the manufacture of bricks and bedding material forroads. The LWD system is usually coupled with Thermal Energy Production (TEP) System for co-generation technology. Thus, leading to generation of electric power on an environmentally friendlybasis.

When laser rays of sufficient intensity irradiates waste material, a highly ionized gas or plasma isformed by vaporization of the material. Any toxic compounds, which are released into the plasmafield, are completely destroyed at the typical operating temperature range of 4,000-5,500°C. The


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reactor is a fully sealed unit and does not vent to the atmosphere, thus eliminating the risk of anyundesirable NOx, sulfide or any other emissions.

The LWD system uses CO2 laser to break down the components of the waste to a molecular level inthe reaction chamber. The highly ionised plasma passes into a secondary chamber in the reactor whereit is subjected to the same energy beam emitted from the laser, by means of a beam splitter. Thefurther reactions that occur raise the temperature in the secondary chamber to levels, which exceed3,500°C. Silica is then added to the reaction chamber where it becomes molten. The remaining solidsand silica mix form a glass-like binding material. This vitreous slag produces a solid inert mass fromwhich any bound contaminants cannot be leached.

The gas that passes from the primary reaction chamber into the secondary chamber is ionized bymeans of an ion generator. Sufficient space charge is produced in this reaction to capture solidparticles that may have escaped the cyclic process. Thus, any particulates from the reactor chambersare effectively removed at this stage. After the completion of ionization the plasma field, formed dueto the combination of laser and electromagnetic radiation and the product material, is sustained byrecycling of sensitized air back to the primary chamber. The end result is a 98% solid waste withminimal measurable emissions. Figure 13-2 gives a process description of the technology.

13.4.2 ApplicationsThe LWD system breaks down complex organics into simple compounds with the evolution of heat,which in turn can be captured, recycled or converted into steam. The steam can either be sold toindustry for heating or for electrical generation. Electricity generation can be done using a steamturbine generator system. Most units can produce at least as much electricity as is required to run theLWD system, and the addition of a TEP system is specifically designed to produce power for sale.Co-generation of electricity and steam production are the saleable by-products of the system andprovide excellent profit potential.

13.5 Potential of Emerging TechnologiesThe three emerging technologies of Plasma pyrolysis, Microwave waste destruction, and Laser wastedestruction could be described as “fringe” technologies at present. However, they are promising inconcept and application and warrant close scrutiny in the next few years in terms of their uptake in thewaste-to-energy arena worldwide.

This is another area where India can allow other countries to implement, develop and “debug” newtechnologies until they reach a point where the risks are reduced and technological difficulties areironed out. On the other hand, it may be that the impediments prove insurmountable, and thetechnology is no longer worth pursuing and cannot be considered for Indian applications. However aclose watch must be maintained on these (and other) technology types and sub-types. India should beready to apply those technologies, which are finally proven in economic, environmental and technicalterms.

13.6 Summary and RecommendationsPlasma Pyrolysis

The plasma pyrolysis process for waste destruction creates harmful byproducts or emissions. Both thesyn gas and the inert solid slag can be beneficially used. The process is thus a totally enclosed wastetreatment system.


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Treatment of mixed wastes using plasma pyrolysis process is efficient and versatile and achieveswaste volume reductions to the order of 200 to 1. In contrast, incineration can achieve, at best, a 10 to1 waste volume reduction.

Moreover, the reducing conditions within the plasma pyrolysis process do not lead to the productionof dioxins, unlike incineration (which is an oxidising process).

Earlier applications of plasma pyrolysis concentrated on using the technique for special wastesdestruction with high efficiencies and minimum emissions. More emphasis is now being given toproduct synthesis gas utilisation. It is now expected that a greater commercial uptake of the Plasmapyrolysis process will take place and significant experience about it will be gained in the next fewyears.

Currently, capital cost of the plasma pyrolysis is high but O & M cost is relatively low since thesystem has only a limited number of moving parts. Over time and with increasing uptake of thetechnology, capital cost per unit is expected to reduce significantly.

Microwave Waste Destruction

No definitive information is available about economic considerations relevant to the process ofmicrowave waste destruction. However, it is clear that this technology has positive benefits for thetreatment of two difficult waste types, namely medical wastes and tyres. The net energy that can beexported to the grid and the less emissions are the attractive factors.

There are now patented processes in which microwave energy is used for the destruction ofhazardous, infectious or otherwise intractable wastes, but without energy recovery. It is also likelythat the process will become applicable to a wider range of wastes. However, these applications mayin turn refine the technology in terms of its potential future waste-to-energy applications. Thus a closewatch needs to be kept on the further development of this technology.

Laser Waste Destruction

The cost of installation, maintenance and operation of the Laser Waste Destruction and ThermalEnergy Production is claimed to be well below that for incinerator facilities of similar capacity.

Heterogeneous wastes or wastes with low combustion energy cannot be efficiently burnt in anincinerator to generate energy, but they can be utilized as a fuel source for these LWD systems.

Control of off-gas and air pollution is also different in the LWD system. In an incinerator, excessiveair is used to increase the mixing and thus improve combustion efficiency, decreasing thermalefficiency. In an LWD system, the off gas is ionized in the photon reaction chamber, thus reducingemissions to oxygen and carbon dioxide at concentrations, which are below EPA standards.

The laser waste destruction technology is new and has not yet been widely adopted. However it showsenough promise to merit continued monitoring of its future commercial success.


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Table 13-1. Comparison between Incinerator and Plasma Thermal Conversion.

Common Incinerator Plasma Thermal Conversion SystemFlame Temperatures 1650oC – 1930oC Torch Plume Temperatures at centerline:

5500oC – 9,000 CThermal Chamber Temps – 980oC to 1370°C Thermal Chamber Temps – 900°C to 2,500°COutputs:

- Residual bottom ash and fly ash- Nitrogen Oxides- Particulates and other air emissions

Outputs:- Benign Silicate – glass Aggregate or- Recoverable metals- Syn Gas (i.e. CO and H2)

Significant Oxygen required – virtuallyeliminating the ability to generate synthesis gas

No Oxygen required, synthesis gas productionefficiency of 80 to 90%

Burns large amounts of fossil fuel No fuels of chemicals – can generate its ownelectricity effectively

Requires large land area for infrastructure andgas scrubbing

Compact system

Table 13-2. Typical Project Costs for 500 TPD Plasma based Combined Cycle PowerPlant

Project Item Cost in INR CroresWaste handling/plasma gasification and syn gas processing 113.57Buildings/site infrastructure and power generation plant 220.59Preoperative Expenses 66.1Contingency (15%) 19.45Total project cost 419.70


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Figure 13-1. Tyre Reduction System-Single Microwave Destruction Line

Inclined TyreFeed


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Figure 13-2. Schematic of Laser Waste Destruction Process

Waste Fuel

Solids Produced - Primarily Carbon

Plasma Field Caustic Soda Scrubber

Electrostatic Precipitator

Gas Broken down to Lighter ElementsSilica Added

Liquification Occurs

Silica combines with Carbon to form Silicon Carbide

Elements RecombineWater bath

Gas Air MixerIonization

Gas Flow to 2nd ChamberCOOL WASTE

Particulate Recycle Co-Generation Steam Turbine Plant


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14 Assessment of Municipal Solid Waste -to-EnergyTechnologies

14.1 IntroductionAn overview of major Waste-to-Energy technologies was presented earlier in chapters 8 to 13. Thesechapters covered biomethanation, incineration, gasification, pyrolysis, and some novel technologies atvarious stages of development besides a review of some alternative waste disposal practices such ascomposting. The latter could be in competition with or may simply be complementary to waste-to-energy options.

Technologies for viable WTE processes are based either on thermal or biological methods forrecovering the energy potential of various urban and industrial wastes. Many proprietary systems areavailable for energy recovery – incineration processes for wastes with adequate calorific value tosustain combustion reactions, gasification and pyrolysis technologies for MSW and other specificindustrial waste types, and anaerobic digestion processes for recovering the biochemical energypotential in the form of biogas. Energy recovery as electric power or as a fuel is a feature of all waste-to-energy systems. All these systems generally involve significant capital and recurring costs.Matching the quality and amount of waste to be processed with an appropriate technology packagerequires diverse expertise and skills in materials management, engineering, finance, judiciary,statutory regulations, besides ecological and socio-economic aspects.

Any one or all the technologies: biomethanation, gasification/ pyrolysis or incineration may beapplicable for a solid waste stream such as MSW with a significant organic content and energypotential. A checklist of physical, chemical and biological properties of MSW generally consideredfor preliminary process selection is given in Appendix 14 A.

All the properties listed in Appendix 14-A are useful in the selection of a process technology(biological or thermal) and for the specification of equipment and accessories for material separationand recovery during pre-treatment of MSW. Chemical properties such as proximate and ultimateanalysis and calorific value are required for a detailed mass and energy balance calculations of allthermal (incineration and gasification/ pyrolysis) processes besides specification of down stream airpollution control system. The calorific value and biodegradable fraction of MSW are relevant forestimating the energy recovery potential of that particular waste.

It is also important to recognize the differences in the quantity, physico-chemical characteristics andseveral other attributes associated with urban and industrial wastes while estimating the energypotential. The industrial wastes (solid or liquid) tend to be more uniform in characteristics (even-though no two plants in general produce identical wastes) and readily available at the site itself for aproposed WTE project. Urban wastes are generated across the city, requiring an elaborateinfrastructure for the collection and transportation of wastes to the proposed WTE facility. The scaleof operations in case of urban waste is also large when compared to industrial waste. Consequently,the urban and industrial WTE opportunities must be considered separately to evolve an appropriate setof evaluation criteria in the two cases.

Among the technologies for energy recovery from urban solid waste (MSW), thermal incineration andlandfill have a long track record of more than two decades. The nineties have also witnessed thesuperior techno-commercial features of gasification processes and a gradual shift away fromincineration systems. A wealth of information is available for the different technology options. This isused as the basis for a technical review of the salient features and an assessment of their relativeranking in the global context.


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Several viable WTE technologies have been implemented during the past two decades with full scaleoperating installations for various industrial process wastewaters. Detailed process information/ dataare not readily available owing to the proprietary nature of many of these applications.

Significant progress has also been achieved during the nineties for exploiting the biochemical energypotential of domestic sewage (MLW) through biomethanation processes with several full-scale plantsare operating successfully worldwide. Since MLW is a dilute waste, no other technology would berelevant as a WTE option.

14.2 Evaluation CriteriaA list of criteria useful for a preliminary evaluation and selection of WTE technologies was presentedin Chapter 8 (section 8.4). This section carries these themes through for developing a set oftechnology evaluation criteria, with both qualitative and quantitative comments on various factors.This involves a numerical ranking system by assigning individual numerical ratings, based on therelative importance of the various factors that can be appropriately incorporated in the analysisprocess.

A list of criteria and ratings form the basic framework of the evaluation checklist has been developedfrom a fully factual basis to the extent possible. (Nevertheless it is possible that some readers willhave a different view on some of the evaluation criteria and on the rankings and weightings given tospecific criteria in this analysis. It is also equally important to recognize that arbitrary rankings haveno place in this evaluation process). The evaluation criteria must be regarded as a convenientscreening tool to enable an assessment of the appropriateness of the technologies. In any one casethere may be less tangible factors that may tend to disqualify or to intervene to make a particulartechnology relevant. Each criterion has been assessed based on both the tangible and intangibleaspects to reflect the individual merits.

All the four promising Waste-to-Energy technology options are considered together with theindividual range of values for quantifying the relative contribution of each factor. The technologiesincluded in this WTE evaluation consist of biomethanation, landfill with gas recovery, gasification/pyrolysis and incineration. This assessment also includes composting for the purpose of comparisonas a waste disposal option for MSW. This analysis will allow an assessment of the suitability of atechnology for treating MSW.

WTE technology options have been analysed using a set of five main evaluation criteria: SystemConfiguration, System auxiliaries, Environmental Aspects, Resource Recovery and CommercialAspects. A uniform and unbiased numerical ranking (0-30 points) is assigned to each of these criteriafor the initial analysis. A maximum of 150 points can be scored by any technology in terms of ajudicious rating of the various input criteria as follows:


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Points %

SystemConfiguration

30 20

SystemAuxiliaries

30 20

EnvironmentalAspects

30 20

ResourceRecovery

30 20

CommercialAspects

30 20

Total 150 100

Each of the above main criteria is also analysed using a set of sub-criteria. The relative significance ofthe latter is represented by an appropriate relative numerical assessment as enumerated below for eachmajor criterion. Table 14.1 gives the complete list of all the main criteria and sub-criteria used intechnology evaluation.

System Configuration (0-30)

This criteria comprises of simplicity and operability, process flexibility and scale-up potential as sub-criteria and these are assigned a numerical rating of 0-12, 0-12 and 0-6 respectively.

Simplicity & Operability: A general rating of total system and accessories has been done, , besidesoperational aspects such as manpower, skill levels, automation versus manual inputs, resources used,etc.

Process Flexibility: Represents the ability to cope with fluctuations in waste composition, waste load,interrupted supplies, process upsets and turn down capability.

Scale-up potential : Represents the modular nature of process equipment and system.

System auxiliaries (0-30)

This criterion comprises of the relevant pre-treatment and post treatment components of the WTEfacility and assigned a numerical rating of 0-20 and 0-10 respectively.

Pre-treatment: Recovery of valuables - plastics, iron (metals), etc. from the wastes and to obtain thedesired proportion of organics in the feedstock for energy recovery.

Post treatment: It involves downstream cleaning of LFG/ biogas/ incineration/ gasification processgases. Product upgrading viz saleable compost, dewatering/ stabilization of sludge frombiomethanation plants, landfill leachate treatment and ash residues from thermal processes.

Environmental Aspects (0-30)

Environmental impacts are considered in terms of air emissions, ground water and surface watercontamination, Green House Gas emissions (GHG), health/ welfare considerations and residual waste


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disposal. Each of these sub-criteria is assigned a maximum score of 6 points for a cumulative score of30 points.Resource Recovery (0-30)

This is an important criterion in evaluating the relative energy potentials and the recovery of by-products i.e. compost and valuables. These are given a numerical score of 20 and 10 pointsrespectively.

Commercial Aspects (0-30)

This criterion comprises of capital cost, O&M cost and track record, this criterion is assigned amaximum score of 12, 12 and 6 points respectively.

Capital cost: It includes cost of the following:

i) all equipment used for material recovery during pretreatment and post treatment (products/ byproducts);

ii) main process equipment (Bioreactor/ Incinerator/ Gasifier and all accessories (up-stream /down-stream));

iii) turbine/ engine for power generation; and

iv) all infrastructure facilities (onsite/ offsite)

Operational cost: It will include various components for successful and sustained operation of thefacility such as manpower, material, spares and supplies, utilities, financing, working margin,overheads and other related expenses during break downs and shut downs.

Track Record: This refers to technology status and operating installations through out the globe.

The relative weightages of technical and environmental factors together represent 60% of the totalassessment points. The cumulative assessment of all the sub-elements of the commercial aspectsrepresent 40% of the total score (150 points) and highlights the significance as a prospective WTEtechnology.

14.3 Technology AssessmentAn evaluation checklist with the ratings for the different main and sub-criteria for the competitiveWaste-to-Energy technology options of biological processes (biomethanation, landfill, composting)and thermal processes (incineration, gasification/ pyrolysis) is given in Table 14.2. This table includescomposting primarily as a waste disposal option for MSW. Several evaluation criteria are relevantindividually for each technology as a WTE option and the scores assigned for each of these influencesare shown in Table 14.2. The logistics in assigning a particular rating for each sub-criteria is discussedin the following section:

A. System Configuration (0-30)

1. Simplicity and Operability (0-12)

Simple systems such as landfill with gas recovery and composting with less skill requirements, lowman-power needs and requiring mainly manual operation and low resource inputs will score high(12). Others like incineration and gasification processes with elaborate accessories (downstream/upstream) and process instrumentation/ process control and significant operability issues (e.g. high


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energy and skill requirements, considerable automation, etc) will score low (4). Moderately complextechnologies such as biomethanation is assigned an intermediate score (8).

Facilities for biomethanation are generally simple in design, with relatively few moving parts and awell-established range of standard equipment. Man-power requirements are not very demanding andsemi-skilled personnel are adequate for routine operation and maintenance. However, it is imperativethat the operators undergo necessary training to recognize the onset of adverse conditions leading toprocess upsets and a sour reactor condition, ultimately leading to failure of the bioreactor. Theevaluation rating for this parameter is set at a high score of 12.

Facilities for landfilling are generally simple in design and consist of sanitary lining, LFG collectionsystem, gasholders, LFG utilization unit, Leachate collection and treatment systems. The requirementsare relatively “low tech” have a positive influence on cost structure. Landfilling will not require highskill levels for the simple operations such as unloading, spreading, rolling and covering. Theevaluation rating for this parameter is set at a high with a score of 12.

Facilities for composting are relatively very simple with windrows or with digester drums. This aspecthas accordingly been assigned a high score of 12.

Incineration systems are generally elaborate with complex equipment and associated pollution controlsystem. Successful operation of the total system will also require a sophisticated instrumentation andprocess control system and skilled manpower. A score of 4 is considered appropriate for this option.

Gasification/ pyrolysis technologies are also highly complex in technical features requiring skilledmanpower and assigned a low score of 4.

2. Process Flexibility (0-12)

Technologies such as landfill with gas recovery that can cope with load, waste type, processdisruptions, etc score high (10). Technologies such as incineration and gasification/ pyrolysis withstrict operational parameters (such as design constraints, physical operating requirements, etc) willscore low (4); those susceptible to at least some disruptive aspect score Low score.

Biomethanation is susceptible to process upsets, and it is necessary to maintain a strict anaerobicenvironment to sustain methanogenic activity. This is assigned an intermediate score of 8. Theprocess flexibility of composting also has been rated as intermediate (8) in view of the long periodsrequired.

Landfilling as a process has an advantage as far as process flexibility is concerned - there is no majorprocess upsets. The methanogenic activity responsible for LFG generation depends entirely on theclimatic conditions of the landfilling site. This parameter has therefore been rated with a high score of(10).

3. Scale-up Potential (0-6)

For truly modular technology types, this parameter will be given a maximum score (6); where thereare some scale-up issues then a low score of (4) will be relevant.

Biomethanation plants can be designed and constructed as modular units for future scale-uprequirements as also the thermal process systems – incineration or gasification.


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Scale-up can be a limiting factor for an existing landfill or composting site. This evaluation parameteris given a rating of 4, since new facilities are unlikely in the present socio-economic scenario.

B. System Auxiliaries (0-30)

4. Pre-treatment (0-20)

The technology, which requires less pre-treatment can score high (16), while an elaborate system willscore low (8). In practice all technology types will require pre-treatment to match process needs .Scores are thus based on the extent of pre-treatment required and will range from 8-16.

It is necessary to treat MSW prior to biomethanation by removing recyclables such as plastic, glassand metals besides inert by size reduction, screening using suitable equipment. For biomethanationtechnology this parameter has been assigned an intermediate score of 12.

The present trend in the U.S., U.K. and other EU countries is to recover all the valuables and reducethe quantities of waste destined for landfill. Consequently, with limited land availability, pre-treatment can become a necessary sequence of unit operations for material recovery. Hence a lowscore (8) would be relevant. Composting will require pre-treatment to remove the recyclable materialto obtain a saleable product. This aspect is accordingly assigned an intermediate score of 10.

Pre-treatment requirements are generally well defined for both the thermal options of incineration andgasification/ pyrolysis due to the need to remove both moisture and inert materials from MSW.Accordingly they are assigned a low score (8).

5. Post-treatment (0-10)

A intermediate score (6) has been assigned to all the technologies, The gas and by-product producedby all these technologies need a post treatment.

Biogas requires H2S scrubbing prior to use as boiler/ engine fuel. The residual sludge also requiresdewatering and stabilization by composting. LFG will require clean up for odour constituents such asH2S and hydrocarbons besides leachate treatment. The final compost with a poor off-take will requireupgrading to improve its quality as a fertilizer to improve its marketability. Downstream clean up ofincineration flue gas for environmental compliance will be elaborate and costly, besides the disposalof ash residues as a hazardous waste or for reuse. Syngas will also require moderate treatment prior touse as fuel and the disposal of ash/ slag residues will also require a post treatment before disposal.With similar downstream add-on treatment needs, all technologies has been assigned a low score (6).

C. Environmental Aspects (0-30)

6. Environmental Impacts (0-30)

Environmental impact considerations are very important in technology selection and have been ratedon a 0–30 scale. This complex parameter will have a high score (25) with fewer environmentalexternalities. If one or more environmental issues count strongly against a technology type then a lowscore has been assigned (5). With some negligent environmental impacts a technology type hasassigned an intermediate rating (15).

The biomethanation process generates biogas, which can be used as a boiler fuel or for powergeneration. Greenhouse gas emission parameters are thus positive and the availability of the reactorresidues as a stabilised compost for agricultural, municipal or residential reuse is generally positive.Biomethanation is, therefore, assigned a high score of 25.


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The landfilling process generates LFG, which is used as a boiler fuel or to produce electricity.Greenhouse gas parameters are positive but there is a very high possibility of ground and surfacewater contamination due to leachate and runoff. The matter of environmental impacts is verysensitive, with landfilling being given an intermediate score of 15.

The process requirements for composting are relatively “low tech” but associated odour problems canbecome a major issue at MSW composting facilities, and the necessary odour mitigation measurescomplicate the process. Development of harmful fungi during the composting process has also beenreported. Consequently an intermediate score of 15 is given for this parameter.

Emission control technology is now available to meet increasingly stringent environmental standardsfor fine particulate atmospheric emissions in Europe and the United States but the extremely high costof this additional equipment makes incineration an increasingly marginal waste-to-energy technology.Fewer new units are being constructed in these countries and many existing facilities have beendecommissioned, or else expensively retrofitted. In the United Kingdom, for example, incineration isno longer supported under incentives for waste-to-energy projects. The negative assessment of allthese aspects for incineration gives it a low score of 5.

Gasification/ pyrolysis technologies have positive environmental connotations, being very low interms of gaseous emissions and producing limited solid waste residues that are inert and which can beencapsulated, if necessary. This assessment, therefore, provides an intermediate score of 15 for thisparameter.

D. Resource Recovery (0-30)

7. Energy and By-products (0-30)

Energy recovery efficiency places the technology types in the order of gasification (20), incineration(16), biomethanation (16), landfill (12) and composting (0). Likewise the residual product generallyhas a low value in all the cases and assigned a low score (4).

Energy recovery in the form of biogas is reasonably high, being equivalent to two-third of the energypotential of the biodegradable constituents of MSW. A total score of 20 has been assigned forbiomethanation.

The full biochemical energy potential of the compostable organic fraction of MSW disposed inlandfill site is not realized. A landfill is also not productive for the initial period of three to five years.The quantum of LFG generated beyond a useful period of 15 to 20 years also tends to decrease. Theseconsiderations entail a total rating of 12 for this technology, since there are no saleable residues.

The energy recovery potential of composting process is nil, and this technology scores a low of 4points from the sale of compost.

Energy recovery potential of incineration process is relatively comparable to biomethanation processand hence this parameter is assigned a score of 20. Likewise gasification yields the maximum energyrecovery and hence this parameter has been assigned a high score of 24.


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E. Commercial Aspects (0-30)

8. Capital Cost (0-12)

Where capital costs are low a technology type achieves a high score (10); compared to a low score of4 for technologies with elaborate equipment.

The all-round cost structure for biomethanation is moderate. Hence it is assigned an intermediatescore of 6. The capital cost structure for landfilling will be relatively less and land costs will be veryhigh, and so merits a low score of 4.

Composting costs would also entail high capital for equipment, and land requirements to establish aneconomically viable facility. Hence a low score of 4 is relevant on these accounts.

Capital costs for waste-to-energy incineration equipment and the associated pollution control systemare very high and consequently, assigned a low score of 4. The capital costs for gasification/ pyrolysisare also relatively very high and have been assessed at a low score of 4.

9. Operation &Maintenance (0-12)

With normal O & M considerations all technology types will achieve a high score (10). Technologieswith major issues of maintenance to sustain routine operations are rated low (4) and the technologieswith moderately complicated maintenance and operational issues will score an intermediate score of6.

The relative simplicity of biomethanation systems means that mechanical maintenance will not be asignificant issue, except perhaps during mechanical breakdowns and this factor has been assigned ahigh score of 10 points. A wide range of day-to-day operations is required for the efficientperformance of a landfill, which will be a significant issue. Break down of the LFG system wouldmean that maintenance becomes a sensitive issue requiring immediate attention. All these issues leadto assign an intermediate score of 6. A low rating of 4 is considered appropriate for composting owingto the fluctuating quality of the finished product compost. A low score of 4 is given for incinerationprocess owing to the significant maintenance requirements associated with process control andinstrumentation and skilled manpower needs. The pollution control cost of the gasification system isrelatively low and an intermediate score of 6 is assigned to gasification technology.

10. Track Record (0-6)

Technology types such as biomethanation, incineration and landfill with gas recovery with well-proven international track records of uptake and performance score high (6); and emergingtechnologies such as gasification score low (3) as also the ones with low public acceptance such ascomposting.

14.3.1 Technology ScoresBiomethanation technology scores an overall rating of 107 out of 150, i.e. 71% with technical (systemconfiguration and system auxiliaries), commercial (resource recovery and commercial aspects) andenvironmental factors contributing 40, 42 and 25 points respectively.

Landfilling technology scores an overall rating of 83 out of 150, i.e. 55% with technical (systemconfiguration and system auxiliaries), commercial (resource recovery and commercial aspects) andenvironmental factors contributing 40, 28 and 15 points respectively.


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Composting technology scores an overall rating of 70 out of 150, i.e. 45% with technical (systemconfiguration and system auxiliaries), commercial (resource recovery and commercial aspects) andenvironmental factors contributing 40, 15 and 15 to the assessment total score.

Incineration technology scores an overall rating of 67 out of 150 i.e. 47% with technical (systemconfiguration and system auxiliaries), commercial (resource recovery and commercial aspects) andenvironmental factors contributing 28, 34 and 5 points respectively.

Gasification/ pyrolysis technology scores an overall rating of 80 out of 150 i.e. 53% with technical(system configuration and system auxiliaries), commercial (resource recovery and commercialaspects) and environmental factors contributing 28, 37 and 15 points respectively.

14.4 Technology RankingThis detailed analysis delineates a comprehensive global picture of the status of the four technologyoptions for energy recovery from MSW, and a comparison with composting as a technology forbeneficial waste reuse. A summary of the technology level score is given in Table 14.3. The overallscores for the various technology options are in the order of 107, 83, 80, 70 and 67 out of 150 forBiomethanation, Landfill with gas recovery, Gasification/ pyrolysis, Composting, and Incinerationrespectively. Accordingly, the overall ranking for the five options considered in this assessment aregiven below:

• Biomethanation (Rank 1)

Biomethanation as a WTE technology option ranks first. Biomethanation has several advantages overall the other technologies with a good track record and less environmental impacts. Biomethanationhas emerged as a mature and preferred WTE technology on a global basis.

• Landfill with gas recovery (Rank 2)

Landfill with gas recovery system ranks second due to system simplicity and a long track record withgood control of atmospheric emissions and lechates, even though it has a low energy recoverypotential.

• Gasification (Rank 3)

Gasification/ pyrolysis processes have emerged as a distinct third choice as a WTE technology withseveral superior attributes compared to incineration.

• Composting (Rank 4)

Composting has failed as a technology option for the disposal of MSW in the North American andEuropean countries with very poor public acceptance.

• Incineration (Rank 5)

Incineration technologies have a long track record with numerous installations world wide forhandling urban and industrial wastes. The recent focus has been on elaborate environmentalcompliance, which has become a very costly option. Incineration technologies have slipped to thefifth position according to this study owing to the competing features of gasification technologies.

14.5 Emerging Global TrendsBiomethanation is positively favored as a mature WTE technology for urban and industrial waste.


Chapter 14-10MWH

Landfill with gas recovery systems have been widely used in developing countries for over twodecades having overcome the concerns associated with atmospheric emissions and leachates, now thatthere are adequate controls in place. The present emphasis is on material recovery facilities withlimited land availability for new LFG facilities in the urban centers and the fast filling up of the sitescurrently in use. This would require only a limited quantity of recalcitrant waste to be sent to landfillsas a repository. The present US and EU directives do not favour any new sites for landfilling. Securedlandfill sites are also required for the ultimate disposal of hazardous wastes at most of these locations.Consequently landfilling will not be a relevant technology option for the disposal of MSW.

Incineration is a mature technology for energy recovery from urban and industrial wastes and hasbeen successfully commercialized in the developed countries, and has a good track record. However,the recent focus has been on environmental compliance, tending to make the capital and operatingcost of the total system very high.

Gasification processes, which rank third in the current evaluation, have the potential to move higherin the hierarchy as this technology matures with an increase in the number of installations worldwide.Additional factors contributing to this potential upswing are the current trends of a shift away fromincineration and landfilling as preferred technology options in the developed countries.

Based on the major findings of the technical evaluation of this study and the present trends indeveloped countries, biomethanation and gasification are emerging as two major competing optionsfor energy recovery from MSW.

14.6 Relevance to IndiaThe ranking of the WTE technologies can be considered to be relevant to Indian urban waste (MSW)as a guideline. The average quality of Indian MSW is generally poor and variable with a highproportion of moisture and inerts. Biomethanation is effectively neutral to elevated moisture content,and while the lower organic content of a typical Indian MSW is not especially positive forbiomethanation, this can be accommodated by process adjustments such as increased retention timeswith a larger reactor volume (admittedly at a cost). The potential presence of a high proportion ofmoisture and inert in Indian MSW can be potentially detrimental to thermal-based waste-to-energytechnologies. The inerts can arise in a number of ways, but street sweeping is a particular contributorbesides construction debris. The present unorganised waste separation practices are an importantsource of revenue for certain sections of society in India. A significant proportion of the paper andplastics are removed and used as resources to sustain recycled product's businesses. Consequently, theneed for any elaborate material recovery facilities will be greatly modified at the proposed MSWtreatment plants in India.

All the above concerns have great relevance to the selection of a suitable technology for waste-to-energy application for MSW. For example, most incineration systems are optimised for U.S. andEuropean wastes that have high fractions of paper, cardboard and plastic, and consequently, arelatively high-energy value. The typical low calorific value Indian MSW stream is generally outsidethe design parameters of most commercially available MSW incineration technologies. The MSWstream in India is, therefore required to be ‘upgraded’ by the removal of inert fractions to obtain RDFas the feedstock.

Technologies such as landfilling with gas recovery and composting can also become viable optionsfor certain locations in India as a short to medium term option.

With the gradual adoption of the various technologies on a large scale in India, the relative weightagefor the commercial factors could become even more important, with most of the technical and


Chapter 14-11MWH

operational inputs becoming routine issues. These aspects would not be potential deterrents totechnology selection for a given WTE application.

Besides the above general observations, there are several specific issues relevant to India that maytend to make different technology options attractive for energy recovery from MSW. Following aresome such aspects: waste and labour availability, operator training, capital cost of equipment,construction and equipment sourcing from within the country, maintenance, royalties, overallcommercial viability, etc.

With the possible exception of some well defined liquid waste types, the only cost effective and viabletechnological option for waste-to-energy application suitable for Indian industrial and municipalliquid waste streams appears to be biomethanation. For liquids such as waste oils, and for other liquidwastes, where the composition is well characterised like distillery spentwash and paper mill blackliquor, the waste-to-energy technological requirements can be precisely specified; it is also possible toadopt certain proprietary gasification/ pyrolysis technologies in waste-to-energy applications.

14.7 Summary and RecommendationsThe evaluation of the applicability of the technologies of biomethanation, gasification/ pyrolysis,incineration and landfilling as Waste-to-Energy options in the global context, and their comparisonagainst composting as a competing technology for beneficial waste reuse, has shown the followingpotential prospects:

• Biomethanation is positively favoured under the considerations of a large range of criteria.

• High rate biomethanation must be considered a high priority for waste-to-energy projects inIndia due to the combination of cost, technology, effectiveness, and environmental benefits.

• Gasification/ pyrolysis has a distinct promise, and although there are limitations to its uptake,these can be circumvented as the technology matures.

• Incineration is being displaced gradually by gasification as a better WTE technology option.

• The present trend is in favour of material recovery facilities and a shift away from landfills forMSW disposal.

• Composting is not a WTE option and does not come out as a meritorious waste treatmentprocess.

• Technologies such as landfill with gas recovery (LFG) and composting can also becomeviable options for certain locations (in India) as a short to medium term option.


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Table 14-1. List of Technology Evaluation Criteria and Numerical Ratings (MSW)

S.No Evaluation Criteria Features and Assessment of Rating Rating Range

A. System Configuration 0-30 (20%)

1. Simplicity &Operability

General rating of total system and accessories assimple, medium and complex (high tech), besidesoperational aspects like man power, skill levels,automation versus manual inputs, resources used, etc.

Simple systems with less skill requirements, lowman power needs and requiring mainly manualoperation and low resource inputs will score high(10-12). Others with elaborate accessories(downstream/upstream) and processinstrumentation/process control and significantoperability issues (e.g.. high energy and skillrequirements, considerable automation, etc) willscore low (3-4). Moderately complextechnologies will be intermediate

0-12

2. Process Flexibility Ability to cope with fluctuations in wastecomposition, waste load, interrupted supplies,process upsets and turn down capability.

Technologies which cope best with fluctuatingload, waste type, process disruptions, etc scorehigh (10-12) Technologies with strict operationalparameters (such as design constraints, physicaloperating requirements, etc.) will score low (3-4);those susceptible to at least one potentiallydisruptive aspect score mid-range values.

0-12

3. Scale-up Modular nature of process equipment

For truly modular technology types thisparameter will be given a maximum score (6);where there are some scale-up issues then a lowscore of (0) will be relevant.

0-6

B. System Auxiliaries 0-30 (20%)

4. Pre-treatment Recovery of valuables, plastics, iron (metals) etc.from the wastes by mechanical equipment, screening,etc. and to obtain the desired proportion of organicsin the feedstock for energy recovery.

With less pre-treatment is required a technologycan score high (15), while an elaborate systemwill score low (5). In practice all technologytypes will require some pre-treatment (simple to

0-20


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S.No Evaluation Criteria Features and Assessment of Rating Rating Rangeelaborate) to match process needs v/s feedstockquality. Scores are thus based on the extent ofpre-treatment required and will range from 5-15.

5. Post-treatment Post treatment involves downstream cleaning ofLFG/biogas/incineration/gasification process wastegases. Product upgrading for saleable compost anddewatering sludges from biomethanation plants,landfill leachates treatment and ash residues fromthermal processes.

If less or no post-treatment is required thetechnology scores high (8-10); a technology typescores low (3-4), depending on whether one ormore of the aspects of product gas (or waste gas)clean-up, residue upgrading, or residue (e.g.. ash)disposal is required.

0-10

C. Environmental Aspects 0-30 (20%)

6. EnvironmentalImpacts

Relevant environmental issues include air emissions,ground water and surface water contamination, greenhouse gas emissions, health/welfare considerationsand solid waste disposal.

This complex parameter will have a high scorewith fewer environmental externalities (25-30).If one or more environmental issues countstrongly against a technology type the scorewill be low (5-7). With some negligibleenvironmental impacts a technology type willget an intermediate rating.

0-30

D. Resource Recovery 0-30 (20%)

7. Resource Recovery(Power, By-products)

Important criteria in evaluating the relative energyrecovery potential.

Power: Energy recovery efficiency places thetechnology types in the order of gasification (20),incineration (15), biomethanation (12), landfill(6) and composting (0). Likewise the residual by-product generally has a low value in all the casesand assigned a low score (4).

0-30

F. Commercial Aspects 0-30 (20%)

8. Capital Cost Capital cost includes

i) all equipment used for material recovery during0-12


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S.No Evaluation Criteria Features and Assessment of Rating Rating Rangepretreatment & post treatment (products/byproducts)

ii) main process equipment(Bioreactor/Incinerator/Gasifier and allaccessories (up-stream/down-stream))

iii) turbine/engine for power generation

iv) all infrastructure facilities (onsite/offsite)

Where capital costs are low a technology typeachieves a high score (10-12); for technologieswith elaborate equipment this factor will scorelow (3-4).

9. Operation &Maintenance

Operational cost will include various components forsuccessful & sustained operation of the facility likemanpower, material, spares & supplies, utilities,financing, working margin, overheads and otherrelated expenses during breakdowns and shut downs.

With normal O & M considerations technologytype achieves a high score (10-12). Technologieswith major issues of maintenance to sustainroutine operation are rated low (3-4).

0-12

10. Track record Technology status, operating installations.

The technology types with well proveninternational and/or national track records ofuptake and performance score high (5-6); andemerging technologies score low (3) as also theones with low public acceptance.

0-6

Total 150


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Table 14-2. Evaluation of Global Waste-to-Energy Technology Options (MSW)

S.No

EvaluationCriteria

Rating Biological Processes Thermal Processes

Biomethanation Landfillwith gasrecovery

Composting Incineration Gasification /Pyrolysis

A. System Configuration

1. Simplicity &Operability

0-12 8 12 12 4 4

2. ProcessFlexibility

0-12 8 10 8 4 4

3. Scale-up 0-6 6 4 4 6 6

Sub Total 0-30 22 26 24 14 14

B. System Auxiliaries

4. Pre-treatment 0-20 12 8 10 8 8

5. Post treatment 0-10 6 6 6 6 6

Sub- Total 0-30 18 14 16 14 14

C. Environmental Aspects

6. EnvironmentalImpacts

0-30 25 15 15 5 15

Sub-Total 0-30 25 15 15 5 15

D. Resource Recovery

7. Energy and by-products

0-30 20 12 4 20 24

Sub-Total 0-30 20 12 4 20 24

E. Commercial Aspects

8. Capital Cost 0-12 6 4 4 4 4

9. Operation &Maintenance

0-12 10 6 4 4 6

10. Track record 0-6 6 6 3 6 3

Sub-Total 30 22 16 11 14 13

Total 150 107 83 70 67 80


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Table 14-3. Summary of Global Technology Evaluation Scores

Technology Evaluation Scores

Technical Commercial Environmental Total Ranking

60 (40%) 60 (40%) 30 (20%) 150 (100%)

A. Biological Options

1. Biomethanation 40 (27) 42 (28) 25 (17) 107 (71) 1

2. Landfill 40 (27) 28 (19) 15 (10) 83 (55) 2

3. Composting 40 (27) 15 (10) 15 (10) 70 (47) 4

B. Thermal Options

4. Incineration 28 (19) 34 (22) 5 (3) 67 (44) 5

5. Gasification 28 (19) 37 (24) 15 (10) 80 (53) 3


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15 Mass and Energy Balances for Urban WTE Facilities

Mass and energy balance calculations are very useful as an audit tool for various unit operations and processes in the system. In any WTE facility, the mass balance calculations will indicate the quantum of waste constituents that gets into various waste disposal streams such as (a) recyclable/ recoverable material (b) landfill and (c) the main energy recovery process – biological/ thermal. Energy balance calculations focus on the main process to assess the net quantum of energy that can be uploaded into the grid. Detailed mass and energy balance calculations are presented for typical capacities of municipal solid waste to energy plant (MSW: 500 TPD) and domestic sewage treatment plant (capacity: 10 MLD).

15.1 Municipal Solid Waste

A typical MSW WTE facility is considered to consist of Pretreatment, Biological/ Thermal Processing, Power generation and Residues Management (Sludge Dewatering/ Composting/ Ash Disposal) stages, as shown schematically in Figure 15.1. Mass and energy balance calculations, require a fairly reliable estimate of the characteristics of the waste feedstock (MSW) for a given urban location. This will also lead to realistic estimates of the process inputs, energy recovery potential and other outputs. The average characteristics of Indian urban wastes used for the mass and energy calculations are given in Table-15.1. MSW generated in most of the urban locations in the country is generally consists of 60 – 70 %, of total solids and 30%-40% of moisture. This total solids is further classified into 65 – 50 % of organic matter and the rest 35 – 50 % are inert matter which includes lesser quantities of plastics, paper, metal, glass, etc. The latter are removed from raw MSW by manual sorting for recovery and reuse (see Appendix 15 A). Consequently, the composition of MSW made available at the WTE facility can be highly varying in nature and require different levels of pre-treatment. MSW available at the WTE facility would perhaps show ± 15%-20% variation in both composition and quantum (tonne/day) and it is necessary to recognize this aspect in all detailed material and energy balance calculations. These calculations are carried out for a typical plant of 500 TPD capacity based on the following assumptions:

• Average characteristics of MSW are assumed constant for all capacities and processes (biological and thermal).

• Gross chemical composition (on wet basis) consists of moisture 35%-45%, organic matter 25%-35% and inerts 25%-35%.

• Physical composition (on dry basis) in (%):

Paper 8-12 Plastic 4-10 Metals and Glasses 0.5-1.0 Sand, Leather, Rubber, Rags, etc. 20-26 Volatile Solids (% of Total Solids) 60-70 Biodegradable (% of V.S.) 55-65

• Approximately two-third of the unprocessed MSW consists of compostable organic matter

which can be used as feed stock for biomethanation process and the remaining portion is separated during pretreatment or manual sorting (by rag pickers) while recovering recyclable material such as plastic, metal, glass, etc. .


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• Solids Retention Time (SRT) of 15 and 20 days for low and high solids biomethanation processes respectively.

• Mesophilic and thermophilic processes operate at 30%-350C and 55%-600C respectively.

• Volatile solids (VS) = 65% of total solids (TS)

• Biodegradable Volatile Solids (BVS) = 60% of VS

• BVS destruction efficiency = 60%

• Biogas generation rate = 0.8 m3 per kg VS destroyed

• Methane content of biogas = 55%

• H2S content of biogas < 0.5%

• Engine thermal efficiency = 38%

• Lower calorific value (LCV) of biogas = 4,800 kcal/Nm3

• Aerobic composting of biomethanation sludge residue is considered to get a stabilised saleable product

• Average calorific value of unsorted MSW is 1000-1200 Kcal/kg (Dry basis)

• Average calorific value of RDF pellets is 3800 Kcal/kg

15.1.1 Biomethanation Technology

An integrated biomethanation system for energy recovery from MSW is shown in Figure 15.2, and includes the four major sections: (a) Pretreatment (b) Anaerobic digestion (c) Power generation and (d) Post-treatment. The important stage of the facility is the anaerobic digestion, and there are two main process design variations.

• Medium solids AD (Wet Process) operating at solids concentration of 10%-15%.

• High Solids AD (Dry Process) operating at solids concentration of 25%-35%.

• The description of various commercial technologies available in India and abroad are given in

Appendix 9A. Mass and energy balance calculations have been carried out for the two main process variations – mesophilic medium solids biomethanation and thermophilic high solids biomethanation.

Figures 15.3 and 15.4 represent the mass and energy balance calculations for a 500-TPD MSW WTE facility based on thermophilic high-solids (dry) anaerobic digestion process. A summary of the mass and energy balance calculations is given in Table 15.2 for MSW processing capacities of 150, 300, 500 and 1,000 TPD, based on both the high and medium solids biomethanation processes. All the process streams are identified numerically (1 to 26) in Figure 15.2, and these are used in Table 15.2 for convenient representation of the various streams. The summary is presented as per the following sequence:

A Pre-treatment section (common for both the processes) (Table 15.2 A)

B Biomethanation and Biogas/Power Generation (Thermophilic Process) (Table 15.2 B)

C Post treatment section (Thermophilic Process) (Table 15.2 C)

D Biomethanation and Biogas/Power Generation (Mesophilic Process) (Table 15.2 D)


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E Post treatment section (Mesophilic Process) (Table 15.2 E) The mass and energy balance calculations for biomethanation process show that on an average, the power generation potential of the unsorted MSW is 1 MW per 100 TPD of MSW.

15.1.2 Gasification Technology

Gasification process is based essentially on the exothermic and endothermic reactions, wherein the exothermic reactions release heat to sustain the gasification process, while the endothermic reactions lead to the generation of combustible fuel gas. These reactions are carried out in different configurations of gasifiers – vertical, horizontal, fixed bed, rotary kiln, multiple hearths and fluidized bed etc. The gasifiers that use air, operates at a temperature ranging between 7000C to 8500C) to produce a low calorific value fuel gas (500 - 600 kJ/m3) and granular char/ash. The system, which uses pure oxygen, operates at a high temperature (1,4000C – 1,6000C) results in generating a flue gas with a calorific value ranging in-between (1,000 – 1,200 kJ/m3) and vitreous slag as residue. Oxygen based units are developed and pilot tested successfully on MSW by Carbide Corporation, as Purox Gasifier, which is no longer in commercial production. (Source: Integrated Solid Waste Management by Tchobanoglous et. al 1993). Brightstar Environmental, Australia has developed a technology - Solid Waste Energy and Recycling Facility (SWERF) for municipal solid waste management. The process has tremendous potential to eliminate waste and reduce greenhouse gas emissions, and at the same time generate electricity. The world’s first SWERF is located in Wollongong Australia, with processing capacity up to 1,50,000 tonnes of MSW annually to produce electricity for approximately 24,000 households. A schematic sketch of the SWERF system is shown in Figure 15.5. The SWERF process consists of the following three components:

• Pre-processing of MSW

• Gasification, and

• Electricity generation Pre-processing involves receipt of the MSW, its sterilisation with steam in an autoclave, and mechanical separation. Steel, aluminium and plastics are recovered for recycling, and a pulp is produced from the organic material. The pulp is fed into a high temperature gasifier that breaks down the solid pulp into gaseous compounds consisting mainly of carbon, hydrogen and oxygen. These elements are reformed into a clean, dry synthetic fuel gas (syngas). The gasification process operates in sealed, pressurised units, with a low volume of emissions, and heats the waste in an oxygen-free environment to produce a clean fuel gas. During the gasification process, the solid waste is not burned as in incineration. This is an environmentally sound and superior alternative for waste combustion.

Syngas is used to drive highly efficient internal combustion engines to produce renewable energy in the form of electricity, which is supplied to the local electricity distribution network for use in homes and businesses in the area. The combustion of clean syngas is very similar to the combustion of natural gas or LPG. As it is a clean gas, it avoids the air emissions usually associated with combustion (incineration) of solid waste. In addition, as syngas is not a fossil fuel, it reduces reliance on using non-renewable resources such as coal for the generation of electricity. In essence, SWERF converts household garbage into green electricity for use in homes and businesses and reduces the amount of domestic waste going to landfill by up to 90%.


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EDL India Pvt. Ltd., New Delhi has an on-going project under implementation to generate 14.85 MW power by gasification from 600 TPD MSW at Chennai. The Solid Waste Energy and Recycling Facility (SWERF) comprises of streamlined integration of following proven components:

• A waste receiving and separation plant that homogenizes the organic material and separates the inorganic materials

• A gasification plant that converts the organic material into a clean, dry synthetic gas (syngas) suitable for combustion in modified gas engines; and

• A power generation plant that converts the syngas into electricity using reciprocating gas engines driving an alternator.

Figure 15.6 and Table 15.3 represent a detailed mass and energy balance calculation for a 500 TPD MSW gasification system based on “SWERF” process promoted by Brightstar Environmental/EDL Australia. All the process streams are identified numerically (1 to 30) in Figure 15.4 and are used for convenience in representing the various process streams. Mass and energy balance calculation show that 11.5 MW of power can be generated from a 500 TPD plant processing unsorted MSW. (Equivalent to 2.1 MW/100 TPD MSW)

15.1.3 RDF/ Incineration Technology

Refuse-Derived Fuel (RDF), commonly refers to solid waste that has been mechanically processed to produce a storable, transportable, and more homogeneous fuel for combustion. The waste is preprocessed to remove incombustible materials, thus increasing the calorific value of the fuel. Technology has now been well established for pelletising the combustibles separated from MSW and RDF has emerged as a very useful substitute for coal as a clean, energy efficient and eco-friendly fuel. Combustion systems for RDF with higher energy content will be compact and more efficient than mass-fired incineration systems. Hot flue gases from the combustion of RDF are converted to high-pressure steam and used for power generation using a steam turbine. The most common method for the production of electricity from RDF is by using steam turbine systems. Steam is produced in a boiler by burning MSW or RDF. The generated steam is used to drive a steam turbine and then condensed back into the boiler as feed water. The steam turbine drives an electricity generator, which supplies onsite power and excess power for export. The system is essentially a scaled – down version of a coal-or gas-fired electricity utility plant. The salient features of mass and energy balance for RDF facility (capacity: 40 TPD) from municipal solid waste (150 TPD) are illustrated below.

Mass Balance Installed capacity (RDF-TPD) 50 A. Raw material input

MSW (TPD) 160 – 180

Binder / Additive (Optional) (TPD) 2

Daily production TPD 40

Monthly production @ 25 days TPM 1000

Additional land requirement for solar-drying of MSW (acres) 2

Electrical load (HP) 375


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Manpower requirement 60

Monthly sales Rs.10,00,000/-

Monthly O & M Rs.6,50,000/-

(Power, Manpower, Consumables / repair / maintenance

Taxes / Water / Insurance, Office / Sales exp. /Any other)

Profit margin Rs. 3,50,000/-

B. Energy Balance

Calorific value of RDF pellets (Kcal/kg) 3800 (average)

Energy Potential (Kcal/month) 3.8 x 109

Coal calorific value (Kcal/kg) 4000

Coal equivalent (tonne / month) 950 Source: Energy From MSW RDF Pelletization – A Pilot Indian Plant, Dr. Pawan Sikka, Department of Science & Technology, Government of India, New Delhi – 110 016

RDF pellets derived from MSW has the potential to generate upto 3 MW electricity per 100 T RDF. Figure 15.7 represents a mass and energy balance calculations for a 500 TPD MSW Fluidized Bed Incineration system for generating 6.2 MW of power.

15.1.4 Landfill Technology

In the landfill, LFG generation from a particular quantity of MSW is the highest in the first two years after waste is filled. During this time, anaerobic digestion of most of the degradable content of food wastes occurs. LFG generation continues after this but at slowly decreasing rates. While gas generation can extend for periods of up to fifty years, in most cases LFG release occurs within five years, because food and garden waste typically comprise a large proportion of all organic materials in MSW. The EPA model (Section 12.1) can be used for a preliminary estimate of the LFG generated at a landfill with particular characteristics. Based on this model a landfill of 100 TPD capacity (serving a population of about 2,00,000) can generate about 3,300,000 m3 of LFG in a year, 375 m3 per hour. The heating capacity of the hourly flow is 4,450 Kcal x 375 m3 = 1650000 Kcal. This will be equivalent to 0.4 MW/100 TPD MSW power with an internal combustion engine requiring 4,000 Kcal to generate one kilowatt (kW) of electricity. Assumptions about climate, composition of waste and landfill management, will not apply equally to all landfills. An accurate assessment for cost estimates of LFG generation can only be done after considering their LFG extraction test.

15.2 Municipal Sewage

The average characteristics of municipal sewage are indicated in Table 15.1 (B). Even though sewage is a dilute effluent with BOD between 200-400 mg/l and COD between 400-750 mg/l, conventional aerobic treatment by activated sludge process entails a high power requirement for handling a large volume of waste generated in most cities. It will be cost-effective to save on energy demands by an alternate two-stage biological treatment consisting of anaerobic-aerobic sequence. The anaerobic stage utilises an UASB bioreactor for recovering the biochemical energy potential of sewage as biogas. Typical mass balance values for the main process streams are indicated in Figure


Chapter 15-6

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15.8. It is seen that a 10 MLD sewage treatment plant has the potential to generate 1,050 Nm3/day of biogas, which in turn can be used to generate power equivalent to 150 kW. Interestingly, this plant has the potential to save 53 kW power over the conventional activated sludge process. Several full-scale plants are in operation in India for treating municipal sewage by anaerobic treatment. They have the dual benefit of energy generation (biogas) and energy savings (though less HP) from downstream aerobic treatment.


Power generation potential of Indian MSW is 1 MW/100 TPD. This is comparable to the potential of 1.1 to 1.2 MW/100 TPD MSW considered abroad for biomethanation process. Generally, gasification/pyrolysis of MSW leads to 70-80 % of the energy inherent in the feedstock to be recovered as energy in the product (gas, oil or solid). The net energy output of a gasification plant will be 2.0 MW per 100 tonnes of MSW processed. The use of RDF pellets, derived from MSW, has the potential to generate upto 3 MW electricity per 100 TPD RDF. Power generation potential for LFG (serving a population of 2,00,000) will be 0.4 MW per 100 TPD MSW. A sewage treatment plant (capacity 10 MLD) has the potential to generate 1,050 Nm3/day of biogas, which in turn can be used to generate 150 kW power. This plant also has a potential to save upto 53 kW power compared to conventional activated sludge process.


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Table 15-1. Average Characteristics of Indian Urban Waste A. Municipal Solid Waste Moisture%

Total Solids%

Inerts%

Organics (Volatile)% TS

Calorific Value * Kcal / kg (Dry basis)

30-40 60-80 35-50 50-65 1000-1200

B. Municipal Liquid Waste pH SS

(mg/L) BOD (mg/L)

COD (mg/L)

Oil & Grease (mg/L)

TDS (mg/L)

7-8.5 150-250 200-400 400-750 15-30 500-800


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Table 15-2. Mass and Energy Balance Summaries - MSW Biomethanation Plants

A) Pre-treatment Section (common for both thermophillic and mesophillic processes)

Capacity (TPD) Identity No.

Stream

150 300 500 1000

1) MSW Feed 150 300 500 1000

2) Large Particles 2 4 4 8

3) Feed To Trommel

148 296 496 992

4) >180mm 14 28 50 100

5) <40mm 89 178 300 600

6) 40-180mm 45 90 146 292

7) Landfill 25 50 83 166

7A) Landfill 20 40 63 126

8) Ballistic Separator

89 178 300 600

9) Recycle 1 1 1 2

10) Magnetic Separator (MSW for AD)

88 177 299 598

B) Biomethanation and Biogas / Power Generation (Thermophilic Process)


Stream

150 300 500 1000

10 MSW for AD 88 177 299 598

11 Sewage / Water 35 60 90 180

12 Steam 50 101 171 342

13 AD Recycle 966 1946 3250 6560

14 AD Feed 1104 2224 3760 7520

15 AD Sludge 138 235 385 770

16 Biogas (Nm3/d) 11880 23760 52500 105000

17 Power (MW) 1.2 2.93 5.0 10.0

17A MW/100 TPD 0.8 1.0 1 1

18 Boiler Feed Water

50 94 205 410


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C) Post Treatment Section (Thermophilic Process)


Stream

150 300 500 1000

15 AD Sludge 138 235 385 770

19 Sludge (1) 50 100 200 400

20 Filtrate 88 135 185 370

21 Sludge (2) 3 6 10 20

22 Total Sludge 53 106 210 420

23 Sludge For Composting 43 86 170 340

24 Recycle 10 20 40 80

25 Centrifugate (m3/d) 85 129 175 350

26 Compost 32 64 125 250 D) Biomethanation and Biogas / Power Generation (Mesophilic Process)


Stream

150 300 500 1000

10 MSW for AD 88 177 299 598

11 Sewage / Water 152 305 516 1032

13 AD Recycle 960 1928 3260 6520

14 AD Feed 1200 2410 4075 8150

15 AD Sludge 219 439 720 1440

16 Biogas (N-m3/d) 11132 22790 50500 101000

17 Power (M-W) 0.96 2.28 4.84 9.68

17A MW/100 TPD 0.64 0.76 0.97 0.97


Chapter 15-10

MWH

E) Post Treatment Section (Mesophilic Process)


Stream

150 300 500 1000

15 AD Sludge 219 439 720 1440

19 Sludge (1) 50 100 200 400

20 Filtrate 169 339 520 1040

21 Sludge (2) 3 6 10 20

22 Total Sludge 53 106 210 420

23 Sludge For Composting 43 86 170 340

24 Recycle 10 20 40 80

25 Centrifugate (m3/d) 163 333 510 1020

26 Compost 30 64 125 250


Chapter 15-11

MWH

Table 15-3. Mass and Energy Balance for 500 TPD MSW SWERF Plant

A) MSW Pre-Treatment

Solid/Liquid Stream Incoming

Waste Pulp Blend

Metal Sales

Clean Fuel

Inert Mix Pressate

1 2 3 4 5 6

Organic Material (tpa) 61848 62456 - 62456 - 855

Inerts and Ash (tpa) 35135 35567 - 6617 28950 415

Water (tpa) 85888 153699 - 149549 4150 89225

Total (tpa) 182872 251722 0 218622 33100 90495

Moisture Content (%) 47% 61% - 68% 13% 99%

Energy Content GJ/T-HHV wet wt.

8 8 - 7 - -

Energy Flow – GH (HHV)

1462980 1462980 - 1462980 - -

B) MSW Gasifier Solid/Liquid Stream Entrained

Pulp Char Syngas Out Internal

Use Stack Losses Condensate

Water

7 8 20 21 22 23

Organic Material (tpa) 61600 740 63757 31879 - -

Inerts and Ash (tpa) 6200 6200 - - - -

Water (tpa) 56174 - - - - -

Total (tpa) 123974 6940 - - - -

Moisture Content (%) 45% - - - - -

Energy Content GJ/T-HHV wet wt.

12 - - - - -

Energy Flow - (HHV) 1462980 - 1147633 323692 90634 - Inorganics (tpa) - - 42 21 - 21 Steam (tpa) - - 15152 7576 7576 15153


Chapter 15-12

MWH

C) Power Generation

Solid/Liquid Stream

Gas to Engine Engine Exhaust

Power Out

24 25 30 Organics 31879 - - Energy Flow (HHV)

1147633 762823 384810

(11.5 MW) D) Waste Heat Recovery Solid/Liquid Stream Boiler

Water Steam Blow

Down WTP

Sludge Hot

Water Wash Water

Raw Water

Excess Water

9 10 11 12 13 14 15 16

Organic Material (tpa) - - 25 830 - 24900 - 18

Fuel Bound Ash (tpa) - - 42 415 - 12450 - 18

Water (tpa) 65736 54780 10956 2075 0 1381452 0 36566

Total (tpa) 65736 54780 11023 3320 0 1418802 0 36603

Moisture Content (%) - - 99.40% 63% - 97.40% - 99.90%


Chapter 15-13

MWH

Figure 15-1. Schematic Process Flow Diagram of an Integrated MSW Biomethanation System

To be taken from separate file “Final 5 Figures_Chapter 15.doc”


Chapter 15-14

MWH

Figure 15-2. Schematic Process Flow Diagram of an Integrated MSW Biomethanation System



Chapter 15-15

MWH

Figure 15-3. Mass Balance Diagram for MSW WTE Project – Biomethanation Technology – Capacity 500 TPD (Thermophillic High Solids Dry Basis)



Chapter 15-16

MWH

Figure 15-4. Energy Balance Diagram for MSW WTE Project – Biomethanation Technology – Capacity 500 TPD (Thermophillic High Solids Dry Basis)


Chapter 15-17

MWH

Figure 15-5. Schematic of SWERF Process

1. MSW Reception

2. Waste sterilised in autoclave

3. Waste separated into organic pulp and recyclables

4. Organic pulp washed and dried

4a. Pulp storage

5. Organic pulp converted to syngas (Gasifier)

5a. Syngas cleaning

6. Power generation


Chapter 15-18

MWH

Figure 15-6. Mass and Energy Balance for 500 TPD MSW Gasification System based on SWERF

Take from separate file – Figures 15-4 & 15-5.doc


Chapter 15-19

MWH

Figure 15-7. Mass & Energy Balance for MSW WTE Facility with Fluidized Bed Incineration – (Capacity 500 TPD)

Take from separate file – Figures 15-6 & 15-7.doc


Chapter 15-20

MWH

Figure 15-8. Process Flow & Mass Balance Diagram for Municipal Liquid Waste To Energy Project –UASB 10 MLD

Take from separate file MLW-r1.doc



16 WTE Project Costs

16.1 Introduction Successful implementation of any technically feasible project is dependent on its commercial viability. The commercial viability of any project is determined by a detailed financial analysis and involves a comprehensive and critical review of its cost estimates and revenue generation potentials. Once the project is assessed to be commercially viable, its financing arrangements are determined to ensure its successful implementation. Illustrative cost comparisons for WTE projects for the waste streams of Municipal Solid Waste and Municipal Liquid Waste are given below. MSW WTE projects are generally implemented by private agencies on the basis of Build Operate & Transfer (BOT), Build Own Operate (BOO), Build Own Operate & Transfer (BOOT), Design Build Operate (DBO) options. Due to high capital investments, these projects require substantial help from financial institutions through term loans and subsidies from government agencies such as IREDA, HUDCO, etc. A brief description of some MSW WTE projects coming up in India together with cost estimates is presented in the next section. A preliminary comparison of major technologies like biomethanation, and gasification are also presented for a typical 1,000 TPD capacity MSW WTE project.

16.2 Upcoming Projects in India Costs for some upcoming projects in India are used to assess current trends. It is necessary to recognize that the first full scale MSW WTE plant is yet to be commissioned as a demonstration plant in India. Nonetheless, several proposals based on biomethanation technology are at various stages of finalisation or scrutiny. In addition, two more plants utilizing gasification technology are also planned for power generation from MSW. Lucknow Nagar Nigam Project Non-conventional Energy Development Agency, (NEDA), Uttar Pradesh, with the assistance of MNES, Government of India, has undertaken a 5 MW WTE demonstration project based on MSW at Lucknow. The project is designed to process 300 tonnes of MSW per day by the medium solids anaerobic digestion process (BIMA digester). The estimated cost of the project is Rs. 80 crores, equivalent to Rs. 16 crores per MW. Work on the project is in progress under an agreement between Lucknow Nagar Nigam and M/s. Asia Bio Energy (India) Ltd., Chennai (a firm promoted by Enkem Engineers, Chennai). The site was visited by MWH on 1st October 2002. (Additional details of the project are given in Appendix 9-H.) Nagpur Project The Nagpur project was approved as a demonstration project by MNES in March 1998. The project was designed to process a maximum of 650 tonnes per day of MSW by high solids anaerobic digestion (DRANCO) process to generate 5.4 MW. The project was awarded under the BOO scheme to CICON Environment Technologies Ltd., Bhopal, M.P. The technical know–how for the project is provided by OWS, Belgium. The project highlights are given in Appendix 9-H.



Hyderabad Project (SELCO) M/s SELCO, Hyderabad, have commissioned an RDF project for making 150 TPD of RDF based on 700 TPD MSW. M/s SELCO are in the process of establishing a power plant based on RDF to produce 6.6 MW of power using moving grate boiler system at a total cost of Rs. 40 crores. (Site Visit by MWH on 18th October 2002. Mumbai Project (Bermaco) A 1000TPD MSW WTE facility based on biomethanation process to produce 11 MW of electrical energy is in the planning stage at a capital cost of 140 crores. Bermaco/ WM Power Ltd is the project proponent. Mumbai Project (Sound Craft) A project designed to process 1,000 tonnes per day of MSW, based on biomethanation, to generate 11.5 MW of electrical energy. The project is awarded to M/s Sound Craft, Mumbai, at a capital cost of Rs.145 crores. Ulhasnagar Project (Wabio) MSW (340 T) along with vegetable market waste (60 T) will be used as the feedstock for the Ulhasnagar project to generate 2.5 MW of electrical energy at a cost of Rs.28 crores. M/s Hydroair Tectonics, Navi Mumbai, will execute it. The technical know-how is provided by Eco-Technology JVV OY, Finland (Wabio Process), based on medium solids biomethanation technology. Chennai Project (Gasification) The construction of the 14.85 MW Chennai power plant from MSW has been undertaken by EDL India Pvt. Ltd on BOO basis. The plant is expected to start functioning during 2003. The project, based on gasification technology, is expected to cost around Rs. 180 crore. The Chennai Corporation will collect and supply 600 tonnes per day of garbage for this plant that is being set up adjacent to the MSW dump at Perungudi, Chennai on a 15-acre plot of land leased to the company for 15 years. Mumbai Project (Gasification) The Municipal Corporation of Greater Mumbai has entered into an agreement that facilitates a gasification based Waste To Energy (WTE) plant at Mumbai's Gorai dumping ground. The Rs. 242 crore plant to be supplied by Energy Developments Limited India (EDL) will gasify 1, 000 metric tonnes of MSW per day to generate 21 MW of electricity.

16.2.1 Cost Estimates Presently, the technology providers for some of the above projects have provided limited data relating to overall investment and operation costs, power generation and quantum of MSW that will be processed. A list of plant and machinery required for a typical MSW biomethanation project is given in Appendix 16 A. The available cost data is summarized in Table 16.1, and includes information on the quantum of MSW to be handled, power generation, process technology and current project status. Six of these projects are based on biomethanation, while two utilize gasification and one uses RDF for power generation by incineration. These projects cover a wide capacity range of 250 –1000 TPD MSW to produce 2.5 to 21 MW power.



Figure 16.1 shows a wide variation in capital cost of Rs.8-16 crores per unit energy generation (MW) for the various projects. Capital cost per MW electrical energy generation gives a preliminary indication of the cost effectiveness of a technology. The capital cost/MW is Rs. 16 crores for the Lucknow project (BIMA), and is the highest amongst all the projects. The capital cost/MW for the Nagpur project is Rs. 8.74 crores, and thus the Nagpur project is the most economical project. The capital cost/MW for Mumbai projects-Bermaco and Sound Craft are Rs. 12.72 crores and Rs. 12.60 crores respectively. It appears that the capital cost per MW energy generation (Table 16.1 & Figure 16.1) tend to decrease as the technologies mature with time. This is evident from the fact that the capital cost per MW energy generation for the Lucknow project in 2000-01 was 16 crores, while the same for Mumbai in 2002-03 is 12.60 crores. Figure 16.2 illustrates the quantum of energy generated for every 100 T of waste treated. The Lucknow project claims to have more energy generation at 1.67 MW/100 T, whereas Nagpur claims the least at 0.84 MW/100 T and this variation is primarily due to characteristics of the waste processed. In the case of biomethanation projects, this ratio has stabilized to around 1 MW for every 100 T of waste treated. However, in both the gasification projects it has been claimed that these projects are two and half times more efficient than biomethanation projects. The energy generation per 100 tonnes of waste for RDF-based incineration is higher than a comparable biomethanation plant. It is advisable to be cautious while using this data for future studies. In many cases, the sources of the estimates fail to provide sufficient information to convert them to a consistent base or to judge the reasons for the differences. For example, the finance charge for the capital investment for a given facility would be significantly affected by the prevalent interest rate at the time of project financing, but many sources fail to note that interest rate. Moreover, the type and composition of the wastes and the plant site conditions in general would affect capital investment, but many sources fail to provide data on these matters. Similarly, the O&M costs are affected by site-specific conditions such as labour rates, labour contracts, safety rules, the size of the work team, and other factors. One of the objectives of the waste-to-energy projects is waste treatment and its safe disposal. Higher the quantum of the waste treated, more is the reduction in the green house gas emission. The quantum of waste treated (Tonnes/day) for a unit cost (Rs. crores) for upcoming projects in India is illustrated in Figure 16.3.

16.3 Typical Municipal Solid Waste to Energy Projects (Capacity: 1000 TPD)

Biomethanation, Incineration and Gasification are the three technological options examined for a preliminary assessment of the commercial viability of a typical 1,000 TPD capacity plant (with 15 years economic life). The following assumptions are made for the purpose of cost comparison:

• The economic life of the project is considered as 15 years.

• Capital cost is considered to be borrowed from the financial institutes and is considered to be paid back in Equated Yearly Instalment at the interest rate of 11% in a period of 15 years.

• Operation and Maintenance costs are considered to increase at the rate of 8% per year, along with the age of the plant, and no major additional capital investments are envisaged during the economic life of the project.



• Revenue from the surplus electric power is considered to be Rs. 3.87/kwh and is assumed to increase further at the rate of 5% per annum.

• The present price of manure is taken as Rs 1,200 and is assumed to increase at the rate of 5% per annum.

• Project realisation period is considered as moratorium period.

• Discount factor is taken as 10%.

As an illustration, the commercial viability of the waste-to-energy projects based on the three technologies is examined on a stand alone basis. The primary findings are summarised below:

• The capital cost of gasification plant is comparatively higher (Rs. 219.54 crores) than for biomethanation (Rs. 90.76 crores). The break-up of the capital cost between pre-treatment, main process and post-treatment, including power generation, for gasification and biomethanation systems is 38, 26, 36% and 30, 45 and 25% respectively.

• The present value of net revenue for biomethanation plant is found to be the highest (Rs. 151.12 crores) followed by gasification (Rs.149.9 crores).

• The net present worth of the net revenue for biomethanation and gasification plants are surplus, indicating that these technologies shall be commercially viable.

It should be noted that this financial analysis is done after making a number of assumptions, and that a case specific financial analysis needs to be done for individual projects to examine their commercial viability.

16.3.1 High and Medium Solids Biomethanation Project The preliminary capital cost and revenue generation are determined for implementing two biomethanation projects - high solids and medium solids anaerobic digestion processes, for capacities of 300,500 and 1,000 TPD. The details are given in Table 16.3. The two sources of revenue generation in these projects are (a) sale of electricity generated (b) compost produced. The costs details given in Table 16-3 highlight the following features:

• The cost of biomethanation project varies between Rs. 10-14 lakhs per tonne of waste treated.

• The high solids anaerobic (dry) process is cheaper by 5% than the medium solids anaerobic (wet) process.

• As the plant capacity increases, the unit capital cost decreases for both the processes.

• Revenue generation in the high solids process is more than the revenue generation in the medium solids process.

• Revenue generation increases with an increase in plant capacity.

• Nearly 40% of the revenue can be generated through the sale of manure. The total quantum of compost produced is the same in both the processes.

• The pay back period of biomethanation project varies between four to six years depending upon the process and the capacity of the plant.

16.4 Municipal Liquid Waste to Energy Projects A conventional sewage treatment process (option 1) is compared with an anaerobic treatment facility with downstream aerated lagoon (option 2) to assess relative economics.



1. Option 1: Activated Sludge Process followed by an anaerobic sludge digestion

2. Option 2: UASB followed by short detention aerated lagoon The following parameters were used for evaluating the technological options:

• Degree of treatment required

• Capital and Operation & Maintenance cost

• Mechanical equipment requirement

• Power requirement, and

• Land requirement

A typical 100 MLD plant is considered for comparison purpose. The capital cost per MLD of sewage treated for Option-1 with ASP works out to Rs. 26.68 lakhs, whereas the same for Option-2 with UASB is Rs.20.37 lakhs. The cost calculations for both options are given in Table 16.4. These cost estimates are further evaluated (Table 16.6) after calculating the cost implications over a period of 15 years. Various assumptions are made for the purpose of cost comparison, such as:

• The residual value of the installations is considered as 15 years from commissioning, i.e. the economic life of the project is considered as 15 years.

• Capital cost is considered to be borrowed from the financial institutes and is considered to be paid back in Equated Yearly Instalment at the interest rate of 11%.

• Operation and Maintenance costs are considered to increase at the rate of 8% per year along with the age of the plant, and no major additional capital investments are considered during the economic life of the project.

• Revenue from the excess electric power is considered to be Rs. 3.87/kwh and is further considered to increase at the rate of 5% per annum.

• The present price of manure is taken as Rs 1,200 and is considered to increase at the rate of 5% per annum.

• Project realisation period is considered as moratorium period.

• Discount factor is taken as 10%.

A comparative analysis has been made to evaluate the alternatives with respect to their potential costs and revenue generation. The analysis shows that:

• The capital cost of a 100 MLD Activated Sludge Plant followed by an Anaerobic Sludge Digestion facility is Rs. 2668.02 lakhs and is 30% higher than the capital cost of a UASB system followed by Aerated Lagoon facility.

• As municipal liquid waste is dilute, the operation and maintenance costs of the plant can be substantially reduced or even recovered to the extent of 100% from the revenue generated.

It should be noted that this preliminary financial analysis is carried out after making a number of assumptions and that a case specific financial analysis needs to be done for individual projects to examine their viability.



16.5 Industrial Waste to Energy Projects In the context of industry, where critical cost minimization and operational streamlining at every juncture is a pre-requisite for success, recent decades have witnessed worldwide a focused search for and development of viable techniques for extracting energy from wastes. This involves multiple benefit to the industry to treat the waste and to recover energy and reuse in the industrial process. This multiple aim is met in the waste-to-energy projects. Biological processes, involving anaerobic digestion of organics, are widely accepted because they are relatively simple, low-cost, self adjusting and versatile. Even though the primary objective of the industrial waste treatment system is to treat the waste, with energy recovery being secondary consequence, cost and revenue generation is a vital aspects of waste to energy projects, it is necessary to focus on cost of treatment and generation of revenue for development of a self-sustainable facility. Each industry is unique in its waste generation spectrum. The nature and characteristics of many industrial wastes are better understood now and the quantum of waste generation is considered as an index of inefficiency in utilizing virgin raw material resources. An comparison has been made between the anaerobic digestion (WTE) system against conventional aerobic system for the following industrial sector (Table 16.5).

• Dairy

• Pulp and Paper Mill

• Sugar Mills

• Distillery

• Maize Starch The following are broad findings

• Capital cost of the anaerobic system is less than the cost of aerobic system.

• The load required for aeration of the same quantum of wastewater is multifold of anaerobic system depending on the wastewater characteristics.

• The cost recovery of an anaerobic system is more than the recurring cost (in terms of extra power required to the run the plant) of a conventional aerobic system.

• For most of the high strength wastewater viz. Starch, distillery, the costs of the investments on the WTE project can be recovered within 3-5 years from commissioning.

16.6 Summary and Recommendations Waste-to-Energy projects are generally implemented by private agencies that evolve an appropriate financing package. Since it is necessary to pay the loans fully back to the lending agency, these projects are required to be commercially viable. Besides, the private entrepreneurs/ agencies also need to be convinced that the proposal would fetch adequate returns over the specified period of time. In principle, biomethanation plants provide a single waste management facility for processing various types of feedstock and concurrently address the issues of energy recovery, valuable recovery/ recycle, waste disposal and socio –economic benefits. Biomethanation seems to be a promising option with disposal of more quantum of waste and requiring less capital cost for unit energy generation.



There is a wide variation (Rs. 8 to 16 crores per MW) in the capital costs based on various Indian technology providers and developers. This cost is expected to reduce as the technology matures in due course. As of now, the reality is that waste-to energy plants require significant financial investment. The estimation made for biomethanation and gasification indicate a continuous revenue surplus increasing every year. However, cost reductions over the preliminary estimates may be possible by careful selection of the design, sizing, and location of the plant, as well as by the selection of commercial markets for biosolids (residues) and recovered energy.



Table 16-1. Highlights of Some Ongoing/ Proposed MSW WTE projects in India

Power Project Cost (Rs.

Crores) Quantum of MSW Sr.

No. Project Location

Technology Financing Mechanism

Status

MW MW/ 100T Total Cost /MW Tonnes/ day Tonnes/ MW

1 Lucknow, UP Biomethanation (Low Solids/ BIMA)

ENTEC, Austria Asia Bioenergy, Chennai

BOO Execution (2001) 5 1.67 74 14.8 300* 60

2 Nagpur, Maharashtra

Biomethanation (High Solids/ DRANCO) GWS, Belgium CICON, Bhopal

BOO Execution (1999) 5.4 0.84 47.3 8.74 650 (max) 120

3 Mumbai, Maharashtra

(WABIO)

Bermaco/ WM Power Ltd,

BOO Planning (2002) 11 1.1 140 12.72 1000 91


Biomethanation

Ericsons, USA

SOUNDCRAFT Mumbai

BOO Planning (2002) 11.5 1.15 145 12.60 1000 87

5 Ulhasnagar, Maharashtra

Biomethanation (WABIO) HYDROAIR, Navi Mumbai

BOO Planning (2002) 2.5 1 28 11.2 250 100



Power Project Cost (Rs. Crores)

Quantum of MSW Sr. No.

Project Location

Technology Financing Mechanism

Status

MW MW/ 100T Total Cost /MW Tonnes/ day Tonnes/ MW

6 Navi Mumbai, Maharashtra

Biomethanation (WABIO) HYDROAIR, Navi Mumbai

BOO Planning (2002) 3.5 0.875 43 12.28 400

(340 MSW + 60 Vegetable waste)

114

7 Chennai, TN Gasification EDL New Delhi

BOO Execution (1999) 14.85 2.475 180 12.12 600 40


Gasification EDL-New Delhi

BOO Planning (2002) 21 2.1 240 11.42 1000 48

9 Hyderabad, A.P RDF-Incineration

SELCO-Hyderabad

BOO Execution (2003) 6.6 0.95 40 6.06 700 106

Note * Organic Fraction of MSW (Wet Basis) Source: Appendix 9G and Appendix 11H of this report and others



Table 16-2. Financial Estimates for 1000 TPD Plant Capacity

Sr. No.

Description Biomethanation *

(1000TPD Plant)

Gasification **

(1000TPD Plant)

1 Capital Costs (Rs Lakhs)

Pre-treatment 2723 8343

Biological/ Thermal Conversion 4084.6 5708

Post –treatment 2269.3 7903

Total Costs 9076.9 21954.0

2 Capital Cost Per MW 907.7 1045.4

3 Operation and Maintenance costs (Rs Lakhs/year)

Maintenance Cost 901.4

Operation Costs including Salaries + License fee + Insurance + Royalty and other operating costs

727.0

Total Operation and Maintenance Costs

975.6 1628.3

4 Resource Recovery (Rs Lakhs/year)

Manure 825.0

By selling of electricity @3.4 Rs/Kwh

2198.0 4936.0

Total Resource Recovery 3188.0 4936.0

5 Present Net Revenue (Rs. Lakhs)

9934.7 7453

Note: Source: * CICON Group, Bhopal ** EDL India Pvt. Ltd, New Delhi Costs implication towards Rupee depreciation + Financing Expenses + Margin money and Interest components are not considered Costs of Land and Site Development not included The electricity tariff is considered as per the MNES policy(3.4/kWh) All costs/prices are based on year 2002 (2002=100)



Table 16-3. Budgetary Project Cost Estimate and Revenue Generation

Capacity (TPD)

Sr. No. Particulars 300 TPD 500 TPD 1000 TPD

High Solids

Medium Solids

High Solids

Medium Solids

High Solids

Medium Solids

A. Budgetary Cost Estimate (Rs. Lakhs)

1 Civil Works (A) 888 1004 1148 1303 2063 2363

2 Plant & Machinery

a) Indigenous 989.71 1088.68 1522.63 1674.89 2740.74 3014.81

b) Imported 1235.05 1235.05 1900.08 1900.08 3420.14 3420.14

Total 2224.76 2323.73 3422.71 3574.97 6160.88 6434.95

3 Misc. Fixed assets 50 50 50 50 80 80

4 Pre-operative costs 150 150 150 150 200 200

5 Contingencies 150 150 200 200 350 350

6 Interest during construction 300 300 500 500 1000 1000

7 Tech. Fees 150 150 150 150 150 150

8 Training Expenses 30 30 30 30 30 30

9 Margin for W.C 80 80 80 80 150 150

Total 4022.76 4237.73 5730.71 6037.97 10183.88 10757.96

4025 4240 5730 6040 10200 10760

B. Revenue Generation & Pay back Period

1 Biogas Production (Cum/day) 31,500 29,900 52,500 49,900 105,000 99,750

2 Electricity (MW)

a) Power Generation (MW) 3 2.85 5 4.75 10 9.5

b) Parasitic consumption (MW) 0.45 0.57 0.75 0.95 1.5 1.9

c) Wheeling and Transmission Losses (MW)

0.10 0.09 0.17 0.15 0.34 0.3

d) Net Electricity for Sale (MW) 2.45 2.18 4.08 3.64 8.16 7.29

e) Annual Operating Hours 7920 7920 7920 7920 7920 7920

f) Units for Sale (kWh *106) 19.4 17.33 32.3 28.89 64.6 57.78

g) Sale Price Rs./kWh* 3.4 3.4 3.4 3.4 3.4 3.4

h) Revenue Rs. Lakhs 659.6 589.2 1098.2 982.3 2196.4 1964.5

3 Bio fertilizer

a) Capacity (TPD) 75 75 125 125 250 250



Capacity (TPD)

Sr. No. Particulars 300 TPD 500 TPD 1000 TPD

High Solids

Medium Solids

High Solids

Medium Solids

High Solids

Medium Solids

b) Annual Production (T) 24,750 24,750 41,250 41,250 82,500 82,500

c) Sale Price (Rs./T) 1,000 1,000 1,000 1,000 1,000 1,000

d) Revenue Rs. Lakhs 247.5 247.5 412.5 412.5 825 825

4 Total Revenue 907.1 836.7 1510.7 1394.8 3021.4 2789.5

5 Less O & M Expenses @ 30% 272.1 251.0 453.2 418.4 906.4 836.8

6 Net Revenue

(Including repayment of loan and interest)

635.0 585.7 1057.5 976.4 2114.0 1952.7

* As per MNES policy



Table 16-4. Financial Estimates of a Typical 100 MLD STP with WTE Facility

Sr. No Description Conventional

(Option 1) UASB (Option 2)

1 Capital Cost (Rs. In Lakhs)

Civil 1901.60 1623.40

Mechanical, Electrical and Instrumentation 766.40 413.79

Total 2668.00 2037.18

2 Capital Cost/MLD (Rs. In Lakhs) 26.68 20.37

3 O&M Cost (Rs. in Lakhs/yr) 838.5 458.61

4 O&M Cost / MLD (Rs. in Lakhs/yr) 8.38 4.58

5 Resource Recovery

Manure 14.21 17.76

Electricity @ Rs 3.4/kWh 89.34 148.92

6 Total Revenue 103.55 166.68

Notes:

Costs implication towards Rupee depreciation + Financing Expenses + Margin money and Interest components are not considered

Costs of Land and Site Development not included

20 % of the sludge produced is considered as utilized in the plant premises and wastage

All costs/prices are based on year 2002 (2002=100)

Electricity tariff is considered as 3.4 /kWh as per MNES policy



Table 16.5 Financial Estimates of a Typical Dairy Plant WTE Facility Sr. No.

Sector Capacity Wastewater Generated (m3/day)

Organic Waste (mg/L) BOD

Capital Cost (Rs in Lakhs)

Connected Load for aeration (HP) (extended aeration activated sludge process)

Biogas Production with 50 % CH4 (m3/day)

Recurring Cost (Rs in lakhs /year) (in terms of extra power)

Cost recovery recovered by biogas to energy generation (Rs in lakhs per year)

Conventional System

WTE System

Conventional System

WTE System

Conventional System

WTE System

Conventional System

WTE System

Conventional System

WTE System

1 Dairy 75,000 ltrs of Milk Processed

1200 800 91 82 70 15 Nil 384 11.43 Nil Nil 23.29

2 Pulp & Paper 50 TPD kraft paper

1500 4000* 104 106 225 70 Nil 2400 32.24 Nil Nil 58.24

3 Sugar Factory**

12000 TCD 4800 600 97.5 100 228 36 Nil 800 17 Nil Nil 9.2

4 Distillery 150 KLD Alcohol

2040 4000* 316.16 9009 218.62

5 Maize Starch 1050 10000* 612.56 4725 114.66 Notes Costs implication towards Rupee depreciation+Financing Expencies+Margin money and Interest components are not considered

Costs of Land and Site Development not included

Plant works for 330 days a year

WTE facility implies UASB system

Electricity tariff is considered as Rs 3.4/-per kWh as per MNES policy All costs/prices are based on year 2002: 2002=100

* - COD

** - Sugar Factory works for 141 days



Figure 16-1. Capital Cost per MW Energy Generation

Figure 16-2. Energy Generation v/s Waste Treated

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n (M

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Figure 16-3. Waste Treated v/s Capital Cost

0.00

4.00

8.00

12.00

16.00

20.00

Nagpu

r

Luckn

ow,U

P

Mumba

i

Mumba

i

Ulhasna

gar

Navi M

umba

i

Chenn

ai (G

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Chapter 8-11MWH

Figure 8-1:Technological Options for Energy Recovery from Urban Wastes

LANDFILLING

URBAN WASTES

LIQUID (SEWAGE)SOLID (MSW)

BIOLOGICAL

COMPOSTING

COMPOST

BIOMETHANATION

INCINERATION

THERMAL

BIOMETHANATION

GASIFICATION PYROLYSIS

BIOGAS

POWER

POWER COMBUSTION

BIOGAS

POWER

FUELGAS

FUELOIL

CHARCOAL

POWER


Chapter 8-12MWH

Figure 8-2 Technology Options for Energy Recovery from Industrial and Farm Wastes

INDUSTRIAL & FARM WASTES

SOLIDSLIQUIDS SEMI-SOLIDS/SLUDGES

BIOMETHANATION SLURRY DEWATERI NG/DRYING

BIOGAS

POWER

RESIDUALSTHERMALEVAPORATION

INCINERATION GASIFICATION PYROLYSIS

POWER FUEL GAS FUEL OIL CHARCOAL


Chapter 8 - 8MWH

Table 8-3. Criteria for Assessment/Selection of Global WTE Technologies*

Criteria Incineration Anaerobic Digestion Gasification/ Pyrolysis

A. Feedstock

Nature of Waste

Industrial

Liquid Not Suitable Suitable Not Suitable

Solid Suitable Not Suitable Suitable

Urban

Liquid Not Suitable Suitable Not Suitable

Solid Suitable Suitable Suitable

Farm

Poultry Suitable Suitable Suitable

Cattle Suitable Suitable Suitable

Desired Feedstock Properties for WTE

Industrial

Liquid - Suitable -

Solid Organics (>50 %)

Moisture (<25 %)

- Organics (>50 %)

Moisture (< 25 %)

Urban

Liquid - BOD (200 – 400 mg/L) -

Solid Calorific Value (drystate)

(1900-2800 kcal/kg)

Volatile Solids

(>60 % TS)

Calorific Value (drystate)

(1900-2800 kcal/kg)

Farm

Poultry Calorific Value (drystate)

(3500 - 3800 kcal/kg)

Volatile Solids

(>60 % TS)


(3500 – 3800 kcal/kg)

Cattle Calorific Value (drystate)

(3200-3700 kcal/kg)

% Volatile Solids

(>60 %TS)


(3200-3700 kcal/kg)

B Technology Features

Technology Status

Industrial Proven Proven Emerging

Urban Proven Proven Emerging

Farm Proven Proven Proven

Energy Recovery Hot combustion gas Biogas Syngas,bio-oils


Chapter 8 - 9MWH


Power generation Steam turbine Gas turbine Gas/Steam turbine

Efficiency 85-90% (based oncalorific value)

50 – 60% (based onvolatiles)

90-95% (based oncalorific value)

Residue Ash Digested slurry Ash, Char

Residue Disposal Landfill Farm land Reuse possible, or asroading material

DownstreamProcessing

Elaborate Air PollutionControl

Sludge stabilization Limited air pollutioncontrol

Operating Conditions

Temperature 900-1200 ºC 35-40 ºC

(mesophilic)

55-60 ºC

(thermophilic)

600 –1400 ºC

Pressure 200-300 mbar 150-250 mbar 250-400 mbar

Reactor Atmosphere Oxidizing (Excess Air) Strictly anaerobic Inert (pyrolysis)/Partially oxidizing(gasification)

SystemConfiguration

Complex Simple Complex

Process Flexibility Low Good Low

Modular Yes Yes Yes

Area requirements

Basis: 300 TPDMSW

Elaborate

(500 –750 m2)

Compact

(100 –250 m2)

Compact

(200 –400 m2)

Capital and O&M Costs

Relative CapitalCost

Very High Medium Very High

O&M High Low Limited (few movingparts)

Commercial viability Less viable owing tocostly downstream airpollution control

Readily viable Varies considerably

Captive Power Significant

(25 – 30 %)

Low

(5 %)

Variable

(5 – 20%)

Royalty 10 % 0-5 % 10%

C.

Technologyupgradation

On going On going On going

D. Environmental Control


Chapter 8 - 10MWH


Air Pollution Dust Collection, GasScrubbing (Elaborate)

H2S – Scrubbing(Compact)

Dust collection, Gasscrubbing (Compact)

Water Pollution Minor Down-stream aerobic Low

Solid/Hazardouswastes

Ash to Landfill Stabilised sludge Ash/Slag (Reuse)

Overall compliance Feasible Feasible Feasible

Environmentalimpacts

Can be minimized(costly)

Minimum Can be controlled(additional costs)

Socio – Economic Aspects

Waste disposal Complete, except for ashto landfill

Complete except forsludge stabilization

Complete, except for ash

Public acceptability Satisfactory Satisfactory Satisfactory

Waste Collection Municipal/Agency Municipal/Agency Municipal/Agency

Power distribution Power Grid Power Grid Power Grid

E.

Facility operation Agency Agency Agency

* Remarks apply to installations abroad.


Chapter 15-13MWH

Figure 15.1 General Schematic of MSW WTE Options

BIOGAS ENGINE/TURBINE POWER

PRE-TREATMENTINCINERATION

MSW

RESIDUALSMANAGEMENT

GASIFICATION(SYNGAS)

BOILER

1. BIOLOGICAL

2. THERMAL

TURBINE

POWER

BY-PRODUCTS


Chapter 15-14MWH

Figure 15.2 Schematic Process Flow Diagram of an Integrated MSW Biomethanation System

Recyclable

Conveyor 10Conveyor Conveyor

Exhaust Gas

Biogas

DewateringUnit

MagneticSeparator

Inclined Rotary Screen Ballisticseparator

Gas Flare

>180 mm

(Landfilling / Recyclable)(Landfilling / Recyclable)

(Recyclable)

GasStorage Dual Fuel Engine Power

Hydraulic Unit Mixing Unit

<40mm

To Landfill

Con

veyo

r

ManualInspection

LargeParticles

MSW

Waste HeatRecovery

Steam

AirCentrifuge

Recirculation

WastewaterETP To Disposal

Sew

age/

Fre

sh W

ater

VibratingScreen

<12mm AerobicMaturation

Compost

>12mAir+Excess Heat

From Heat Recovery

Water

Air

POWER GENERATION

ANAEROBIC DIGESTION

POST TREATMENT

PRE TREATMENTHomogenising

Drum

Digesters

Digester Feed

1

2

3

4

5

6

7

8

9

11

12

17

7A

13

26

14

15

16

19

18

20

21

22 23

24

25

Biogas Cleaning System


Chapter 15-15MWH

Figure 15.3: Mass Balance Diagram – Biomethanation Technology - Capacity 500 TPD (Thermophillic High Solids Dry Basis)Conveyor

Steam 171

Exhaust Gas

52500 Nm3/d Biogas

DewateringUnit

MagneticSeparation

Trommel Screen Conveyor Ballisticseparator

Flare

HomogenisingDrum

(>180 mm)

50(Landfill / Recyclable)

146

40-180mm63 TPD(Landfilling / Recyclable)

1 (Recyclable)

Gas Storage(500 m3)

Dual Fuel Engine Power(5.0 MW)

3753760

Digester feedHydraulic Unit Mixing Unit

300(<40mm)

83 to (Landfill)

300

Con

veyo

r

Conveyor

496

ManualInspection

Large Particles4 (Landfill)

500

MSW

83

Waste Heat Recovery

Air

200

175

10

Centrifuge

Recirculation 3290

Wastewater

165 m3/D

ETP To Disposal

Sew

age/

Fre

sh W

ater

210

VibratingScreen

<12mm

170Aerobic Maturation Compost 125

>12mm40 Recyclable AIR+EXCESS HEAT FROM HEAT RECOVERY

299

Units: TPD

Water205 m3/day

Air

POWER GENERATION

ANAEROBIC DIGESTION

POST -TREATMENT

PRE -TREATMENT


Digester4 x 5540 m3


Chapter 15-16MWH

Figure 15.4: Energy Balance Diagram – Biomethanation Technology - Capacity 500 TPD (Thermophillic High Solids Dry Basis)

7210KW

Stack508 KW

299 TPDMSW

AnaerobicDigester

Dual Fuel/ low BTUGas Engine

2 x 2700 KW

CompostingPlant

CaptiveConsumption

* Radiation Loss 750 + 400 =1150 KWE

To grid4250 KW

3210KW

5000 KWElectrical Output

2850KW

750 KWBiogas = 52500 NM3/dayLCV = 4800 K. cal.Heat in Gas = 52500 x 4800

24 860 = 12210 KW

Steam7.125 T/Hr

*

*Waste HeatRecoverySystem

12210KW


Chapter 15-18MWH


1516

BOILER WATER TREATMENT

MSW PROCESSINGINERT

REMOVALPLUG SCREW

FEEDER GASIFICATION GAS COOLING

POWER GENERATION

INERT LANDFILL

10 11 13 12 14 62 21 23 25

1

2 4 7 20 2430

5

3

8

9

RAW WATER

(WASTE HEAT RECOVERY)

EXHAUST

RECYCLE


Chapter 15-19MWH


301498

82

Landfill8240-180 mm

146

Conveyor

Stack

Ash25

Power(6.2 MW)

ConveyorMagneticSeparator

Trommel Screen Ballisticseparator

>180 mm

50 (Landfilling / Recyclable)

(Recyclable)1

<40mm - 302

ManualInspection


500MSW

RDF INCINERATION/POWER

POST TREATMENT

PRE TREATMENT

Screw Press

118 m3/DWastewater

PelletiserRDF Pellets183

(CV 4000 kcal / kg)

Fluidized BedIncinerator/Boiler(70 % efficiency)

Steam Turbine(25 % efficiency)

MultipleCyclonesESPScrubber

HomogenizingDrum 64

(Landfill/Recycling)

302

UNITS -TPD


Chapter 15-20MWH

Figure 15-8. Process Flow & Mass Balance Diagram for Municipal Liquid Waste-To-Energy Project – UASB 10 MLD

POST TREATMENT

Q = 5TSS = 80 mg/L

Q = 9970COD < 165 mg/LTSS <100 mg/LBOD < 50 mg/LQ = 35

TSS = 65 kg TSS/cum

UASB Reactor(3500 m3)

Q = 10000COD = 550 mg /LTSS = 250 mg/LBOD = 200 mg/L

Sludge Drying Beds

Facultative AerobicLagoon

Exhaust Gas

Flare Gas Holder(500 m3)

Dual Fuel Engine 150 kWPower

Air

POWER GENERATION

PRE TREATMENT(OPTIONAL)

Biogas = 1050 cum / dayWith 85 % CH4

H2S Scrubber

Sludge

CAPACITY : 10 MLD

Air

Disposal

Q : FLOW (cum/day)

Q = 9970COD < 100 mg/LBOD <30 mg/LTSS <50 mg/L

ANAEROBICDIGESTION


MWH Appendix 9A -1

Appendix 9-A

Commercial Biomethanation Technologies

9.A.1 Technologies with Indian Collaborators

9.A.1.1 SMAG Process

Developer: Reva Technologies - India

Description:

The Structured Media Attached Growth (SMAG) is a patented technology. This anaerobic treatmentsystem is a fixed film, fixed bed reactor and is packed with specially designed plastic media toprovide a very large surface area for the anaerobic bacterial film to grow and become immobilized.This media has a void ratio of 95% and provides surface area of 95 to 105 square meters in each cubicmeter volume. The entire media is kept submerged in the reactor content. The micro-organismsattached to specially designed media metabolise organic matter in the

wastewater and produce methane rich biogas which can be used as non-conventional energy sourcefor generation of steam & power.

The structured media attached growth (SMAG) technology offered by us has inherent multipleadvantages like Quick Restart, Low Area Requirement, High Reliability, Continuous Generation ofBio-gas with an extremely attractive PAY-BACK period of less than two years.

This process can be used for treatment of high strength wastewater like distillery, pharmaceutical etc.

Partial List of SMAG Installations :

S.No. Projects Type ofIndustry

Capacity

1 Dhampur Sugar Mills Ltd., Dhampur,U.P.

Distillery 800 m3/dCOD : 120000 mg/l

2 Kesar Enterprises Ltd., Baheri, UttarPradesh

Distillery 450 m3/dCOD :100000 mg/l

3 Gauri Industries Ltd., Gauri-Bidnaur,Karnataka


4 SLN Distillery Pvt. Ltd., Dharwad, Distillery 450 m3/d

Digester Media


MWH Appendix 9A - 2

S.No. Projects Type ofIndustry

Capacity

Karnataka COD : 100000 mg/l

5 Kanoria Chemicals & Ind.Ltd.,Ankeleshwar , Gujarat


6 Simbhaoli Sugar Mills Ltd., Simbhaoli,U.P.


7 Royal Distillery Pvt. Ltd., Daman Distillery 575 m3/dCOD : 120000 mg/l

8 PVK Distilleries Ltd., Varanasi, U.P. Distillery 600 m3/dCOD : 100000 mg/l

9 Malladi Drugs & Pharmaceuticals Ltd.,Ranipeth, T.N.

PharmaceuticalIndustry

120 m3/dCOD : 120000 mg/l

10 Emmellen Biotech Pharmaceuticals Ltd.,Mahad, M.S.


120 m3/dCOD : 120000 mg/l

11 Deccan Sugars Ltd., Samalkot, A.P. Distillery 225 m3/dCOD : 100000 mg/l

12 Andhra Sugars Ltd., A.P. Distillery 225 m3/dCOD : 90000 mg/l

13 Hanumanth Kali Vara Prasad BabuChemicals Pvt.Ltd., Hanuman, JN, A.P.


14 Sri Indra Distillery Pvt. Ltd., Tanukau,A.P.


15 Vijayshree Chemicals India Ltd.,Mathura, U.P.


16 Penguin Alcohols Pvt. Ltd., Canacona,Goa


17 Ashwini Biopharma Ltd., Tirupati, T.N. PharmaceuticalIndustry

200 m3/dCOD : 120000 mg/l

18 Emmellen Biotech Pharmaceuticals Ltd.,Mahad, M.S.


90 m3/dCOD : 120000 mg/l

19 Malladi Drugs & Pharmaceuticals Ltd.,Ranipeth, T.N.


200 m3/dCOD : 120000 mg/l

20 Empee Sugars & Chemicals Ltd.,Nellore, A.P.


21 Avon Organics Ltd.,Sholapur, M.S.


140 m3/dCOD : 100000 mg/l

22 Dhampur Sugar Mills Ltd., Dhampur,U.P. - Second Repeat order for 3rddigester


23 Samson Dist. Pvt. Ltd.Davangere, Karnataka

Dist. 800 m3/dCOD : 120000 mg/l


MWH Appendix 9A - 3

Contact Information:

Reva Enviro System Pvt. Ltd.9, Sunderlal Rai Path,Ramdaspeth,Nagpur - 440 010MaharashtraTel No : 91 - 0712 - 544817 / 544818Fax No. : 91- 0712 – 544813E-Mail : [email protected]


MWH Appendix 9A - 4

9.A.1.2 Biomethanation Technology - BIMA (Biogas Induced Mixing Arrangement) HighRate Digesters

Developer: M/s ENTEC Engg. Pvt. Ltd., Austria

Indian Counter Part: M/s Enkem Engg. Pvt. Ltd, Chennai

Description:

M/s Entec have developed and patented an unique system of anaerobic digesters to treat high organicwaste with high solids concentration.

The salient features of these digesters are as follows:

• Can handle solid concentration upto12% i.e. 1,20,000 ppm of suspended solids.

• No mechanical moving parts for mixing

• Control of scum and sediments

• In built biological desulphuration system

The most important aspect of BIMA digester is that it does not employ any mechanical moving partslike mixers, agitators, compressors etc. for mixing the contents of anaerobic digesters. The bio-gasgenerated from the system is used for mixing the contents of anaerobic digesters. Hence, the nameBIMA digesters i.e. the Bio-gas Induced Mixing Arrangement digesters. The detailed operatingprinciple with sketches is shown in Figure 1 and Figure 2, M/s. Entec have executed more than 50Biomethanation plants in Europe, Japan, Taiwan, Korea, etc. for various substrates like distillerywaste, starch industry waste, cattle manure, poultry litter, piggery waste, slaughter house waste,municipal solid wastes (garbage), food processing waste, industrial waste etc.


MWH Appendix 9A - 5

Figure 1: Cross Section of BIMA Digester


MWH Appendix 9A - 6

Figure 2: Operating Principle of BIMA Digester

1. Main chamber 2. Central tube3. Upper chamber 4. Distribution & mixing wings5. Substrate feeding pipe 6. Substrate effluent pipe7. Gas discharge pipe 8. Ground sludge pipe9. Mixing shafts 10. Gas dome11. Mixing valve 12. Substrate starting level13. Rising substrate level in the upper chamber

14. Pressed & decreasing substrate level in the main chamber

15. Highest substrate level, in upper chamber 16. Lowest substrate level in main chamber17. Fresh substrate feed 18. Inner basin in upper chamber19. Outer ring-basin in upper chamber 20. Wall diving upper chamber into (18) and (19)21. Overflow-wall


MWH Appendix 9A - 7

BIMA Digester – Operating Principle

Biogas Induced Mixing Arrangement (BIMA) Digester, is capable of handling upto 12% solidsand can be operated at very high loading rates. The digester has the following advantages:

i. Since the digester can handle wastes with high solids content (upto 10% dry matter) and cansupport high concentration of biomass, smaller digester with shorter retention time arepossible. This translates to reduced capital cost.

ii. Reduced installation, servicing and maintenance cost as there are no mechanical mixing partsfor mixing

iii. High reliability of the process on account of good control of scum and sediments.

iv. As no short-passes are possible on account of the chamber system, “plug flow” effect iscreated in the digester.

The BIMA digester can handle upto a maximum of 12% solids and does not require mechanicaldevices (such as agitators, screw mixers, lancers with compressors) to accomplish mixing in thedigester. BIMA digester is of the high rate type, and require significantly reduced volume toaccomplish effective degradation.

Moreover, in conventional digesters an energy equivalent of about 26 watts/m3 needs to be providedin order to accomplish complete mixing. Hence, appreciable energy needs to be provided toaccomplish mixing in conventional digester system. In comparison, an energy equivalent of about 70watts/m3 is generated during mixing in the BIMA digester, which is about three times that required toaccomplish complete mix, and hence there would be no mixing problems in BIMA digester. Besidesmixing, this energy is also adequate to prevent the formation of any scum/sediment in the digester.Further, as indicated earlier, this energy is derived from the biogas generated in the system (withoutthe need for any mechanical device like agitators), and therefore the operating costs would besignificantly lower.

The versatility and superiority of the BIMA digester over the conventional digester system can beseen from the following table which compares the two digester systems. Additionally, the BIMA canbe configured to prevent the formation of scum or sediment. As this waste has a tendency to formscum, the digester would be suitably designed to prevent any scum formation at the top of thedigester. Further, the BIMA digester has a sand trap to periodically drain the sand/silt, if any, fromthe bottom of the digester. This implies that the process of washing of the feed could be dispensedand the waste after segregation could be fed to the shredder and then to the dissolution unit.

BIMA digester is divided into three separate sections, being connected liquid and gas wise. Thethree sections are the main chamber, the upper chamber and the central tube, to which the feed-pipe isconnected. In this central tube a pre-hydrolysis of the substrate takes place. Most of the biogas isgenerated in the main chamber through the decomposition of organic materials. By closing anautomatic valve in the gas pipe between the two chambers the gas produced in the main chamber iscollected there, which in turn displaces an equal amount of the digested substrate into the upperchamber, building a level difference and thus a gas pressure in the main chamber. When the requiredlevel is achieved (mixing pressure), the gas pressure is released by opening the automatic valve in thegas connecting pipe. Thus the substrate displaced into the upper chamber flows back to the mainchamber with high velocity. A portion of the waste flows to the main chamber through the mixingwings while the rest flows back through the mixing shafts. On account of this, fresh substrate, scumand sediments are perfectly remixed with the contents of the main chamber. Thus the new pre-hydrolysed substrate is mixed with active biomass in the digester. Another portion of the digested


MWH Appendix 9A - 8

substrate which flows out through the mixing shafts, pours onto the surface of the main chamber, thusavoiding formation of scums.

Projects/ (India)

M/s Enkem Engineers Pvt. Ltd. in collaboration with Entec Environment Technology. Ltd., Austriahave executed/executing following biomethanation plants.

Solid Waste Biomethanation Plants

a. Slaughter house solid waste biomethanation plant (60 tons/day) to generate biogas usingBIMA digester. (50% MNES Grant)

b. 1.5 MW power plant using BIMA digester at Namakkal, Tamil Nadu 200 tons/day poultrylitter.(with MNES subsidy ).

c. Implementing Biomethanation plant for cattle manure (235 tons) to produce biogas and 1MW power at Ludhiana, Punjab Energy Development Agency.

d. BIMA digester is proposed to treat Organic fraction of Municipal Solid Waste to generate 5.0MW power at Lucknow.


Enkem Engg. Pvt. Ltd.824, Poonamallee High Road,Kilpauk (Near KMC)Chennai 600 010Tel : 6411 362, 6428 992Fax : 6411788E-mail : [email protected], [email protected]

Developer :

Entec - Environmental TechnologyUmwelttechnik GmbHShilfweg 1A-6972 Fusbach/AustriaTel: +43-5578-7946Fax: +43-5578-73638E-Mail: [email protected]


MWH Appendix 9A - 9

9.A.1.3 DRANCO Process

Developer: OWS, Belgium (DRANCO)

Indian Counter Part: Cicon Environment Technologies Ltd.

Description:

The DRANCO process consists of a thermophilic, one-phase anaerobic fermentation step which isfollowed by a short aerobic maturation phase. This flexibility of DRANCO Technology allows thetreatment of a wide range of different input materials. The digested residue is extracted from thedigester, de-watered to a TS-content of about 50% and then stabilised aerobically. DRANCO digesterdoes not have any internal mixing arrangement so the raw MSW (after pretreatment) is mixed withrecirculated digestate and fed into the digester from the top. The digestate is withdrawn from thebottom of the digester.

Process Characteristics

• thermophilic or mesophilic, one-phase anaerobic fermentation system

• high waste stream flexibility

• proven and stable high-rate digestion process

• simple and reliable digester design: low maintenance, low wear

• no mixing inside digester

• controlled external inoculation

• high biogas yield and biogas production

• reduced surface area required

• automated process control.

Process Parameters

• digester loading: 10 to 20 kg COD/m³ reactor/day

• retention time in the digester: 15 to 30 days

• biogas production: 100 to 200 m³ of biogas per ton of waste

• electricity production: 170 to 350 kWh per ton of waste

Contact Information :

Prashant Sahu (Managing Director)Cicon Environment Technologies Ltd.Plot 61-B, Kasturba Nagar,Bhopal 462 024Tel: 91-755-789446, 280 499, 273 609Fax: 91-755-582331e-mail : [email protected]

[email protected]


MWH Appendix 9A - 10

Developer :

Organic Waste Systems nvDok Noord 4B-9000 Gent - BelgiumTel (+32)-9-233.02.04Fax (+32)-9-233.28.25E-mail: [email protected]



9.A.1.4 Wabio Anaerobic Digestion Process

Developer: Ecotechnology, JVV OY, Finland

Indian Counter Part: Nestler EcoTec Pvt. Ltd., Navi MumbaiHydroair Techtonics (PCD) Pvt. Ltd., Navi Mumbai

Description:

Wabio Anaerobic Digestion Process is developed by Ecotechnology JVV OY of Finland. It is onestage, medium concentration anaerobic digestion process operating in the mesophillic temperaturerange with solid concentration 10-20% range. The process involves two stages. First stage is thepretreatment stage where the garbage is received and is followed by hand picking belt conveyor andan electro magnet. After segregation, the material is shredded to smaller pieces ranging from 25-50mm. The shredded material is screened. The second stage (Wabio) consists of feed preparation tankswhich receive the screened material and a slurry of 15% solid concentration is made. The slurry isthen pumped to bioreactors where the process of digestion takes place. The products of bioreactorsare methane rich gas from the top and sludge/slurry from the bottom. The supernatant liquid, near thetop, is sent for recirculation to make the slurry. Gas is stored in the gas holder. Part of this gas isused for mixing the contents in the bioreactors. From the gas holder the gas is sent to gas engines toproduce electricity.

Sludge/ slurry from the bottom of the bioreactors is sent to filter press for dewatering. Afterdewatering, the filtrate is sent back to the feed preparation tanks. The remaining dewatered cake hasorganic fertilizer value.

Projects/ demonstrations:

Vassa in Finland and Bottrop, Germany.


Mr. N. D. ChhabriaNestler EcoTec Pvt. Ltd., Hydroair Tectonics (PCD) Pvt, Ltd.,30 Sadhna, 4th Floor, Nowroji Gamadia Road 116 Raheja Arcade, Sector 11,Mumbai-400026 Plot No 61, BelapurTel: +91-22-282 5846 Navi Mumbai 400 614Fax: +91-22-367 6053 Tel: +91-22-756 4347E-Mail: [email protected] Tele Fax: +91-22-756 4364

E-Mail: [email protected]: www.hydroair.com

Developer :

Valkhärventie 202130 EspooFinlandTel: +9+358-43577477Fax: +9+358-43577488Web: www.ecotechnology.fi



9.A.1.5 Linde-KCA-Dresden GmbH

Developer: Linde - Germany

Indian Counter Part: Linde Process Technologies (I) Pvt, Ltd., Vadodara

Description:

Linde-KCA-Dresden GmbH, a wholly owned subsidiary of Linde AG, Wiesbaden, in association withLinde BRV Biowaste Technologies AG and, following the acquisition of the technologies andexperience of the "Mechanical-Biological Waste Systems" product line of Austrian Energy &Environment, has become a leader in the field of mechanical-biological waste treatment. We have sofar completed a number of digestion and biogas plants as well as treatment and composting plants forvarious types of waste.

We plan and build plants for the following types of waste:

Biowaste from separate collection systems, Residual waste, Mixed waste/household waste,Household-type industrial waste Kitchen waste Differing types of biogenic waste from commerce andindustry Market waste Garden and vegetable waste Animal manure Sewage sludge

Wet Digestion

Single-stage and two-stage wet digestion processes can be run in thermophilic or mesophilic modedepending on the type of input material. They are designed to produce biogas at high yield rates. Theircharacteristic features are an automatic separation of contaminants in the wet preparation stage(pulper, drum screen) and safe waste handling in closed systems. The characteristic feature of ourtechnology is the digestion reactor with gas recirculation using a centrally located recirculation tube.

Digestion residues from wet digestion plants like these have a very low contaminant content and canbe used for the production of high-grade composts.

One preferred application of the wet digestion process is the co-digestion of biowaste and sewagesludge and/or agricultural waste (manure).



Dry digestion

Dry digestion is a thermophilic or mesophilic process using horizontal plug flow reactors with arectangular cross-section.

The digestor is normally provided with an upstream aerobic pre-treatment for hydrolysis andsystematic acidification. The reactor is designed for handling waste with total solid concentrations of15 % to 45 % TS in the digestion substrate.

This process can handle most types of waste, such as green waste, biowaste or commercial waste, butis particularly suitable for the treatment of waste rich in solids (high TS content) such as residual ormixed waste.

Contact Details

Linde Process Technologies India Private LimitedNutan Bharat Society, AlkapuriBaroda-390 005, GujaratTel: 0265-336319, 336196/Fax: 0265-335213

Developer:Linde-KCA-Dresden GmbHPostfach 210353D-01265 DresdenGermanyTel: +49 3 51 45 600Fax: +49 3 51 45 60 202



9.A.1.6 TBW-biocomp Process

Developer: TBW, Germany

Indian Counter Part: Mailhem Engineers Pvt. Ltd., Pune

Description:

Organic waste is fed through a wheel loader into the rotary screen at the receiving station, separatingthe flow of material into a coarse fraction comprising shrubbery trimmings and the like and a finefraction made up of vegetable peelings, etc. The separated coarse fraction is forwarded to thecomposting plant. On separate conveyors, the different fractions are run through a magnetic separatorthat removes any iron-containing particles. The vibration unit uniformly distributes the flow ofmaterial onto the downstream sorting belt. Parallel belts carry the material to the enclosed sortingplatform, which is also connected to the biofan by a space ventilation system at this point, anyremaining troublesome material, e.g. plastic, is sorted out. This combination of different techniquesmakes it possible to achieve a high level of seperation efficiency. After sorting, the fine fraction issent to the pulper for mixing with liquid separated.

Batches of prepared fine fraction are pumped out of the feed tank into the first-stage fermenter(reactor), where a process temperature of 35°C is maintained, special propeller-type agitators keep theslurry homogeneous. It takes approximately two weeks for she slurry to pass through the first reactorfrom top to bottom, with stirring at each level. Then, by way of the reactor's bottom drain, the activesludge proceeds on to the second reactor, which it enters from the bottom. An ingenious substratecontrol setup enables separation of any fines that have been released by the decomposition of organicsubstances in the interest of optimal decontamination/disinfection in combination with high rates ofdigestion, a temperature of about 55°C is maintained in the second reactor. Again, it takesapproximately two weeks for the slurry to pass through the reactor, this time from bottom to top at theend of those two weeks, at least 60% of the substrate's original organic content will have beenconverted into biogas. The reactors are equipped with flexible gas-collecting membranes that serve asquasi pressureless interim gas storage spaces. The batches of digested sludge are press-dewatered withthe liquid returning to the process via the separator and the filter cake being mixed with mature crudecompost for subsequent compostation

The reactors continuously produce a combustible mixture of raw gases that have to be cleaned anddried before they can be converted into electricity and heat. A biocatalytic process reduces thehydrogen sulfide from gas. Electricity and heat are generated from the biogas in cogenerating modulesthat consist chiefly of a water cooled, diesel-type aspirating engine, an induction generator and anexhaust heat exchanger. The module efficiency is in excess of 90%. A biogas-fueled combined-cyclemodule extracts roughly 1.5 kWh (el) and 3 kWh(therm) energy from each cubic meter of biogas. Thespecific emissions are even lower than those produced by a comparable internal combustion engineequipped with an oxygen sensor emission control system (three-way catalytic converter). The thermalenergy yield covers the plant's heating and hot water requirements. The combined anaerobic/aerobicprocess supplies the energy required for the composting process- some 50 - 100 kWh per ton oforganic waste - and has enough left over to feed the public power grid


Mailhem Engineers Pvt. Ltd.,14, Vishrambag Society,Senapati Bapat RoadPune 411 016Tel: +91 20 400 2285Tel. Fax: +91 20 400 2286



Developer:

TBWBaumweg 10d-60316 FrankfurtGermanyTel: +49 699 43 5070Fax: +49 699 43 0711



9.A.1.7 Kompogas Process

Developer: Kompogas – Switzerland

Indian Counter Part: Greentech Environmental Systems

Description:

All conventional processes for disposing of organic waste such as landfills, incineration orcomposting have their drawbacks. On the other hand, utilising them with the aid of Kompogas offersnumerous advantages. Thus, the end products obtained are compost to VKS guidelines, CO2 neutralfuel, gas, electric power and heat.

To produce energy from yard and kitchen waste, the organic waste is first freed of foreign matter andthen fed to the fermenter. In the entirely enclosed reactor operating according to the anaerobicprinciple (with absence of oxygen), microorganisms transform the organic substance present in thematerial into compost and biogas. The thermophile fermentation process takes place at a temperatureof 55 to 60 degrees Celsius and lasts for 15 to 20 days. During this time, undesirable germs and weedseeds are reliably eliminated.

Today's Kompogas plants recycle the biogenous waste supplied day in, day out while optimallyutilising the energy it contains. The biogas produced during the degradation process is converted intoelectrical and thermal energy, ensuring self-sufficient operation and generating considerable surplusenergy. The biogas may be upgraded to natural gas standards for fuelling cars and/or for being fedinto the natural gas network. From one metric tonne of organic waste, 130 cubic metres of biogas areextracted, corresponding to about 70 litres of petrol (gasoline). Kompogas (biogas), which can be usedas a fuel for vehicles or for co-generation units in order to generate electric power, is today consideredto be one of the most environmentally friendly, CO2-neutral sources of energy available to a broadsegment of the population.

The high-quality, hygienic compost is used by private individuals, in agriculture and in gardening.Kompogas compost and the liquid fertiliser are valuable, natural fertilisers (certified for organicagriculture), which allow impressive harvest results to be achieved.

In addition to its high specific gas yield, this process is mainly characterised by its high operating andprocess reliability, thanks to the experience gained to date. The new modular plant design reduces thecapital cost requirement. A large part of the plant construction work can be done by local companies.

Ensures ecological utilisation of biogenous waste closes the materials cycle (compost and liquidfertiliser). Generates considerable amount of CO2 neutral energy satisfies hygienic requirements.Proven process - numerous Kompogas plants in operation around the world.

Contact Information:Asit NemaGreentech Environmental SystemsF-200, Sarita ViharNew Delhi 110 044Telefax : 91 11 695 40 84e-mail : [email protected]



Developer:Kompogas AGRohrstrasse 36CH-8152 GlattburggSwitzerlandTel: +41 1 809 71 33Fax: +41 1 809 71 10Web: www.kompogas.ch



List of Technology Providers in India

Sr. No. Technology Provider1. Director

National Environmental Energy Research Instt.Nehru Marg, Nagpur – 400 020Ph. 0712-223893, 222725Fax: 0712-222725

2. Dr. Ramesh DaryapurkarDy. General ManagerLars Enviro Pvt. Ltd.218, Balaji NagarS.A. RoadNagpur – 440010Tel : 91-0712-233775 / 224130Fax : 91-0712-235567 / 224140

3. GENLAshirwad, 29/B, Lokmanya ColonySurvey No 89/90, KathraPune – 411038Tel : 91-95212-364730Internet : [email protected]

4. Hydroair Tectonics (PCD) Pvt., Ltd.,116 Raheja Arcade, Sector 11,Plot No 61, BelapurNavi Mumbai 400 614Tel: +91-22-756 4347Tele Fax: +91-22-756 4364E-Mail: [email protected]: www.hydroair.com

5. Linde Process Technologies India Private LimitedNutan Bharat Society, AlkapuriBaroda-390 005, GujaratTel: 0265-336319, 336196/Fax: 0265-335213

6. Lt. Col. Suresh Rege (Retd.)Mailhem Engineers Pvt. Ltd.,14, Vishrambag Society,Senapati Bapat RoadPune 411 016Tel: +91 20 400 2285Tel. Fax: +91 20 400 2286

7. Mr. Anand KothanethVice PresidentBatliboi Environmental Engg. Ltd.99/2, 99/3, N.R. RoadBangalore – 560002Tel : 91-080-2235061, 2, 3



Sr. No. Technology ProviderFax : 91-080-2235085

8. Mr. Asit NemaGreentech Environmental SystemsF-200, Sarita ViharNew Delhi 110 044Telefax : 91 11 695 40 84e-mail : [email protected]

9. Mr. Bimal DharSr. Manager – Business DevelopmentUtility Powertech LimitedS-168 Greater Kailash Part INew Delhi – 110048Tel : 91-011-6281667 / 1670 / 6293363Fax : 91-011-6489518

10. Mr. K.S. ShivaprasadDirector (Technical)Zen Global Resources & Energy Ltd.1, Sriram Nagar, South StreetAlwarpet, Chennai – 600 018Ph. 044-4994059, 4996946Fax: 044-4996811

11. Mr. Mukesh GroverGeneral Manager – Process and Business DevelopmentDegremount India Ltd.Water and the EnvironmentSCO-4, Sector – 14Gurgaon – 122 001Ph. 124-305549, 305564Fax:305551Email:[email protected]

12. Mr. N. D. ChhabriaNestler EcoTec Pvt. Ltd.,30 Sadhna, 4th Floor, Nowroji Gamadia RoadMumbai-400026Tel: +91-22-282 5846Fax: +91-22-367 6053E-Mail: [email protected]

13. Mr. Naresh VermaVice President (MKTG)UEM India LimitedD-19 KalkajiNew Delhi – 110019Tel : 91-011-6421634 / 6447825 / 6239718Fax : 91-011-6239801



Sr. No. Technology Provider14. Mr. P. Sumbramani

DirectorEnkem Engg. Pvt. Ltd.824, Poonamallee High Road,Kilpauk (Near KMC)Chennai 600 010Tel : 6411 362, 6428 992Fax : 6411788E-mail : [email protected], [email protected]

15. Mr. R.D. MehtaGen. Manager (Business Div.)Paramount Pollution Control Ltd.Paramount ComplexGotri Road, Race CourseBaroda – 390 007Ph. 0265 – 336111, 6183647Fax : 6186369

16. Mr. Tony DavidMarketing OfficerWestern Bio-Systems Ltd.65/1-A, Akarshak, 2nd FloorOpp. Nal Stop, Karve RoadPune – 411 004.Ph. 0212-349159, 332345Fax: 0212-348321

17. Mr. V. NandakumarCustomer Service DivisionHindustan Dorr Oliver Ltd.,Dorr-Oliver House121 Rukmini Lakshmmipathy RoadEgmore, Chennai – 600 008Tel : 8554183 – 82, 8555Fax : 85553728

18. Prashant Sahu (Managing Director)Cicon Environment Technologies Ltd.Plot 61-B, Kasturba Nagar,Bhopal 462 024Tel: 91-755-789446, 280 499, 273 609Fax: 91-755-582331e-mail : [email protected]

[email protected]

19. Quantum Tech LL.C.127 Satyam Estate163/164 ErandwanePune – 411 038Ph. 0212-360076/362847



Sr. No. Technology Provider20. Reva Enviro System Pvt. Ltd.

9, Sunderlal Rai Path,Ramdaspeth,Nagpur - 440 010MaharashtraTel No : 91 - 0712 - 544817 / 544818Fax No. : 91- 0712 – 544813E-Mail : [email protected]

21. The DirectorEnvirod Projects Pvt. Ltd.,Avadhpuri Road6, LakhanpurKanpur – 208024Tel : 91-0512-580208 / 580061 / 583226Fax : 91-0512-582532



9.A.2 Technologies without Indian Collaborators

9.A.2.1 High solids Anaerobic Digestion

Developer: NREL, U.S. Department of energy, Licensee Alpha-Gamma Developed by Dr.Christopher Rivard currently with PINNACLE

Description:

High-Solids Anaerobic Digestion (HSAD) technology is a microbial bioconversion process thatrecycles organic solid waste into fuel gas and a nitrogen-enriched compost. The process can beapplied to many different wastes, agricultural waste, sewage and industrial sludge, green waste, andmunicipal waste. Wastes may be treated separately or combined to achieve waste treatment flexibilityand economy of scale.

The continuous HSAD process can be readily integrated into existing industrial plants and municipalsolid waste sorting facilities. HSAD is an application of a proven conventional low-solids anaerobicdigestion system. In the anaerobic digestion, bacterial and fungal actions convert organic materials inthe liquid waste to biomass and biogas. Anaerobic digestion reduces the organic content of thewastewater to levels that can safely be released back to the environment.

The HSAD system applies this same technology to create a new “high-solids” process that cansuccessfully utilize solid organic waste feedstocks. The solid phase fermentation reduces the requiredequipment volumes and associated capital and operating costs, while the bioreactor’s volumetricproductivity is significantly increased. Conventional anaerobic digestion feedstock typically contains1-2% solids. In contrast, HSAD feedstocks are up to 50% solids.

The key element of the HSAD process is a proprietary closed-system design developed throughNREL sponsorship. This system utilizes equipment modified from the chemical processing industry toprepare organic solid wastes and load the HSAD bioreactor. Inside the bioreactor, a uniqueconsortium of thermophilic microorganisms converts the organic carbon into cell mass and biogas.Therefore it is also described as “Anaerobic Composting”.

The biogas produced is captured and converted to electricity or steam and heat. The effluent from thebioreactor produces two products: a moist, compost material and liquid fertilizer.

Even though, The HSAD process is specifically designed to recycle solid organic waste, but it easilyprocesses combinations of solid and liquid, municipal or industrial wastes. Blends of rapidlydegrading feedstocks, such as fats, oils, and grease, and slower degrading materials including paperand yard waste, make superior feedstocks. Blended feedstocks provide consistency of compositionwith improved process control and higher conversion rates.

This is a closed odorless system that recycles up to 90 % of the organic carbon in the solid organicwaste material into biogas. The process reduces the volume of the solid feedstock by as much as 70%,the resultant is marketable compost.

Projects/ Demonstrations:

Pinnacle Biotechnologies International, Inc. is currently operating a Pilot Demonstration Unit (PDU)of the High Solids Anaerobic Digestion process in Stanton, California. This demonstration facilitydigests 3 ton per day of municipal solid waste (MSW) and food processing waste to methane andcompost.




National Renewable Energy Laboratory1617 Cole BlvdGolden,CO 80401-3393Tel: +1-303-275-3000

PINNACLE Biotechnologies6559 Jungfrau WayEvergreen, CO 80439Tel: +1-303-674-3236Fax: +1-303-674-0006



9.A.2.2 CBI Walker/Enning ESD™ System

Developer: CBI Walker Inc.

Description:

The CBI Walker/Enning ESD™ System was developed by CBI Walker, Inc., a subsidiary of ChicagoBridge and Iron Company. The key to the ESD system is the blending of the optimum egg-shapedvessel with effective and efficient liquid mixing to enhance digester performances.

The double curvature shape, reduced top liquid surface area, and liquid mixing of egg-shapeddigesters eliminate scum and grit build-ups, dead zones, and the need to take the digesters out ofservice for cleaning. This contrasts with conventional digesters, which even with the use of mixingsystems, must be periodically cleaned.

The ESD system provides the full design volume, and hydraulic residence time (HRT), throughout thefacility design life. The full HRT is realized because the ESD digester does not have scum and gritbuild-ups or dead zones.

Gas tight vessel design reduces the potential for odors associated with anaerobic digestion. Biogascollects in the top cylinder and flows directly to gas storage and utilization equipment. Pumped liquidmixing eliminates foaming problems predominant in gas mixing systems. Additionally, operatingcosts are lower, since the pump works only against losses in the piping system.

There are two liquid mixing systems developed by CBI Walker:

• CBI Walker/Enning System

• Jet Pump System

CBI Walker/Enning SystemCBI Walker/Enning System follows traditional, proven German practice. This system utilizes amechanical mixer with draft tube assembly for the main mixing mode, and an exterior re-circulationpump and heat exchanger to maintain the digester at the most efficient temperature range (95 ºF-100 ºF ). This re-circulating stream is also used to maintain the walls of the vessel free of sludgeaccumulation.

Jet Pump SystemThe Jet Pump mixing system utilizes a jet pump with draft tube assembly and external heat exchangerto mix and heat the vessel. The size, location, and number of jet nozzles is dependent on the size ofthe vessel and characteristics of the raw sludge. The main advantages of this system are lower mixingenergy requirements and no moving parts inside the digester. {(13) internal ref. 26 }


Lincoln, Nebraska, USA ESD facilitySan Francisco, California, USA ESD facilitySt. Charles, Illinois, USA ESD facility




CBI Walker, Inc.1245 Corporate Blvd.Aurora, IL 60504USATel: +1-708-851-7500Fax: +1-7-8-851-9392E-Mail: [email protected] (media inquiry)Web: www.cbi-nv.com



9.A.2.3 BTA Process

Developer: BTA - Germany

Description:

BTA GmbH & Co. KG has developed and continuously improved the BTA-Process since 1984, isholding various patents and is worldwide realising BTA-Plants resp. parts thereof together with itslicensees and co-operation partners. Then BTA mainly is acting as know-how provider. In the scopeof realisation of individual BTA-Plants or parts thereof BTA additionally undertakes engineeringwork and further tasks in the area of plant construction. (Those further performances are followingexplained in relation to singular realised BTA-Plants resp. parts thereof).

BTA Biotechnische Abfallverwertung GmbH & Co. KG was formed in Munich in 1984. Theobjective was the further development of the then unknown "BTA Process" and its introduction in themarket.

This process was a new combination of wet pre-treatment and anaerobic digestion for the utilizationof the organic fraction and therefore the largest single portion of the waste stream from domestic,commercial and agricultural sources. Furthermore, the process is able to treat the residual waste inorder to minimize the volume of and the hazards posed by a residual repository. The process wasinitially developed in the Pilot-plant in Garching and following a great number of tests were realizedthere to gain experiences with various kinds of waste and to adjust the technology for the treatment ofthe different waste streams.

By means of the wet pre-treatment non-biodegradable components of the waste are efficientlyremoved and a homogenous pulp is produced. In the following digestion system the degradableorganics are anaerobically digested producing biogas and anaerobic compost. Besides the productionof high quality compost the BTA-Process is producing enough biogas to cover the energy demand ofthe plant itself and in addition to feed a surplus yield into the public energy net. Thus, the largerportion of the organic waste is used as a source of renewable energy and by the CO2-neutralproduction of biogas an important contribution to the conservation of the world climate is made.

The BTA-Process was developed to transform biowaste (OFMSW organic fraction of municipal solidwaste) from households, commercial and agricultural waste into high-grade biogas and valuablecompost.For example the following feedstock can be used:

• Organic components of municipal solid waste (mixed waste)

• Source separated organic waste from households (e.g. kitchen leftovers)

• Food waste from restaurants, canteens and markets

• Waste from food processing industries

• Waste from slaughterhouses (e.g. rumen content)

• Waste from agriculture (e.g. manure)

• Sewage sludge as well as the rake fraction from sewage plants

• Residual waste - environmental aware deposition of residual waste requires reducing theorganic portion of the waste so that no further chemical or biological reaction is likely tooccur in the landfill. This can be achieved by using the BTA-Process.



Results:

• Substantial waste volume reduction

• Environmentally benign treatment of waste

• Maximum energy recovery

• Reduction of CO2-emissions

• Production of high grade compost

The process consists of two major steps: Mechanical wet pre-treatment and biological conversion.

In the waste-pulper the feedstock is mixed with recirculated process water. Contaminants like plastics,textiles, stones and metals are separated effectively and gently without any handsorting by means of arake and a heavy fraction trap. From the contained organics a thick pumpable suspension (pulp) isproduced which can be easily handled and digested.

An optional but essential further component of the process is the grit removal system which separatesthe still remaining finest matter like sand, little stones and glass splinters by passing the pulp througha hydrocyclone. Thus the plant is protected against increasing abrasion.

According to the plant capacity and the kind of energy- and compost utilization various concepts ofthe biological step can be offered:

First the so-called one-stage digestion, fermenting the produced pulp within one single step in onemixed fermentation reactor. This concept enables to use the BTA technology even for comparativelysmall decentralized waste management units. Existing digestors (i.e. on a sewage plant or agriculturalbiogas plants) can be used which results in an essential reduction of invest- and operating costs.

For plants with a capacity of more than 50,000 t/a the multi-stage digestion was developed, separatingthe pulp in a solid mass and a liquid phase by using a dewatering aggregate. The liquid, alreadycontaining dissolved organic components, is directly pumped into a methane reactor remaining therefor a methanisation of 2 days. The dewatered solid material, still containing undissolved organic



components,is once more mixed up with water and fed into a hydrolysis reactor. After 4 days the mass isdewatered again and then the liquid is filled into the methane reactor.

By distributing the degradation process on different reactors (acidification, hydrolysis andmethanisation) optimal growth conditions for all groups of micro organisms can be adjusted. Thisallows a rapid and extended degradation of the organics resulting in a high yield of biogas. Withinonly a few days 60-80% of the organic substance are converted into biogas.

As a further variation for plants with medium capacity the two-stage digestion is available: basing onthe multi-stage concept but without a solid/liquid separation. The pulp is fed into a mixed hydrolysisreactor which is following connected with an also completely mixed fermentation reactor. To enableoptimal hydrolysis conditions a part of the fermentation reactor content is fed back into the hydrolysisreactor.

In case of plant extension, the completion of a stage is possible without any problems. For thetreatment of food waste an additional sanitation step will be integrated. The water demand of allprocess variations is met by recirculating the water which is contained in the waste. Excess water isled into a sewage plant.

So in all, a plant designed according to the BTA-Process and/or operating with BTA-Pre-treatment orparts thereof represents a technology with a high flexibility allowing an adaptation to the specificneeds of each client and to fit the specific conditions of each single case.

Products

Products of the process are biogas and compost.



The biogas consists of 60-65% methane. Due to its high heating value the gas is a valuable source ofenergy with a large scope of application. The biogas production is far surpassing the energy demandof the plant itself. Converted into electricity and heat the surplus can be fed into a public network.

After a short aerobical treatment (1-3 weeks) the anaerobic compost is plant compatible. The stablecrumbly structure improving root growth and aeration is superior to peat and yard waste compost.Due to its structure, the high percentage of organic substance, its low heavy metal and salt content aswell as its good balance of nutrients BTA compost has a large range of agricultural and horticulturalapplication.


BTA Biotechnische Abfallverwertung GmbH & Co KGRottmannstrasse 18D-80333 MunchenGermanyTel: +49 89 520 460-6Fax: +49 89 523 23 29Web: www.bta-technologie.de



9.A.2.4 Valorga Process

Developer: Steinmuller Valorga, France

Description:

The Valorga process was designed to treat organic solid waste. It is thus adapted to the treatment ofmixed municipal solid waste, source sorted household waste (biowaste), organic residual fraction afterbiowaste collection (grey waste).

An installation for treatment of organic waste according to the Valorga process is made up of a unitfor the reception and the preparation of waste, an anaerobic digestion unit, a compost production unit,a biogas utilisation unit, an air treatment unit and optional, an excess-water treatment unit.

The reception and preparation unit is made up of a bascule bridge to weight the collection lorries uponarrival in the factory. The weighed waste enters into a closed pit situated in the reception hall or aclosed unloading hall with a foul air extraction system. the preparation unit includes calibration, bag-opening and size reduction designed according to the waste to be treated. The shredded waste isfinally conveyed through conveyors and hopper in order to bring the product to the anaerobicdigestion unit. In the case of mixed waste or gray waste treatment the sorting unit is adapted to thecomposition of the waste to be treated. Steinmüller Valorga can join forces with other industrialpartner and sorting unit equipment suppliers in order to meet the requirements of waste sorting.

The anaerobic digestion begins with dilution and mixing of the waste in the form of a thick sludge,with a high dry matter content (20% to 35% depending on the type of waste), giving a reduction in thevolumes of fermentation. Heating is provided by steam injection. The mixture is introduced at thebottom of the reactor with a piston pump. The digestion itself that takes place in fermenters underanaerobic conditions. The temperature can be in the mesophilic range (± 40°C) or thermophilic range(± 55°C). The Valorga fermenter is a vertical cylindrical digester with a plug-flow transfer of thematter. The digester has a vertical median inner wall on around 2/3 of its diameter. The introductionand extraction orifices are at the base of the fermenter on either side of this inner wall. The inner wallforces fermenting matter to follow a circular movement in order to go around it, so that waste mayonly be extracted after having covered the whole surface of the digester. This specialised geometry,along with a limited level of recycling for fermented matter, guarantees that waste will spend aminimum of around 3 weeks in the fermenter. This aspect is vital for a perfect hygienisation ofcompost. To insure an optimal level of degradation in the digester, the matter should behomogenised. The particularity of the fermenting matter is that it is abrasive as it contains fine inertparticles. Any mechanical system built to mix such matter would suffer great wear and tear. Valorga'spatented mixing system is pneumatic: biogas is injected through injectors into the base of the reactorunder pressure. A great advantage of this mixing system is that no mechanical mixing equipment isused in the fermenter, which would necessitate opening and maintenance of the digester, thus puttingit out of action. The biogas used for the mixing turns in a closed circuit The compression of biogas ismade by a two level compressor (8 bar pressure). The gravity extraction and the pressing of thedigested matter: the digested product taken out of the digester then undergoes a mechanical pressingprocess, resulting in a solid fraction and a liquid sludge The sludge treatment in order to separate thesuspended solids. A part of the clarified process water is used for dilution of the incoming waste. Theremaining part is either discharged into the sewage network or transferred to the excess watertreatment unit. The solid fractions are transferred to the aerobic post-treatment unit.

This unit is designed to produce a high quality organic amendment from the matter extracted from thedigesters. It involves the maturation and drying of the digested matter in a closed building underdepression, where the product is stored during at least 2 weeks and eventually removed and aerated.This aerated compost is refined further and packed and sold.




Steinmuller Valorga SarlClaude Saint-Joly1300 avenue Albert EinsteinImmeyble Strategie ConceptParc du Millenarie – BP 51F-34935 Montpellier Cedex 09FranceTel: +33 4 67 994 100Fax: +33 4 37 994 101Web: www.steinmuller-valorga.fr



9.A.2.5 PFMSW Methanization - WAASA® Process

Developer: Alcyon Engineering S.A., Switzerland

Description:

In landfills the degradation of organic matter takes many decades, with biogas emitted into theatmosphere, usually without any energy recovery. In a WAASA® plant the same process takes onlytwo weeks and the biogas is utilized as fuel for energy production.

The other by-product, the humus, is fully stabilized, and suitable for use in landscaping andenvironmentally remedial works. Humus produced from source-sorted MSW is also suitable for usein agriculture and in horticulture.

Prior to the methanzation, a patented feed preparation vessel, the MixSeparator™, removes plastics,cork, etc. and solid impurities, like glass, ceramics, sand, gravel etc.

The heart of the WAASA® process is the patented digester, called TwinReactor™, which operates inthe thermophilic temperature range (550C). The process can also be applied in the mesophilictemperature range (350C). The choice between the two types of operation will depend solely oneconomical considerations.

A WAASA® plant normally consists of one or more parallel processing lines. The digesters arestationary and installed upright. The size of one reactor can go up to 3,000 m3. This will handle thewaste generated by a population of approximately 200,000 people. For larger waste quantities two ormore parallel reactors are required.

Depending on the size, the digesters are made either of steel or of reinforced concrete. The reactorscan also be built inside bedrock.

The degrading of organic matter takes place in the digesters where methanogenic bacteria convertorganic substances into biogas and humus matter. The retention time of material in the process is 15-20 days. The bioreactor substrate is effectively mixed by means of a bubble column created by thecirculated biogas and by mechanical devices.

For the mesophilic process the digested slurry is pasteurized in order to ensure hygienic safety. Thepasteurization takes place is closed vessels, in which the slurry is kept at a temperature of 700C for 3ominutes. For the thermophilic process pasteurization is not necessary.

After pasteurization the slurry is mechanically dried to a total solid content down to 25% to 35%. Ata later stage, storing properties, aesthetic appearance, and usability of humus can be improved bypost-aeration and by screening.

The humus by-product is fully processed and stabilized and is thus suitable for landscaping, gardeningand agriculture.

Combining methanization and composting processes on the same site could provide many advantages:

• Methanization will treat wet waste, e.g. the putrescent fraction of the municipal solid waste,wet garden trimmings, etc.

• Composting will treat dry waste, e.g. ligneous biomass waste, bark residues etc.



Key Benefits

• Green waste management improved, no anaerobic digestion during composting, no compostcompaction, better compost aeration

• Lower composting station, operational costs

• No local nuisance (no order, no leachates)

• Methanization/composting equipment optimization

• Complementary technologies: methanization excess water will be used for compost watering.After methanization, humus needs 10 days for maturation. It will be mixed to the compostflow. This improves the quality of the compost, resulting in improved fertilizer quality (betterC/N Ratio).

Contact Details

Alcyon Engineering S.A.15, AV. Des BaumettesCH-10202 RENES (Switzerland)Tel : + 41 21 637 37 37Fax: + 41 21 637 37 30Email : desk@alcyon .ch



List of International Technology Providers

Sr.No.

Technology Provider

1. AAT GmbHKelhofstraße 12A-6922 WolfurtAUSTRIATel: 43 5574 65190Fax: 43 5574 65185e-mail: [email protected]://www.austria.org.tw/English/AAT.htm

2. AD Technology, Ltd.Chris ReynellWindover Farm, Longstock StockbridgeHampshire SO20 6DJUNITED KINGDOMTel: 44 1264 810 569Fax: 44 1264 810 131

3. ADI Systems, Inc.Suite 3001133 Regent StreetFredricton, New BrunswickCANADATel: 1 506 452 7307Fax: 1 506 452 7308e-mail: [email protected]://www.adi.ca/

4. Alcyon Engineering S.A.15, AV. Des BaumettesCH-10202 RENES (Switzerland)Tel : + 41 21 637 37 37Fax: + 41 21 637 37 30Email : desk@alcyon .ch

5. ANMAN Machinenbau und UmwelttschutzanlagenWaterbergstraße 11D-28237 BremenGERMANYTel: 49 421 694 580Fax: 49 421 642 283

6. Arge BiogasWalter GrafBlindergaße 4/10-11A-1080 ViennaAUSTRIA43 14 064 579



Sr.No.

Technology Provider

7. Bio Recycling Technologies IncJim Hamamoto6101 Cherry AvenueFontana, CA 92336USATel : 1 909 899 2982Fax : 1 909 899 9519

8. Biocel/Heidemij Realisatie BVWilem ElsingaPostbox 139NL-6800 AC AmhemTHE NETHERLANDSTel: 31 26 377 8304Fax: 31 26 442 6984

9. Bioplan A/SLivørvej 21DK-8800 ViborgDENMARKTel: 45 86 613 833Fax: 45 86 626 836e-mail: [email protected]://www.bioplan.dk/

10. Bioscan A/SPoul Ejnar RasmussenØrbækvej 101, PO Box 426DK-5220 Odense SØDENMARKTel: 45 66 157 071Fax: 45 66 157 771e-mail: [email protected]://www.bioscan.dk/

11. BKS Nordic ABPO Box 6035FabriksgatenS-781 06 BorlängeSWEDENTel: 46 243 370 38Fax: 46 243 375 73

12. BRV Technologies Systeme GmbHWestfalenstraße 208D-48165 MünsterGERMANYTel: 49 250 129 106Fax: 49 250 129 108

13. BTA Biotechnische Abfallverwertung GmbH & Co KGRottmannstrasse 18D-80333 MunchenGermanyTel: +49 89 520 460-6Fax: +49 89 523 23 29, Web:www.bta-technologie.de



Sr.No.

Technology Provider

14. BWSCBurnmeister & Wain Scandanavian Contractors A/SErik Breiner KristensenGydevang 35, Box 235DK-3450 AllerødDENMARKTel: 45 48 140 022Fax: 45 48 140 150

15. C.G. JensonStenvej 21DK-8270 HøjbjergDENMARKTel: 45 86 273 499Fax: 45 86 273 677

16. Carl Bro Environmental A/SBent RabenGranskoven 8DK-2600 GlostrupDENMARKTel: 45 43 486 060Fax: 45 43 964 414e-mail: [email protected]://www.carlbro.dk/

17. CBI Walker, Inc.1245 Corporate Blvd.Aurora, IL 60504USATel: +1-708-851-7500Fax: +1-7-8-851-9392E-Mail: [email protected] (media inquiry)Web: www.cbi-nv.com

18. CiTEC International Ltd OyRune WestergårdPO Box 109SF-65101 VaasaFINLANDTel: 358 6 324 0700Fax: 358 6 324 0800e-mail: [email protected]://www.citec.fi/

19. Dobbie & Co LtdJohn Winders42 The Green, EwellSurrey KT17 3JJUNITED KINGDOMTel: 44 181 393 3192



Sr.No.

Technology Provider

20. Dranco Organic Waste SystemsWinfried SixDok Noord 4B-9000 GentBELGIUMTel: 32 9 2330 204Fax: 32 9 2332 825http://www.ows.be/

21. DSD Gas und Tankanlagenbau GmbHLars KlinkmüllerPablo Picasso Straße 45D-13057 BerlinGERMANYTel: 49 30 929 010Fax: 49 30 929 0114

22. Duke Engineering & ServicesHarold BackmanPO Box 1004Charlotte, NC 28201-1004USATel: 1 704 382 8570Fax: 1 704 382 3105http://www.dukeengineering.com/

23. Eco-TecEco-Technology JVV OYTerho JaatinenValkärventie 2SF-02130 EspooFINLANDTel: 358 9 4357 7477Fax: 358 9 4357 7488

24. Entech Umwelttechnik GmbHShilfweg 1A-6972 FussachAUSTRIATel: 43 5578 7946Fax: 43 5578 73638e-mail: [email protected]://www.austria.org.tw/English/Entec.htm

25. Enviro-Control LtdPaul Stafford26 Forsythia Drive, Greenways, CyncoedCardiff CF2 71 1PUNITED KINGDOMTel: 44 1222 734 738Fax: 44 1222 549 909



Sr.No.

Technology Provider

26. Ferm Tech, Inc.Dirk QuartemontGretelweg 2D-53819 NeunkirchenGERMANYTel: 49 2247 89 789Fax: 49 2247 89 694

27. Haase Energietechnik GmbHOliver MartensGadelanderstraße 172D-22531 NeumünsterGERMANYTel: 49 4321 8780Fax: 49 4321 87829e-mail: [email protected]://www.haase-energietechnik.de/

28. HGCHamburg Gas ConsultGuido GummertHeidenkampsweg 101D-20097 HamburgGERMANYTel: 49 40 235 33 0Fax: 49 40 235 333 730

29. IMK BEG Bioenergie GmbHKonrad Adenauerstraße 9-13D-45699 HerningGERMANYTel: 49 2366 305 262Fax: 49 2366 305 230

30. Ionics Italba, SpAVia G. Livraghi /BI-20126 Milano MIITALYTel: 39 226 000 426, Fax: 39 227 079 291

31. Jysk Biogas A/SKjeld JohansenHaals Bygade 15DK-9260 GistrupDENMARKTel: 45 98 333 234Fax: 45 98 678 711

32. Kompogas AGRohrstrasse 36CH-8152 GlattburggSwitzerlandTel: +41 1 809 71 33Fax: +41 1 809 71 10Web: www.kompogas.ch



Sr.No.

Technology Provider

33. Krüger A/SKarsten BuchhaveKlamsagervej 2-4DK-8230 ÅbyhøjDENMARKTel: 45 8746 3300Fax: 45 8746 3420http://www.kruger.dk/

34. Larsen EngineersS. Ram Shrivastava700 West Metro ParkRochester, New York 14623-2678USATel: 716 272 7310Fax: 716 272 0159

35. Linde-KCA-Dresden GmbHDr. Helmut HubertPostfach 120184D-01003 DresdenGERMANYTel: 49 351 456 0207Fax: 49 351 456 0272

36. Maltin Pollution Control Systems LtdChris MaltinGould’s House, HorsingtonSomerset BA8 0EWUNITED KINGDOMTel: 44 1963 370 100Fax: 44 1963 371 300

37. Motherwell Bridge Envirotech LtdPO Box 4, Logans RoadMotherwell ML1 3NPUNITED KINGDOMTel: 44 1698 266 111Fax: 44 1698 269 774

38. National Renewable Energy Laboratory1617 Cole BlvdGolden,CO 80401-3393Tel: +1-303-275-3000

39. NNRNellemann, Nielsen & Rauschenberger A/SLars BaadstorpV. Kongevej 4-6DK-8260 Vibe JDENMARKTel: 45 86 147 111Fax: 45 86 140 088



Sr.No.

Technology Provider

40. NSRNordvästra Skånes Renhållnings ABDag Lewis-JonssonS-251 89 HelsingborgSWEDENTel: 46 42 107 570Fax: 46 42 107 793

41. Paques Solid Waste Systems BVMarten BennenPostbox 52NL-8560 AB BalkTHE NETHERLANDSTel: 31 514 60 8500Fax: 31 514 60 3342e-mail: [email protected]://www.paques.nl/default.htm

42. Pinnacle Biotechnologies International, Inc.Brian Duff6559 Jungfrau WayEvergreen, CO 80439USATel: 303 674 3236Fax: 303 674 0006e-mail: [email protected]://www.pinnaclebiotech.com/

43. Prikom/HKVPoul LyhneEnghavevej 10DK-7400 HerningDENMARKTel: 45 99 268 211Fax: 45 99 268 212

44. Projektrör ABGunnar ÖrnPO Box 7256S-183 07 TäbySWEDENTel: 46 8 732 5334Fax: 46 8 732 5344

45. Purac ABDaniel LingPO Box 1146S-22 105 LundSWEDENTel: 46 46 191 900Fax: 46 46 191 919



Sr.No.

Technology Provider

46. R.O.M.Recycling Organischer Materialien AGRolf WetterMattstraßeCH-8502 FrauenfeldSWITZERLANDTel: 41 52 722 4660Fax: 41 52 722 4042

47. RPARisanamento Protezione Ambiente, SpAStr. Del Colle 1A/1 - Loc. FontanaI-06074 PerugiaITALYTel: 39 755 171 147Fax: 39 755 179 669

48. Schwarting-UHDE GmbHLise Meitnerstraße 2D-24941 FlensburgGERMANYTel: 49 461 999 2121Fax: 49 461 999 2101Http://www.schwarting-umwelt.de/

49. Snamprogetti SpAMr. BassettiVia Toniolo 1I-61032 FanoITALYTel: 39 721 881 769Fax: 39 721 881 952

50. SPISrl Societa Produzione IdrosanitariVia per Borgomanero - Reg. PuliceI-28060 ComignagoITALYTel: 39 322 50 146Fax: 39 322 50 334

51. Steinmuller Valorga SarlClaude Saint-Joly1300 avenue Albert EinsteinImmeyble Strategie ConceptParc du Millenarie – BP 51F-34935 Montpellier Cedex 09FranceTel: +33 4 67 994 100Fax: +33 4 37 994 101Web: www.steinmuller-valorga.fr



Sr.No.

Technology Provider

52. SWECO/VBB ViakAnna LindbergPO Box 34044S-100 26 StockholmSWEDENTel: 46 8 695 6239Fax: 46 8 695 6240

53. TBW GmbHAndreas KriegBaumweg 16D-60316 Frakfurt am MainGERMANYTel: 49 69 9435 070Fax: 49 69 9435 0711

54. Unisyn Biowaste TechnologyMatt LyumWaimanalo, HIUSATel : 808 259 8877Fax : 808 259 5267

55. Wehrle Werk AGPeter SchalkBismarckstrasse 1-1179312- EmmendingenGERMANYTel: +49 7641 5850Fax: +49 7641 585106

56. WMC Resource Recovery LtdPeter Cumberlidge2, Eaton Crescent, CliftonBristol BS8 2EJUNITED KINGDOMTel: 44 117 973 7993Fax: 44 117 973 3167


MWH Appendix 9B - 1

Appendix 9-B

Status of Biomethanation in Representative Countries

Status information of biomethanation in the following countries are given below:

• Austria

• Belgium

• Canada

• Denmark

• Germany

• Greece

• Italy

• The Netherlands

• Norway

• Portugal

• Sweden

• Switzerland

• United Kingdom

Country Reports of Anaerobic digestion of Ago Industrial Waste1

1 Source: http://www.ad-nett.org/html/country.html


MWH Appendix 9B - 2

9.B.1 Austria

Anaerobic Digestion Status Report AustriaBraun, R. and Steffen, R.

Dissemination

In Austria information on anaerobic digestion in agricultural related areas is mainly disseminatedthrough several existing local networks and interest groups. Due to this fact no further disseminationnetwork was established. The Institute for Agrobiotechnology (IFA) acts as the binding link betweenthe different networks and AD-interest groups. The main existing association in agricultural area isthe ARGE Biogas, which has 14 special consultants for anaerobic digestion.

The IFA - full scale anaerobic digestor using cattle slurry together with pharmaceutical wastes as co-substrate, is used as demonstration plant for scientific research. Visitations of the plant for interestgroups, politicians and operators are organized as required.

A direct link from the IFA web-page to the AD-Nett homepage exists. Furthermore the instituterepresents AD-Nett on national congresses, seminars and workshops.

Existing Networks

Academy for Environment and Energy (Akademie für Umwelt und Energie),Schloßplatz 1, 2361 Laxenburg(M. Mayer)ARGE Biogas (Arbeitsgemeinschaft Biogas) - Naturschutzbund SalzburgArenbergstraße 10, A-5020 Salzburg or Blindengasse 4/10-11, A-1080 Wien(W. Graf)Austrian Biomass Association (Österreichischer Biomasse-Verband)Franz Josefs-Kai 13, A-1010 Wien(H. Kopetz)

Funds and Sources for Subsidies

Österreichische KommunalkreditTürkenstr. 9, A-1090 WienFonds zur Förderung der gewerblichen WirtschaftKärntnerstraße 21-23 A-1010 Wienrelated Federal Ministries (as described under chapter 3.1)Governments of the 9 Austrian ProvincesAgricultural Chambers of the respective provinces (Landwirtschaftskammern der einzelnenBundesländer)

Existing Information

BIOGAS FILM - planning, construction and operation, 15 min., English and German. ARGE Biogas,Arenbergstr. 10, A-5020 Salzburg; can be ordered for the price of 175,- ATS.BIOGAS TAGUNG - Der derzeitige Stand der Technik und die Möglichkeit der Biogasnutzung in derLandwirtschaft und der Industrie sowie als kommunale Entsorgungstechnik - Symposium, 25. - 26.April 1996, Landwirtschaftliche Fachschule Edelhof, A-3910 ZwettlBOXBERGER, J. (1997): Landwirtschaftliche Biogasanlagen. ÖKL-Baumerkblatt Nr. 61; Österr.Kuratorium für Landtechnik; A-1041 Wien.


MWH Appendix 9B - 3

BOXBERGER, J. (1998): Sicherheitstechnik für landwirtschaftliche Biogasanlagen. ÖKL-MerkblattNr. 62; Österr. Kuratorium für Landtechnik; A-1041 Wien.BRAUN, R. (1999): Anaerobe Abfallbehandlung. Entwurf ÖWAV-Richtlinie; Österr. Wasser- undAbfallwirtschaftsverband, ÖWAV; A-1010 Wien, Marc-Aurel Str. 5.GRAF, W.: Broschüre Biogas für Österreich. Bundesministerium für Land- und Forstwirtschaft, A-1010 WienHÄUSLER, F. (1981): Erfahrungsbericht über landwirtschaftliche Biogasanlagen in Österreich, Wien,1981, ÖKL (Landtechnische Schriftenreihe, 86)HIMMEL, W. (1982): Berichtsband zum Biogas - Statusseminar Graz 6. - 7. Mai 1982; Inst. fürBiotechnologie, Mikrobiologie und Abfalltechnologie, Techn. Univ. Graz, A-8010 GrazMITTEILUNGSBLATT "Nachwachsende Rohstoffe": Quarterly publication of the FederalAgricultural Technology School (BAL Wieselburg); A-3250 Wieselburg.MAGAZIN "ÖKOENERGIE": monthly publication of the University for Agricultural Sciences andthe Austrian Biomass Association; A-1010 Wien.PADINGER, R. (1986): Biogas in der Landwirtschaft - Erkenntnisse und Perspektiven;Forschungsgesellschaft Joanneum Graz, A-8010 Graz

Research Institutions Concerned with Anaerobic Digestion

Univ. Agricultural Sciences ViennaInst. for Agrobiotechnology (IFA), Dept. Environmental BiotechnologyKonrad Lorenz Strasse 20, A-3430 Tulln(R. Braun; R. Steffen; M. Grasmug; F. Steyskal)Inst. for Agricultural, Environmental, and Power Engineering, Dept. for Agricultural Machinery &Operational TechnologyPeter Jordan-Strasse 82, A-1190 Vienna(J. Boxberger, T. Amon)

Technical Univ. ViennaInst. for water quality and waste management, Dept. for water quality management(Institut für Wassergüte u.Abfallwirtschaft Abteilung für Wassergütewirtschaft)Karlsplatz 13 / 2261, A-1040 Wien(H. Kroiss, N. Matsche, K. Svardal)Institute for process, fuel and environmental engineering, Inst. für Verfahrenstechnik,Brennstofftechnik und UmwelttechnikGetreidemarkt 9, A 1060 Wien(K. Mairitsch)

OthersJoanneum Research, GrazInstitut for Energy Research (Institut für Energieforschung)Steyrergasse 17, A-8010 Graz(J. Spitzer)Federal Agricultural Technology School (Bundesanstalt für Landtechnik, BAL Wieselburg)Rottenhauser Str 1, A-3250 Wieselburg an der Erlauf ( NÖ );currently no activities in ADLandwirtschaftliche Fachschule EdelhofContinuous comparative studies with 3 small scale agric. biogas plants since 1980(J. Graf)


MWH Appendix 9B - 4

Governmental and Private Institutions concerned with AD

Federal ministriesMinistry for the Environment, Youth and FamilyStubenbastei 5, A-1010-Wien, AustriaMinistry for Agriculture & ForestryStubenring 1, A-1010-Wien, AustriaMinistry for Science and TransportMinoritenplatz 5, A-1014 Wien, Austria

OthersFederal Environmental Agency (Umweltbundesamt)Spittelauer Lände 5, A-1090 Wien, AustriaÖsterr. Kuratorium für Landtechnik (ÖKL)Schwindgasse 5, A-1041 Wien(G. Jüngling)O.Ö. EnergiesparverbandLandstraße 45, A-4020 Linz(E. Grübl)Academy for Environment and Energy (Akademie für Umwelt und Energie),Schloßplatz 1, A-2361 Laxenburg(M. Mayer)Austrian Association for Water and Waste Management (Österr. Wasser- und Abfallwirt-schaftsverband, ÖWAV)Marc Aurel Straße 5, A-1010 Wien(W. Lengyel)

Private Companies Concerned with Anaerobic Digestion

Austrian Energy & Environment (AE&E)Siemensstraße 89, A-1211 ViennaPlanning and construction(J. Lahnsteiner)Bauer Friedrich G.m.b.H.Oberegging 90, A - 3373 KemmelbachPlanning and construction(F. Bauer)Bioenergetica - Energieerzeugungsanlagen GmbHSchwanthalergasse 8, A-4910 Ried im InnkreisPlanning and constructionBIOS I GesmbHUntergrafendorf 8, A-3071 BöheimkirchenConstruction(H. Schmied)BioTrend GesmbHHochheide 33, A-4202 HellmonsödtPlanning and construction(W. Ecker)Elektro Technik Pichlmaier (ETP)Boder 135, A-8786 RottenmannPlanning(R. Pichlmaier)Entec - Environmental Technology, Umwelttechnik GmbH


MWH Appendix 9B - 5

Schilfweg 1, A-6972 FussachPlanning and construction(P. Stepany)Ing. Lehner Landwirtschaftsbau GesmbHThomas-Bohrer-Straße 15, A-9020 KlagenfurtConstructionSattler Textilwerke OHGSattlerstraße 45, A-8041 GrazConstruction, gas storage tanks,TCS - Technical Consulting Steyskal GmbHKonrad Lorenz Straße 20, A-3430 TullnPlanning and construction(F. Steyskal)VSP Anlagenbau GmbHArlbergstr. 101, A-6900 BregenzPlanning and construction(H. Pfefferkorn)Dipl.Ing. Friedrich WaltenbergerAm Bachlberg 8, A-4040 LinzPlanning(F. Waltenberger)Wolf Systembau GesmbHFischerbühel 1, A-4644 ScharnsteinConstruction

Technical Scale Treatment Plants

There are no official documents or references on existing biogas plants in Austria available. Based onrecent estimations and various personal communications (Graf, 1999), the following plants arecurrently in operation:90 Agricultural biogas plants (4 under construction)88 Domestic sewage sludge digesters31 Landfill gas reclamation plants (19 under construction)20 Anaerobic Industrial waste water pretreatment plants3 Domestic biowaste treatment plantsThe respective 86 agricultural biogas plants correspond to an installed electrical capacity of 3,300kWe and a total electrical energy production of 25 GWhe per year (Graf, 1999).

References:HAUER, I. (1993): Biogas-, Klärgas- und Deponiegasanlagen im Praxisbetrieb. ÖKL LandtechnischeSchriftenreihe Nr. 192; Österr. Kuratorium für Landtechnik; A-1041 WienBRAUN, R. (1997): Biologische Abfallbehandlung. In: „Umweltbiotechnologie", Studie des UBA,A-1090 WienBRAUN, R. (1997): Anaerobtechnologie für die mechanisch biologische Vorbehandlung vonRestmüll und Klärschlamm. Studie des BMUJF, A-1010 WienGRAF, W. (1999): personal communication on existing Austrian agricultural biogas plantsÖWAV (1997): Entgasung von Deponiekörpern. Heft 110. Österreichischer Wasser- undAbfallwirtschaftsverband (ÖWAV), A-1010 Wien

Further information:

R. Braun and R. Steffene-mail : [email protected]


MWH Appendix 9B - 6

9.B.2 Belgium

Anaerobic Digestion of Agricultural and Agro-Industrial WasteThe State-of-the-Art in BelgiumApril 1997Edmond-Jacques NYNS, PhD,Retired Professor of Bioengineering

Belgium is a federation of three regions : the Flemish region (Flandres), the Walloon (frenchspeaking) region (Wallonie) and the region of Brussels (Bruxelles Capitale). Government is federalwith responsibility for various activity delegated to the regions. Waste management is such an activityand each of the three regions manage it independently.

In Flandres, agricultural (mainly animal) waste management is of major concern because of intensivestock rearing and pig farming. Little has been done hitherto to favour anaerobic digestion (AD).Numerous digesters were built on individual farms in the '80s but it is thought that few of these arestill operational. Recently, a region subsidy of BF 1 (ECU 0.025) has been allocated to each kWhelectricity produced from renewable energy sources. It is thought that this will be a positive influencefor large scale biogas systems such as landfills but will not necessarily stimulate the uptake of smallfarm scale AD plants. In addition to this development there have been indications that a large scalebiogas plant would be constructed for an association of farmers with the help of public subsidies.More will be written on this in an update of the present state-of-the-art.

In the region of Brussels and Wallonie, the problem of agricultural (and animal) waste is less acute.As a result there is little interest in farm-scale anaerobic digestion. The situation is very different foragro-industrial waste, however. In 1980, public help to applied research was a federal matter.Research was launched on the process of anaerobic digestion at the University level, but industrialinvolvement was encouraged in the research. Consequently by 1985 industries were established aimedat the AD of agro-industrial waste (water) treatment market. By 1995, these industries had expandedtheir market across the World. Together with The Netherlands, Belgium is a pioneer in anaerobicagro-industrial waste (water) treatment. More details on these achievements will appear in the updatesof the present state-of-the-art.


MWH Appendix 9B - 7

9.B.3 Status of Anaerobic Digestion in Canada

Type of waste that could be treated

Anaerobic Digestion (AD) processes are not common in Canada. They are currently used in someareas of Canada to treat municipal sludge, paper mill wastewater, potato processing plant wastewaterand cheese factory wastewater. These industries treat their wastewater to solve environmentalproblems and eliminate cohabitation problems. Energy recovery and utilisation is a secondary issue.

The other type of wastes that could be treated by AD processes are: swine, dairy and poultry manureslurries; slaughterhouse wastewater; other food processing and municipal organic wastes.

Main Driving Force:

The main driving forces for AD in Canada are the environmental regulations. For some industry ADis the most economical option to treat their wastes. If the energy cost increases in the future, it islikely that interest in AD will increase. Another driving force is the relationship of industry with itsneighbourhood. Some industries are interested in AD to eliminate nuisance problems such as odours,pathogens etc.

Past and Present History

Some industries have been using AD for twenty years and the technology is becoming more popularwith industries producing high strength wastewater. From 1973 to 1986 several AD processes wereresearched, developed and installed on Canadian farms. These projects were carried out throughresearch contracts with engineering firms and universities. None of the 28 projects is still in operationtoday. Various problems were experienced including unstable systems and difficulties in operationand the plant were found to be labour intensive and not cost effective. It was concluded thatapplication of this technology to Canadian farms is not profitable and cannot be recommended.

Developments in the near Future

Development of low cost and easy to operate AD processes which control odour efficiently andreduce the pollution potential of high strength wastewater is required. There is also a need forprocesses which operate at low temperatures (10 - 20oC), because of the Canadian climate.

Main Players in the Future

Municipalities; food processing industries; dairy, swine and poultry farmers.

Support Available

At the present time there is limited funding available to support research and development of ADprocesses


MWH Appendix 9B - 8

9.B.4 Status of Anaerobic Digestion in Denmark

Introduction

Nineteen centralized biogas plants and 18 on-farm biogas plants currently operate in Denmark andfurther new plants are under construction or planned.

The development of biogas plants based on animal manure has been predominantly undertaken incentralised plants. Today these plants function well both technically and economically. At thecentralised plants the animal manure is transported from the farms to the biogas plants. The residue isreturned after digestion for use as a fertilizer. The manure may be co-digested with different wasteproducts from the food-industry. Total biomass input to the plants (including waste) ranges from10.000 and 160.000 tons per year.

The biogas program

The first biogas plants based on animal manure were built in the 1970's. About 40 small plants werebuilt, but most of them were closed after a relatively short period, mainly due to technical problems.

At the end of the 1980's the Danish Energy Agency launched a programme to develop large scalecentralised systems. The programme aimed to clarify whether technical development, combined withthe need to address agricultural and environmental issues could result in stable economics. Tencentralised plants were built with up to 40 percent grant funding. The DEA programme examined theeconomics, technical development, operational processes as well veterinary, agricultural andenvironmental issues.

In parallel with this programme an industry for construction of biogas plants has been developed. Theencouraging results from the programme have lead to the construction of further plants, and today 19centralised biogas plants are in operation.

The focus in Denmark has been on centralised plants, because they offer a possible solution to farmersfacing legislation on storage capacity for animal manure and demands related to environmentalfactors. Sixteen of the plants are owned by farmers in cooperatives. Three plants are owned bymunicipalities. The biogas plants have not been developed solely for energy production; they alsoaddress environmental and agricultural issues, such as waste recycling. In addition, centralisedanaerobic digestion plants have encouraged the establishment of distribution systems for the optimalutilization of the fertilization value of the waste.

Future

In total the centralised biogas plants currently produce 2.2 PJ. The Danish government energy planaims to change energy consumption from fossil fuels to a supply with 30-35 percent from renewableenergy sources. This includes doubling biogas production from anaerobic digestion of farm wastesbefore the year 2000 and a four-fold increase before the year 2005. To fulfill this ambitious targetdevelopment of biogas plants needs to be changed from centralised plants to on-farm plants.Experience from centralised biogas plants should enable development of reliable commercial-scaletechnology and reduced costs for on-farm anaerobic digestion in the near future.


MWH Appendix 9B - 9

Further Information:

Further information on Danish biogas plants can be obtained through:Herning Municipal Utilities, Enghavevej 10, DK-7400 Herning, orThe Danish Energy Agency, Landemaerket 11, Dk-1119 Copenhagen KNumber of biogas plantscentralised19on-farm18Figures of the centralised plantsBiomass10.000-160.000 ton per year30-450 ton per dayBiogas production 1.000-20.000 Nm3 per dayDigestors, size 750-7.900 m3

Members, to deliver manure 6-80


MWH Appendix 9B - 10

9.B.5 The German Biogas Association

Objectives and structure

The "Fachverband Biogas"(German Biogas Association) a non-governmental organisation and trustfor no gain was established in 1992. The main objective are promotion, furtherance and disseminationof a sustainable technology linked within the natural nutrient circle. It is an amalgamation of operatorsand manufacturers of biogas plants, engineers, researchers and consultants, agricultural groups,scientific institutions and organisations involved in the dissemination of other renewable energysources. There are presently 400 members including 60 companies and institutions. The Association isheaded by a 5 person steering committee, representing operators of biogas plants, planners,constructors and research institutions. Several regional groups in Germany and adjoining countrieshave been established to meet local demands and to build up an advisory network. Specialist teams(meeting 3-5 times a year) work on different concepts and solutions in the field of quality/safetystandards, organic waste fermentation, schooling and training, public relations and agriculture.

Agricultural Biogas Plants

At present 380 biogas plants are in operation throughout Germany, 250 plants have been constructedin the last 2-5 years. The average investment costs for a farm scale plant are DM 250.000.-. There are11 large scale plants treating agricultural, agro-industrial or organic household with investment costsranging from DM 5-20 Mil per plant.

Main Activities of the German Biogas Association

• Organisation of Site visits to biogas plants and operators.• Holding seminars, conferences, exhibitions, each January "Biogas in the agriculture" .• Provision of know-how and training and arranging for assistance from experts.• Technology transfer, including a quarterly newsletter.• Lobbying Achievements.• Well established network in Germany and several neighbouring countries, recognised

as important Association for Biogas in Germany.• Promotion of improved quality standards.• Establishment of safety rules.• Development of module construction to reduce investment costs

Major obstacles for the dissemination of Biogas Technology.

• Uncertain national and EU policies towards the existing national law of supplyingelectricity from renewable energies to the public grid (Stromeinspeisegesetz).

• National and EU regulations/laws regarding waste management (spreading ofdigested organic matter) and emissions from cogeneration units.

• Strict health protection laws and hygienic regulations concerning infectious diseasesspread by organic material.

• Uncertain financial support and electricity prices, strict tax laws.• Ongoing standardisation for further cost reduction is needed.• Biogas technology is not recognised as climate protection technology




Barbara Klingler, Michael KöttnerFachverband BiogasAm Feuersee 8D- 74592 Kirchberg/Jagst- Weckelweiler Baden-WuerttembergTel: +49 7954 1270Fax: +49 7954 1263



9.B.6 Present State of Biogas in Greece

During eighties, a few efforts for biogas applications were carried out in Greece. The feedstock ofthem was animal excrements and wastes from food processing industries (oil olive mill wastes). Someof them were demonstration projects that after enthusiasm and insurance of scientific support werefallen into disuse. This was mainly due to the lack of information, proper infrastructure, state interestand financial incentives. Nowadays, the legislative infrastructure, financial instruments and socio-economics conditions (public awareness for environment protection, coming deregulation of energymarket, etc.) have changed the whole story.

The last three years, the Ministry of Development has located 176 billion GDr for applications ofRenewable Energy Sources (RES), Rational Energy Use (RUE) and Energy Savings (SA) through theEnergy Operational Programme (Measure 3.4). In the framework of that Programme two biogasplants have be approved (total installed power almost 20 MWe) exploiting sewage sludges and landfillbiogas. Additionally, the Ministry of Development has granted six applications (permissions) forpower plants exploiting biogas; the total installed power amounts 21 MWe. It is expected thatsignificant interest will be expressed for biogas applications in the next coming Energy OperationalProgramme of the Greek government.

The operated biogas plants are presented in the Table 1. Additionally there are other five biogas plantsthat are under commissioning.

Table 1. Biogas plants and production in Greece, 1998

Types of biogas plant Amount ofplants

ProductionGWh/year

ProductionTJ

Wastewater treatment plants 2 158.3 569.9

Landfill plants 1 2.1 7.56

Industrial waste treatment plants 2 7.025 25.3

Manure based plants (Centralised co-digestion Farm scale plants)

1* 0.394 1.4

Total 6 604.2*The current biogas plant exploits animal manure and additionally sewage sludge

Status of Anaerobic Digestion of Agro-Industrial Wastes in Greece

Anaerobic digestion (AD) for biogas production is seldom used for animal manure and agro-industrialwastes treatments in Greece at the moment. This is mainly due to the lack of information, properinfrastructure, state interest and financial incentives.

Sheep, goats and lambs breeding represents the highest percentage of Greek Livestock but thatbreeding is mainly shepherded, so the produced manure is spread all over the grazing land. On thebasis of the EUROSTAT figures (1995) including all the kinds of breeding animals, the animalmanure production is estimated up to 38,000 ton/day. The potential users for biogas productionthrough AD would be focused on intensive livestock such as medium-large scale livestock units.

The number of breeding animal heads and the medium-large scale units for cattle, pig and chickenbreeding are presented in the following Table 2:



Table 2: Medium-large scale livestock units in Greece (Agricultural Bank of Greece, 1996)

1. Category 2. Number of Units 3. Breeding animal heads

Cattle 580 69,328

Brood sows 448 105,793

Chickens 361 20,042,050

These units constitute the potential resource for biogas production under optimum conditions. It isestimated that AD of the manure produced by those units could result in a methane production almost0,5 million m3/day and energy potential over of 400 kTOE.

The common practice of manure management is the collection in anaerobic lagoons. After thestabilisation and sedimentation process the sludge is discharged in an open anaerobic lagoon (5 mdeep) which is stratified in two phases: the upper aerobic zone and the anaerobic zone underneath it.Due to aeration in the stabilisation tank slurry odour is controlled. In cattle raising farms, manure iscollected on impermeable platform where liquid from dung heap discharges in septic pool.

In both cases, the disposal of slurry or the solid manure spreading are carried out on landfarmaccording to the "Codes of good agricultural practice for the protection of the waters from nitratepollution". These guide lines define the timing of the disposal as for instance when the weatherconditions are favourable for avoidance of run-off, or the retention time of slurry in anaerobiclagoons, even though the amounts of liquid manure for certain crops, etc.

Agro-industries prefer wastewater treatment systems that satisfying two factors, cost-effectivenessand appliance with national legislation. The anaerobic digestion is used only for specific reasons suchas high level of organic load and afterwards the produced biogas burnt on flare. Nonetheless, theopportunities for anaerobic digestion exploiting agro-industrial wastes are great. Biogas applicationswill have more chances for success when there is a combination of by-products from cheese factories,oil olive mills, etc. with animal excrements. Livestock units that incorporate the whole chain ofproduction for instance slaughter, trade feeding stuffs, etc. would be potential investors for singlebiogas plants. The installation and operation of co-digested biogas plants is a very promisingalternative as it is shown from similar cases in Sweden, Denmark, Holland and Germany. Theincreased investment cost, the Greek countryside morphology and the required strength cooperation oflocal productive sectors come into conflict with other parameters such as public awareness forenvironment protection, coming deregulation of energy market, etc. Although the biogas schemes as asolution to energy saving and environment protection should be promising for Greece for the timebeing.



9.B.7 Status of Anaerobic Digestion of Animal and Agro-industrial wastes in Italy

In Italy the diffusion of Anaerobic Digestion plants for farm and agro-industrial wastes started at thebeginning of the eighties and lasted about ten years. During that period, more than hundred farmbiogas plants and about twenty five large agro-industrial plants were built. A survey carried out byENEA in 1983 showed that over 60 farm manure anaerobic digesters were in operation and more than20 were under construction at that date (Tilche et al., 1983). The growth lasted only few more years,during which some public funds for anaerobic digestion were still available.

Most of farm plants were treating pig wastes, that in Italy represents an "industrialised" animalfarming, carried out in large and very large units without land, while most of agro-industrial plantswere treating distillery effluents.

Also some centralised projects for digesters treating wastes of many different farms started duringthese years.

Since then the situation has changed substantially, particularly because many of the systemsconstructed at that time are no longer in operation. The causes can be found in the motivations that ledto the installation of the initial systems. In reality, energy saving was only one reason, and not themain one, for farmers to build a digester. The "hypothetical" treatment benefit offered by thetechnology was often the most important reason, because "industrial" farms had to treat their waste inorder 1) to reduce the amount of land needed for its spreading or 2) to reach discharge standards.

Though anaerobic digestion may ensure substantial removal of carbon (expressed as COD andBOD5), it leaves very high levels of nitrogen and phosphorus, and this makes attempts to completethe treatment technically and economically unfeasible. The understanding of this "bitter" truthcertainly led to a decrease in the use of anaerobic digestion in animal wastes applications.

The problem for many of the installed reactors was that processes and technologies developed for theindustrial world were transferred to the agricultural world. These plants were not suited for farms dueto construction costs, technological complexity, relatively small net energy production and expensivemaintenance.

Moreover, the farms on which these systems were installed were not always the most appropriatesites for the characteristics of the animal wastes and for the small advantages obtained by a low netenergy production in winter - when thermal needs are the highest - and a high energy waste during thesummer. The image of the technology therefore went down.

Many of the farm-biogas system producers surveyed in 1983 no longer operate in this sector, and inmany cases those still working in the field have shifted their attention to the agro-industrial area. Onthe other hand, most of agro-industry digesters, realized more for pollution control needs, continuedsuccessfully their operation.

At the end of the eighties, a new generation of simplified low cost plants for animal (mainly pig)wastes, usually obtained from covering anaerobic lagoons with flexible covers, arrived on the market.These systems have been developed not only for the purpose of energy recovery but also forcontrolling odours and stabilizing the wastes. Their success is witnessed by the number of them -around fifty, from an un-official survey carried out among manufacturers - built until now, themajority of which are still working. The systems operate at ambient temperature or at a more or lesscontrolled temperature.



After 1993-94, the farm market is more or less still, due to lack of public funds and the shortening ofprofit margins in animal husbandry. Nevertheless, a provision of the Italian government of 1992 thatoffered incentives for self-production of electric energy from biomasses, paying 270 ITL/kWh (0.135ECU/kWh) (value of April 1996) against an average cost of 160-180 ITL/kWh (0.08 - 0.09ECU/kWh) gave some impulse to the market of biogas linked to co-generation. However, this rule istoday under revision due to public budget restriction.


Dr. Andrea TilcheENEA - Section of Wastewater Treatment and Water CycleVia Martiri di Monte Sole, 440129 Bologna – ItalyTel. : +39-51-6098735Fax : +39-51-323388e-mail: [email protected]

Dr. Sergio PiccininiCentro Ricerche Produzioni Animali-CRPAEnvironment DivisionC.so Garibaldi, 4242100 Reggio Emilia – ItalyTel. : +39-522-436999fax : +39-522-435142e-mail: [email protected]



9.B.8 Status of Anaerobic Digestion for Animal Waste in the Netherlands

Introduction

Potential renewable energy in the Netherlands from anaerobic digestion of the 1.5 million tonsavailable organic waste and 4.5 million tons of animal manure is 125 million m3 natural gasequivalent or a saving of 4 PJ (Dc Boo, 1997).

Since the mid-seventies biogas technology has been promoted as part of the Dutch government policytowards diversification of energy supply and reduction of fossil fuel consumption in order to reducecarbon dioxide emissions. In the eighties technology for farm scale digestion of animal manure wasfurther improved although this concept was not very successful due to decreased energy prices.

Manure digestion in the Netherlands was restricted to three types of processes:

1.Farm scale digestion2.One medium scale demonstration project for central manure digestion for eight farmers at Daersum3.One full scale digestion plant combined with complete processing of pig manure at PromestHelmond

A total of 32 farm and full scale digestors were in operation between 1978 and 1993. To ourknowledge these sites are no longer operational. The complete failure of farm scale digestion was dueto low energy prices since the mid eighties and the low biogas production by the use of manure thatwas usually aged during storage. High costs for maintenance and repair were also experienced due tomany technical failures and the lack of professional technical assistance. Farm scale digestors becametoo expensive and labour intensive. In 1995 Promest Helmond and the Deersum sites also closed. ThePromest Helmond site closed as farmers were unwilling to pay for the asking price for manureprocessing and the company became bankrupt. The Deersum plant closed because of the lack ofavailable organic waste as they had to compete with composting which has became popular since1991.

In summary, the reasons why digestion of manure in combination with organic waste stream did notdevelop any further are as follows:

• low return for biogas and electricity (low prices)

• low cost for processing organic matter by means of composting

• tight regulation on alternatives for fresh manure like digestate

In the past there was also insufficient collaboration effort between the agricultural sector, energysector and the waste sector for the introduction of this technique. Communication between involved orinterested parties was too poor.

Current Situation

Since 1997 the future for manure digestion has improved due to the following developments:

• Increased price for disposal of organic waste due to the ban on landfilling of organicmatter

• Higher prices for renewable energy



• The need for selective manure distribution due to stronger manure legislation

• Lower capital/investment costs due to lower interest rates and fiscal incentives such asvamil and green investments.

• As mentioned earlier no anaerobic digestion plants for animal waste currently exist inthe Netherlands. Work is now underway to start new projects on digestion ofcombined animal and organic waste.

• One of the first actions in the Netherlands will be to start a strategy group for manuredigestion with organic additives.

Through discussion and feedback the strategy group aims to bring the following information to light:

• The market for the digestion of mixed manure and organic matter

• Available technology in the market place

• New technology initiatives

• And the promotion of manure digestion

• Bottle necks in the field of legislation and application of manure

The Netherlands has a sound knowledge on anaerobic digestion technology due to past projects andcurrent projects in the field of anaerobic digestion of green waste, the chance of successful manuredigestion plants is therefore relatively high. One key factor to success is effective, continuedcommunication and co-operation with all interested parties. The establishment of a national interestgroup is therefore an essential start.


Further information on anaerobic digestion in The Netherlands can be obtained through contactingEdward Pfeiffer at NOVEM, Cathrijnesingel 49, PO Box 8242, 3503 RE Utrecht, The Netherlands,Phone +31 30 2393631, Fax +31 30 2316491, e-mail: [email protected]. For more informationon anaerobic digestion of animal manure and organic waste in the Netherlands the "Country report onanaerobic digestion - 1995" is also available.



9.B.9 Anaerobic Digestion in Agriculture and Agro-Industry in Norway

Introduction

In spite of very little historic tradition in production and treatment of biogas, Norway has passed 60biogas production units. Most of them were built in the last few years. Only 2 of the plants are inagriculture and 2 plants in agro-industry. The rest are AD-reactors in wastewater treatment plants(17), AD-reactors in cellulose industry (3 plants) and landfill gas extraction systems (ca. 40 plants).Almost none of them are built for energy reasons - about 50% of the gas produced is flared.

The reason for this is based on political decisions, the shape of the country and the special (historic)energy situation.

Norway is mainly rocks and mountains and has an enormous coastline. Cheap electricity from hydropower and enough wood for personal heating has made no need of other/alternative energy sources.

Politically agriculture has been protected to maintain our own food production and district policy.Every year much money combined with regulations and restrictions are used to encourage people tostay in their regions. Combined with fear of diseases this means that farmers are not allowed to raiseas much animals as they want. Normally one unit of pigs are 600 animals, hens 2000 etc.

This means that most farms are spread out, the amount of manure locally is too small for AD-reactorsand most farmers have land for using the manure.

Up to this day only a few people have been involved in anaerobic digestion.

In 1996 one project has been integrated in a R&D programme and groups of farmers started someAD-calculations.

The growing interest for new renewable energy, environmental protection and source separation maygive anaerobic digestion a new future in Norway.


Energisystemer as,Aaslyvn 9, N-3215NorwayE-mail: [email protected] - The Norwegian Bioenergy AssociationWergelandsveien 23b, N-0167 OsloNorwayE-mail: [email protected]



9.B.10 Status of Anaerobic Digestion in Portugal

In Portugal there are regions with high concentration of pig farms such as Santarem, Leiria, Montijoand Rio Maior. In these regions are operating 4 centralized biogas plants at Lourinhã, Rio Maior andLeiria. About 90 farm scale plants are operating in the central and the southern part of the country.

The centralised biogas plants operate with not very satisfactory results, due to an inappropriate choiceof treatment method. The most common used technologies are anaerobic digestion with biogasproduction (plugflow, upflow anaerobic sludge blanket, conventional digestion and anaerobic filter),activated sludge, composting treatment lines. Co-digestion of manure and other substrates does nottake place in Portugal. The actual distribution of biogas systems in each economical activity areshown in table 2.

Table 3. Actual distribution of biogas systems in each economical activity.

Economical Activity Installed systems (%)

Pig-breeding 71

Poultry 8

Bovines 5

Milk food 3

Distilleries 1

ETAR* 12

TOTAL 100*Integrated systems in domestic sludge treatment stations.

The national programme "Energia" supports the biogas production activities as part of the renewableenergy production and support projects promoted by public or private entities. Workshops are anusual method to promote and stimulate biogas production. Environmental benefits as well as thepossibility of the initial investments amortisation, in reduced periods of time (3 to 7 years), with thecommercialisation and/or use of the produced energy, are underlined as the driving force to integratebiogas in the energy sector.

The main problems are the insufficient incentives, high investment costs and low income obtainedfrom the first projected digestors. The lack of monetary incentives affects the possibilities ofimproving the technical knowledge and results in a low quality of constructions and equipment, a lowlevel of maintenance of the existing plants and a deficient control and exploration of the systems.

There is optimism in Portugal about the future of biogas, even though there is very little publicawareness about it. The public is aware of the problems concerning water effluent pollution andeverybody wish solutions to be found. That brings biogas in a favourable position, as a possibility ofnon-pollution and energetic valorisation of drains built by combined agricultural and food-industriesand sludge from domestic effluents' treatment stations.



9.B.11 Status of AD of agro-industrial wastes in Sweden

Over the last 2-3 years, five full scale plants have been constructed in Sweden and are currently inoperation or in start up. In addition, one plant is under construction (spring 1997).

The amount of feedstock to be treated ranges from 26000 to 80000 tonnes per year in the first phase.In a second phase more waste may be received, such as source separated municipal solid waste(SSMSW) and rendering material from slaughter houses. All of the plant are wet continuous digestersand are operated as mesophilic or thermophilic one stage, completely mixed, conventional reactors.All plants have equipment for hygienization of the waste at 70°C in order to guarantee an appropriatekill of the most abundant pathogens. The feedstocks consist mainly of liquid manure andslaughterhouse waste. In some cases MSW and wastes originating from restaurants and industry arealso included.

All plants are in the vicinity of major agricultural districts and the digester residue is distributed as aslurry fertilizer. Concentrations of heavy metals are very low. In fact, in some cases concentrations arelower in the waste than in the manure (data not shown). These values guarantee that farmers willaccept the digester residue as a soil supplement. Thus far finding a market for the end products has notbeen a problem. Four plants are upgrading (or are planning to upgrade) the biogas and compressing itto be used as a vehicle fuel. The use of vehicle fuel, mainly for buses, is related to the price forelectricity and heat in Sweden, which is currently low. The other plants produce electricity and heatfor district heating or only heat.

In addition to the growing interest in AD of wastes over the last few years, there is also an interest inAD of ley crop silage as an additional source of organic wastes. Pilot- and laboratory studies areunderway at JTI.


Dr Åke Nordberg, Swedish Institute of Agricultural Engineering (JTI), Box 7033, S-750 07 Uppsala,Sweden. Tel: + 46 18 67 32 97, Fax: + 46 18 67 33 92e-mail: [email protected]



9.B.12 Swiss Country Report on Anaerobic Digestion in Agriculture

Introduction

Biogas production in Switzerland has a relatively long tradition in waste water treatment. The firstanaerobic digesters were built in the thirties for the stabilization of sewage sludge. Initially the biogaswas flared. Sometimes perfumes had to be added in order to prevent complaints from theneighbourhood about odour nuisances.

However, the first plants, operated primarily for the sake of energy production were constructed inagriculture in the seventies. Swiss farmers were among the first in Europe who started to build biogasplants after the first energy crisis. Digesters were optimally farm integrated and adapted to the typeand volume of the respective farm waste. Hence, every installation was unique and prices remainedrather high with the consequence that with the decreasing prices of the oil the construction of newinstallations came to a halt.

Since 1990 when Switzerland started to promote renewable energy again within the program "Energy2000", a few new plants were erected digesting bio- and food wastes together with manure.

About 100 farm scale biogas plants are in operation in Switzerland. Three installations are treatingsolid waste, all the others are running on liquid manure with addition of chopped straw (1.5 to 3 kgper animal and day). One of the solid waste digesters is a four vessel batch system made ofprefabricated, concrete side walls with a sandwich insulation and a floating plastic cover. A secondone is an upright cylindrically shaped, continuous flow reactor where the waste is pumped upwardsthrough an inner cylinder and flowing down by gravity through an outer cylinder. The third and lastsolid waste digester is a down-flow pilot plant of 10 m3 operated by Nova Energie at the SwissFederal Research Station, FAT in Tänikon.

Except for five, all of the liquid digesters are operated in a continuous flow mode. The predominantconstructions are either upright cylinders made of concrete or glass fiber reinforced plastic, or sunk inground concrete digesters of either rectangular or cylindrical shape. The digester volumes range from30 m3 to over 600 m3. All of the digesters are stirred mechanically. Some of them are connected tostorage tanks covered with gas tight plastic membranes storing at the same time the gas from thereactor and the gas produced during post fermentation in the storage tank.

The five systems not fed continuously as mentioned above are so called accumulation systems wherethe gasthight and insulated storage tank is heated, thus serving at the same time as reactor.

All but one biogas system are operated on individual farms. Centralized anaerobic digestion is notcommon at all. The only two central biogas plants serving two respectively three farmers are co-digesting slurry with vegetable and source separated organic waste and paunch manure.

Originally, the major motivation for the construction of the plants was "energetical independence"followed by "improvement of the fertilizer quality". In recent years however, the two priorities wereexchanged. The production of electricity became important when the price was fixed to SFr. 0.16 perkWh for renewable energy. Over 60 of the 100 digesters are equipped with CHP.


Please contact [email protected] for more information.



9.B.13 Status of Anaerobic Digestion for Agricultural Wastes in the UKApril 1997Ian Higham

Introduction

About 45 farm-scale digesters have been installed in the UK since 1975. Many of these digesters wereinstalled with the aid of a capital grant which is no longer available. These digesters have been usedfor all types of animal manure: pig, cattle and chicken. Typically, the digesters have been between 50and 1000m3 and have generated gas for on-farm heating only. A few digesters have been fitted withsmall CHP engines. Many farmers sell some of the digestate to local householders for use as afertiliser and soil conditioner.

Of the 45 units installed, only about 25 are currently operating. These farm-scale digesters havesuffered from several problems. Some of the most common have been an inability to maintain amesophilic temperature during the winter months, pipe blockages, digester pH instability andequipment failures. The two main causes of these problems have been inadequate design and lack ofoperator training, both of which should be relatively easy to rectify. However this history of poorperformance has left the technology with a bad reputation amongst many farmers. It should be notedthat most of those farmers continuing to operate digesters now have a good knowledge of theiroperation and their plants are running reliably.

Current Situation

Very few farm scale digesters have been installed in the last few years since the removal of grantfunding. Recent interest has focused on larger centralised schemes due to support available from theNon-Fossil Fuel Obligation (NFFO). To date seven centralised anaerobic digesters have receivedNFFO contracts, one under NFFO3 in 1995 and six under NFFO4 in 1997, as shown in Table 1. Allof these projects are in development and none have yet proceeded to construction. It is hoped that atleast one of these projects will be built in the next 12 months.

These NFFO projects are mainly based on chicken litter but there is some use of pig slurry, cow slurryand turkey litter. The NFFO rules also allow up to 20% by dry weight of food processing waste and itis expected that most projects will take advantage of this. Although the NFFO contracts are forelectricity only, it is possible that some of the projects will be developed as CHP, where a suitableheat load is available.

Table 4: Developer and Capacity

Developer Capacity (MW e)

Attwell Farms Ltd 0.30

LRZ Ltd 1.05

Agtec Ltd 1.00

Agtec Ltd 2.00

Agtec Ltd 0.50

Agtec Ltd 0.60

North Tamar Business Network 1.43



Current development activities

There are several ongoing activities for the promotion of anaerobic digestion in the UK. Theseactivities are being developed in partnership between the Department of Trade & Industry and BritishBiogen (the biomass industry trade association). The main elements of this work are:

• Good practice guidelines;

• An industry working group.

The good practice guidelines are being produced through a consensus building exercise involvingrepresentatives of the biomass industry, government departments, regulatory bodies, environmentalbodies and local authorities. The guidelines are intended to inform interested parties and ensure thatdevelopments proceed in a responsible manner which balance the concerns of the various parties.

The industry working group has been set up to establish a co-ordinated approach to the developmentof anaerobic digestion. It is hoped that this group will avoid replication of effort, provide a forum forshared experience and most importantly enable resources to be focused on the key barriers facing theindustry.

The current emphasis of the industry is on integrated management systems. It is recognised thatanaerobic digestion can fulfil several functions:

• Farm waste treatment;

• Renewable energy;

• Nutrient application control;

• Soil conditioning.

The industry considers that, to be successful, it will have to exploit all of these functions in aneconomic manner and this is the challenge that will be faced in the next few years.


Contact Ian Higham at ETSU, Harwell, Didcot, Oxfordshire, OX11 0RA, UK. Tel: +44 12 35 43 2762, Fax: +44 12 35 43 39 90, e-mail: [email protected].


MWH Appendix 9C- 1

Appendix 9-C


This Appendix presents a tabulated listing of some 50 representative worldwide examples ofcommercially established biomethanation facilities. Details of some of these examples are given inAppendix 9 D. Further details about many of these examples can be found on the CADDETRenewable Energy website (www.caddet.co.uk).


MWH Appendix 9C- 2


No. Project / Document Title Plant/Location Country Feed Stock

1. Brecht MSW Plant Brecht Belgium Presorted MSW

2. Helsingor MSW Plant Helsingor Denmark Presorted MSW

3. Amiens MSW Plant Amiens France Unsorted MSW

4. Production of biogas and compost fromlarge quantities of Korean food wastes

Anyang City Korea Food Waste, MSW

5. Fermentation of separately collectedvegetable, garden and fruit waste

Tilburg TheNetherlands

Vegetable GardenAnd Fruit Waste

6. Large-scale batch-wise anaerobicdigestion of vegetable garden and fruitwaste produces biogas

Arnhem TheNetherlands

Vegetable GardenAnd Fruit Waste

7. Centeralised biogas plant for animal,industrial and municipal waste

Sinding-Orre Denmark Animal, Industrial,Municipal Waste

8. Thorso centralised biogas plant Thorso Denmark Animal, Industrial,Municipal Waste

9. Co-digestion of manure with industrialand household waste

Kristianstad Sweden Animal, Industrial,Municipal Waste

10. Anaerobic digestion of sewage sludge atKingsbridge, Devon

Kingsbridge,Devon

UnitedKingdom

Sewage Sludge

11. The power of organic waste Ghent Belgium Sludge, OrganicIndustries Waste,Pre-SortedBiowaste, FatSludge

12. Danish biogas plant with separate line fororganic household waste

Vaarst-Fjellerad Denmark Slurry, PresortedHousehold Waste,Fatty Sludge,BleachingClay(Bentonite)

13. The Vita Company of Wezep (potatopeeling company )

Wezep TheNetherlands

Potato IndustrialWaste Water

14. Additional income for farmers fromwaste processing

Frauenfeld Switzerland Manure And FarmWaste

15. Farm power from efficient anaerobicdigestion of animal wastes withphotovoltic supplement

Hayato-cho,Kagoshima,

Japan Farm Waste

16. Texas Tech University's Animal ScienceFarm

Texas United States Farm Waste

17. Biogas recovery from chicken manurefor electricity and heat production

Rijkers poultryfarm, Nistelrode

TheNetherlands

Chicken Manure


MWH Appendix 9C- 3


18. Darrell Smith Farm Princeton, NC United States Poultry waste

19. Anaerobic digestion of farm waste in theUK

Walford collage,Shropshire

UnitedKingdom

Dairy And PiggeryWaste

20. A centralized thermophillic biogas plantin Ribe, Denmark

Ribe Denmark Dairy/Cattlemanure

21. Blaabjerg Plant Norre Nebel Denmark Dairy/Cattlemanure

22. Foster Brothers Farm Middlebury, VT United States Dariy/Cattlemanure

23. Mason Dixon Farm Gettysburg, PA United States Dairy/Cattlemanure

24. Arizona Dairy Company Hgley, Arizona United States Dairy/Cattlemanure

25. Warrnambool Milk Products (WMP) :Anaerobic Digestion for Steam and HotWater

Warrnambool,Victoria

Australia Dairy Waste

26. Fairgrove Farms Inc. Sturgis, MI United States Dairy waste

27. Lindstrom Welch, MN United States Dairy waste

28. Cooperstown Holstein Co. Farm Cooperstown,New York

United States Dairy waste

29. Agway farm research center Tully, New York United States Dairy waste

30. Oregon Dairy Farms Lititz, PA United States Dairy waste

31. Craven Dairy Farms Cloverdale, OR United States Dairy waste

32. AA Dairy Candor, NY United States Dairy waste

33. M&M Dairy Fontana, CA United States Dairy waste

34. Cushman Dairy North Franklin,CT

United States Dairy waste

35. Langerwerf Dairy Durham,California

United States Diary waste

36. Skinnerup on-farm biogas plant with gasstorage

Skinnerup Denmark Dairy WasteSlurry, Fish OilSludge

37. Sindrup on-farm plant for animal andindustrial waste

Sindrup Denmark Dairy Waste, FoodIndustry Waste

38. Biogas combined heat and power insweden,

Trädgårdsstaden,Laholm

Sweden Dairy Waste,Organic WasteFrom Industries

39. Anaerobic Digestion of Piggery Wastesin Victoria

Berrybank Farm,Victoria

Australia Piggery Waste


MWH Appendix 9C- 4


40. Ejstruplund storage tank biogas plantwith soft-top cover

Ejstrup Denmark Piggery Waste

41. Royal Farms Tulare, California United States Piggery waste

42. Churchill Co-op Hecton, MN United States Piggery waste

43. Mccabe Farms Mt. Pleasant, IA United States Piggery waste

44. Rock Knoll Farms Lancaster, PA United States Piggery waste

45. Valley Pork Seven Valleys,PA

United States Piggery waste

46. Barham Farms Zebulon, NC United States Piggery waste

47. Carrol’s Foods Inc. Warsaw, NC United States Piggery waste

48. Lou Palmer Farm Morrilton, AR United States Piggery waste

49. Martin Farm South Boston,VA

United States Piggery waste

50. Sharp Ranch Tulare, CA United States Piggery waste


MWH Appendix 9 D - 1

Appendix 9-D

Case Studies

The Appendix has detailed description of twenty-biomethanation projects located world wide.These sheets contain descriptive information, technical details and (sometimes) performanceinformation, economic and environmental data.

• Brecht MSW Plant, Brecht, Belgium

• Helsingor MSW Plant , Helsingor, Denmark

• Amiens MSW Plant, Amiens, France

• Production of biogas and compost from large quantities food wastes, AnyangCity, Republic of Korea

• Fermentation of separately collected vegetable, garden and fruit waste, Tilburg,The Netherlands

• Large-scale batch-wise anaerobic digestion of vegetable garden and fruit wasteproduces biogas, Arnhem, The Netherlands

• Centeralised biogas plant for animal, industrial and municipal waste, Sinding-Orre,Denmark

• Thorso centralised biogas plant, Thorso, Denmark

• The Vita Company of Wezep (potato peeling company ), Wezep, The Netherlands

• Farm power from efficient anaerobic digestion of animal wastes with photovolticsupplement, Hayato-cho, Kagoshima, Japan

• Texas Tech University's Animal Science Farm, Texas, United States

• Biogas recovery from chicken manure for electricity and heat production, Rijkerspoultry farm, Nistelrode, The Netherlands

• A centralized thermophillic biogas plant, Ribe, Denmark

• Blaabjerg Plant, Norre Nebel,Denmark

• Foster Brothers Farm Middlebury, VT, United States

• Mason Dixon Farm Gettysburg, PA,United States

• Warrnambool Milk Products (WMP) : Anaerobic Digestion for Steam and HotWater Warrnambool, Victoria, Australia

• Skinnerup on-farm biogas plant with gas storage, Skinnerup, Denmark

• Sindrup on-farm plant for animal and industrial waste, Sindrup, Denmark

• Ejstruplund storage tank biogas plant with soft-top cover, Ejstrup, Denmark



9.D.1 Brecht MSW Plant

Location: Brecht, Belgium

Feed material: Presorted MSW

Description:

DRANCO (Dry Anaerobic Conversion) process, a second variation of dry process, has beentreating 10,500 tons per year of pre-sorted municipal solid waste in Brecht, Belgium, since mid1992. The garbage is comminuted in a homogenizing drum and sieved over a 40 mm screen. Theoversize is landfilled, and the fraction less than 40 mm is mixed intensively with digested residue,heated with steam to a temperature of 50 – 55 0C, to kill any faecal coliform, and pumped into thedigester. The digester has a volume of 808 m3 and after about 18 days of digestion, the residue isdewatered to a solids concentration of ca, 60% by means of a screw press. The press liquid ispartially used to adjust the total solids concentration inside the digester to about 35%. The presscakes are aerobically composted during 10 days to get Humotex, a stabilised and pathogen-freeproduct for soil amendment. The methane yield is 90 Nm3/ton of wet garbage giving a biogaswith 55 % methane content. The biogas is used to produce process steam 290 kw power.

The digester has been upscaled to a volume of 1810 m3 to treat 20,000 ton of biowaste per yearcorresponding to the source separated organic waste of the Greater Salzburg area (Austria) withabout 300,000 inhabitants. The performance parameters of the DRANCO process are: a biogasproduction rate of 4.5 Nm3/m3 reactor day and loading rate of 13 kg Total Volatile Solid/m3

reactor day.



9.D.2 Helsingor MSW Plant

Location: Helsingor, Denmark

Feed material: MSW

Description:

BTA process uses wet digestion to process 20,000 tons of municipal solid waste in Helsingor,Denmark from late 1991. In the BTA process, a pulper grinds and suspends presorted refuse intoa 10 % solid solution. A rake fishes out the lighter fraction (mostly plastics and textiles) andleaves heavier non-digestibles (such as bonem stone and glass) trapped at the bottom of thepulper. The suspension produced from the organic fraction is heated to 700C, then transferred to acentrifuge for solid – liquid separation. The liquid is then converted to biogas in the methanereactor.

Undissolved solids are fed to a hydrolysis reactor, which breaks down complex organics intomolecules accessible to methanogenic bacteria. Solid retention time for the hydrolysis processesaverage two to four days and that for methanization, one to two days. Separating hydrolysis frommethanization allows optimal control of the process and cuts the treatment time significantlycompared with single stage digestion. In less than one week, more than 60 percent of thefermentable substances can be turned into biogas, compared with around 40 percent conversion ina conventional single stage digestion.

The waste water burden from wet process is also much lower than that from landfill leachate orfrom aerobic composting. BTA process produces 400 – 500 liters per tons of waste with abiological oxygen demand of 0.6 g/L, so it can be treated in a conventional waste water treatmentplant.



9.D.3 Amiens MSW Plant

Location: Amiens, France

Feed material: Unsorted MSW

Description:

An automated sorting unit first removes metals, plastics, paperboard, glass inerts. The remainingorganic fraction is mixed with recycled water from the compost drying press to form a 30-35percent solid sludge, which is pumped into one of the plant’s three digesters. To avoid the movingparts that would otherwise be required for mixing, part of the biogas coming off the top of thefermenter is sparged back into the bottom of the column. Residence time in a reactor is aboutthree weeks and the biogas yield is 99 Nm3/ton of municipal solid waste, or 146 Nm3/ton ofsorted organic fraction.

The Amiens plant runs at 370C using mesophilic bacteria and producing 5.5 million Nm3/year ofbiogas. The biogas is purified and supplied to gas pipeline, the residue of digestion is utilized forsoil amendment or incinerated to produce heat.

The design parameters of the digester and some operating conditions of Valorga processdemonstration plant are summarized in Table 1. And the performances of the process at thoseconditions are tabulated in Table 2.

Table 1 Design Parameters Operating Conditions of the Valorga Process

Parameters and Operating Conditions Values

Reactor Volume (m3) 500

Stirring Methods Pneumatic/gas recycle

Hydraulic Retention Time (Days) 15

Solid Retention Time (Days) 15

Reactor Temperature (0C) 37

Inhabitants Served (Person) 25000

MSW Treated (tonnes/year) 8000

Types of Feed MSW (sorted on-site)

Feed Concentration (g TS*/dm3) 350

Feed Volatile Solids (% of TS) 58.6*TS = Total Solid



Table 2 Performance of the Valorga Process Digester

Parameters of Performance Typical Value

Hydraulic Retention Time (Days) 15

Organic Loading Rate (kg TVS*/m3 day) 13.7

Gas Production Rate (Nm3/m3 day) 4

Methane Yield (m3/kg TVS) 0.23

Methane Concentration (vol. %) 65

TVS removed (%) 45* TVS = Total Volatile Sold

According to the performances described in Table 2, a plant using 50,000 tons per year of organicfraction of municipal solid waste can produce approximately 20,000 tons (dry basis) of humusand 5 million Nm3 of methane gas a year.



9.D.4 Production of biogas and compost from large quantities of Korean foodwastes

Location : Anyang City, Kyunggido; Republic of Korea

Feed material: Food Waste

Description:

One of the major goals of the Korea Institute of Energy Research (KIER) is to develop and applynew technologies for the recovery of energy from various wastes including municipal solidwastes (MSW). The project dealing with the production of biogas and compost from largequantities of Korean food wastes is a co-operative effort between KIER, the Korea Ministry ofTrade, Industry, Energy, and Halla Engineering and Heavy Industries, Ltd.

The project was first initiated to resolve the problem of food waste management in Korea.Problems of Korean food waste are caused first of all by its ever-increasing volume and by itshigh moisture and salt content. Highly urbanised and populated towns in Korea do not haveenough space for landfill and the high moisture and salt content of food waste hinders effectiverecycling for compost production or incineration for energy recovery. The anaerobic processplant of this project, located at the Anyang City incinerator site, produces biogas and humus fromthe treatment of 5 tonnes/day MSW containing approximately 3 tonnes of food waste.

The major achievements of this project are;

1) development of a two-phase anaerobic process optimised for Korean food waste treatmentand biogas (energy) recovery;

2) development of a sorting pre-treatment process suitable for Korean MSW collection systems;

3) demonstration of the feasibility of Korean food waste treatment as one component of anintegrated waste management system including landfill and incineration.

The process was verified to be suitable for energy recovery from pre-sorted food waste in Korea.A plant sorting 15 tonnes/day of pre-sorted food waste using this process is under construction inEuiwang City for initial start-up in March 1997.

Technical Data

The two-phase anaerobic process consists of two reactors in series with capacities of 15 m3 and45 m3 operated in acidic and methanogenic conditions. The effluent of the methane reactor isrecycled. In steady state operation, when 5 tonnes of MSW is treated, about 0.9 and 1.1 tonnes ofplastic and other non-degradable material are removed by means of a drum screen and acidreactor (by gravity) respectively. About 100kg of humus (70% moisture), 230 m3 of biogas (70%methane) and 2 tonnes of anaerobically treated waste water are produced from three tonnes offood waste. It is estimated that around 73% of the degradable waste is converted to biogas.

Performance Data



Several lessons have been learned through the operation of the pilot process;

Although pre-sorted at the collection stage, inclusions such as bones, shells and metal pieces inplastic food waste bags caused several unexpected problems including clogging in the conveyorline, hoppers and pipelines;Modifications were made in the pre-treatment equipment (hoppers, drumscreen, conveyors etc.),pipe lines and acid reactor to resolve these problems;For the disposal of non-biodegradable inclusions and waste-water treatment it is desirable to havethe incinerator or landfill and waste-water treatment located nearby;The process systems should be automatically controlled;The process is estimated to be the most feasible and effective for the recovery of energy fromKorean food waste, provided that the waste is pre-sorted and treated in co-operation with theincinerator.

Economic Data(Note: $ is the US dollar)

In case of the 15 tonnes/day food waste treatment capacity, the operational cost of the plant wasestimated to be $25/tonne of food waste. Treatment and the construction costs were estimated tobe $435/tonne of MSW in Korea. However, no more landfill sites are available for the disposal offood waste in Korea because of environmental impacts such as leachate and bad odour etc.

Environmental Data

Urban areas in Korea are particularly good locations for the application of anaerobic digestiontechnology for waste food treatment and the recovery of energy from high moisture food wastebecause of nearby energy demands. The process occupies and is confined to a small space.



9.D.5 Fermentation of separately collected vegetable, garden and fruit waste

Location : Tilburg, The Netherlands

Feed material: Vegetable, garden and fruit waste

Description

The aim of this project is to demonstrate the use of the Valorga digestion process for thefermentation of separately collected vegetable, garden and fruit waste. Although the process hasbeen in existence for a number of years, this is the first application in the fermentation of purelyorganic waste.Anaerobic fermentation of waste has several advantages:

- Reduction of waste volume;

- Optimisation of recycling;

- Production of biogas;

- Production of an environmentally friendly compost;

- Reduction of the carbon dioxide emissions;

- Existing landfill gas upgrading unit can be used.

In the Valorga process, the vegetable, garden and fruit waste (VGF) is preheated to 60°C and fedin to a reactor vessel. Because of the preheating of the feedstock, the average temperature in thereactor is 37°C, ideally suitable for anaerobic digestion. The stock remains in the reactor for 18days.

Optimum mixing is achieved by pumping pressurised biogas into the reactor and also by placinga vertical baffle wall inside the vessel. Part of the digested VGF is recirculated after leaving thereactor, the rest is fed to a dewatering unit where water is removed mechanically. The residue isstabilised aerobically; effluent water is partially cleaned and discharged, partially fed back to thedigestor.

The biogas emanating from the process is used in the plant itself; a surplus can be fed to thenational gas grid or be converted into electricity.

Technical Data

Design capacity 52,000 tonnes of VGF/yearSurface Area 10,000 m2Conversion Time 18 daysNet Biogas Production 110 m3/tonne =5,720,000 m3/yearMethane Content 55 % =3,146,000 m3/yearSurplus electricity 152 kWh/tonne =7,904,000 kWh/yearCompost Production 0.7 tonne compost/tonne VGF =36,000 tonne of compost/yearWaste Water 0.1 tonne of water/tonne of VGF = 5,200 tonne of waste water/year (where VGF is vegetable, garden and fruit waste)



Performance Data

Assuming a calorific value of the biogas of 19.7 MJ/m3 (55% methane, 45% inert gas) the annualproduction of biogas is equal to 112,700 GJ, the equivalent of 3,500,000 m3 of Groningen naturalgas (31.6 MJ/m3). The electricity produced from this gas amounts to 9,412,000 kWh/year,1,518,000 kWh of which is consumed by the plant itself.



9.D.6 Large-scale Batch-wise Anaerobic Digestion of Vegetable Garden and FruitWaste Produces Biogas

Location : Arnhem, The Netherlands

Feed material: Vegetable, garden and fruit waste

General Description

The aim of the project is to demonstrate, at an industrial scale the application of the BIOCELsystem for the digestion of vegetable, garden and fruit waste (VGF), to show that it is ready formarket introduction.

BIOCEL is an anaerobic conversion technique for vegetable, garden and fruit waste. A batch-wise fermentation process generates biogas, which in turn is converted into electricity. A mixtureof vegetable, garden and fruit waste and structure material is fed into a mixing and sieving unit,where the material is mixed with inoculum. The mixture is then fed to two 400 to 600 m3

concrete digesters, in which it is digested anaerobically during 22 days at a 35°C temperature.Methane, emanating from the digesters, is used to generate electricity. Leachate is collected at thebottom of the vessel, heated and fed back to the digester. Some of the digested material isreturned to the mixing drum to act as an inoculum; the rest is processed into compost.

The demonstration project shows that the BIOCEL system produces energy and contributes to thereduction of CO2 emissions. Furthermore, the project produces compost by thermal drying of thefermentation residue. The final product has a composition and a degree of stability comparable tothose of aerobically fermented compost. Finally the project shows the economic feasibility ofanaerobic fermentation, which is essential for further application.

Technical Data

Capacity 35,000 tonne/yearSurface Area 6,000 m²Conversion Time 22 daysBiogas Production 100 m3 of gas/tonne of VGF = 3,500,000 m3/yearMethane Content Biogas 55 %Final Product 0.43 tonne/tonne of VGF = 1,505,000 tonne/yearWaste Water Production 0.44 m3/tonne of VGFDry matter content 65 % by weight(where VGF is vegetable, garden and fruit waste)

Performance Data



At a calorific value of the biogas of 19.7 MJ/m3, (55% methane, 45% inert gas), the annualproduction of biogas is equal to 69,000 GJ/year, the equivalent of 2,200,000 m3/year ofGroningen natural gas (31.6 MJ/m3). The electricity produced from this gas amounts to 5,775,000kWh/year, 1,365,000 kWh of which is consumed by the plant itself.



9.D.7 Centralised Biogas Plant for Animal, Industrial and Municipal Wastes

Location : Sinding-Orre, Denmark

Feed material: Animal, Industrial and Municipal Wastes

Description

In 1984 the Sinding-Orre Civic Association discussed how to ensure a cost effective heat supplynetwork for the small urban areas around the town of Herning based on alternative energy. Acommittee was appointed consisting of representatives from the civic association, farmers andmunicipality. After several meetings it was decided that the municipality of Herning shouldestablish the biogas plant while a new supplier association (farmers) should be responsible fortransportation and distribution of manure to and from the plant. The plant was built in 1987/88and involved the production of biogas from the thermophilic digestion of pre-sorted and source-separated household waste.

Several problems were solved and identified during the first year of operation and a number ofinteresting features were implemented e.g. a method for treating source separated householdwaste (now in permanent use). Facilities for receiving and converting different types of industrialwaste were also developed. The technique for using the organic fraction of household waste isnow technically reliable and financially satisfactory. It includes pre as well as post sorting ofplastics in order to ensure a clean fertilizer for the farmers.

Water and hydrogen sulphide are removed from the biogas before it is compressed, piped andsold for electricity and heat production to two local plants (a district heating plant in Sinding anda combined heat and power plant in Tjorring). The electricity is distributed through the electricitygrid.

Technical Data

Manure suppliers 35

Digestion tanks 21,000 m3

Process temperature 53°C

Process time 15-16 days

Annual consumption (1995);Animal waste 36,000 tonnesIndustrial and municipal waste 16,000 tonnesTotal 52,000 tonnes

Performance Data



Annual biogas production in 1995 was 3,142,878 m3.

Approximately 30% of the biogas is used as process heating at the biogas plant



9.D.8 Thorso Centralised Biogas Plant using Animal, Industrial and MunicipalWaste

Location : Thorso; Denmark

Feed material: Animal, Industrial and Municipal Wastes

Description

In 1991 a group of farmers initiated the establishment of a centralised biogas plant in co-operation with representatives of the local municipality and the district heating plant of Thorso.The main objective was partly to supply Thorso with environmentally favourable energy andpartly to improve environmental conditions in agriculture. The biogas plant was built in 1993 andbecame operational in 1994. It is owned by a co-operative society with 68 manure suppliers asmembers.

The features of the plant are;- digestion at 53°C (thermophilic process) during an average period of 15-16 days;

- surplus fertiliser distributed among plant breeders in the area;

- simultaneous utilisation of biogas and natural gas at peak hours (dual-fuel).

Presently approximately 76% of the biofuel is manure, 20 % industrial waste and 4% municipalwaste. Slurry storage facilities have been established at the farms with a total volume of 90,000m3. Three slurry vehicles bring the manure to the biogas plant.

The co-operative society makes provision for storage and sale of surplus fertiliser.

Thorso biogas plant is equipped with a large gas storage tank where the gas is collected primarilyfor use at peak times when electricity production is most valuable.

Biogas is transported through a 3.2 km gas pipe to Thorso Combined Heat and Power plant whichcan burn pure biogas, pure natural gas or a mixture. However, the biogas has first priority andapproximately 67% of the energy production is based on biogas. The plant supplies heat to 442households and institutions and sells the electricity to the regional electricity utility.

Technical Data

Manure suppliers 68Transportation of slurryfrom the farms to the biogas plant 3 slurry vehicles

Process temperature 53 °CProcess time 15-16 daysDigestion tanks 4,650 m3

Nominal manure capacity 280 m3/dayAverage manure circulation 300 m3/day (110,000 m3/year)



Animal waste 200 tonnes/day (76%)Industrial waste 50 tonnes/day (20%)Municipal sludge 10 tonnes/day (4%)Gas storage 2,790 m3

CHP engine generator units:2 each with a capacity of 660 kWDistrict heating plant supplies - 442 households and institutionsEmissions: Varying negligible amounts of SO2, NH3 and NOx.

Performance Data

Biogas 2.16 million m3/year

Nominal capacity:CHP plant power 1.3 MWCHP plant heat 1.64 MW



9.D.9 The Vita Company of Wezep (Waste from a Potato Peeling Company ProvidesBiogas for Electricity Production)

Location : Wezep, The Netherlands

Feed material: wastewater from potato peeling industry

General Description

The Vita Company of Wezep, The Netherlands, produces vacuum-packed peeled potatoes. Theprocess generates about 700 m3/day of waste water, which has to be cleaned prior to beingdischarged into the sewer. The water treatment unit incorporates an anaerobic digestion stage,which produces biogas which previously was simply burned off. In this project, a new, biogas-fired three-pass fire-tube steam boiler has been installed next to an existing natural gas firedboiler. The steam generated by this new boiler is fed to the existing steam grid.

Results from this project are of interest to the foodstuff industry in general as well as to othercompanies where polluted water is subjected to anaerobic treatment.

Technical Data

Waste water flow 700 m3/day.

The waste water before the process has a concentration of 8,000 to 10,000 mg organics per litre.After the digestion process the concentration is 1,500 to 2,000 mg/litre. These values are based onChemical Oxygen Demand (COD). The digestion process provides a purification of 85% on CODor a purification of about 75% in total.



9.D.10 Farm Power from Efficient Anaerobic Digestion of Animal Wastes withPhotovoltaic Supplement

Location : Hayato-cho, Kagoshima; Japan

Feed Material: Farm Waste

Description

In conventional fermentation processes (anaerobic digestion) in which animal excreta are dilutedand then heated, much of the methane produced is used in the heating especially in winter. This isobviated by a new process in which undiluted excreta are separated into liquid ingredients andsolid residues by a screw press. Most of the organic matter is concentrated in the liquid which isfermented undiluted. This process has the following advantages;

(1) Fermentation of highly concentrated readily decomposable substrates uses only 20-30%of the total methane production, even in winter, as compared to 70-80% in conventionalprocesses;

(2) The separated solid residues readily rot down into compost.

Together with a photovoltaic generator the process powers a gas engine generator to form ahybrid generating system, at a 1,000 pig farm owned by an agricultural cooperative at Hayato-cho, Kagoshima. The photovoltaic system allows gas to be conserved for the hours of darknessand thus the hybrid system is a reliable power source.

Technical Data

2,300 kg of liquid are squeezed each day from the excreta of 1,000 hogs. From this liquid, 85 m3

of gas with a 63% methane concentration is produced in a fermentation tank with an effectivevolume of 60 m3, under the following conditions: fermentation temperature of 34°C, retentiontime in the tank of 21 days, concentration of volatile substances in the liquids of 12%, and thevolumetric loading of organic matter at 5.8 kg/m3 a day. The hybrid generating system comprisesa 25 kW gas engine generator, a 30.24 kWp photovoltaic generator and a storage battery with acapacity of 192 kWh.

Performance Data

Approximately 19 m3/day of gas are consumed in heating the fermentation tank. Thus, the gasavailable to the gas engine generator is 66 m3/day. This, it is estimated, enables a daily 125 kWhto be generated. It is estimated that the photovoltaic system can generate 33,600 kWh/year(during daylight hours), a daily average of 92 kWh.



9.D.11 Texas Tech University's Animal Science Farm

Location : Texas; United States of America

Feed material: Farm waste

Description

About five million head of cattle are reared annually on some 200 feedlots in the high plains ofTexas. An integrated anaerobic methane demonstration unit has been constructed at the TexasTech University's Animal Science Farm to make use of the waste of a 1,000-head cattle operationand a 280-sow farrow-to-finish swine operation in New Deal, Texas. The potential energy thatcan be produced from cattle on the high plains of Texas approaches 4 million kWh/day.

Objectives of the demonstration include :

1) successful operation and monitoring of a membrane-covered anaerobic pit coupled with apond to produce biogas for fueling Stirling thermal engines and driving a flat plate turbinecoupled to an electric generator;

2) production, monitoring and modeling of nutrient cycling throughout an integrated wastetreatment system;

3) demonstration of aquaculture production through synergistic processes.

The data collected will be used to test production models of similar systems that have alreadybeen developed but not completely verified. Project data will be shared with agriculturists,developers and managers for purposes of advancing industrial anaerobic lagoon systems. Theinstallation is part of the Western Regional Biomass Energy Program. Contributors includeEnvironmental Hazard Control Inc. Global Scientific Inc. and Williams and Peters ConstructionCompany Inc.

Technical Data

Biogas is produced anaerobically in a pit 3.25 m² (35 ft²) in area and 3.05 m (10 ft) deepand captured by a membrane covering the pit. Pipes connected to the centre of themembrane cover transfer the gas to a nearby building where it is burned in a series ofheaters to produce hot water. The heated water is passed to;

a pond for production of purple sulphur bacteria and transition to a combined aerobic-anaerobic environment;a shallow pond for production of aquatic plants, such as duckweed, for extraction ofnutrients;a pond for production of fish, principally tilipia.

The water is recycled back to the farm.



Hot water is also pumped through a closed coil back into the anaerobic pit to optimize gasproduction and then returned to the heater for recycling. Excess gas can be used to generate steamfor a turbine or to fire a Stirling engine.

Performance Data

The demonstration facility is projected to yield sufficient excess biogas to support a 35 kWelectrical generator.

Economic Data

The use of animal wastes to provide energy for integrated animal feed and aquaculture operationshas the potential to produce several hundred million dollars of revenue in Texas. Aquatic plantsand fish can be used as feed ingredients for confined animal production operations and theworldwide aquaculture market has expanded dramatically.

The integration of anaerobic energy fermentation systems with aquaculture production can help toreduce the United States' reliance on imports of aquaculture products.

Additionally, this technology could be moved into Mexico in conjunction with a project now inplace to identify and map natural resources (vegetation, agricultural lands, water and waterquality). Landsat scenes could be used to identify significant water streams or possible sites forinstallation of anaerobic digesters and their associated forms of energy production.

Environmental Data

The integrated system has the capability of improving its immediate environment byextracting nitrogen compounds, capturing gaseous emissions, and enhancing wildlifehabitat in wetlands. The facultative pond helps control odour.



9.D.12 Biogas Recovery from Chicken Manure for Electricity and Heat Production

Location : Nistelrode, The Netherlands

Feed material: Chicken manure

Description

The Rijkers bv poultry farm in Nistelrode has built a biogas plant which uses chicken manure togenerate electricity and to heat the house and poultry house.

Part of the manure is fermented directly and part is dried to a dry matter content of 50%. In orderto make the chicken manure pumpable, pig manure is also added.

The methane gas extracted generates electricity by means of a gas engine and generator. Thewaste heat is used to heat the buildings and the fermentation tank.

Technical Data

The manure from approximately 45,000 laying hens is removed daily with a manure removalsystem and discharged into an 80 m3 cellar behind the poultry house. Since the manure has to bepumped it has to be made liquid. This is achieved by adding pig manure, flocculation silt andwater or return fluid from the post-storage of the fermented manure. From the cellar, the manureis pumped to the fermenter.

The digester itself consists of three compartments: the main digestion compartment (75 m3), asecondary digestion compartment (35 m3) above it and a channel connecting the two. In the maincompartment, the manure begins to digest. A gas mixture of methane (64%) and carbon dioxide(36%) is formed, causing the pressure in the bubble above the fermenting manure to rise. The gaspressure passes part of the manure up through the channel into the secondary digester. When theliquid in the secondary digester reaches the overflow level, some of it flows out of the digesterand into a storage bunker, while fresh manure is added to the main digester compartment. The gasvalve is then opened and the manure in the secondary digester flows back into the main digestercompartment. This causes the fresh load to be mixed with partially digested manure, and theprocess starts again.

The fermented mixture is stored in a silo from which the fluid portion is returned to the mixingand metering pit. A ballon weighted with a concrete ring floats in the silo containing thefermented manure. The gas is stored in the ballon for subsequent use by the combined heat andpower plant. The gas drives a gas engine to which a generator is coupled. The heat generated bythe engine is used for the heating system. The system also comprises a boiler fired by biogas ornatural gas. This boiler heats the building and the manure fermenter.

It emerged that optimum production was obtained from a daily supply of 6.1 m3 of chickenmanure, diluted with 2.3 m3 of pig manure, 1.9 m3 of flocculation silt and 2.3 m3 of return fluid.

Performance Data



During the measurement period, daily production of 932 m3 of biogas was achieved. Thecomposition of the gas was approximately 64% methane and 36% carbon dioxide.

The following estimates were made on an annual basis from 1986 data;

Plant operating hours 7,750 hours/year;Electricity generated for own use 310,600 kWh/year;Electricity generated and supplied to the national grid 29,900 kWh/year;Amount of heat produced 689,750 kWh/year;Heat used by the fermenter 169,000 kWh/year;Used for heating farm buildings 163,000 kWh/year;Heat extracted by the emergencycooler and not used 358,000 kWh/year.Biomass mixture:Chicken manure 1,970 m3/yearPig Manure 742 m3/yearFlocculation sludge 614 m3/yearTotal 3,326 m3/yearBiogas data:Maximum production 295,545 m3/yearAverage production 236,436 m3/year



9.D.13 A centralized thermophillic biogas plant

Location: Ribe, Denmark

Feed material: Cattle manure

Description:

The plant receives approximately 500 wet tons per day of slurry, about 2/3 of which is dairymanure. The plant has three digesters, each 1,750 cu m insulated steel tank, for a total of 5,250cu m (1.4 mil gal total). For process operating calculations the plant uses 4,656 cu m of digestervolume which gives a hydraulic detention time of 11 days. The Ribe plant started in 1990 in themesophilic temperature range of operation, then increased temperature up to thermophilic rangewithout any problem. Dairy manure slurry is about 10 percent solids; other slurries are lessconcentrated, so the overall mix to the digesters is about 9 percent solids content.

“Degassed” slurry is hauled back to about 20 storage tanks located near the individual farms orclusters of farms in the same trucks which bring in the slurry. Manure from dairies is picked upon a schedule depending on volume, and may be once per week or twice per month. It was statedthat the manure should be as fresh as possible, say not more than one or two months old as amaximum. In response to a question on how the plant would work if the plant was fed only cowmanure, the answer was: “There is no economy in cow manure; must get the other wastes ormake system very cheap.” The plant is allowed to bring in up to 25 percent of industrial organicwastes which generate tipping fees and produce more gas to sell than does an equivalent volumeof dairy slurry.

The methane content of the biogas on June 11, 1998 was 66.9 percent, but is usually in the 63-64percent range. Without the industrial waste, it was stated that the methane percentage would belower, say 60 percent. H2S in the biogas is limited to 700 ppm. The plant computer screenmonitor showed 200 ppm on June 11. Plant has a system to add a small amount of air to the gas(new technology) to oxidize H2S, but it is used very infrequently. The gas pressurization systemhas never been used, and was a waste of money. Gas is piped at low pressure, about 2 km, to alarge gas plant which has two biogas engine/generators and three larger natural gasengine/generators. The power plant produces power during peak electric rate periods and useswaste heat to provide hot water to the town for space heating and domestic hot water produced byheat exchangers at individual residences. The power plant also has some standby boilers toprovide heat for the town if the engines are down, and has a large water tank to store heat. Thestandard of housekeeping at the power plant was very high. All areas of the plant appeared to beclean and corrosion-free.

The three digesters are run in parallel at thermophilic temperature. The digesters are stirred withone slow speed (reported to be 20 rpm) stirrer for each tank with motor and gear box mounted onthe top of the tank.

The heat of the digested slurry is captured by heating the incoming slurry. Of the three heatexchangers in series, the first two are extracting heat from the hot slurry, and the third is using hotwater to give the final boost of temperature to the feed slurry. The plant has experienced struvite(magnesium ammonium phosphate) formation when slurry cools, and must clean the heat



exchangers with acid once per week. The plant has the capability for direct steam injection intothe digesters, particularly in the winter to maintain digester temperature.

The digesters at the plant have never been cleaned. The take-off pipe apparently has beensufficient to remove grit on a continuous basis. The plant does clean the feed slurry storage tankstwice per year.

Strong odors at the plant are from industrial slurries. Air is displaced from the waste holdingtanks when new wastes are added. This air is vented to the atmosphere, but apparently dissipatesbefore reaching any complaining neighbors. This problem can be fixed, if a problem, andapparently has been dealt with more aggressively at other plants by venting foul air to combustionunits.

The Ribe Plant and the Blaabjerg Plant have about the same staffing level. The operation of theplant and of the slurry trucks for collecting and transporting animal manure and returningdigested slurry is performed by four people total. Transport of industrial slurry and operation ofthe power plant is in addition to this manpower. The four persons are able to maintain a 7 day perweek, 24-hr coverage of the plant through automation, trouble signals, on-call arrangementamong the four and careful scheduling, such as collecting sufficient slurry by Friday for thedigesters to be fed over the weekend.


Ms. Else JensenRibe Biogas A/SKoldingvej 19DK-6760 Ribe, DenmarkTel: +45-75-410410Fax: +45-75-423245



9.D.14 Blaabjerg Plant

Location: Norre Nebel Denmark

Feed material: Dairy manure

Description:

The plant receives approximately 400 wet tons per day of slurry, about 60 percent of which isdairy manure. The plant has two digesters, each 2,500 cu m insulated steel tank, for total volumeof 5,000 m3 (1.3 million gal total). For process operating calculations the plant uses 5,000 m3 ofdigester volume which gives a hydraulic detention time of 15 days. The plant started in1996 inthe thermophilic temperature range.

The overall set-up and operation is similar to the Ribe Plant. However, the digesters are bigger.Also, since the power plant is very close by, hot water from the power plant is used for heatingthe digester with heat exchange piping on the internal walls of the digesters instead of with livesteam. Also, fiber separation from the digested slurry is a component of the system. The intent isto burn the separated fiber in the adjacent power plant with wood and other solid fuels, but thesystem was not operational at the time of the visit, and there was indication that the system mayhave some technical problems.

The mixing propellers in the digesters rotate at 10 rpm; there are two propellers, 3 m in diameter,on the center shaft inside the 13.7 m diameter tank. The top propeller blade is one ft. below thetop liquid surface, and the other blade is near the bottom of the tank. Incoming feed is through apipe inside the digesters and discharges above the liquid level in the tank. Digested slurry is takenoff near the bottom of the tank. There is also a withdrawal pipe which reaches to the bottom ofthe cone and from which a vacuum pump truck may connect and remove grit from the digester.

The methane content of the biogas on June 12, 1998 was 62 percent. H2S in the biogas was 2000ppm, and through the removal system (air oxidation discussed above) was reduced to 100-200ppm

The heat of the digested slurry is captured by heating the incoming slurry. Of the three heatexchangers in series, the first two are extracting heat from the hot slurry, and the third is using hotwater from the power plant to give the final boost of temperature to the feed slurry. The plant hasan acid system to control the struvite problem.

Foul air is collected and burned in a combustion unit.

In delivering digested (“de-gassed”) slurry to the farmers, the operators are careful not to bring inwaste from a pig farm then take back digested slurry in the same truck to the same or another pigfarm. This is for disease control. Pig farmers are very concerned about this. It is all right to gofrom “dairy to dairy, but not pig to pig,” so the operators are careful to be sure that the truckcarrying digested slurry to the pig farmer was previously filled with dairy manure, not pigmanure.



There was 400 to 500 cu m of sand in the incoming waste holding tanks after 1 ½ years.

There were two gas engines/generators, each 400 kw.


Burmeister & Scandinavian ContractorP.O. Box 235Gydevang 35, DK 3450 AllerødDenmarkTel: + 45-48-14 00 22Fax: + 45-48-14 01 50



9.D.15 Foster Brothers Farm

Location: Middlebury, VT, USA

Feed material: Dairy manure

Description:

Contact was Mr. Robert Foster, but also had discussions with Mr. James Foster and Mr. JeffreyGraves. From the site visit: milk cows are on concrete 100 percent of the time and bedded withsaw dust; manure (probably 12 percent solids) is scraped by a small tractor in the barns directlyinto a manure wagon which is pulled by tractor over to the digesters and bottom dumped into thedigester feed tank. There also are two steel tanks to store other liquid organic wastes, such as milkwhey, and there has been a practice to feed this additional material into the digesters with goodresults in terms of gas production.

Unfortunately, the building covering the feed area, digester and gas holder caught fire in March1998 and put the system out of operation, except that the digester is continuing to be fed, but notheated. A new gas bag has been ordered, and repairs are planned this summer. The fire was notcaused by the digestion/energy recovery system, but by a wood stove used to keep people warmnear the two steel tanks used for storing whey or similar liquid waste.

Flow is in parallel through two plug flow digesters; digester cover is the gas bag. There has notbeen a crusting problem probably because the manure is thick, not diluted with flush water whichresults in solids separation and floating.

The plant is reported to produce 1250 kw-hr/day of electricity, but has not supplied power to thepower grid for years because the price went down. Price started around $0.05 per kw-hr, but hasgone down to about $0.015 per kw-hr. Power is used on the farm.

H2S in the biogas is removed through a home made system with a drum of marble chips,apparently but unknowingly, a system similar to the Danish plants (the H2S removal mechanismwas not well understood on the farm, but it worked so no one has paid much attention to it).

Heating of the digesters is through hot water pipes near the floor of the digesters. Hot water isproduced from engine cooling and heat exchange on the exhaust gas from the engines.

Digested slurry (probably 9 percent solids) is run through one FAN screw press which has had itsmotor and gear box replaced with American models, because of the expense of the Germanreplacement parts(only German parts left are the screen and screw); dewatered product is used asa major component for the Foster family soil amendment business which is adjacent and larger inbusiness volume than the dairy business itself.

Liquid (probably 6 percent solids) after the screw press is piped to and stored in a large earthenpond and later pumped to the farm fields in the summer, in accordance with regulations, to beused as fertilizer.



This site visit pointed out the use of the digested manure along with other material for soilamendment products, all agricultural wastes in accordance with organic certification procedures.Overall estimate is that cow manure is 50 percent of the products, and that Foster manure is 70percent of the total cow manure of their soil amendment products, because they do collect cowmanure from another dairy (undigested) and compost this manure along with their own digestedmanure. The soil amendment business was up to $2.5 million last year, but lost money, so hasretrenched and is expected to be $1.5 million this year, as compared with the dairy part of thebusiness which is about $1.2 million per year. Material is purchased from outside to blend withdigested and composted cow manure. For chicken manure, they pay transportation costs only; forpurchase of solids from another dairy they pay $4.90 per CY plus transportation, at a price of $1per mile for a 25 to 30 CY load; normally they have to pay at least $1.25 per mile or a bit higherat $1.50 per mile for quality (reliable) service of a 48 ft dump trailer which may hold 60 CY offairly dry material, say 30 percent moisture and 1200 to 1400 lbs/CY. When asked about themarket value of digested manure solids as it comes off the screw press, one answer was “maybe$12 per ton.” Another answer was “$5 per CY loaded out - transportation would be buyer’sresponsibility.”


Robert FosterTel: + 1-802-388-0156



9.D.16 Mason Dixon Farm

Location: Gettysburg, PA, USA

Feed material: Cow manure

Description:

Ninety percent of the manure is mechanically scraped (3 m /min.) from the floors into galleys,and flows by gravity to a holding tank. The remaining 10 percent of the manure is collected byan old flush system and flows to a settling basin prior to entering the holding tank. Water for theflush system is recirculated from the settling basin.

The manure slurry flows first through a “loop” digester, and then through two plug flow digestersin series. A new digester is planned to be added to provide 30 days retention time. The “loop”digester is a 28 m diameter, cylindrical, covered tank, 4 m. high, with a center wall running fromone side of the tank through the middle of the tank and ending short of the opposite tank wall toleave a 2 m opening at the end of the wall. Manure slurry enters the tank on one side of thecenter wall, travels around the wall to the other half of the tank, and exits not far from theentrance, thus traveling in a complete loop through the tank. Manure slurry enters and exits theloop digester through pipes located about 1 m from the top of the tank and near the center wall.All the digesters have rigid concrete covers.

Heating of the loop digester is accomplished through hot water pipes hung from the center wall.Hot water is produced from engine cooling and heat exchange on the exhaust gas from theengines. The heating pipe location causes the manure slurry in the loop digester to move up thecenter wall, away from the center wall, down the outside wall of the tank, and across the bottomtoward the center wall. Thus, there is a roll in the tank. The crusting problem which had occurredbefore the loop digester was installed has been solved. The solution is attributed to the roll in theloop digester, but can also be attributed to the increased solids concentration of the feed slurryresulting from increasing use of mechanical manure scraping instead of flush systems. Manurewill cake on hot water pipes and prevent heat transfer if pipes are hotter than 145 °F. Manure isheated to 105 °F in the loop reactor only (temperatures and heating not verified).

The biogas produced in the digesters is held in a gas bag which is sealed by liquid around theskirt (60 ft x 60 ft) and covered by a metal building. There are no treatment processes in place toremove hydrogen sulfide (H2S) from the biogas. The biogas was once tested and reported to be 55percent methane.

The biogas is used directly to power an engine/generator to produce electricity. During the twodays of the visit, only one engine was running and indicated 85 kw output. Essentially nothing ismeasured except electrical output. A new energy building with new engine/generators is underconstruction and planned for completion this summer. Mr. Waybright believes that they willproduce 300 kw when another digester is added to give 30 days hydraulic retention time.

The digested slurry is run through two FAN screw presses (German-made equipment). Thedewatered product is used for soil amendment and is planned for use as cow bedding material.The liquid is stored in a large earthen pond and pumped to fields as fertilizer.



This site visit pointed out several considerations for a financially successful operation. First, theefficiency of manure collection was apparent. All manure fed to the digesters was fresh. Nomanpower was needed to collect the manure, except for the periodic operation of the remainingold flush system which is planned to be abandoned in favor of the mechanical scraping systemnow collecting 90 percent of the manure.

Second, the owners-operators of the system are capable and inclined to operate, repair and makethe system work without need for expensive outside help. The Mason Dixon owners areinnovative, determined and comfortable with the biological, mechanical, and electrical elementsinvolved with the system. This situation probably did not exist in the cases of owners of manypast projects which have failed. The fact that Mason Dixon is constructing a new two-storyelectrical/mechanical building is confirmation of nearly twenty years of technical and economicsuccess, and their expectation of continued success in the future.

Third, the liquid stream from the system is conveniently managed without much cost. It flows bygravity from the screw press to the large (several acres) holding pond from which it is pumped tothe growing fields. The nutrients are recycled to the fields and reduce the need for otherfertilizers.


Mr. Richard Waybright1800 Mason dixon RoadGettysburg, PA 17325Tel: + 1-717-334-4056



9.D.17 Warrnambool Milk Products: Anaerobic Digestion for Steam and HotWater

Location : Warrnambool, Victoria; Australia

Feed material: Dairy Waste

General Description

Warrnambool Milk Products (WMP) is one of Australia's largest cheese making sites, and islocated at Allansford on the outskirts of the city of Warrnambool (population 25,000.) WMP is ajoint venture company established in 1993 and owned by two dairy farmer cooperatives, UnitedMilk Tasmania and Warrnambool Cheese and Butter Factory Cooperative.

A separate company on the same site, Protein Technology Victoria, which is jointly owned by theventure partners, takes whey from the cheese making process and converts it into whey proteinconcentrate powder by ultrafiltration and spray drying. The whey powder is sold as a high proteinfood ingredient.

Dairy wastes typically produce a high strength industrial wastewater. The total Chemical OxygenDemand (COD.) loading on the bulk volume fermenter (BVF) ranges from 45,000 kg / day to100,000 kg / day. Before this effluent can be discharged for further treatment at the localwastewater treatment plant, some pretreatment is required. Both the COD and suspended solidsneed to be reduced. This reduces the load on the town's wastewater treatment plant and the tradewaste charges levied on WMP.

Following a change in ownership of the plant, a new Environmental Protection Authority (EPA)agreed that a new waste treatment process was needed. Various treatment technologies wereconsidered and it was decided that anaerobic, as an alternative to aerobic, treatment was the mostcost effective process for treating the high COD load of the wastewater.

Technical Data

The project was designed by Kinhill in association with ADI of Canada, who provided the bulkvolume fermenter(BVF). The system was put in place in 1993. It comprises of a lined lagoon ofdimensions 100 metres by 70 metres by 35 metres by 8 metres deep. Associated technologyincludes a floating membrane cover (XR5), a gas collection system, a sludge re-circulatingsystem and a programmable logic controller (PLC) to enable the gas transmission system to workefficiently. The overall system is conceptually simple, but optimisation of the biological andbiochemical technology is operationally complex, and requires skilled plant supervision.

Operating Characteristics

Wastewater parameter ValueVolume treated (average) kilolitres /day) 1,000 - 3,000COD of inflow (tonnes per day) 20 - 100BOD of inflow (milligrams per litre) 10,000 - 25,000



Suspended solids of inflow (tonnes per day) 1.4 - 4COD of outflow (tonnes per day) 1 - 3BOD of outflow (milligrams per litre) less than 400Suspended solids of outflow (tonnes per day) 1 - 4Biogas generated (cubic metres per day) 18,000 - 40,000Composition of biogas generated:methane (%) 50carbon dioxide (%) 50water vapour (%) n.a.hydrogen sulfide (parts per mullion) 600other (%) n.aBiogas recovered (cubic metres) 18,000-40,000

Performance Data

The system has operated at 98% to 99.75% efficiency for BOD removal and 98% efficiency forCOD removal. Given the system was designed to run on 45 tonnes per day COD and that theoperational loading sometimes reaches 90 tonnes per day, these are considered excellent results.By contrast, the suspended solids were expected to be 550 mg /litre. They are running at less than1000 mg / litre which may be due to excess gas production in the quiescent zone of the reactorkeeping the sludge particles suspended.

The captured methane is being used to produce steam for a 4 MW hot water boiler that maintainsa 35°C temperature in the BVF. A 10 MW steam boiler to evaporate the milk for the dryer and a5 MW hot water boiler for the factory are currently powered by natural gas. They have beenequipped with dual fuel burners, and are awaiting commissioning for the use of the methanecaptured on site.

Economic Data

Capital costs for anaerobic treatment processes tend to be higher than for aerobic treatmentprocesses. Variable costs tend to be lower. Costs are expressed in AU$ (where AU$ is theAustralian Dollar.)

Capital costs

Item Amount ($)Design and construction of the digester 3,000,000 - 4,000 000Heat exchanger plus boiler 40,000 - 150,000Equalisation tank 300,000Blowers 75,000Gas flares 70,000Sludge take-off 40,000Total 5,000,000 - 6,000,000



Variable costs (typical)

Item Amount ($)Labour 85,000Materials 196,799Trade waste charges 609,000Other (R&D, sludge disposal, consulting) 474,318Total 1,465,113

The variable costs per cubic metre of methane recovered without the trade waste charges areabout 15 cents.

Environmental Data

A local planning permit and EPA works approvals were required to construct the system. Becausethe system is covered, it did not need the same EPA approvals as an open system would haverequired.



9.D.18 Skinnerup On-farm Biogas Plant with Gas Storage

Location : Skinnerup, Denmark

Feed material: Dairy Waste slurry and fish oil sludge

Description

In April 1996 a new on-farm biogas plant of the "Smedemester" type was put into operation nearThisted in Jutland. The innovative feature of this plant is a total gas storage of 465 m3, allowingthe farmer to produce electricity at the time of the day when it is most valuable. A small 65 m3

gas storage was established from the beginning but a bigger storage (400 m3) was added in July1996.

12-13 m3 of slurry and 300-500 litres of fish oil sludge is mixed in a prestorage tank every day.From there it is pumped into a digestion tank (200 m3) six times per day. At the same time acorresponding quantity of degassed slurry is displaced to a storage tank.

The daily gas production varies from 300 m3 (slurry only) to 970 m3 (boosted with fish oilsludge). The gas is burned in a motor generator and the electricity sold to the public grid.Electricity production varies between 600 and 1,870 kWh/day.

The farm is almost entirely heated by biogas which saves about 75,000 litres/year of fuel oil. Thefarmer takes advantage of peak load electricity prices by storing the biogas at night and runningthe motor generator only during peak hours.

Electricity prices varies as follows: (including a government subsidy (tax refund) of DKK0.27/kWh)(Note DKK is the Danish krone).

Electricity Load Price DKK/kWhpeak 0.77intermediate period 0.64off peak 0.41

Technical Data

Digestion tank 200 m3 (vertical steel tank)

Process temperature 40 - 48 °CAverage digestion time (1996) 12 daysBiomass consumption (1996):slurry approx. 370 m3 per monthfatty agricultural waste approx. 12 m3 per monthGas storage:



Small: gasbag in container 65 m3Large gas storage in round arch hall 400 m3

Caterpillar motor/generator set 87 kW (electricity) Accumulator tank for heat 10 m3 Substituted fossil fuels 75,000 litres fuel oil

Performance Data

Calculated annual electricity production 350,000 kWh



9.D.19 Sindrup On-Farm Plant for Animal and Industrial Waste

Location : Sindrup, Denmark

Feed material : Dairy Waste and Food Industry Waste (e.g. Piggery waste and fish oil sludge)

Description

Since 1988 five on-farm biogas plants of the "Smedemester" type have been built in Denmarkwith digesters of 150-200 m3. They normally use manure from the individual farm possiblysupplemented by organic waste from the food industry to boost gas production.

The plant in Sindrup consists of a 150 m3 horizontal, insulated steel tank with built-in heatingpipes for process heat. The plant digests pig slurry from the farm without using considerableamounts of cut straw. Extra gas is produced by adding relatively concentrated liquid agriculturalwaste, usually fish oil sludge.

Slurry from the piggery is mixed in the pre-storage tank with fish oil sludge from a separate tank.From there it is automatically pumped into the steel tank six times per day and digested at 35-40°C. Formation of a float layer is prevented by slow moving, horizontal stirrers with irregularrods. When material is pumped into the steel tank from the pre-storage tank a correspondingquantity of degassed slurry is displaced to a cement storage tank.

The first year's biogas was only used for heat production. Since gas production was high aCombined Heat and Power plant was installed in 1992.

Over the years annual electricity production has been between 275 and 382 MWh. Heatproduction from the gas engine is utilised as process heat and heating for farm buildings(calculated annual production over the years from 550 to 750 MWh).

The plant digests manure at lower costs than some centralised plants. The economy is good due tolow capital and operational costs, efficient gas utilisation and additional economic benefits fromimproved fertiliser value.

Technical Data

Annual consumption (1995):

Liquid manure 4,277 m3Industrial waste 58 m3

Nominal capacity:Biogas (app.) 800 m3/dayElectricity (motor generator) 60 kWHeat 180 kWDigestion tank 150 m3Pre-storage tank 20 m3Process time approx 12 days



Process temperature 35-40 °C

Animal herd:Cows 550Pigs 12-13,000 /yearSubstituted fossil fuels 110-150 tonnes coal

Gas utilisation (1995):\Gas production per m3 of feedstock (biomass 171,763 m3/4335 m3 39.5 m3/m3

Gas utilisation is at the same level as some centralised biogas plants.

Performance DataProduction (data from several sources)

1993 1994 1995 Gas production m3 147,881 242,641 171,763Electricity production kWh 372,469 382,032 268,481Heat production kWh Not measured

The gas production decreased in 1995 due to experiments.



9.D.20 Ejstruplund Storage Tank Biogas Plant with Soft-Top Cover

Location : Ejstrup; Denmark

Feed Material : Piggery waste

General Description

The first prototype Soft-Top (a PVC membrane mounted on a float ring) plant in Denmark wasput into operation in 1994. The aim of building a storage tank biogas plant is to lower investmentcosts by using a standard slurry tank as biogas digester. At Ejstruplund the existing 500 m3 slurrytank was fitted with a heat spiral at the bottom and a Soft-Top cover which apart from collectingthe gas also prevents dilution by rainwater in the storage tank and emissions of ammonia andmethane. To make the plant independent of industrial waste the plant exclusively digests slurry.

Input to the plant is approximately 5 m3 pig slurry per day with no appreciable cut straw content.Active digester volume is about 450 m3 apart from spring when the fertilizer is spread over thefields. Slurry is digested with a long retention time and low process temperature. The first yearprocess temperature was 20-22°C, the second year it will be reduced to 15°C to find the optimalprocess temperature in relation to gas production and process heating.

Slurry is pumped daily from an existing pre-storage tank into the digester. Degassed slurry ismoved to a newly-built storage tank by means of spillover. Gas is accumulated by means of thegas proof Soft-Top and led from the digester to a gas boiler in a nearby small container whichalso contains an oil boiler, the gas blower and a compression control system. The heat produced isused as process heating and to heat the farm buildings.

Technical Data

Nominal capacity:Biogas 120 m3/day

Annual consumption (1995):Pig manure 1,714 m3

Digestion storage tank 450 m3

Process temperature (1995) 20 - 22 °C

Degassed slurry storage tank 1,200 m3

Average digestion time (1995) 99 days

Gas utilization (1995):Gas production per cubic metre biomass 19 m3/m3

Performance Data

Annual gas production (1995) 32,382 m3.



During 1995 the plant has been self-sufficient with heat. Approximately 30% of the heatproduction was used for process heating. The oil-boiler was used during the three days when thedegassed slurry was being spread over the fields.

Economic Data(Note: DKK is the Danish krone).

Investment DKK 550,000

Grant DKK 550,000 (including costs for a measurement and evaluationprogramme)

Results 1995 DKKValue of heat production 19,838Operation costs 13,500Revenue 6,338Interest and depreciation 9,590Ordinary result before tax -3,252Ordinary result after tax 6,743

The investment is especially low since the former slurry storage tank was re-used as digestiontank.

The economy at Ejstruplund on-farm plant is good due to low capital and operational costs, andadditional economic benefits from improved fertilizer value.

Environmental Data

During the first year of operation daily injections of 2% air into the gas in the digestion tank wereintroduced. The aim was to reduce the sulphur content of the gas. Within a week hydrogensulphide (H2S) was reduced to 200 ppm. Ever since 2% air is automatically injected into the gas.

Long road haulage of manure and fertilizer is not needed at on-farm plants. Petrol /diesel oil arethereby saved and heavy traffic on small roads avoided.


MWH Appendix 9E- 1

Appendix – 9E

Biogas for Power Generation and Other Applications

9.E.1 Composition and Uses

The main constituent of biogas is methane (50-80% CH4) together with carbon dioxide (25-50%) andsmall quantities of hydrogen sulphide.

At normal atmospheric temperature and pressure biogas has a calorific content of 5500 Kcal/m3 (60 %methane) and is highly flammable.

The energy potential of biogas is assessed by the quantity of methane present in the gas. Thepercentage of methane present in biogas varies depending on a wide variety of process conditions, themost important of which are; the composition of the feedstock such as C:N ratio and the relativequantities of proteins, carbohydrates and fats, and the type of process. For instance the percentage ofmethane in biogas from digestion of sewage sludge under mesophilic temperature conditions istypically 60-65%. Biogas from digestion of vegetable wastes and the organic fraction of MSW has50-55% CH4. Some biomethanation processes can produce high quality biogas containing upto 80%methane.

The second major constituent of biogas is carbon dioxide (CO2) which, together with methane,generally constitutes 95-98% of biogas. It is a stable non-flammable gas and does not contribute to theenergy potential of biogas. Small percentages of other gases such as hydrogen sulphide, ammonia andwater vapour are also present in biogas and these gases do not contribute significantly to the energypotential of biogas. In addition there are usually traces of other gases such as hydrogen, nitrogen andsome hydrocarbons. Of these minor constituents, hydrogen sulphide (H2S) and water vapour areparticularly relevant with respect to practical issues in the use of biogas.

Biogas produced in a biomethanation reactor is saturated with water vapour. The percentage of watervapour in the biogas is dependent on the ambient temperature of the process and on factors such as themethod of mixing. In mesophilic fully-mixed reactors, the amount of water vapour in biogas directfrom the reactor vessel is approximately 2-3% by volume.

When biogas leaves the reactor, the relative ambient temperature outside the reactor affects itstemperature. Typically, cooling of the gas takes place resulting in condensation of water vapour ingas pipeline, gas storage vessels and equipment. The resulting condensate will flow by gravity to thelowest point of the pipeline, and unless there are adequate means of collection and disposal, thiscondensate can cause blockages and interfere with normal mechanical operation of the process andenergy generation systems.

Condensate due to cooling biogas also contains traces of gases like hydrogen sulphide in dissolvedform. The generation and appropriate disposal of condensate must be adequately dealt with in theprocess and mechanical design of a biomethanation system.

The amount of hydrogen sulphide present in biogas depends mainly on the composition of thefeedstock, especially the relative quantity of proteins and other sulphur containing compounds. H2Sin biogas may vary from less than 100 ppm to levels as high as 5,000 ppm, depending on the type ofwastes being digested. For instance, the concentration of H2S in biogas derived from digestion ofsewage sludge ranges typically from 100 – 1000 ppm. In contrast, the typical H2S level in biogasfrom digestion of animal slurries may range from 1,000 to 5,000 ppm.

During the combustion of biogas, hydrogen sulphide is converted to sulphur dioxide (SO2), which ishighly soluble and dissolves in water vapour to produce sulphuric acid. At high temperature and


MWH Appendix 9E- 2

moisture inside the combustion chamber, combustion gases may be highly corrosive, and this is animportant factor affecting many practical uses of biogas.

Taking into account the presence of CO2 and other gases which do not contribute to the energypotential, the average calorific value of biogas from the majority of applications, such as fromtreatment of sewage sludge and animal wastes and industrial wastewaters ranges from 5000-5750Kcal/m3. A typical value given for biogas containing, nominally, 60% CH4, 38% CO2 and 2% othergases is 5325 Kcal/m3 at normal temperature and pressure.

Biogas has a wide variety of uses and has been a practical source of energy for over a hundred years.For instance, it is recorded that biogas produced in sewers in Victorian England was used as a fuel topower street lamps.

Biogas is also highly explosive when mixed with air in a confined space therefore its utilization mustbe carefully controlled. One method of control is the zoning of plant and equipment according to thepotential presence of biogas (hazardous zones), which determines the electrical status (explosion-proof) of equipment to be used in that zone.

In most cases biogas is used at the site of production, but in some cases gas is distributed by pipelinefor use in the community. Distribution of uncleaned biogas to individual houses in villages ispractised in some countries with warm climates. At some of the larger Central Anaerobic Digestion(CAD) plants in Denmark, biogas is upgraded (cleaned) to the standard required for pipeline qualitynatural gas and is added to the natural gas distribution network.

One of the important considerations in the use of biogas is the volume of gas storage required. Biogasfrom a digester system is produced continuously but many methods of energy use are intermittent andvary during the day (e.g. cooking, lighting and powering engines for work). This requires anintermediate gas storage facility, which is also used to provide a reasonably constant low-pressuresupply. In most low-technology biomethanation systems, gas storage is incorporated as part of thereactor. Most biomethanation systems in temperate countries utilise one or two different methods ofgas storage: the bell-over-water gas holder; and the gas storage bag of which there are a variety oftypes.

The double membrane type of gas holder can provide the largest storage volumes and is gainingpopularity. Compared to bell-over-water gas holders in which gas usage pressure is provided by theweight of the gas bell, the double membrane gas holder systems require the continuous use of airpumps to provide gas pressure, resulting in constant and significant parasitic electrical energydemand.

9.E.2 Low Technology Applications

The most common use of biogas occurs in the very large number of domestic biogas plants in warmclimates, mainly India and China. These systems process mainly animal wastes, operate at ambienttemperature and do not require an input of process heat. Thus all the biogas produced is available foruse and is mainly utilised in relatively low technology applications; of which the most common are:

• lighting;• cooking; and• as a fuel for internal combustion engines used for a variety of tasks including

pumping, electricity generation, milling, etc. (These engines are often unmodifieddiesel engines using a typical mixture of 90% biogas and 10% diesel)


MWH Appendix 9E- 3

In these systems the gas is stored and used at low pressure, the efficiency of conversion is relativelylow, and the H2S content of the gas is tolerated by the relative simplicity and robustness of theequipment.

9.E.3 Medium to High Technology Applications

Process Heat Use in Boilers

In controlled biomethanation systems in which the temperature is maintained above ambient(generally at mesophilic or thermophilic temperatures), the most common use for biogas is generationof process heat in boilers. A wide variety of boiler equipment is available for use.

In general, boilers can tolerate hydrogen sulphide, so gas cleaning is not required prior to use,although the gas should be as moisture-free as possible. Cast iron heat exchangers are leastsusceptible to corrosion and operation at high temperatures is also beneficial. In colder climates whereflue gases condense, corrosion will occur and stainless steel are generally used.

At a smaller scale, conventional boilers designed for fuel such as liquified petroleum gas (LPG) ornatural gas are sometimes converted for use with biogas. In most cases, due to the need to providestart-up and standby heating, boilers are configured as multiple-fuel systems able to use fuel oil, LPGor natural gas as a secondary start-up/standby fuels. Smaller boilers are usually naturally aspirated anduse gas at low pressure directly from the storage vessel but, in most cases above 50kW output, the gasis pressurised by centrifugal pumps or fans and the boilers have forced-air ventilation. Conversionefficiency of such boilers is typically in the range of 75-85%.

In temperate countries, biogas which is surplus to the process heating requirements of the digestionsystem is often used in separate boilers to generate hot water for other uses. This includes domesticheating, cooking, hot water and space heating for industrial uses.

Flares

The treatment of sewage sludge in temperate countries is usually carried out through a mesophilicfully mixed process in which the feedstock is the sludge, typically with a dry solids concentration of4-6%. In the majority of these systems the biogas is used in boilers solely for maintaining processtemperature, and the surplus biogas, usually amounting to 10-50% of production is flared to theatmosphere. This may appear to be wasteful, but in those cases where the feed sludge is less than 4-5% in dry solids, the heat available from combined heat and power (CHP) would not be sufficient tomaintain process temperature.

Combined Heat and Power (CHP) Systems

Currently the most efficient method of energy conversion and utilization of biogas is through CHPsystems. CHP is now commonly used in temperate countries for decentralised power generationusing natural gas as a primary fuel. Alternative fuels which can be used include oil, LPG and biogas.Thousands of CHP systems are in operation worldwide at biogas plants and at landfill sites, rangingfrom small units of 10kW capacity to large systems of over 1MW capacity. Compared to boilers,CHP units can achieve overall conversion efficiencies of more than 90%, with the larger systemsyielding up to 38% of electricity conversion efficiency.


MWH Appendix 9E- 4

High Speed Reciprocating Internal Combustion Engines

Methane is a high-octane fuel. Most CHP systems in operation worldwide involve high-speed high-compression engines, typically converted diesel engines. The following data illustrates a typicalenergy balance of a CHP system operating on biogas from a medium sized sludge digestion plant.

Quantity of gas available (m3/day) 5000

Calorific Value (K cal/m3) 5500

Total energy content of biogas (kW) 1279

Average gas consumption rate by CHP unit (m3/h) 208

Electric efficiency (%) 30

Thermal efficiency (%) 55

Electrical power output (kW) 384

Useable thermal power (kW) 703

Total useable energy (kW) 1087

Total efficiency (%) 85

Thermal output of engine cooling system (kW) 422

Thermal output of exhaust/oil heat recovery system (kW) 281

In most cases a CHP unit is designed to operate continuously. In some cases however operation is fora limited period each day to maximise returns from peak generating periods, and this requires extragas storage capacity.

The operating and maintenance costs of this type of CHP system are significant. Internal combustionengines require frequent maintenance involving regular oil and filter changes and replacement ofcomponent parts, and the engines generally have a limited lifetime which is typically around 20,000hours in total. One of the reasons contributing to this is the presence of hydrogen sulphide in thebiogas and this is a significant problem for internal combustion CHP systems. Hydrogen sulphidecauses corrosion of wearing surfaces such as bearings, and most CHP systems designed for use onbiogas are specially converted to enable increased tolerance to hydrogen sulphide. Nevertheless, thisis usually only to levels below 200 ppm. Since hydrogen sulphide concentrations in biogas are usuallygreater than this, often by a substantial margin, these concentrations must be reduced prior to use inCHP systems.

In order to improve the economics of CHP processes using reciprocating internal combustion engines,a variety of alternative power systems are being developed.

Sour-Gas Engines

Some internal combustion engines will tolerate high concentrations of hydrogen sulphide and stillhave long lifetimes. These engines are usually designed to run at low RPM. Maintenance costs arelow but overall conversion efficiencies for these engines are substantially lower than the high-speedengines . For example, a 100 kW sour-gas two-stroke valve-less single-cylinder engine typicallyoperates at speed between 200-600 RPM, with low combustion pressure allowing operation on biogaswith lower calorific content. The electrical conversion efficiency is lower than 25%.


MWH Appendix 9E- 5

Steam

Instead of direct conversion of the chemical energy in biogas to primarily mechanical and thermalenergy in internal combustion engines, biogas may also be used to generate steam. This can then beused to provide combined heat and power in a piston steam engine. There are several advantages tousing a steam engine to generate CHP and these include:

- higher tolerance to hydrogen sulphide (i.e. steam boilers will tolerate higher levels of H2Sthan will internal combustion engines)

- lower maintenance costs (i.e. less oil/filter and parts replacement, and longer lifetime)

The main disadvantages are lower conversion efficiencies to electricity and higher capital costs.However, the efficiency of this type of steam engine has been greatly increased. For instance, a 500kWe Spilling steam engine needs approximately 5 t/hr of steam (inlet pressure 28 barg, temperature350 °C, back pressure 0.5 barg). The operating costs are approximately 25% that of a typical internalcombustion engine and the expected lifetime is more than 30 years.

Some small reciprocating steam engines are also being developed. At the other end of the scale, inlarge-scale steam CHP systems, steam is generated in a high-pressure steam boiler and used in aturbine to generate electricity.

Dual Fuel Engines

In case there is a shortfall in biogas generation it is desirable to have additional alternate fuelavailable for power generation. The option used before was to use a dual fuel engine i.e.basically an engine designed for diesel, which can use biogas to supply part of the fuelrequirement. A dual fuel engine is basically a diesel engine with a conversion kit to run theengine with diesel and biogas (or any other suitable gas). This works on the diesel cycle.Gaseous fuel is added to the air, which is included at air intake manifold or beforeTurbocharger. This mixture of air and gas is compressed in the cylinder just as aircompressed in normal IC engine. At the end of compression, diesel is injected through aconventional fuel system. This pilot injection acts as a source of ignition. The percentagesubstitution of diesel by gas depends on the type and composition of gas used and enginesdesign. The only disadvantage of this type of engine is that, it always requires diesel as a partof its total fuel supply. The amount of diesel required ranges from 7% for lean burn engine toas high as 40% for small indigenous engines. This continuous use of diesel represents notonly a problem for operations but also a continuous financial drain.

Some other aspects of interest in the selection of proper engine are as follows:

• Dual fuel engines will allow generation of power when biogas is not available.• Use of fuel oil and biogas as dual fuel is not offered by any engine manufacturer.• If use of diesel exceeds 10% then interest subsidy from MNES is not available.• Dual fuel engines tend to be modified diesel engines with use of diesel as ignition source.

The only disadvantage of gas only engines seems to be inability to produce power whenbiogas is not available.


MWH Appendix 9E- 6

Pure Gas Engines

These are internal combustion engines coupled with alternator. The mixture of air and gas arecompressed in the combustion chamber and ignited by spark plug. The mechanical energydeveloped is converted into electrical energy by the alternator. Biogas is very well suited for theoperation of gas engines, since the knock-resistant methane and the high amount of CO2 contained init permit a methane number of over 130. These engines are designed with state of the arttechnology running on 100% biogas further, this genset can be controlled and monitoredautomatically.

The spark – ignited gas engine has lesser level of emission over a gas-diesel (dual-fuel) engine. Thelean-burn engine principle adopted in the gas engines results in extremely low NOx emissions,therefore the additional secondary treatment of exhaust gas can be avoided. The combustionchamber configuration of gas engines can be specially developed to ensure efficientcombustion. The other advantage of gas engine is generally used as a combined heat and power. Incomparison to gas turbines, combined heat and power plants with gas engines has a higher electricalefficiency and lower capital investment. The overall conversion efficiency of a gas engine depends onthe following two factors

• Requirement of thermal energy at the plant site• Operating hours

Imported engines tend to be of the high compression ratio, slower speed variety and havehigh efficiency of around 40%. On the other hand the indigenous engines operate at lowcompression ratio and high speed and have low efficiency of around 32%. Offsetting thislower efficiency is the much lower capital cost of indigenous engine.

The following are some of the possibilities of utilization of waste heat recovered from the gasengines:

• To generate hot steam, which can be used in various applications• To produce Chilled air/fluid through absorption chillers.• In case of biomethanation plants the waste heat can be used to heat the digesters

Stirling Engines

The high maintenance costs and limited lifetime of high-speed reciprocating engines operating onbiogas has driven the development of other power systems which are more tolerant to hydrogensulphide. An example is the Stirling external combustion engine, the principle of which has beenknown for many years. The basis of operation is a closed cycle (similar to a refrigerator) where apressurised working gas (such as helium or nitrogen) is alternately heated in a hot cylinder and thencompressed in a cold cylinder. The heat input from the combustion of fuel in the combustion chamber(similar to that of a boiler), is transferred to the working gas through a heat exchanger. Theexpansion/contraction cycle of the working gas is mechanically harnessed to generate electricity,while the waste heat is recovered.

Because the mechanical system of such an engine is not exposed to the combustion gases, the systemis much more tolerant to impurities in the biogas, and will also work with a variety of other fuels.Stirling engines are still in the development phase and are currently available only as small co-generation units. Conversion efficiency to electricity is low; i.e.

Overall conversion efficiency (%) 87Conversion to electricity (%) 19Conversion to thermal energy (%) 68


MWH Appendix 9E- 7

Gas Turbines

Gas turbines are being developed for use in CHP systems but these are less efficient, except at largescale of around 1 MW. The advantage of a gas turbine compared to an internal combustion engine islower maintenance costs and a longer lifetime.

Microturbines

Microturbines are small combustion turbines approximately the size of a refrigerator with outputs of25 kW to 500 kW. They evolved from automotive and truck turbochargers, auxiliary power units forairplanes, and small jet engines and are comprised of a compressor, combustor, turbine, alternator,recuperator, and generator.

Microturbines offer a number of potential advantages compared to other technologies for small-scalepower generation. These advantages include a small number of moving parts, compact size, light-weight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize wastefuels. They have the potential to be located on sites with space limitations for the production ofpower. Waste heat recovery can be used with these systems to achieve efficiencies greater than 80%.

The individual manufacturer’s contacted were as follows:

1. Jenbacher, Austrian, gas only engine represented by COGEN, Pune2. Anglo-Belgian Corporation, Belgian, dual fuel engine3. Cummins India Ltd., Indian, both dual fuel and gas only engines4. Greaves Ltd., Indian, both dual fuel and gas only engines5. Wartsilla, French dual fuel engine6. Caterpillar, American, gas only engine and dual fuel engine7. M.W.M. German, dual fuel as well as gas only.8. Hyundai – Ulstein – Bergan, Korean, gas only.9. Alstom

Fuel Cells

While the principle of fuel cells has been known for 100 years, the arrival of this technology in theenergy market is also relatively recent, due to the development of new materials. A fuel cell produceselectricity and heat by chemical rather than mechanical means by converting the chemical bondenergy of hydrogen (in methane) and oxygen directly to produce water, electricity, and heat.

In the fuel cell, a catalyst on the anode converts the hydrogen ions in the fuel gas into negativelycharged electrons and positively charged ions. The electrons flow through an external load to thecathode. The hydrogen ions migrate through the electrolyte to the cathode where they combine withoxygen and the electrons to produce water. Since individual cells only produce a small voltage, thecells are arranged in series to provide the required level of power.

Recent technological developments have reduced the capital cost of fuel cells, and there are now asmall number operating worldwide at wastewater treatment plants and landfill sites, generatingelectricity from biogas. Since fuel-cells also generate heat, they can substitute for conventional CHPsystems in biomethanation plants which require process heat. Fuel-cells operate chemically and haveseveral advantages over the use of internal combustion engines. These include:

- higher conversion efficiencies to electricity (up to 50%)


MWH Appendix 9E- 8

- greater reliability and less downtime

- lower operation and maintenance costs

- longer operating lifetime

- low level emissions

- tolerant to hydrogen sulphide

There are currently five different types of fuel cell – most of which are still in the development stage.These are:

Fuel Cell Type Operating Temperature Conversion Efficiency(to electricity)

Alkaline (AFC) 150 °C 40-50%Phosphoric Acid (PAFC) 200 °C 40-45%Molten Carbonate (MCFC) 650 °C 50-57%Solid Oxide (SOFC) 1000 °C 45-50%Proton Exchange Membrane (PEM) 50-150 °C 30-40%

Of these types, only the alkaline fuel cell is not suitable for use with biogas, and only the PAFC hasreached commercial viability. One of the reasons is the high operating temperatures required. In thecase of PEM systems, the constraining issue is the high cost of the platinum catalyst.

The conversion efficiency to electric power is typically 5% greater than for a similar size internalcombustion CHP system, but overall efficiency is less. The main disadvantage is the capital cost.Information from International Fuel Cells states: “The installed cost is approximately $4500/kw. Sitestart-up and unit testing costs are approximately US$15,000 per unit. The 200 kW product costsapproximately US$850,000 per unit, excluding installation. Multi-unit installations run betweenUS$775,000 to US$800,000 per unit”.

Although currently capital costs are substantially higher than conventional CHP systems, it is clearthat the rapidly increasing development and use of fuel cells will reduce costs and further increaseefficiency.

Production and Use of Thermal Energy from CHP

The majority of CHP systems currently use internal combustion engines. These CHP systems convertmost of the gross energy of biogas (55-60%) to hot water obtained from cooling of the engine andrecovery of heat from exhaust gases (with engine cooling being approximately two thirds of the totalheat output).

In temperate countries, substantial amounts of process heat are required to maintain digestertemperature in order to raise the temperature of the incoming waste and overcome system temperaturelosses, especially in winter. Thus there is a natural use for the thermal energy produced from CHPsystems.

One of the important aspects of a CHP installation is matching of the constant heat output from theCHP system to the changing heat demand of the digester (which varies according to ambienttemperature conditions). During the warm ambient temperatures of summer, excess heat is producedby the CHP over and above digester heat requirements. This heat must be alternatively used ordisposed of. In temperate countries with a wide variation between winter and summer ambient


MWH Appendix 9E- 9

temperatures there is a considerable seasonal variation in the amount of process heat required andexcess heat is usually disposed to atmosphere via a heat-dump radiator. Heat dump radiators requireelectrical power, increasing the parasitic electrical load of the system and reducing nett electricaloutput. In warm climates where efficient recovery of heat is not required for process heat, the CHPsystem need not incorporate heat recovery from exhaust gases, thus minimising the amount of surplusheat that must otherwise be disposed.

Thus it is often difficult to find a use for all the excess heat from a CHP system, especially in warmercountries and during the summer season of temperate countries, thus resulting in a loss of efficiency.Of course conventional fossil-fuel power stations also have this problem.

In order to overcome this and maximise the energy potential of the biogas, some countries such asDenmark distribute the excess heat from biomethanation plants to urban district heating schemes, orutilise one of a number of other energy distribution strategies.

9.E.4 Use as a Vehicle Fuel

General

Biogas has been used as a vehicle fuel for many years. During World War II for instance, some publicvehicles in the United Kingdom operated on biogas, with gas stored in low-pressure gas bags on theroof of the vehicles. There is currently increasing interest in the use of biogas as a vehicle fuel andthere are several instances in which biogas from large sewage works and landfill sites is being refinedand used as a fuel for public utility vehicles such as buses.

There are two main problems relating to use of biogas as a vehicle fuel. Thus, with an averagecalorific content of only 23 MJ/m3, on a volumetric basis biogas has a very low energy contentcompared to petrol or diesel at approximately 36 MJ/litre. Therefore, for practical purposes, thebiogas must be compressed prior to use as a fuel for transport. Also, because carbon dioxide typicallycomprises 35-40% of biogas and contributes nothing to the calorific value, it is advantageous toremove this prior to compression in order to improve the energy content of the biogas. When cleaned,biogas is essentially the same as natural gas, which is increasingly becoming used as a vehicle fuel insome countries.

Also, since high pressure increases the susceptibility of mechanical equipment to corrosion caused byH2SO4, hydrogen sulphide must be efficiently removed before compression.

Compression of Methane for Storage and Transport

This requires a significant amount of electrical energy. The direct electrical energy (kW) required tocompress methane to levels typically necessary in storage systems is approximately 5% of the grossenergy content (kW) of the gas. When conversion losses of hydrocarbon fuels to electricity areincluded, this energy loss increases to over 30%.

Storage systems usually comprise a bank of high-pressure cylinders at a maximum pressure of 350bar. Vehicles containing high-pressure cylinders can refuel from this high-pressure storage and fueltransfer takes place simply by the pressure differential.

Due to the lack of commercial re-fuelling stations dispensing biogas in most countries, the range forvehicle operation on biogas is generally limited to the area in the vicinity of the processing plant.However, some countries (e.g. Holland, New Zealand) have extensive networks of CNG (compressednatural gas) stations which allows greater flexibility. Alternatively, vehicles may have dual fuel (gas-petrol) systems.


MWH Appendix 9E- 10

9.E.5 Gas Cleaning Systems

Removal of Hydrogen Sulphide from Biogas for Use in CHP Systems

Internal combustion CHP systems require reduction of hydrogen sulphide concentrations in thebiogas. The most common methods are as follows.

Iron Oxide Filters

Hydrogen sulphide may be removed from the gas stream by passing through a filter system containingiron oxide. The iron oxide may be in various forms such as mixed with wood chips, or in pellets.Hydrogen sulphide combines readily with iron oxide in the absence of oxygen to form iron sulphide.Subsequent exposure of iron sulphide to air (oxygen) causes re-oxidation of the iron sulphide to ironoxide. This mechanism thus allows the filter medium to be regenerated (in an exothermic reactionproducing heat) for a limited period, but replacement of the medium is required periodically. As themedium breaks down, there may be some reduction in H2S removal efficiency.

Dosing the Reactor with Salts such as iron (Ferric) Chloride

Ferric chloride is a compound widely used in effluent treatment. When added to a biogas reactor, itcombines with sulphur during the digestion process, thus producing insoluble particles of ironsulphide and preventing its conversion to hydrogen sulphide. This is a low capital cost method ofbiogas cleaning, suitable for situations where ferric salts can be obtained cheaply. Although suitablefor reduction of high levels of H2S, this method has lower limits of hydrogen sulphide removal, withpractical removal limits in the region of 100-200 ppm.

Biological Removal of Hydrogen Sulphide

This process entails removal of H2S by sulphide-oxidising bacteria (thiobacillus). These bacteria areautotrophic (i.e. they use the carbon dioxide present in the biogas for their carbon requirements) andalso require only small quantities of oxygen. Two methods are in common use, for both of which thecontrol of additional air is important to avoid production of an explosive mixture (6-12% biogas inair).

Addition of Air to the Digester

A controlled volume of air (typically 5% of gas production) is added to the digester gas space. Themethod relies on formation of a layer of sulphur-oxidising bacteria on the surface of the digestingwastes, thus allowing the use of mechanical mixing systems that do not disturb the surface of thedigesting wastes, but precluding the use of gas recirculation mixing systems.

Gas Scrubbing method was developed in Denmark and is now commonly used on Danish CAD(centralised anaerobic digestion) plants, and can be used with any type of mixing system. A separategas scrubbing process is installed in which biogas is passed through a vessel filled with filter media onwhich bacteria grow. Air is proportionately added to the gas stream in such a way that all the oxygenis utilised by the bacteria, thereby reducing hydrogen sulphide levels in the biogas (but adding traceamounts of nitrogen). Digestate is periodically pumped over the media, with this providing a foodsource for the bacteria

Removal of Hydrogen Sulphide to Low Levels

Compared to the requirements for the use of biogas in CHP systems (100-200 ppm hydrogen sulphideas an upper limit for this impurity), the biogas required for compression and use as a vehicle fuel musthave H2S concentrations reduced to less than 10 ppm.


MWH Appendix 9E- 11

Methods of achieving this have been discussed earlier. Of these, the method of dosing digesters withferric chloride is not suitable in this case due to an inability to reduce concentrations to the low levelsrequired.

Probably the most frequently used method is that of activated carbon filters. Here hydrogen sulphideis catalytically converted to sulphur which is absorbed by the carbon. The optimum conditions are anoperating pressure of 7-8 bar and temperatures of 50-70 °C.

Removal of Carbon Dioxide

Water Scrubbing

Carbon dioxide will dissolve to a significant extent in water at relatively low pressures. The mostfrequently used method is water absorption in which, following removal of hydrogen sulphide, thebiogas is compressed to approximately 7 bar and passed through a water column under pressure. Atthis pressure carbon dioxide will readily dissolve in the water. This system will typically remove over95% of the CO2. The water is usually recirculated since it may be re-used following a period ofexposure to normal atmospheric pressure, which releases the dissolved carbon dioxide to atmosphere.In this method, the cleaned product gas is saturated with water vapour, which must first be condensedprior to compression.

Carbon Molecular Sieves

Carbon molecular sieves are used for industrial separation of gases and for cleaning of biogas for useas a vehicle fuel. Following removal of hydrogen sulphide under pressure and using different meshsizes of the sieves, carbon dioxide in the biogas may be temporarily absorbed onto the activatedcarbon. The carbon dioxide can be discarded when the pressure is released. This method can producegas containing over 96% methane and with very low concentrations of water vapour.

Membrane Systems

Carbon dioxide may also be removed by membrane systems. Such systems are increasingly beingused for industrial gas separation and cleaning, and are now used in most large scale processes (over500-1000 m3/hour) in which biogas is refined for use as a vehicle fuel. In this case, high-purity carbondioxide may also be recovered for sale for industrial use. There are two types of membrane systems:

High pressure membranes

Membranes made of acetate-cellulose and which may be designed to selectively allow certainmolecules to pass through. High gas pressures are necessary and this requires significant amounts ofelectrical energy. In these systems the efficiency of methane recovery is typically around 80% asthere is approximately 20% methane remaining in the final carbon dioxide stream. Membranelifetimes are typically three years. Capital and operating costs are high.

Gas liquid absorption membranes

This is a new low-pressure separation process in which a microporous hydrophobic membraneseparates the gaseous phase from the liquid phase. Molecules of carbon dioxide flowing in onedirection diffuse through the membrane and dissolve in the liquid containing an amine solutionflowing on the other side of the membrane. This solution can be regenerated by heating, releasingpure CO2 which can in turn be recovered and sold for industrial use. This method will produce over96% pure methane from low-grade biogas. The normal operating pressure is only 1 bar and thuscapital and operating costs are reduced.


MWH Appendix 10A- 1

Appendix 10 A

Incineration Technologies And Developers

The information which follows regarding developers and technologies is extracted from varioussources (see references) and does not express Montgomery Watson’s views or endorsement inany way.

1. Energy Products of Idaho (EPI)

Type of System /Technology: Bubbling-type fluid bed

EPI is a limited partnership company with headquarters in Coeur d’Alene, Idaho. EPI specializesin designing and fabricating fluid bed combustion systems.

The EPI incineration system uses a bubbling-type fluid bed concept that accepts a prepared 10-cmtop size RDF. Within the bed, RDF particles are exposed to a vigorously turbulent hotenvironment that promotes rapid drying, gasification and char burnout. In the bed EPI’sproprietary design features provide continuous removal of oversized noncombustible materials.The hot gases from the bed are passed through a boiler to generate the high-pressure, superheatedsteam that is used either to produce electricity or for process applications.

The combustion technology offered by EPI is presently at the point of commercial availability.EPI has installed five furnaces in the U.S., with capacities of more than 50 ton/day, burning RDFfuel.


Energy Products of Idaho Tel: +1+215-248-5244

8014 Germantown Road Fax: +1+215-248-2381

Philadelphia, PA 19118 USA


MWH Appendix 10A- 2

2. Pedco Incorporated

Type of System /Technology: Rotary Cascading Bed Combustors (RCBC)

Pedco Incorporated has its headquarters in Cincinnati, Ohio. The firm has developed rotarycascading bed combustors (RCBC). The Pedco RCBC is, in essence, a robust solid-fuel burnerand heat-recovery system. Among other solid fuels, such as coal or wood chips, it can burnprepared MSW. Pedco’s basic business is the design of combustion systems using the RCBCconcept.

The RCBC burner comprises a rotating, horizontal, cylindrical combustion chamber. A bundle ofboiler tubes projects into one end of the chamber. The rotational speed of the chamber is highenough to keep a substantial fraction of the bed material continually airborne. This activityproduces an environment similar to that of a fluid bed but, in this case, a mechanically fluidizedbed. The hot falling solids cascade across the whole diameter so that the boiler tubes aresubmerged in hot fuel and bed material. The hot solids recycle preheats the combustion air,drying and igniting the incoming fuel.

Pedco has two furnaces operating in the U.S.- a development unit at North American RayonCorporation and a specialized unit based on Pedco design principles used by a commercialhazardous waste management firm near Houston, Texas. The plants are reported to have shownacceptable reliability, environmental emissions, and basic operability and maintainabilitycharacteristics.


Pedco Incorporated Tel: +1+513-784-0033

216 East 9th Street, 5th Floor Fax: +1+513-241-7958

Cincinnati, Ohio 45202 USA


MWH Appendix 10A- 3

3. Wheelabrator Environmental Systems Inc.

Type of System /Technology: Reciprocating grates with waterwall boilers

Wheelabrator Environmental Systems Inc. is a unit of Wheelabrator Technologies Inc., and is oneof the pioneer developers of energy and recycling technologies.

The company has designed and constructed a waste-to-energy facility in Gloucester County, NewJersey, in the U.S. In this facility, the waste is transferred by overhead cranes from the storagearea to the feed hopper of each combustion unit. The waste is moved on to a reciprocating gratethrough the furnace, where combustion temperatures exceed 2500 °F. Air from the reception areais blown in above and below the grates to fuel a complete combustion process in the furnace andto maintain negative pressure over the reception area, thus preventing the escape of dust andodors. A waterwall boiler above the grate area produces superheated steam which is used to drivea turbine-generator, which in turn produces electricity.

Wheelabrator Environmental Systems Inc. have also built waste-to-energy plants in other parts ofthe United States.


Wheelabrator Environmental Systems Inc. Tel: +1+603-929-3000

Liberty Lane Fax:

Hampton, NH 03842 USA


MWH Appendix 10A- 4

4. Ogden Waste to Energy Inc.

Type of System /Technology: Martin reverse reciprocating stoker grate

Ogden Waste to Energy, Inc. (OWTE) is a wholly-owned subsidiary of Ogden Energy Group,and designs, builds, owns and operates waste-to-energy facilities. It has an exclusive technologyagreement with Martin GmbH of Germany, for North, Central and South America (excludingBrazil), and in Israel. The technology has been in operation for more than 30 years in more than170 operating facilities.

An Ogden Martin waste-to-energy facility features the proprietary Martin reverse reciprocatingstoker grate on which refuse is burned. Furnace combustion temperatures reach up to 2,000 °Fand convert water into high pressure/high temperature steam (860 psig/830 degrees Fahrenheit) todrive a turbine which generates electricity. The combustion temperature and operating efficiencyof an Ogden facility destroys odors, breaks down and oxidizes organic compounds and destroyscertain otherwise persistent organic contaminants.

The most recently completed facility by OWTE is in Montgomery County, Maryland. This 1800ton-per-day waste-to-energy facility is capable of producing up to 63 MW of electricity and is thefirst project to accept all of its waste via a custom railway system. This facility employsenvironmentally sensitive pollution control systems, specialized equipment for nitrogen oxidesreduction, and a mercury abatement system, as well as scrubbers and baghouses for particulatesand a lime injection system for acid gas removal.


Ogden Corporation Corporate Headquarters Tel:

Two Pennsylvania Plaza Fax: +1+212-868-3558

New York, NY 10121 U.S.A.


MWH Appendix 10A- 5

5. The Barlow Group, Inc.

Type of System /Technology: Patented Inclined Fluidized Bed combustion

Barlow Projects, Inc. (BPI) was established in 1994 to develop waste-to-energy projects using aproprietary mass burn combustion technology developed by the Barlow Group, Inc. BPI's targetmarket includes two primary segments; existing WTE facilities that have a significant need forcombustion and emissions control upgrades, and new projects sized between 100 and 500 tonsper day. BPI will design, build and operate these facilities and will participate in both publiclyand privately owned projects.

The heart of a Barlow waste-to-energy facility is the patented Inclined Fluidized Bed combustionsystem (IFB). The IFB process represents the latest development for combustion systems in theindustry. This mass burn design does not require any fuel preparation and has no moving partsexposed to the combustion zone. Waste is agitated and moved through the combustion zone via apatented pneumatic process. The IFB is designed and built in standard size modules. Eachmodule is shop fabricated and delivered to the facility site for final assembly.


The Barlow Group, Inc. Tel: +1-970-226-8557

2000 Vermont, Suite 200 Fax: +1-970-226-8559

Fort Collins, Co 80525 USA


MWH Appendix 10B- 1

Appendix 10-B

Municipal Waste Combustion and Tires-to-Energy Facilities in U.S.


MWH Appendix 10B- 2


MWH Appendix 10B- 3


MWH Appendix 10C-1

Appendix 10-C

Experience With Up-Take of Incineration Technology in Selected Regions of theWorld1

10-C-1 Africa

Incineration and waste-to-energy (WTE) remain little-used options for MSW in Africa. Oneenergy recovery plant was recently constructed in Tanzania with foreign assistance. Ifsuccessful in the long run, this experience would show how efficient and safe operations atsuch a facility can be sustained with local resources. Local capacity to sustain safe andefficient operations at such facilities is a key consideration in weighing the appropriateness ofthis technology for African cities. These considerations include local technical capacity tomaintain and service the facility, the availability of basic spare parts, the scheduledreplacement of pollution control equipment, and the effective implementation of a monitoringprogramme to protect public health from plant emissions.

The Senegalese have conducted research into refuse-derived fuel (RDF). However,implementation of this system faces the same considerations listed above for incineratortechnology in general. The high cost of pre-processing RDF poses an additional obstacle toits safe and cost-effective implementation in Africa.

Medical waste incinerators are used in the major hospitals of cities in South Africa. However,across most of Africa, many such facilities have no environmental controls and oftencomprise nothing more than combustion of medical and chemical wastes in an oven or openpit. High capital and operating costs make incineration and WTE inaccessible technologiesfor most African cities. Another limiting factor is the lack of infrastructure to support thistechnology. This includes human and mechanical resources as well as institutional controls.Furthermore, incineration in Africa would not be feasible if the waste stream is indeed 70%(wet basis) putrescible organic content, as is widely assumed. Under these conditions,incineration is likely to be an energy-consuming rather than energy-producing option.Characterisation of the MSW stream would first be necessary to establish the feasibility ofincineration and WTE from MSW in Africa. To date, such city-specific information islargely unavailable.

1 UNEP International Environmental Technology Center document


MWH Appendix 10C-2

10-C-2 Asia – East / Pacific

Incineration processes are capital-intensive and skilled manpower is required for operationand maintenance. Up-to-date, full-scale incinerators are currently in service only in cities ofthe more industrialised countries such as Australia, Hong Kong, Japan, Singapore, SouthKorea, and Taiwan. High capital investment, high operating and maintenance costs, andstringent air pollution control regulations have severely limited the use of incineration fordisposal. These constraints are likely to intensify, rather than abate.

Singapore operates three plants, all of the same design, incinerating 90% of the daily 5,800ton of MSW collected. No sorting of wastes is carried out before the MSW is fed to theincinerators (except that bulky wastes are crushed). The wastes are mixed and burned usingrotating roller grates. Auxiliary oil burners are used to start up the combustion process.Combustion is self-sustaining in some cases, while at other times wood is added. In general,the combustible fraction of MSW is high and in some instances has been raised by moisture-reducing compaction at transfer stations. Total electrical energy recovered from the plants isabout 60 MW (250 to 300 kwh/ton MSW incinerated), and some of this is used to run theincinerator operations.

Incineration plants in Japan, South Korea, and Taiwan are of similar design to those ofSingapore. Hong Kong has closed its incinerators because they could not meet air pollutionstandards, but new plants are under consideration. Authorities in South Korea are concernedabout local opposition to incinerators and are exploring ways to resolve such conflicts. Plansthere call for the incinerated portion of the waste to rise from 3% in 1994 to 20% by 1999.There are many incinerators in Japan: Tokyo alone has 13. Some MSW incineration facilitiesin Japan are of two stages: pyrolysis, followed by thermal combustion. Some Japanese citieshave made their MSW incinerators the centre of community complexes with indoor gardens,meeting halls, second-hand shops, and offices of NGOs.

Incineration will remain popular in cities such as Singapore, Hong Kong, Taipei, and Tokyoas there is a lack of landfill sites. There is, however, considerable controversy aboutgreenhouse and other gases released by incineration.

In the developing countries of Asia, however, there have been many problems with importedincinerators. Some are not operated at a high enough temperature to destroy pathogens, andmay also contribute to air pollution due to lack of environmental controls. The high moisturecontent and low calorific content of MSW in these countries means that at presentincineration is not an efficient process for waste disposal.Bangkok has installed conventional incineration plants at two of its landfill sites mainly forthe incineration of hazardous wastes collected; one has recently been shut down. There isongoing consideration of incineration in Thailand, but there is also local opposition.

China has one or two incinerators in cities like Shenzheng and Leshan. The one in Shenzhengwas purchased second-hand from Hong Kong, when that city decided it could not beretrofitted to meet anti-pollution standards, but it has proved too expensive for Shenzheng torun. Nevertheless, Beihai, Shenyang, Guangzhou, Beijing, and Shanghai have all begunconstructing pilot plants, with foreign assistance. One reason given is that, although theMSW is not currently suitable for incineration, engineers want to gain operational knowledgefor the future.

Surabaya, Indonesia has an imported incinerator that can only operate at two-thirds of itsdesign capacity because the wastes need to be dried on-site for five days to make themincinerable. Even without air pollution control mechanisms, the cost of incinerating the waste


MWH Appendix 10C-3

in this instance is roughly 10 times greater than the cost of sanitary landfilling in otherIndonesian cities.

In cities of developing countries in the Asia-Pacific region open burning of refuse is commonat landfill sites, to reduce volume. This is especially the case where the authority cannotafford bulldozers to compact the deposits.

Often refuse is burned by households at sundown as a means of disposal and to generatesmoke to drive away mosquitoes in developing countries. This contributes to air pollution incities and towns, particularly as there is now much plastic in the household wastes. Someauthorities encourage this backyard burning as it reduces the amount of MSW they have tocollect.


MWH Appendix 10C-4

10-C-3 Asia – South and West

Waste in the low-income economies is generally low in paper, plastic, and other combustiblesas compared to high- or middle-income economies (although source separation programmeswill bring about some changes in this respect in the future). As a result, large-scaleincineration requires auxiliary fuel. Trained manpower is usually not available to operate andmaintain a controlled combustion incinerator or waste-to-energy (WTE) plant. High capitalcosts and stringent maintenance requirements are further discouragements.

Almost all large cities, however, have experimented with incinerators. The first failure of amunicipal waste incinerator in the region was in Calcutta in the late 19th century; the mostrecent was in Delhi in the early 1980s. There is an abandoned plant in Jeddah, Saudi Arabia.In the cities of Mecca and Medina in Saudi Arabia several incinerators are still operating asother disposal options are not available. Beirut is debating building a WTE plant, and someSaudi Arabian cities are considering converting existing incinerators to recover energy. Noexamples of successful and operating WTE plants have been reported.

Incinerators are in use in hospitals in the higher- and middle-income economies in the centralpart of the region. These incinerators are installed and maintained by private companies andmonitored by the local environmental authority. A few hospitals and clinics in the northernarea and the Indian subcontinent also use incinerators to dispose of their waste, but most ofthese cannot attain a high enough temperature to be safe.


MWH Appendix 10C-5

10-C-4 Latin America and the Caribbean

Virtually no incinerators operate in Latin America or the Caribbean, although there have beena number of feasibility studies. To date, however, the costs of this technology are far too highto be considered by local governments as an appropriate waste management technology.

One municipal incinerator did operate in Mexico City; however, the facility was closed in1992 because it could not meet emission standards. MSW incinerators were also tried in SãoPaulo and Buenos Aires, but they are not operative at the present time. In these casesoperation and maintenance costs were too high. Other cities, such as Santiago, have assessedthe feasibility of implementing an incinerator but concluded that such an application was noteconomically viable. Barbados has one tiny (one ton/day) incinerator for processing wastesoriginating in the port. Private financing for this facility was arranged by the company thatprovided the incinerator; the government is now repaying the loan.


MWH Appendix 10D-1

Appendix 10-D

Overview of Current Status of Incineration Technology in India

10-D-1 Overview of Incineration Technology in India

In India, incineration technology is generally not viable for MSW due to low calorific valueand smaller volumes available for a central facility. The technology for incineration is notavailable indigenously and import options are highly capital intensive. Despite all thisincineration will remain an option for future and experience gained in this venture will bevery useful. In the meanwhile, incineration on smaller scale with or without energy recoverywill continue to be a viable option in a number of locations for power generation based onagro residues like rice husk, ground nut shells etc. Some examples of incineration plants inIndia have been discussed below.

10-D-2 The Delhi Incineration Experience:

During 1980s a design and construction contract was signed between Danish firm VolundMiljoteknik A/S and the Government of India to set up an incineration plant at New Delhi at acost of Rs. 220 million or US$ 6.9 million (May 94). The 300 TPD plant was set up usingDanish technology with assistance from Danida. The plant comprised two Volund 150 tonsper day rotary kiln incineration units, rated to produce 385 °C steam and driving a condensingturbine. It was also expected to generate 3.7 MW power for local grid. The operationalexperience was not satisfactory. The desired calorific value of garbage could not bemaintained as a result of prior segregation due to market mechanisms and scavengers.

10-D-3 MSW to RDF at Chennai:

UCAL RDF Limited, Chennai has developed a technology for the conversion of MSW into aclean burning fuel. The continuous process consists of step-wise removal of all noncombustible matter in MSW. The isolated combustible component is compacted to obtainRDF. They are executing a project for 5 MW RDF based power plant being setup at Chennai.UCAL RDF Limited has been commissioned to reactivate the 3.7 MW. Delhi basedincineration power plant. They are also working on an RDF plant at Vijaywada with acapacity to handle 200 tonnes per day of municipal solid waste.

Newam Power Company Limited and the Tamil Nadu Industrial Development CorporationLimited (TIDCO) are jointly setting up a project at Perungudi, Chennai to process 600 tonnesper day of MSW and convert it into 200 tonnes per day of RDF with 24% moisture content,11% Ash , 42% volatile matter, 23% fixed carbon, 65% Volatile matter and calorific value of3410 kcal/kg which can be used directly as a fuel. The estimated project cost is Rs. 19 crores.The subsidy from MNES is Rs. 1.5 crores. The capital cost of power generation is expectedto be Rs. 4 crore per MW.

The process for the conversion of garbage into fuel includes the following steps:• The raw garbage is collected by pay loaders and taken by conveyors to the rotary drier.• Metals are removed from the dried garbage by magnetic separation.• The combustible portions are pneumatically separated by density differentiation.• The combustible portion of the garbage is converted into pellets in the pellet machine.• The pellets are then fed to the boiler to generate steam.• The steam is fed into the turbine to generate electricity.• The electricity thus generated is fed to the Electricity Board Grid.


MWH Appendix 10D-2

The raw material will be made available by the Corporation of Chennai at Rs. 10 per tonne.The Chennai Metropolitan Water Supply and Sewerage Board has given 10 acres of land onlong lease to the company. The technology has been sourced from M/s. Henley Burrowes andCo. Ltd. Worcestor, UK.

10-D-4 Hazardous Waste Incinerator, Sandoz (India) Limited:

Sandoz (India) Limited has developed a Hazardous Waste Incinerator in collaboration withSchool of Energy, Bharathidasan University, Tiruchirappaly, Tamil Nadu. The Research andDevelopment work commenced in 1988 with the objective of developing a cost effective andappropriate technology for incineration of about 150 to 200 tonnes of toxic waste per annum.In a pilot plant installed at the University, more than 300 tonnes of different type of wasteshave been test incinerated.The collaboration project resulted in design of a commercialincinerator which was installed at Sandoz India’s Kolshet Works, Thane in December 1993.Commissioning trials were concluded in the first quarter 1994 and the plant is now fullyoperational and giving desired performance.

10-D-5 MSW to RDF plant , Hyderabad:

M/s SELCO International Hyderabad, Andhra Pradesh has installed a MSW pelletizationplant of 700 TPD capacity based on pelletisation technology developed by the Department ofScience and Technology (DST). The pellets would be used as an industrial fuel initially andultimately for 6 MW power generation. The properties of the RDF fluff and pellets are givenbelow:

RDF-FLUFF RDF-PELLETSPHYSICALShape Irregular CylinderSize (long/dia) mm 10 to 15 / 3 to 10 8 to 40 / 8 to 60Bulk density Kg/m3 400 approx. 600 to 700PROXIMATE ANALYSISMoisture 3 - 8 % 3 - 8 %Ash Content 12 - 20 % 12 - 20 %Volatile matter 50 - 65 % 50 - 65 %Fixed Carbon 12 - 18 % 12 - 18 %ULTIMATE ANALYSISMoisture 3 - 8% 3 - 8%Mineral matter 15 - 25 % 15 - 25 %Carbon 35 - 40 % 35 - 40 %Hydrogen 5 - 8 % 5 - 8 %Nitrogen 1 - 1.5 % 1 - 1.5 %Sulphur 0.1 - 0.2 % 0.1 - 0.2 %Oxygen 25 - 30 % 25 - 30 %Gross Calorific value 3000 - 3500 K cal / Kg. 3000 - 3500 K cal / Kg.

At present the RDF fuel is successfully used in various industrial boilers / furnaces.M/s.SELCO International is now engaged in setting up a 6.6 MW power plant at Elikatta(V),Shadnagar, Mahaboobnagar (Dist) based on moving grate boiler system at a total cost ofRs.40 crores (site visit by MWH on October 12,2002).


MWH Appendix 10D-3

10-D-6 Fluidized Bed Combustion of Municipal Solid Waste, Hyderabad:

RDF Power Projects Limited are in the process of establishing a power plant based onmunicipal solid waste at Hyderabad. The power plant to be set up at a cost of Rs. 40 croreswill process 700 metric tonnes of Municipal Solid Waste per day and produce 9 MW ofpower. RDF Power Projects Limited have a technical and financial tie-up with M/s PowerTherm Limited and M/s Lohning International Pvt. Ltd, Australia

The proposed process, the Lohning Brothers system is a new system for waste disposal whichuses the heat produced from rubbish to create electricity. It has very low emission levelswhich are below the current world standards. More than 10 high temperature fluidized bedcombustion plants based on this technology have been built in Australia and overseas forvarious types of wastes. The process contains the Waste Pre-Treatment systems, EffluentTreatment System, Liquid Treatment System, etc.

Ferrous and iron ferrous metals and glass will be automatically sorted out from the incomingwaste. Aqueous rubbish such as vegetables and fruits can be squeezed by screw press toremove the water. This type of sorting shredding and dewatering technique results in thecalorific value of the refuse entering the furnace to rise to a much higher level. This facttogether with the activity of the Spouted Fluidized Bed Combustor to burn waste with upto65% moisture means no auxilliary fuel is required for combustion. The combustion unitincludes a computerised control system.

In the furnace an effective burning is achieved by adjusting the combustion conditions. Thisis automatically controlled and monitored. Waste heat recovery and steam generation forlocal use and power production can be combined with the Spouted Fluidised Bed CombustorUnit. The heat generated by the waste combustion process is sent to a boiler to produce steamand the steam is then fed to a turbine generator thereby producing electricity.

The Australian process has made improvements to the fluidised bed combustion method ofthe Spouted Fluidised Bed Combustion (SFBC) system which is identifiable with fluidisedbed technology applied commercially and popularly overseas over the past 50 years.However its system is different from conventional fluidized bed combustors because of theactive bed produced by the high pressure of sparge tubes.

There is no electric power consumption from the public utility. The plant is designed tocombust the municipal waste and generate electricity of which around 10% is used within theplant to sell consumption.

10-D-7 DIEG Process :

Vasantdada Sugar Institute , Pune has developed a process for distillery spentwash calledDIEG (Drying Incineration Energy Generation).A prototype system has been commissionedat Krishna SSK Ltd., Maharashtra. (Details are covered in Section 3.3 of R & D Report i.esection on R & D Achievements of major National Institutions).

10-D-8 Fluidized Bed Soda Recovery System at Shreyans Paper:

Shreyans Paper, Ahmedgarh (Punjab) has 80 TDP paper production capacity based onbagasse and straw (wheat/rice). Black liquor from cooking agricultural residues has highsilica content and cannot be concentrated to high solid contents to enable its burning inconventional recovery systems. Shreyans Papers has installed a fluidized bed soda recoverysystem. Weak black liquor is concentrated to 25-35% in sextuple effect evaporators to avoid


MWH Appendix 10D-4

hard scale formation and it is further concentrated to 40 - 45% by flue gas in Venturi Scrubberand Cyclone system. Concentrated black liquor is the feed for the Fluidized Bed Reactor(FBR) burning 75 ton solids per day

The weak black liquor from agricultural residues has the characteristic following :

a. Total dissolved solids : 8.5 to 9.8%b. Residual active alkali : 1.85 gm/l as NaOHc. pH : 11.2d. Organic compounds (by loss of ignition) : 72%e. Inorganic compounds (by difference) : 28%f. Carbon © : 38%g. Silica (SiO2) : 4.2%h. Sodium (Na) : 18.5%i. Hydrogen : 4.2%j. Gross calorific value (Dry) : 3300 Kcal/kg

Heavy Black Liquor (concentration 40 – 45%) is pumped to a specially designed feed gun,which sprays the liquor either with compressed air or steam into the upper free gas space (freeboard) of Fluidized Bed Reactor. In the free board water is evaporated by the hot gasesgenerated by combustion. As the partially dried liquor solids falls into the fluidized bed, theburning of black liquor solids takes place and the temperature of the fluidized bed ismaintained at 680 – 700oC. Organic material is converted to carbondioxide and water vapourwhile the inorganic part is converted into sodium carbonate in pellet form, silica goes withsodium carbonate pellets and can be segregated in green liquor clarifier. The latter iscausticized using lime and NaOH recycled for pulping. In this system chlorides contentshould be maintained below 1% to avoid lump formation in the bed.

The fluidized air blower being the heart of the fluidized bed reactor requiring 500 BHP ispreferably run by steam turbine on co-generation principle with inlet steam pressure of 42kg/cm2 and exhaust steam pressure of 8 to 9 kg/cm2. The exhaust steam will be utilised in thepulp mill and in ejector of ME Evaporator. 2.5 MW Turbo generator has been installed totake care of extra load created by Fluidized Bed Recovery System as well as to reduce powerpurchased from State Electricity Board.

Salient Features are :

• Chemical Recovery is more than 85%• Smooth and trouble free operation of the plant• It occupies minimum floor area• Initial investment is low as well as gestation time is very low• No smelt formation, therefore the chances of explosion are eliminated• Carryover with flue gas is controlled by Wet Scrubbers.• It is suitable for any cellulosic raw material being used for paper making• No auxiliary fuel is required• Power generation potential

10-D-9 Energy Recovery from Bagasse by Co-generation :

India, as the world’s largest producer of sugar, has an attractively viable option in sugarcane.Crushed sugarcane, or bagasse, a waste product of the sugar industry, has the potential toprovide five to ten percent of India’s power needs. In 1997-98 India produced 12.8 million


MWH Appendix 10D-5

tons of sugar, and nearly 70 million tons of bagasse1. Bagasse can be used in "cogeneration"power plants wherein both steam and electricity are produced. Considering the results ofvarious studies conducted by government and private sources [like Ministry of Non-Conventional Energy Sources (MNES), USAID/Winrock International/IDEA Inc., TataEnergy Research Institute (TERI) and Indian Renewable Energy Development Agency(IREDA)], the market potential for cogeneration from the Indian sugar industry is assumed tobe of 3,500 MW.

In 1996, realizing the urgent need for promoting cogeneration, the Indian Ministry of Non-conventional Energy Sources (MNES) of the Government of India instituted a comprehensiveNational Bagasse-based Cogeneration Program with a package of financial incentives tobagasse cogeneration project developers to use advanced technologies, to encourage surpluspower production in sugar mills.

Some of the recent cogeneration projects in the sugar industry received technical and financialassistance from USAID under the Greenhouse Gas Pollution Prevention (GEP) Project to helpIndia in its efforts to clean the environment. The program focuses on demonstration andcommercialization of bagasse-based cogeneration plants that rely on supplemented biomassfuels rather than on fossil fuels. Sugar mills that received USAID assistance include: ThiruArooran Sugars Limited, EID Parry (India) Limited, The Dhampur Sugar Mills, DharaniSugars and Chemicals Limited and the Godavari Sugar Mills.

State-wise potential of bagasse based co-generation projects is given below:

States Cogeneration potentialMaharashtra 1000Uttar Pradesh 1000Tamil Nadu 350Karnataka 300Andhra Pradesh 200Bihar 200Gujarat 200Punjab 150Others 100

(Source: MNES Annual Report, 1999-2000)

Thiru Arooran Sugar Ltd. (TASL) at Tirumandankudi, Tamil Nadu:

Thiru Arooran Sugar Ltd. (TASL) Tirumandankudi plant was one of the three projectsselected for evaluation of its cogeneration potential by USAID. Government of Tamil Nadualso initiated an innovative scheme for promotion of bagasees cogeneration in June 1993.

This policy framework and USAID’s technical assistance enabled TASL to establish its firstlarge-scale bagasse-based cogeneration project in the country. It commissioned a 16.68 MWcogeneration plant in Tirumandankudi in 1995 and added another 9.74 MW in 1996. USAIDprovided a grant that resulted in another 18.68 MW cogeneration plant being commissioned atKollumangudi in 1997. As of January 2000, TASL had a total installed capacity of 47.1 MWwith an export potential of 23.4 MW during the sugar season and 33.0 MW during the off-season.

1 ELECTRICITY FROM SUGARCANE WASTE, by G. V. JoshiSource: http://www.india-syndicate.com


MWH Appendix 10D-6

While bagasse is the primary fuel in both these cogeneration plants, off season requirementsof fuel, over and above the saved and purchased bagasse, are being met by lignite until suchtime that an alternative biomass resource becomes available .

Shree Doodh Gana Krishna Sahakara Sakkare Karkhane Niyamit, Karnataka :

The Karnataka Power Transmission Corporation Limited (KPTCL), in June 2001, enteredinto power purchase agreements (PPAs) with three non-conventional energy projects,including two mini-hydel projects, with a total capacity of 31 MWs.

The first PPA was for a 24-MW bagasse based co-generation power plant of Shree DoodhGana Krishna Sahakara Sakkare Karkhane Niyamit, Chikkodi at Nanadi village of Belgaumdistrict. The plant will generate 97 MUs [Million Units (million kWh)] of power every year.

All the three projects were expected to be commissioned in 18 to 24 months. As per the PPA,the KPTCL will buy power from these companies at a rate of Rs 3.16 per unit as against itsaverage power purchase cost (conventional energy) of Rs 1.60 per unit.

The co-generation unit would create a win-win situation for the sugar factory as well as thecane growers as this would help the factory make additional profits which would help pay thedues of canegrowers on time.

Besides this, The Triveni Sugar Group (Uttar Pradesh),Godavari Sugar Mills(Karnataka),TheVasantdada Farmers Co-operative Sugar Factory at Sangli(Maharashtra), The JawaharFarmers Co-operative sugar factory at Hupari, near Kolhapur (Maharashtra), -based ShreeDutta co-operative sugar factory, Shirol (Maharashtra) and Rajarambapu Patil co-operativesugar factory, Sakharale (Maharashtra) have immediate plans to implement cogenerationfacilities to realise the potential benefits.


MWH Appendix 11A- 1

Appendix 11-A

Patented Gasification and Pyrolysis Technologies

It is beyond the scope of this Appendix 11-A to present an exhaustive list and to discuss in detail allthe available technologies and processes of gasification and pyrolysis. However, we have attempted tocompile from various existing sources a list of processes and technologies currently in existence andbeing used. Partial lists of various technologies and gasifier manufacturers are given in the Appendix11-B and Appendix 11-C. It should also be noted that this list does not necessarily expressMontgomery Watson’s view or endorsement of any of the listed technologies. Further investigationsare required, using site-specific criteria, to select a particular process for use in any particularapplication.

“IEA Bioenergy” and “CADDET Renewable Energy Programmes” (1998) have identified aroundforty advanced thermal conversion plants for various waste feedstocks in the report “AdvancedThermal Conversion Technologies of Energy from Solid Waste”. Similarly, in “Pyrolysis &Gasification of Waste - A Worldwide Technology & Business Review” recently published by theenvironmental consulting company Juniper, there is detailed discussion of over sixty processes andtechnologies.

In 1996 “National Renewable Energy Laboratory” (NREL) undertook a detailed technologyevaluation of thermal processes for the treatment of municipal solid waste. During the project overforty firms were initially contacted and subjected to set screening criteria. A final seven processeswere investigated further, with two of these being novel thermal processes and five being gasification.

This Appendix is primarily prepared based on information provided by process developers, fromavailable literature, or from information available on the Internet.

Considering the above approach and limitations, the following sixteen projects have been selected todemonstrate variations in gasification and pyrolysis technologies.

1. TPS Termiska Processer AB (TPS) Technology

2. Proler International Corporation

3. Thermoselect Inc.

4. FERCO Gasification Process

5. PulseEhnanced™ (ThermoChem)

6. RENUGAS Gasification Technology

7. Biomass IGCC Sydkraft AB and Foster Wheeler Energy International Inc.

8. Foster Wheeler Acfb Gasification Process

9. STORE and ARP Processes

10. Texaco Gasification Process (TGP)

11. Biosyn Process

12. Plasma Gasification

13. BG-Systems™ Gasifier

14. The Rotating Cone Technology

15. Waterwide™ Lineal Hearth Gasification and Closed coupled gasifier

16. Thermogenics Gasification Systems


MWH Appendix 11A- 2

A brief write-up of available information on each of the above representative advanced thermalconversion technologies is presented below, in the following format:

Developer

Treatment Technology

Developmental Stage

Description

Projects / Demonstrations

Contact Information


MWH Appendix 11A- 3

11.A.1 TPS Termiska Processer AB(TPS) Technology

Developer: TPS Termiska Process (TPS)

Treatment Technology: Circulating fluid bed gasifier with dolomite cracker

Developmental Stage:

The product of the TPS effort is well developed and demonstrated technology for gasification of RDFwith subsequent conversion to electricity. The technology offered by TPS is presently close to thepoint of commercial availability.

Description:

The main focus of TPS is on small-to-medium scale electricity production plants using biomass andrefuse-derived fuel as feedstocks. Their technology involves starved-air gasification of RDF in acombined bubbling and circulating-bed (cracker). Fuel gas generated at the plant is either burned in aboiler to generate electricity or used as a fuel in an adjacent lime kiln operation.


7.2 MJ/h prototype began in 1986. Pilot Plant is in Greve-en-Chianti, Italy


Erik Rensfelt, and Lars WaldheimStudsvik AB S.611 82Nyköping, SwedenTel: +46-155-22-1385, +46-155-22-1382Fax: +46-155-26-3052E-mail: [email protected], [email protected]: www.tps.se/


MWH Appendix 11A- 4

11.A.2 Proler SynGas Process

Developer: Proler International Corporation

Treatment Technology: Rotary reactor gasifier and cyclic ash vitrifier


The process is being demonstrated in a 1.8-Mg/h (2-t/h) plant in Houston, Texas.

Description:

The Proler SynGas Process is a patented technology that reforms hydrocarbon-containing wastes intoa reactor gas. Although the process was originally developed for the gasification of automobileshredder residue (ASR), limited runs have demonstrated its suitability for gasifying municipal solidwaste. The process accepts pre-shredded material and produces a fuel gas suitable for powergeneration. The residues are discharged in the form of commercially useful vitrified by-products aswell as wastes acceptable for landfills.


Proler pilot plant, Houston, Texas, USA


Proler International Corp.4265 San Felipe, Suite 900Houston, Texas 77027, USATel: +1-713-963-5944 & 1-713-627-3737Fax: +1-713-627-2737E-Mail:Web:


MWH Appendix 11A- 5

11.A.3 Thermoselect® Gasification System

Developer: Thermoselect Inc.

Treatment Technology: Raw waste gasifier


Thermoselect as of 1996 was not interested in selling the technology. However, they are prepared toenter into the following arrangements: 1) Provide a licensed facility to an owner on a turnkey basis,2)Enter into a joint operating venture with an owner,3) Work with a developer, community, financegroup, or technology provider

Description:

Thermoselect SA is a privately held Swiss company created to commercialize the Thermoselectprocess, for which over 31 patents have been issued. The process is a fully developed method ofgasifying municipal solid waste and industrial raw wastes without apparent adverse impact on theenvironment. The residue is converted into what are described as commercially useful by-products. Astandard design has been developed for a two-line, nominal 480-Mg/d system housed in an industrialbuilding. Large capacity systems are offered by adding multiples of the “standard” modules.

Projects / Demonstrations:

The Thermoselect demonstration facility is located at Fondotoce, Italy.


Thermoselect, Inc.Columbia Center Suite 230210 W. Big Beaver RoadTroy, MI 48084, USATel: +1-810-689-3060Fax: +1-810-689-2878


MWH Appendix 11A- 6

11.A.4 FERCO Gasification Process

Developer: Battelle has licensed its BHTGS for the North American market toFuture Energy Resource Corporation (FERCO) in Atlanta, Georgia.

Treatment Technology: Circulating fluid bed gasifier and combustor


A commercial-scale demonstration is at Burlington Electric’s McNeil generation station inBurlington, Vermont, using whole tree wood chips.

Description:

The Battelle High Throughput Gasification System (BHTGS) is an indirectly heated, two-stageprocess that uses circulating fluidized bed (CFB) reactors. In a high-throughput gasifier, refuse-derived fuel or other biomass feedstocks are gasified in a CFB to a medium-heating value gas (500 to600 Btu/sft³ ), using steam without oxygen as the fluidizing medium. Residual char is consumed in anassociated CFB combustor.


Burlington Electric’s McNeil generation station in Burlington, Vermont, USA.


Inge B. Frentheim, President & CEOFERCO3500 Parkway Lane, Suite 440Norcross, GA 30092,USATel: +1-770-662-7800, +1-770-662-7807Fax: +1-770-662-7807E-Mail: [email protected]: www.future-energy.com

Battelle Columbus505 King AvenueColumbus, Ohio 43201-2693, USATel: +1-614-424-4958Fax: +1-614-424-3321


MWH Appendix 11A- 7

11.A.5 PulseEnhanced™

Developer: Manufacturing and Technology Conversion International, Inc.(MTCI) licensed to ThermoChem Inc.

Treatment Technology: Pulse-heated circulating fluid bed gasifier


Plans for a commercial plant to handle up to 655 t/d RDF at a landfill site have reached the designstage in 1996. Testing of RDF has been done on a 7-kg/h unit only. Although they have achievedremarkable progress in scaling-up their system for black liquor, successfully demonstrated scale-upfrom the pilot plant to a larger size would be prudent before this system can be expected to becommercial.

Description:

The Manufacturing and Technology Conversion International, Inc. (MTCI) Steam Reforming Processis an indirectly heated fluidized bed reactor using steam as the fluidizing medium. Under license fromMTCI, ThermoChem, Inc. (TC) has the exclusive right to apply its PulseEnhanced™ heater andsteam-reforming technology to a variety of applications.


In 1991 and 1992, a 15 t/d demonstration unit was operated using rejects from a cardboard recyclepaper mill in Ontario, California. This same unit, relocated to TC’s test facility in Baltimore, has sinceprocessed coal, wood chips, and straw.

At a pulp mill in New Bern, North Carolina, MTCI and TC have built a five-heater fluid-bed steamreformer that can process 120t/d black liquor. A unit of similar size has been built in Tamilnadu,India to process organic solids from several food industries.


ThermoChem, Inc.13080 Park StreetSanta Fe Springs, CA 90670, USATel: +1-310-941-2375Fax: +1-310-941-2732


MWH Appendix 11A- 8

11.A.6 RENUGAS® Gasification Technology

Developer: IGT (Institute of Gas Technology), Department of Energy (DOE)initiative with principal industrial partner, Future Energy ResourcesCompany (FERCO)

Treatment Technology: IGT RENUGAS® single pressurized bubbling-fluidized-bed gasifier


Demonstration stage

Description:

IGT developed the RENUGAS® gasification technology specifically for the conversion of biomass tolow (5 MJ/Nm3)—or medium (15 MJ/Nm3)—heating-value gas (Lauet al., 1993). Biomass is fed to asingle pressurized bubbling-fluidized-bed gasifier vessel for efficient transfer of energy released byendothermic volatilization and gasification reactions. The process has been tested during more than250 hours of steady-state operation at feed rates up to 10.9 Mg/day (12 TPD) and at pressures up to3.45 MPa (500 psia) in a 0.292 m (0.96 ft) diameter by 3.1 m (10.2 ft) high-fluidization zone.


Hawaii RENUGAS ProjectThe project is a multi-phase effort located at Hawaii Commercial and Sugar Company's (HC&S) Paia,Maui, Hawaii, sugar mill. In the first phase, the Pacific International Center for High TechnologyResearch (PICHTR) directed the construction and commissioning operations of the gasifier. Otherteam members were HC&S, the Hawaii Natural Energy Institute (HNEI), and IGT. A total of about110 hours of operation at pressures up to 165 psia and feed rates up to 39 Mg per day (40 tons perday) were achieved. This phase of the project was completed early in 1996.


Institute of Gas Technology1700 South Mount Propect RoadDes Plains, Illinois 60018-1804, USATel: +1-708-798-0591Fax: +1-708-768-0600


MWH Appendix 11A- 9

11.A.7 Biomass IGCC Sydkraft AB and Foster Wheeler Energy International Inc.

Developer: Sydkraft AB and Foster Wheeler Energy International Inc.

Treatment Technology: Pressurized circulating fluidized bed gasifier


R & D. Start-up phase was completed during spring 1996 and the plant is now available for researchand development work. A demonstration program was launched in1996, which continued until June,2000.

Description:

The gas generated is burned in the combustion chambers and expands through the gas turbine,generating 4 MW of electricity. The gas turbine is a single-shaft industrial gas turbine. The fuelsupply system, fuel injectors and the combustors have been redesigned to suit the low calorific valuegas (5 MJ/nm³).


The plant is located in Värnamo, Sweden, and the technology used in the power plant is based ongasification in a pressurized circulating fluidized bed gasifier. The gasification technology isdeveloped in co-operation between Sydkraft AB and Foster Wheeler Energy International Inc.


Foster and Wheeler Development Corp.12 Peach Tree Hill RoadLivingston, NJ 07039, USATel: +1-201-535-2332Fax: +1-201-535-2242

Sydkraft ABSE-205 09, Malmö, Sweden


MWH Appendix 11A- 10

11.A.8 Foster Wheeler Acfb Gasification Process

Developer: Foster Wheeler

Treatment Technology: Atmospheric Circulating Fluidized-bed gasification


Demonstration/ commercial scale demonstration

Description:

The atmospheric CFB gasification system consists of a reactor, a uniflow cyclone to separate thecirculating bed material from the gas, and a return pipe for conveying the circulating material to thebottom of the gasifier. From the uniflow cyclone, hot product gas flows into the air preheater, whichis located below the cyclone.


Lahden Lämpövoima Oy Kymijärvi power plant, Lahti, Finland.


Foster and Wheeler Development Corp.12 Peach Tree Hill RoadLivingston, NJ 07039, USATel: +1-201-535-2332Fax: +1-201-535-2242E-mail:Web: www.fwc.com



11.A.9 STORS and ARP Processes

Developer: Foster Wheeler Environmental Corporation

Treatment Technology: Sludge to Oil Recovery System (STORS) and Ammonia RecoveryProcess (ARP)


The STORS and ARP processes have been previously demonstrated. The STORS technology hasbeen successfully tested on a pilot scale basis at the Battelle facility in Hanford, Washington. Theammonia recovery technology has been successfully tested on a bench scale basis in Columbus, Ohio,and on a pilot scale basis at a wastewatertreatment plant in Staten Island, New York.

Description:

The STORS process is designed to treat primary sludge at a rate of 5 dry tons per day. The ARPsystem will treat the water effluent from the STORS process to remove ammonia and recover it asammonium sulfate. Design data from the pilot system operation will demonstrate the process viabilityand will aid in refining the designs for their commercial application.

The commercial application of the STORS process is the volume reduction of municipal sludgedisposed at landfills. The commercial application of the ARP design includes both the treatment andrecovery of ammonia from water effluent from the STORS process and the treatment of ammonia inthe water effluent from municipal sludge dewatering operations.

STORS Process


The Sludge to Oil Recovery System (STORS) and Ammonia Recovery Process (ARP) pilotdemonstration facility located at the Colton Municipal Facility in Colton, California.


Foster and Wheeler Development Corp.12 Peach Tree Hill RoadLivingston, NJ 07039, USATel: +1-201-535-2332Fax: +1-201-535-2242



11.A.10 Texaco Gasification Process (TGP)

Developer: Texaco's Montebello Research Laboratory (MRL) South El Monte,California

Treatment Technology: Refractory-lined reactor


The TGP has operated commercially for nearly 45 years on feeds such as natural gas and coal, andnon-hazardous wastes such as liquid petroleum fractions, and petroleum coke. Texaco’s gasificationprocess is currently licensed in the U.S. and abroad. The TGP was evaluated under the EPA SITEProgram in January 1994 at Texaco's Montebello Research Laboratory (MRL) in South El Monte,California.

Description:

TGP was conducted under the U.S. Environmental Protection Agency (EPA) Superfund InnovativeTechnology Evaluation (SITE) Program. The TGP is a commercial gasification process that convertsorganic materials into syngas, a mixture of hydrogen and carbon monoxide. The feed reacts with alimited amount of oxygen (partial oxidation) in a refractory-lined reactor at temperatures between2,200 degrees and 2,650 degrees F and at pressures above 250 pounds per square inch gauge (psig).Texaco reports that the syngas can be processed into high-purity hydrogen, ammonia, methanol, andother chemicals, as well as clean fuel for electric power. The TGP can process a variety of wastestreams. Virtually any carbonaceous hazardous or non-hazardous waste stream can be processed in theTGP as long as adequate facilities are provided for pretreatment and storage.


Texaco maintains three pilot-scale gasification units, ancillary units, and miscellaneous equipment atthe Montebello Research Laboratory (MRL), where the SITE demonstration was conducted. Eachgasification unit can process a nominal throughput of 25 TPD of coal.


Texaco, Inc., Montbello Research Lab329 North Durfee Ave.El Monte, CA 91733, USATel: +1-310-908-723Fax: +1-310-692-4625E-Mail:Web: http://www.texaco.com

Richard B. ZangTexaco Inc.2000 Westchester AvenueWhite Plains, NY 10650, USATel: +1-914-253-4047Fax: +1-914-253-7744



11.A.11 Biosyn process

Developer: Kemestrie Inc. and its partners

Treatment Technology: Bubbling fluidized-bed gasification


Pilot project

Description:

The technology can be applied to organic residues from any source, such as sorted urban waste, peat-moss and straw, as well as wastes from various industries, such as wood, oil, rubber and agro-food.Waste must be sorted beforehand to remove metal, glass and inorganic matter. To maintain highperformance, inorganic matter concentrations should be kept low.


Pilot unit GRTPC, at Université de Sherbrooke, Canada


Mr. Nicolas Abatzoglou, Director, Energy and EnvironmentKemestrie Inc.4220 Garlock, Sherbrooke, QueecJ1L 2P4, CanadaTel: + -819-569-4888Fax: + -819-569-8411E-Mail: [email protected]: www.enerkem.com



11.A.12 Plasma Gasification

Developer: RCL USP's Plasma Partner

Treatment Technology: USP Plasma Gasification using plasma arc

Developmental Stage: Not known

Description: Not available



Houston Northcutt Blvd., Suite 3Mt. Pleasant, South Carolina 29464Tel: +1-843-509-8919Fax: +1-843-856-2329E-Mail: [email protected]: http://www.usplasma.com/Contact_Us/contact_us.html



11.A.13 BG-Systems™ Gasifier

Developer: BG Technologies LLC

Treatment Technology: Fixed-bed, down-draft gasifier


Commercial scale including several plants built in India. 400 installations ranging from pumpingwater to industrial power to thermal energy systems for industrial drying and steam generation or usedin burners to generate heat for drying applications.

Description:

BG-Systems converts a variety of woody and agricultural biomass feedstocks into a clean combustiblegas mixture through a high temperature pyrolysis process. The gas, normally called "producer gas",consists of three combustible gases: hydrogen, carbon monoxide and methane.

Applications:

• Power generation: Industries producing wood or agricultural wastes such as saw mills, palmoil factories, and rubber plantations.

• Drying/baking: Agro-process industries requiring scrubbed gas for direct application on foodproducts such as tea drying, coconut drying and bakeries.

• Process heat: Industries where the unscrubbed hot gas can be burned in boilers, furnaces, andkilns.


Gujarat Energy Dev. Agency, India (500kW wood from energy plantation), Eastern Shore WoodProducts, USA. Customer contact: Tom Johnson, +1-410-742-5540. Several other 10-500kW plantsworldwide.


10480 Little Patuxent Parkway, Suite 400Columbia, MD 21044, USATel: +1-410-740-3025Fax: +1-208-728-8983E-Mail: [email protected]



11.A.14 The Rotating Cone Technology

Developer: BTG Biomass Technology Group B.V.

Treatment Technology: Rotating cone technology


After having demonstrated the rotating cone technology on a scale of 50 kg/hr, BTG is designing aproject that is aimed at scaling-up of the pyrolysis technology to a scale of 200 kg biomass per hour.The project is a last preparatory step before commercialization of the technology.

Description:

The rotating cone reactor is a gas-solid contactor that has been developed at the University of Twente(Chem. Eng. Sci., 5109, 1994).

Models Available

BTG 50P - 50 kg/hr biomass throughputBTG 200P - 200 kg/hr biomass throughput


Project: Scaling-up of the rotating cone reactor to 200 kg biomass per hourPartners: Kara Engineering Almelo B.V.(NL), CIEMAT (SP) and Univ. Rostock (GE)Project: Development of advanced fast pyrolysis processes for power and heatPartners: Aston Univ. (UK), BHF-IWCT (GE), Hicks Hargreaves Ltd (UK), Kara Engineering

Almelo B.V. (NL) and Ormrod Diesels (UK)Project: Design and operation of a bench scale bio-oil production unitPartners: KARA Engineering Almelo B.V.


Biomass Technology Group BVPantheon 12, 7521 PR EnschedeThe NetherlandsTel: +31-53-4862287Fax: +31-53-4325399E-Mail: [email protected]

Mr. K. ReindersKARA Energy systems BVPlesmanweg 27, 7602 PD AlmeloThe NetherlandsTel: +31-546-876580Fax: +31-546-870525E-Mail: [email protected]



11.A.15 Waterwide™ Lineal Hearth Gasification and Closed Coupled Gasifier

Developer: Renewable Energy Corporation Ltd.(formally CombustionConsultants Ltd.)

Treatment Technology: Waterwide close coupled gasifier


Many of Waterwide plants have been installed worldwide in the last twenty years. Many of these arethe earlier, smaller plants, which are still in operation.

Description:

The Waterwide Lineal Hearth Gasifier was developed in the 1970’s. The key to the Waterwidetechnology is the Close Coupled Gasification, this method controls emissions during combustionrather than after combustion process. Final burnout is at very high temperature in a cyclonic system,which ensures all smoke and volatile matter is eliminated.

The company has designed a standardized range of factory-built modules. These modular plants arefully automated, and the machines have no moving parts in the high temperature zone.



Combustion Consultant Ltd.37 Parkhill Road, R.D. 2HastingsNew ZealandTel: +64-6-875-0734Fax: +64-6-875-0098E-Mail: [email protected]: www.waterwide.co.nz



11.A.16 Thermogenics Gasification Systems

Developer: Growth and Development Corporation, and Thermogenics, Inc.

Treatment Technology: Several styles of gasification systems


Commercially available

Description:

GDC, Inc. (headquarters in Alexandria, Virginia), with its teaming partner Thermogenics, Inc.(headquarters in Albuquerque, NM), are privately owned corporations specializing in development ofintegrated waste-to-energy systems based on patented gasification and water purificationtechnologies.

Thermogenics Gasification Systems are suitable for direct use in standard internal combustionengines.

Projects/ Demonstrations: Not available


Admiral Daniel J. Murphy USN (Ret.) Chairman and CEO,Growth and Development Corporation, Inc.5422 Wycklow CourtAlexandria, VA 22304, USATel: +1-703-671-0335Fax: +1-703-671-9824 E-Mail: [email protected]: http://www.acepos.com/index.htm


MWH Appendix 11B- 1

Appendix 11-B

A Partial List of Various Processes and Technologies1

1 Main source: Pyrolysis & Gasification of Waste, A Worldwide Technology & Business Review,published by Juniper Consultancy Services Limited

1. ABB2. AAE3. Alcyon4. Andco Torrax5. Ande6. B9 Energy7. Balboa8. Battelle / Ferco9. Beven Recycling10. BG Systems11. Brightstar Synfuels12. BPI13. Compact Power14. Conrad/ Kleenair15. Dynamotive16. Ebara17. Energy Developments18. EPI19. Enerkem20. Ensyn21. ESI/ Enersludge22. Foster Wheeler23. GTS Duratek/ Proler24. Hebco25. Heuristic Eng./ Envirocycler26. JND Kara27. Kvaerner ChemRec28. Lurgi29. Mitsui30. MTCI/Thermochem31. Nexus32. NKK33. Nippon Steel34. Noell35. Organic Power

36. Peat37. PKA38. PRME39. Proler40. Pyrovac41. Resorption42. RGR Ambiente43. Sacone44. Serpac45. Siemens46. Takuma47. Technip48. ThermoChem49. Thermogenics50. Thermoselect51. Texaco52. Thide53. TPS54. Traidec55. Uhde56. Von Roll57. Waste Conversion

Systems/Nathaniel58. Waste Gas Technology (UK) Ltd59. Waste to Energy/ Ventec60. Waterwide61. Wellman


MWH Appendix 11 C- 1

Appendix 11-C

Partial List of Gasifier Manufacturers1

Name Country Gas heatingvalue(MJ/Nm3)

TK Energi AS Denmark

Babcock Borsig Power, Austrian Energy Austria 10 - 13

Baxi A/S Denmark

Procone Vergasungssysteme GmbH Switzerland 5

Meurer Maschinen Germany 4

PPS Pipeline Systems GmbH Germany

Babcock Borsig Power, Austrian Energy Austria 2.5-6.0

UET -Umwelt- und Energietechnik GmbH Germany 4.4-8.5

Gas Energietechnik Germany

Rheinbraun Germany

NOELL-KRC Energie- und Umwelttechnik GmbH Germany

Maskinfabrikken REKA Denmark

Ensofor SA Switzerland 4.1

Danieli Ambiente S.R.L. Italy

C.C.T. SPA Italy >1200 kcal/kg

Condens Oy Finland

Carbona Oy Finland 4.5-5.6

Krupp Uhde GmbH Germany >5.0

VER GmbH Germany 4.1

Costich Company United States

Imbert GmbH für Energie und Umwelt Germany 4.4

Easymod Energiesysteme GmbH Germany 5-6

AHT Pyrogas Vertriebs GmbH Germany 4.5

Lurgi Energie und Umwelt GmbH Germany 4.2-5.9

TPS Termiska Processer AB Sweden 4-6

Kvaerner Pulping AB Power Division Sweden

Kemestrie's Inc - BIOSYN Canada

1 Source: ©1999-2000 Gasifier Inventory. Generated: 05-Jul-2000Questions? Comments? Contact the Gasifiers Inventory by calling +31 53 489 2897, faxing to +31 53 489 3116or mailto:[email protected].


MWH Appendix 11 C- 2

Name Country Gas heatingvalue(MJ/Nm3)

Heuristic Engineering INC. Canada 100 BTU

Pyroban Ltd United Kingdom

Sur-Lite corporation United States

Chevet France

Wellman Process Engineering Ltd United Kingdom 4.9

Third Generation, Ltd United Kingdom

Thermogenics United States

Thermochem Inc (MTCI) United States

PRIMENERGY, Inc United States ~6.0

Cratech United States

CLEW- Thermal Technologies, Inc. United States

Chiptec Wood Energy Systems United States

Brightstar Synfuels Co. United States

BG Technologies, LLC United States

B9 Energy Biomass Ltd United Kingdom 5.1

MELIMA Markus Meier Switzerland

Ansaldo Vølund A/S Denmark

Foster Wheeler Energia Oy Finland 5

Rural Generation Ltd United Kingdom

Stork Thermeq B.V. Netherlands 4-5

KARA Energy Systems BV Netherlands 4.0-5.5

Xylowatt SA Switzerland 4-5

Ventec Waste to Energy Ltd United Kingdom

Battelle Columbus Laboratories, BCL United States

Martezo France 4-5


MWH Appendix 11 D- 1

Appendix 11-D

Gasification Related Useful Documents

1. Mahrling, P.; Vierrath, H. (June 1989). Gasification of Lignite and Wood in the LurgiCirculating Fluidized-Bed Gasifier. EPRI GS-6436. Frankfurt am Main, Germany. LurgiGmbH. Available from Electric Power Research Institute, Palo Alto, CA.

2. Anderson, R.O. (1993). Ms6001FA - An Advanced Technology 70 MW-Class 50/60 HertzGas Turbine. Available from General Electric Company, Schenectady, NY.

3. Gas Turbine World 1992-93 Handbook (1993). Fairfield, CT: Pequot Publishing Inc.

4. Breault, R.; Morgan, D. (October 1992). Design and Economics or Electricity Productionfrom an Indirectly Heated Biomass Gasifier. TR4533-049-92. Columbus, OH: BattelleMemorial Institute. Work performed by Tecogen Inc., Waltham, MA.

5. Wiltsee, G. A. (November 1993). Strategic Analysis of Biomass and Waste Fuels for ElectricPower Generation. EPRI TR-102773. Sevenson Ranch, CA: Appel Consultants, Inc.Available from Electric Power Research Institute, Palo Alto, CA.

6. Ebasco Environmental. (October 1993). Wood Fuel Cofiring at TVA Power Plants. Contract3407-1. Sacramento, CA: Ebasco Services Inc. Available from the Electric Power ResearchInstitute, Palo Alto, CA.

7. Bain, R. (January, 1992). Material and Energy Balances for Methanol from Biomass UsingBiomass Gasifiers. Golden, Colorado: National Renewable Energy Laboratory.

8. Feldmann, J.; Paisley, M.A. (May 1988). Conversion of Forest Residues to a Methane-RichGas in a high-throughput Gasifier. Columbus, Ohio: Battelle Columbus Laboratory.

9. Weyerhauser et al. (June 1995). New Bern Biomass to Energy Project, Phase 1 FeasibilityStudy. NREL/TP-421-7942. Golden, CO: National Renewable Energy Laboratory. Workperformed by Weyerhauser, Inc.

10. Anderson, R. O. (1993). MS6001FA - An Advanced Technology 70 MW-Class 50/60 HertzGas Turbine. Available from General Electric Company, Schenectady, NY.

11. 100-MW Nevada IGCC Operational Next Year. (July-August 1995). Gas Turbine World. pp.30-32

12. Corman, J.C. (September 1986). System Analysis of Simplified IGCC Plants. DOE/ET-14928-2233. Morgantown, WV; Morgantown Energy Technology Center. Work performed byGeneral Electric Company Corporate Research and Development, Schenectady, NY.

13. Electric Power Research Institute. (June 1993). TAG - Technical Assessment Guide. EPRITR-102276-V1R7 Volume 1: Rev. 7. Palo Alto, CA.

14. Simons Resource Consultants and B. H. Levelton and Assoc. Ltd. (December 1983). ENFORProject C-258, A Comparative Assessment of Forest Biomass Conversion to Energy Forms.Report to Energy, Mines, & Resources Canada. v. III pp.4-38

15. Northern States Power et al. (May 1995). Economic Development Through Biomass SystemsIntegration - Sustainable Biomass Energy Production. NREL/TP-421-20517. Golden, CO.Work performed for the National Renewable Energy Laboratory and the Electric PowerResearch Institute by Northern States Power, Minneapolis, MN.

16. Craig, K.R., Bain, R.L., Overend, R.P., (October 1995). "Biomass Power: Where Are We,Where Are We Going, and How Do We Get There? The Role of Gasification." Proceedingsof EPRI Conference on New Power Generation Technology. San Francisco, CA.


MWH Appendix 11 D- 2

17. Craig, K.R., M.K. Mann, R.L. Bain. (October 1994). "Cost and Performance Potential ofAdvanced Integrated Biomass Gasification Combined Cycle Power Systems." Published in"ASME Cogen Turbo Power '94, 8th Congress & Exposition on Gas Turbines inCogeneration and Utility, Industrial and Independent Power Generation." Portland, OR. ISBNNo. 0-7918-1213-8

18. Double, J.M.; (1988). Design, Evaluation and Costing of Biomass Gasifiers. Doctoral Thesis

19. Weyerhauser. (1992). Gasification Capital Cost Estimation Obtained from mark Paisley inpersonal correspondence, August, 1994. Battelle Columbus Laboratory.

20. Battelle. (January 1993). Operation and Evaluation of an Indirectly Heated Biomass GasifierPhase Completion Report. Contract YM-2-11110-1. Golden, CO. National Renewable EnergyLaboratory

21. Levelton, B.H., Sawmill and Small Scale Combustion Systems, Published in Proceeding of"Energy Generation and Co-Generation from Wood." p. 80-26.

22. Gas Turbine World 1992-93 Handbook (1993). Fairfield, CT: Pequot Publishing Inc.

23. Esposito, N. T. (June 1990). A Comparison of Steam-Injected Gas Turbine and CombinedCycle Power Plants: Technology Assessment. EPRI GS-2387-4. Palo Alto, CA: ElectricPower Research Institute. Work performed by Jersey CP&L, Morristown, NJ.


MWH Appendix 11F- 1

Appendix 11-F

Experience of Gasification Technology in India

11.F.1 Biomass Gasification:

In India, Gasification of biomass is being promoted by the Ministry of Non-Conventional EnergySources. Ministry is promoting three main uses of biomass. These are improved cookstoves, biomassgasification system for power generation, water pumping and biomass based power generation.

The Programme on Biomass Gasification is being implemented with the following objectives:

Development and promotion of conversion and utilization technologies, such as biomass briquettingand gasification, for various end-use applications in rural and urban sectors;R&D on biomass production and gasification.

The National Programme on Biomass Gasification provides for financial support of upto 30-60%depending upon the capacity of target groups i.e., socially oriented projects or individual/entrepreneurs. Greater focus has been laid on promotion of village electrification as well as onindustrial and commercial applications. Grid connected gasifier based power generation systems havealso been taken up for promotion and the first of such projects – a 500 kW system based on woodgrown in Govt. owned energy plantations has been commissioned.

The Gasification Programme is one of the first biomass power programmes to have been initiated bythe Ministry. The Programme intends to promote development, demonstration and commercializationof biomass gasifier based systems for water pumping, mechanical power and thermal applicationsand, generation of electrical energy for captive industrial applications or for rural electrification. Anetwork of research institutions has been built up over the years for developmental work on variousfacets of biomass gasification. Some of the activities are development of application packages; testingand evaluation; characterization of biomass materials; etc. Present generation of biomass gasifier-dualfuel engine power packs can use a variety of woody biomass materials for power generation upto 500KW (electric) with around 80% diesel displacement. More versatile gasifiers, using powdery biomassare also reported to have been successfully tried. Rice husk, coconut shells, etc. are some othermaterials reported to have been successfully tried in gasifiers. The gasifiers are almost exclusively ofdown draft, atmospheric pressure design and are primarily designed for firing woody biomass. Somepreparation, especially sizing and moisture control of biomass, is necessary before firing into thereactors. The cooling/cleaning systems have also evolved considerably and at present gas qualitiessuitable for operation of dual fuel engines are being guaranteed. On the engine side, fully indigenousmanufacturing capabilities exist, in the capacities of interest. Around 1744 gasification systemsaggregating to 40 MW equivalent capacity has so far been installed in the country.

India is among the world leaders in biomass gasification technology. Though developmental effortsstarted only in early eighties, today there are atleast six manufacturers who offer state-of-art units ofupto 500 Kwe. Technology for these systems has been developed and commercialized indigenously,either with the support of Government or Central Research Institutions, or by the private sectormanufacturers themselves. Biomass Gasifiers manufactured in the country have been exported toUSA, countries in Asia, Europe and Latin America.

11.F.2 Proposed Power Plant from MSW in Chennai by EDL

Work on the construction of the 14.85 MW power plant from Municipal Solid Waste at Chennai isexpected to start in the first quarter of 2002. EDL India Pvt. Ltd., has undertaken to set up the planton a build-operate-own-basis, the plant is expected to start functioning during 2002-03. The company,


MWH Appendix 11F- 2

was working towards attaining the financial closure for the project which was expected to cost aroundRs. 180 crore, with a debt equity ratio of 70:30. The equity component will be met by EDL Australia(of which EDL India is a subsidiary) and its associates. The plant will be set up adjacent to the MSWdump at Perungudi (about 1,100 tonnes of garbage per day) in the southern outskirts of the city, on a15 acre plot of land leased to the company for 15 years by the Chennai Corporation. On its part, thecorporation will collect and supply 600 tonnes per day of garbage.

The municipal waste would be initially pre-treated by autoclaving with steam at 130 to 1500C tosterilise the waste and produce a pulp-like material.

The remaining pulp would fed be into a gasifier operating at 1100 0C in the absence of oxygen.

There is no creation of dioxins since the process is not exposed to air and there is no combustion orincineration. Dioxins are facing criticism from environmental groups across countries for causingdisruption of the human endocrine system.

The process breaks down the garbage into molecules of carbon, hydrogen, oxygen and nitrogen. Thiswill again be reformed to a synthesis gas, which will be used to fuel the power plant.

According to EDL, out of every tonne of garbage that will be fed into the plant 80 per cent will comeout as electricity, 10 per cent will be recycle material and 10 per cent will go for further reprocessing.

Since there would be no combustion, there would be no ash at the end of the process. The remainingchar is safe enough to be used as a soil additive for agriculture.

EDL Australia is in the process of setting up a similar plant in Wollongong, Australia which will beable to process 1.5 lakh tonnes of waste to generate electricity for 20,000 households.

11.F.3 Indirect Gasification Process (Esvin Advanced Technologies Ltd., Chennai,Tamil Nadu)

For Distillery Spentwash :

EsvinTech Ltd. has developed a package system for distillery spentwash involving IndirectGasification of the concentrated spentwash to produce a fuel gas and to recover the inorganics in drypowder form in a fluidized bed gasifier.

The innovative features of Esvin Tech’s indirect gasification technology are the following:

The inorganics in the spentwash is recovered from the fluidised bed in the dry powder form which canbe directly used as fertiliser.

It converts all the organic matter in the spentwash to clean medium-calorific value gas.The sulphur in the spentwash is recovered as sodium sulphide in contrast to pollution of air throughSO2

as in the case of incineration.

The inherently low NOx emissions make the pulse combustor an environmental friendly device.

A part of the gas generated in the process is refired in the pulse combustor to make the system fuelself-sufficient.


MWH Appendix 11F- 3

A net export gas is available from the system, which can be refired in an utility boiler to raise steamand in turn produce power or alternately the gas produced can be fired in a gas turbine directly tomake the effluent treatment plant to work as a cogeneration system.

The system is modular in nature and has high turn-down ratio, hence offering good operationalflexibility and also makes it an ideal system for capacity expansions.

Trials have been successfully completed in the demonstration plant consisting of a complete full-scalemodule of the gasification system (capable of handling spentwash from 30 KLD distillery) at SPB,Erode to validate the design basis for commercial prototype installations. The optimum size of thedistillery has been determined to be 60 KLD for a self-sufficient system giving a good balance ofsteam and power generation and requiring no auxiliary fuel to sustain the process.

The efforts of Esvin Tech to provide a package system for handling distillery spentwash with minimalgeneration residual secondary pollutants would certainly meet statutory stipulations. Thesetechnologies should be readily acceptable to some of the large distilleries in the country who cantackle their environmental pollution problems and benefit from economies of scale of operations, eventhough the former includes an additional intermediate step of drying. In summary, distilleries nowhave the option of implementing pollution control projects in a phased manner tackling each of theresidual pollutants by add-ons or alternatively a single-step technology for addressing the majorenvironmental problems of disposal of spentwash.

For Small Agro-based Paper Mills:

An innovative Indirect Gasification Technology jointly developed by Esvin Advanced TechnologiesLimited (Esvin Tech) and their American Principals M/s Manufacturing and Technology ConversionInternational (MTCI) Inc. claims to have made a breakthrough in handling straw based liquors(emanating from Agro-based paper mills using straw pulping process) which are difficult to handlethrough conventional combustion system. A full scale Demonstration Plant has been set up in SouthIndia in 1993 with the funding assistance of USAID offered through their PACT and EMCATProgrammes. Large quantities of Rice Straw Liquor were treated in this demo unit to establish thetechnical feasibility of the system to handle such spent liquor. This demo plant has been furtherperfected with the funding assistance from Ministry of Environment and Forest (MoEF), Govt. ofIndia under their Cleaner Technology Division. Figure 1 Shows the schematic diagram of ESVINGasification process evolved for caustic recovery from rice straw based paper mill black liquor.


MWH Appendix 11F- 4

11.F.4 Power From Solid Wastes Using Cyclone Gasifier

Scientist at the Combustion Gassification Propulsion Laboratory, Indian Institute of Science havedeveloped cyclone gassifiers which can utilise organic matter such as leaves, vegetable wastes andother materials which on dry basis have calorific values comparable to other biomass like wood foreither thermal or electrical power generation. Any combustible powdered material in reasonably dryform (moisture level of 15%) can be gassified to obtain producer gas in the cyclone gasifier.

Clean gas is produced which can be directly used in an IC engine

Extra energy required for briquetting is avoided

Material with high ash content can be handled.

Transportation of wastes for long distance is avoided.

The cyclone gasifier system consists of a cyclone reactor along with the feeding system, the ignitionsystem, the gas cooling and cleaning system or a gas burning system depending on whether the gas isused in an IC engine or for thermal applications. The cleaned gas has a calorific value of 4.5 – 5MJ/Nm3 and has a dust and tar level under 100 ppm. This gas can be used in a diesel engine to replace80% of the diesel. This route is economical and recommended when the power level is about 1 MWeor less.

At higher levels the gas can be utilised in a boiler to raise steam and generate power through the steamturbine route. This does not require cooling and cleaning of the gas.

Cyclone gasifiers have been satisfactorily used with rice husk, sugarcane trash, saw dust and othermaterials.


MWH Appendix 12A- 1

Appendix 12 AEC – Landfill Regulation

Council Directive 1999/31/EC of 26 April 1999 on the landfill of wasteOfficial Journal L 182 , 16/07/1999 p. 0001 – 0019

Text:

COUNCIL DIRECTIVE 1999/31/ECof 26 April 1999on the landfill of waste

The council of the european union, has adopted this directive

Article 1: Overall objective

1.With a view to meeting the requirements of Directive 75/442/EEC, and in particular Articles 3 and 4thereof, the aim of this Directive is, by way of stringent operational and technical requirements on thewaste and landfills, to provide for measures, procedures and guidance to prevent or reduce as far aspossible negative effects on the environment, in particular the pollution of surface water,groundwater, soil and air, and on the global environment, including the greenhouse effect, as well asany resulting risk to human health, from landfilling of waste, during the whole life-cycle of thelandfill.

2. In respect of the technical characteristics of landfills, this Directive contains, for those landfills towhich Directive 96/61/EC is applicable, the relevant technical requirements in order to elaborate inconcrete terms the general requirements of that Directive. The relevant requirements of Directive96/61/EC shall be deemed to be fulfilled if the requirements of this Directive are complied with.

Article 2: Definitions

2 (g)” Landfill” means a waste disposal site for the deposit of the waste onto or into land (i.e.underground), including

- internal waste disposal site (i.e landfill where a producer of waste is carrying its own wastedisposal at the place of production ), and

- a permanent site (i.e more than one year ) which is used for temporary storage of waste.

But exceeding :

- facilities where waste is unloaded to permit its preparation for further transport for recovery,treatment or deposal elsewhere, and

- storage of waste prior to recovery or treatment for a period less than three years as a generalrule, or

- storage of waste prior to disposal for a period less than one year;

Article 3: Scope1. Member States shall apply this Directive to any landfill as defined in Article 2(g).

2. Without prejudice to existing Community legislation, the following shall be excluded from thescope of this Directive:


MWH Appendix 12A- 2

- the spreading of sludges, including sewage sludges, and sludges resulting from dredgingoperations, and similar matter on the soil for the purposes of fertilisation or improvement,

- the use of inert waste which is suitable, in redevelopment/restoration and filling-in work, or forconstruction purposes, in landfills,

- the deposit of non-hazardous dredging sludges alongside small waterways from where they havebeen dredged out and of non-hazardous sludges in surface water including the bed and its sub soil,

- the deposit of unpolluted soil or of non-hazardous inert waste resulting from prospecting andextraction, treatment, and storage of mineral resources as well as from the operation of quarries.

Article 4: Classes of landfill

Article 5: Waste and treatment not acceptable in landfills

Article 6: Waste to be accepted in the different classes of landfill

Article 7: Application for a permit

Article 8: Conditions of the permit

Article 9 : Content of the permit

Article 10: Cost of the landfill of waste

Article 11: Waste acceptance procedures

Article 12: Control and monitoring procedures in the operational phase

Article 13: Closure and after-care procedures

Article 14: Existing landfill sites

Article 15: Obligation to report

Article 16: Committee

Any amendments necessary for adapting the Annexes to this Directive to scientific and technicalprogress and any proposals for the standardisation of control, sampling and analysis methods inrelation to the landfill of waste shall be adopted by the Commission, assisted by the Committeeestablished by Article 18 of Directive 75/442/EEC and in accordance with the procedure set out inArticle 17 of this Directive. Any amendments to the Annexes shall only be made in line with theprinciples laid down in this Directive as expressed in the Annexes. To this end, as regards Annex II,the following shall be observed by the Committee: taking into account the general principles andgeneral procedures for testing and acceptance criteria as set out in Annex II, specific criteria and/ortest methods and associated limit values should be set for each class of landfill, including if necessaryspecific types of landfill within each class, including underground storage. Proposals for thestandardisation of control, sampling and analysis methods in relation to the Annexes of this Directiveshall be adopted by the Commission, assisted by the Committee, within two years after the entry intoforce of this Directive.

The Commission, assisted by the Committee, will adopt provisions for the harmonisation and regulartransmission of the statistical date referred to in Articles 5, 7 and 11 of this Directive, within two


MWH Appendix 12A- 3

years after the entry into force of this Directive, and for the amendments of such provisions whennecessary.

Article 18 : Transposition

1. Member States shall bring into force the laws, regulations and administrative provisions necessaryto comply with this Directive not later than two years after its entry into force. They shall forthwithinform the Commission thereof.

When Member States adopt these measures, they shall contain a reference to this Directive or shall beaccompanied by such reference on the occasion of their official publication. The methods of makingsuch a reference shall be laid down by Member States.

2. Member States shall communicate the texts of the provisions of national law which they adopt inthe field covered by this Directive to the Commission.

Article 19 : Entry into force

This Directive will enter into force on the day of its publication in the Official Journal of theEuropean Communities.

Article 20: Addressees

This Directive is addressed to the Member States.

Done at Luxembourg, 26 April 1999.

ANNEX I

General Requirements for All Classes of Landfills

1. Location

2. Water control and leachate management

3. Protection of soil and water

4. Gas control

5. Nuisances and hazards

6. Stability

7. Barriers

ANNEX II

Waste Acceptance Criteria and Procedures

This work by the technical Committee, with the exception of proposals for the standardisation ofcontrol, sampling and analysis methods in relation to the Annexes of this Directive which shall beadopted within two years after the entry into force of this Directive, shall be completed within three


MWH Appendix 12A- 4

years from the entry into force of this Directive and must be carried out having regard to theobjectives set forth in Article 1 of this Directive.

1. General principles

2. General procedures for testing and acceptance of waste

3. Guidelines for preliminary waste acceptance procedures

4. Sampling of waste

ANNEX III

Control and Monitoring Procedures in Operation and After-Care Phases

The purpose of this Annex is to provide the minimum procedures for monitoring to be carried out tocheck:

• that waste has been accepted to disposal in accordance with the criteria set for thecategory of landfill in question,

• that the processes within the landfill proceed as desired,

• that the environmental protection systems are functioning fully as intended,

• that the permit conditions for the landfill are fulfilled.

1. Meteorological data

2. Emission data: water, leachate and gas control

3. Protection of groundwater

A. Sampling

B. Monitoring

C. Trigger levels

4. Topography of the site: data on the landfill body


MWH Appendix 12B- 1

Appendix 12 BUSEPA – Landfill Regulation

The Resource Conservation and Recovery Act (RCRA) Subtitle D approach uses a combination ofdesign and performance standards for regulating MSW landfills. USEPA’s Subtitle D rule, publishedOctober 9, 1991, also establishes facility design and operating standards, groundwater monitoring,corrective action measures, and conditions (including financial requirements) for closing municipallandfills and providing post-closure care for them. A phased implementation of the regulations beganon October 9, 1993. A current version of 40 CFR Parts 257 and 258 should be consulted to determinethe applicable deadline dates for each type and size of municipal landfill. State programs for landfillregulation are required by Sub-title D to incorporate the federal regulations into the state codes.Recommended practices described in this chapter are consistent with Subtitle D rule requirements.State regulations under Subtitle D may be flexible to accommodate local conditions.

RCRA creates a framework for federal, state, and local government cooperation in controlling thedisposal of municipal solid waste. While the federal landfill rule establishes national minimumstandards for protecting human health and the environment, implementation of solid waste programsremains largely the responsibility of local, state, or tribal governments. Under the authority of RCRA,the USEPA regulates the following:

• Location Restrictions: airport safety, flood plains, wetlands, fault areas, seismic impactzones, unstable areas

• Design Criteria: liners and groundwater protection

• Groundwater Monitoring and Corrective Action: groundwater monitoring systems,groundwater sampling and analysis, detection monitoring, assessment monitoring, assessmentof corrective measures, selection of remedy, implementation of corrective action program

• Closure and Post-Closure Care: closure criteria, post-closure care requirements

• Financial Assurance Criteria: financial assurance for closure, financial assurance for post-closure care, financial assurance for corrective action

• Operating Criteria: procedures for excluding hazardous waste, cover materials, diseasevector controls, explosive gasses control, air criteria, access requirements, run-on/run-offcontrol, surface water requirements, liquids restrictions, record keeping.

State and Local Requirements

State regulations vary widely, but usually landfill engineering plans are submitted to the appropriatestate-level regulatory body for review and approval. State standards are ordinarily more extensive thanRCRA standards and ad-dress concerns specific to a particular geographic region. Procuring thevarious permits required to open and operate a landfill may take several months to several years,especially if there is public controversy regarding the site. Five-to-seven-year planning and permittingperiods are becoming more common. State or local governments may require:

• a solid waste landfill plan approval

• a conditional-use zoning permit

• a highway department permit (for entrances on public roads and in-creased traffic volume)

• a construction permit (for landfill site preparation)

• a solid waste facilities permit


MWH Appendix 12B- 2

• a water discharge/water quality control permit

• an operation permit (for on-going landfill operations)

• a mining permit for excavations

• building permits (to construct buildings on the landfill site)

• a fugitive dust permit

• an air emission permit

• a closure permit.

Other federal agencies have established standards that will also affect the identification of potentialsites. For example, Federal Aviation Administration Order 5200.5 establishes a zone within whichlandfill design and operational features must be used to prevent bird hazards to aircraft. Owners oroperators proposing to locate a new landfill or a lateral expansion within a five-mile radius of apublic-use airport must notify the affected airport and the FAA.


MWH Appendix 12C- 1

Appendix 12 C

India – Landfill Regulation

Regulation for Indian Landfill Sites

Site Selection

1. In areas falling under the jurisdiction of "Development Authorities' it shall be the responsibility ofsuch Development Authorities to identity the landfill sites and hand over the sites to the concernedmunicipal authority for development, operation and maintenance. Elsewhere, this responsibility shalllie with the concerned municipal authority.

2. Selection of landfill sites shall be based on examination of environmental issues. The Departmentof Urban Development of the State or the Union territory shall co-ordinate with the concernedorganisations for obtaining the necessary approvals and clearances.

3. The landfill site shall be planned and designed with proper documentation of a phased constructionplan as well as a closure plan.

4. The landfill sites shall be selected to make use of nearby wastes processing facility. Otherwise,wastes processing facility shall be planned as an integral part of the landfill site.

5. The existing landfill sites which continue to be used for more than five years, shall be improved inaccordance of the specifications given in this Schedule.

6. Biomedical wastes shall be disposed off in accordance with the Bio-medical Wastes (Managementand Handling) Rules, 1998 and hazardous wastes shall be managed in accordance with the HazardousWastes (Management and Handling) Rules, 1989, as amended from time to time.

7. The landfill site shall be large enough to last for 20-25 years.

8. The landfill site shall be away from habitation clusters, forest areas, water bodies, monuments,National Parks, Wetlands and places of important cultural, historical or religious interest.

9. A buffer zone of no-development shall be maintained around landfill site and shall be incorporatedin the Town Planning Department's land-use plans.

10. Landfill site shall be away from airport including airbase. Necessary approval of airport or airbaseauthorities prior to the setting up of the landfill site shall be obtained in cases where the site is to belocated within 20 km of an airport or airbase.

Facilities at the site

11. Landfill site shall be fenced or hedged and provided with proper gate to monitor incomingvehicles or other modes of transportation.

12. The landfill site shall be well protected to prevent entry of unauthorised persons and stray animals.

13. Approach and other internal roads for free movements of vehicles and other machinery shall existat the landfill site.


MWH Appendix 12C- 2

14. The landfill site shall have wastes inspection facility to monitor wastes brought in for landfill,office facility for record keeping and shelter for keeping equipment and machinery including pollutionmonitoring equipments.

15. Provisions like weighbridge to measure quantity of waste brought at landfill site, fire protectionequipments and other facilities as may be required shall be provided.

16. Utilities such as drinking water (preferably bathing facilities for workers) and lightingarrangements for easy landfill operations when carried out in night hours shall be provided.

17. Safety provisions including health inspections of workers at landfill site shall be periodicallymade.

Specifications for land filling

18. Wastes subjected to land filling shall be compacted in thin layers using landfill compactors toachieve high density of the wastes. In high rainfall areas where heavy compactors cannot be usedalternative measures shall be adopted.

19. Wastes shall be covered immediately or at the end of each working day with minimum 10 cm ofsoil, inert debris or construction material till such time waste processing facilities for composting orrecycling or energy recovery are set up as per Schedule I.

20. Prior to the commencement of monsoon season, an intermediate cover of 40-65 cm thickness ofsoil shall be placed on the landfill with proper compaction and grading to prevent infiltration duringmonsoon. Proper drainage berms shall be constructed to divert run-off away from the active cell of thelandfill.

21. After completion of landfill, a final cover shall be designed to minimize infiltration and erosion.The final cover shall meet the following specifications, namely :-

(a) The final cover shall have a barrier soil layer comprising of 60 cms. of clay or amended soil withpermeability coefficient less than 1 x 10-7 cm/sec.

(b) On top of the barrier soil layer, there shall be a drainage layer of 15 cm.

(c) On top of the drainage layer, there shall be a vegetative layer of 45 cm to support natural plantgrowth and to minimize erosion.

Pollution prevention

22. In order to prevent pollution problems from landfill operations, the following provisions shall bemade, namely :-

(a) Diversion of storm water drains to minimize leachate generation and prevent pollution of surfacewater and also for avoiding flooding and creation of marshy conditions.

(b) Construction of a non-permeable lining system at the base and walls of waste disposal area. Forlandfill receiving residues of waste processing facilities or mixed waste or waste havingcontamination of hazardous materials (such as aerosols, bleaches, polishes, batteries, waste oils, paintproducts and pesticides) minimum liner specifications shall be a composite barrier having 1.5 mmhigh density polyethylene (HDPE) geomembrane, or equivalent, overlying 90 cm of soil (clay or


MWH Appendix 12C- 3

amended soil) having permeability coefficient not greater than 1 x 10-7 cm/sec. The highest level ofwater table shall be at least two meter below the base of clay or amended soil barrier layer;

(c) Provisions for management of leachates collection and treatment shall be made. The treatedleachates shall meet the standards specified in Schedule - IV;

(d) Prevention of run-off from landfill area entering any stream, river, lake or pond.

Water Quality Monitoring

23. Before establishing any landfill site, baseline data of ground water quality in the area shall becollected and kept in record for future reference. The ground water quality within 50 meters of theperiphery of landfill site shall be periodically monitored to ensure that the ground water is notcontaminated beyond acceptable limit as decided by the Ground Water Board or the State Board orthe Committee. Such monitoring shall be carried out to cover different seasons in a year that is,summer, monsoon and post-monsoon period.

24. Usage of groundwater in and around landfill sites for any purpose (including drinking andirrigation) is to be considered after ensuring its quality. The following specifications for drinkingwater quality shall apply for monitoring purpose, namely :-

S. No. Parameters IS 10500: 1991 Desirable limit(mg/I except for pH)

1. Arsenic 0.05

2. Cadmium 0.01

3. Chromium 0.05

4. Copper 0.05

5. Cyanide 0.05

6. Lead 0.05

7. Mercury 0.001

8. Nickel -

9. Nitrate as NO3 45.0

10. pH 6.5-8.5

11. Iron 0.3

12. Total hardness (as CaCO3) 300.0

13. Chlorides 250

14. Dissolved solids 500

15. Phenolic compounds (as C6H5OH) 0.001

16. Zinc 5.0

17. Sulphate (as SO4) 200


MWH Appendix 12C- 4

Ambient Air Quality Monitoring

25. Installation of landfill gas control system including gas collection system shall be made at landfillsite to minimize odour generation, prevent off-site migration of gases and to protect vegetationplanted on the rehabilitated landfill surface.

26. The concentration of methane gas generated at landfill site shall not exceed 25 per cent of thelower explosive limit (LEL).

27. The landfill gas from the collection facility at a landfill site shall be utilized for either directthermal applications or power generation, as per viability. Otherwise, landfill gas shall be burnt(flared) and shall not be allowed to directly escape to the atmosphere or for illegal tapping. Passiveventing shall be allowed if its utilisation or flaring is not possible.

28. Ambient air quality at the landfill site and at the vicinity shall be monitored to meet the followingspecified standards. namely :-

S. No. Parameters Acceptable levels

(i) Sulphur dioxide 120 --/m3 (24 hours)

(ii) Suspended ParticulateMatter 500 --g/m3 (24 hours)

(iii) Methane Not to exceed 25 per cent of the lower explosive limit(equivalent to 650 mg/m3)

(iv) Ammonia daily average(Sample duration 24 hrs) 0.4 mg/m3 (400 --g/m3)

(v) Carbon monoxide 1 hour average : 2 mg/m3

8 hour average : 1 mg/m3

29. The ambient air quality monitoring shall be carried out by the concerned authority as per thefollowing schedule, namely:-

(a) Six times in a year for cities having population of more than fifty lakhs;

(b) Four times in a year for cities having population between ten and fifty lakhs.

(c) Two times in a year for town or cities having population between one and ten lakhs.

Plantation at Landfill Site

30. A vegetative cover shall be provided over the completed site in accordance with the followingspecifications, namely :-

(a) Selection of locally adopted non-edible perennial plants that are resistant to drought and extremetemperatures shall be allowed to grown;

(b) The plants grown be such that their roots do not penetrate more than 30 cms. This condition shallapply till the landfill is stabilised;

(c) Selected plants shall have ability to thrive on low-nutrient soil with minimum nutrient addition;


MWH Appendix 12C- 5

Closure of Landfill Site and Post-care

31. The post-closure care of landfill site shall be conducted for at least fifteen years and long termmonitoring or care plan shall consist of the following, namely :-

(a) Maintaining the integrity and effectiveness of final cover, making repairs and preventing run-onand runoff from eroding or otherwise damaging the final cover;

(b) Monitoring leachate collection system in accordance with the requirement;

(c) Monitoring of ground water in accordance with requirements and maintaining ground waterquality;

(d) Maintaining and operating the landfill gas collection system to meet the standards.

32. Use of closed landfill sites after fifteen years of post-closure monitoring can be considered forhuman settlement or otherwise only after ensuring that gaseous and leachate analysis comply with thespecified standards.

Special provisions for hilly areas

33. Cities and towns located on hills shall have location-specific methods evolved for final disposal ofsolid wastes by the municipal authority with the approval of the concerned State Board or theCommittee. The municipal authority shall set up processing facilities for utilization of biodegradableorganic wastes. The inert and non-biodegradable waste shall be used for building roads or filling-upof appropriate areas on hills. Because of constraints in finding adequate land in hilly areas, wastes notsuitable for road laying or filling up shall be disposed of in specially designed landfills.


MWH Appendix 12D- 1

Appendix 12 D

UK– Landfill Tax

UK Landfill Tax and Environmental Bodies (1999)

As part of move towards environmentally focused taxation in the UK, a landfill tax of £7 per tonne foractive waste and £2 per tonne for inactive waste was introduced, through provisions made in theFinance Act 1996, on 1 October 1996. In the March 1998 budget, the standard rate was raised to £10per tonne, which took effect from 1 April 1999, whilst the lower rate for inactive waste was frozen at£2 per tonne. In the March 1999 budget the standard rate was given a yearly increase, or 'landfillescalator', of £1 per tonne per year for a period of 5 years (culminating in a rate of £15 per tonne in2004/5). Inert wastes used in the restoration of landfill sites and quarries are to be exempt from 1October 1999. Much of the income from the tax helps to pay for reductions in employers' labour costs,by funding a reduction in the main rate of employers' National Insurance contributions (this reductionbeing announced in the 1995 budget, and taking effect from April 1997). As such, the landfill tax is agood example of 'green' taxation, in that it shifts the burden of tax from labour onto the consumptionof resources.

For environmental organisations, a potential bonus lies in the detail of the Landfill Tax, as set out inthe Landfill Tax Regulations 1996. This is the provision for landfill operators to claim a credit for upto 20% of their tax liability, if it is voluntarily donated to approved Environmental Bodies (EBs)through the Landfill Tax Credit Scheme. Up to £100 million a year could be made available forapproved environmental purposes, provided landfill operators provide some cash support as well, inthe ratio of £1 cash to release a credit for £9 from their tax liability. In essence, if you can gain £1000cash support from a landfill operator, they can claim back £9,000 from their landfill tax liabilitywhich they would pay directly to you to make your project worth £10,000.

Criteria for approval are set out in the Landfill Tax Regulations, which describes a number ofapproved purposes (or 'object' ) within which EBs can work. The approved objects, given in section33(2) of the regulations, include:

• The provision of education, information or research and development to encourage the use ofsustainable waste management practices such as waste reduction and recycling (object C).

• The creation of wildlife habitats or conservation areas in the vicinity of a landfill site (objectD).

• Remediation, restoration and amenity improvement of past waste management sites or otherindustrial activities which, in their present state, are not able to support economic or socialactivity (objects A and B).

• Maintenance, repair or restoration of religious, historic or architecturally interestingbuildings in the vicinity of a landfill site (object E).

It is object C of the regulations which relates directly to waste management. Recent amendments toobject C has meant that, from 1 January 2000, approval may be given to activities which encouragethe development of products from waste, or markets for recycled waste.

Two key points of the Landfill Tax Credit Scheme to recognise are:

1. donating landfill operators are not allowed to gain direct benefits from their donations, and;

2. it does not remove from landfill operators the legal duties they have to remediate sites underpresent environmental legislation.


MWH Appendix 12D- 2

In reality, unlocking a potential £100 million for environmental projects would rely on landfilloperators providing up to £10 million in hard cash each year. While this is very unlikely to happen,some landfill operators will recognise the potential for levering up cash for projects as part of theirown investment in community activities. As such, £224 million (representing 73% of the maximumpotential credits of £305 million) has been claimed in credits since commencement of the Scheme inOctober 1996 up until April 2000. In this connection, a number of national environmentalorganisations are negotiating projects with the major waste management companies that operatelandfill sites. Much potential also exists for local projects to contact local and regional landfilloperators, especially with a view to match funding Local Projects Fund applications andEnvironmental Action Fund grants.

The job of identifying landfill operators to support your work should be treated in the same way asyou would approach any private company for support - with researched and targeted proposals basedon need. However, remember that in some cases, part of your approach will involve promoting theideas behind EBs to a landfill operator that may be quite new to the world of project sponsorship andcommunity affairs. The challenge is great but the rewards could be even greater.


MWH Appendix 15A -1

Appendix 15-A

Pre-Treatment and Recovery of Valuable Materials from Municipal Solid Waste

It is necessary to separate out reusable and recyclable material from MSW either at the source ofgeneration or at a material recovery facility (MRF). A list of unit operations used for the purpose ofrecovering valuable materials from MSW is given in Table 15A.1.

Table 15A.1: Unit Operations for Pretreatment and Sorting of MSW

Unit Operation Function

Shredding

Hammer Mills Size reduction/all types of wastes

Flail mills Size reduction, also used as bag breaker/all types of wastes

Shear shredder Size reduction, also used as bag breaker/ all types of wastes

Glass crushers Size reduction/ all types of glass

Wood grinders Size reduction and trimmings/ all types of wood wastes

Screening Separation of over and under sized material, trommel alsoused as bag breaker/ all types of wastes

Cyclone separator Separation of light combustible materials from airstream/prepared wastes

Density separation

(air classification)

Separation of light combustible materials from air stream

Magnetic separation Separation of ferrous metal from commingled wastes

Densification

Bailers Compaction into bales/paper, cardboard, plastics, textiles,aluminum

Can crushers Compaction and flattening/aluminum and tin cans

Wet separation Separation of glass and aluminum

Weighing facilities Operational records

Unit operations used for the separation and processing of separated and commingled wastes aredesigned (1) to modify the physical characteristics of the waste so that waste components can beremoved more easily, (2) to remove specific components and contaminants from the waste stream,and (3) to process and prepare the separated materials for subsequent uses.

Flow diagrams must be developed for the separation of the desired materials and for processing thematerials, subject to predetermined specifications. A process flow diagram for a MRF is defined asthe assemblage of unit operations, facilities and manual operations to achieve the following specificgoals. (1) identification of the characteristics of the waste materials to be processed, (2) specificationsfor recovered materials, and (3) the available equipment and facilities. A typical process flow diagramfor a MRF employing manual and mechanical separation of materials from MSW is illustrated inFigure 15A.1.


MWH Appendix 15A -2

Figure 15A.1 Process Flow Diagram for separating and recovering valuables from municipalsolid waste

Source: Integrated solid waste management Tchobanoglous G, Theisen H and Vigil S.A. , McGraw Hill (1993)

The major separation equipment consists of shear shredder, trommel screen, vibrating screen,magnetic separator, air classifiers, cyclone and a system of conveyors. There is a wide choice of suchequipment from several vendors, who supply all material handling and separation units for mineral,cement, coal, fertiliser and allied industries/applications. Selection of the various equipment andaccessories for the separation/ recovery of materials from municipal solid waste involves a judiciousexercise of selecting and matching process/duty requirements from locally available designs andspecifications of standard units.


MWH Appendix 16A-1

Appendix 16-A

List of Plant and Machinery for MSW Biomethanation Plant

A. Plant and Machinery

Sr. No. Equipment

1 Conveyors (Inter-stage)

a. Lift Conveyor

b. Sorting belt

c. Uptake belt

d. Reject Belt

e. Shredded Sieved Material Belt

2 Pumps

a. Drain Pit Pump

b. Filter Pump

c. Drain Pump

d. Fresh Water Pump

e. Sludge Pump

3 Bunker (fabricated Item)

4 Refining Sieve

5 Chain Conveyor

6 Dosing Screw Conveyors(2, 3, 4 m)

7 Waste Gas Burner

8 Flocculation System

- Floc. Prep. Unit

- Dosing Pump

- Flocculator

9 Pressure Relief Valve

10 Mixing unit

- In MSW section

- In Compost section

11 Piping & Valves(Gas Liquid Composting)

12 Container for compost

13 Sediment Trap & others

14 Screw Conveyors (8, 10,12 m lengths)

15 Gas Holder (Fabricated steel)


MWH Appendix 16A- 2

Sr. No. Equipment

16 Gas Holder Hardware

17 Dosing Unit

18 Storage Tank

19 Hydraulic Unit for Feed Pumps

20 Biogas Boosters

21 NaOH dosing system

22 Pressure Relief Valve Rupture Type

23 Aerators

24 Clarifier

25 Housing

26 Structural Support

27 Rotary Screen

28 Flame arrestors

29 H2S Scrubber

30 Temperature indicators (Dial Type)

31 Pressure gauges (pumps, blower)s

32 Gas Flow Meter (each Reactor)

33 Fresh Water meter

34 MCC Electricals

35 Gas Supply

36 Waste Heat Recovery Boiler

36 Centrifuge (capacity10 Cum/Hr)

38 Vibrating Screen

39 Homogenisation Drum

40 Oil Storage Tank

41 Blowers for Maturation Sec.

42 Diesel Storage Tank

43 Magnetic Belt

44 Trucks and Forklifts


MWH Appendix 16A- 3

B. Particulars of Indigenous Machinery

Sr. No. Equipment

1 Ventilation System (Power Plant)

2 Piping fittings, valves, pumps, ducting for utilities and exhaust gas system

3 Instrumentation

4 DM Plant

5 Crane

6 DG Set (300 KVA capacity)

7 NGR

8 Transformer 3.3/11KV (ONAN type, with On Load Tap changer

9 Station Transformer 3.3/0.43 KV off circuit tap changer

10 3.3KV & 11 KV Switchgear

11 Cables (HT & LT)

12 415V, Switchgear

13 P.M.C.C.

14 Potential and current transformer in switchyard

PT (75 VA burden)

CT (75 VA burden)

15 Battery and battery charger

16 Lightning arrester

17 Master Control Panel

18 Switchyard including metering unit

19 Overhead Line - 11 KV,

20 MCC Electricals

C. Details of Imported Plant & Machinery

Sr. No. Equipment

1 Feed Pumps

2 Press

3 Engine with Alternator #

4 Spares for genset

National Master Plan for Development of Waste-to-Energy in IndiaAddendum for Technical Memorandum on Waste-to-Energy Technologies

MWH Addendum 2- 1

1. Capital cost data for four gasification technology options for MSW gasification systems hasbeen compared. As discussed during the Banagalore meeting, "Evaluation of Gasification andNovel Thermal process for the Treatment of MSW, National renewable energy Laboratory,Colorado, USA, August 1996" is the data source used for this purpose and same isreproduced below.

S.No Technology Reference1 Termiska Processor Table 4.12 Proler Table 5.13 Battelle Table 7.14 Thermochem Table 9.1

The above cost data have been suitably amended by using appropriate correction factor(Process Industry economic- An International Perspective by David Brennan, Institution ofChemical Enginneers, 1998) to take into account engineering, equipment and constructioncosts for a preliminary estimate of similar projects to be proposed for India. The correctionfactor for engineering, equipment and construction are 0.6,0.99 and 0.49 respectively

The Table Addendum 2-1 gives a preliminary estimate of gasification technology options forIndia based on the above analysis.

S.No Technology Engineering Equipment Construction Total

US $ INRCrores

US $ INRCrores

US $ INRCrores

MillionUS $

INRCrores

1 Termiska 13125000 39.38 153800000 761.31 3750000 9.19 170.675 809.872 Proler 13300000 39.90 153825000 761.43 167.125 801.333 Battelle 2892000 8.68 77640000 384.32 80.532 392.994 Thermochem 482000 14.53 86891000 430.11 91.733 444.63

The total plant capacity and expected net power generation potential of the Four abovementioned technologies are presented in Table Addendum 2-2.

S.No Technology Plant Capacity Net Power Cost / MW

1 Termiska 1760 54.85 14.76

2 Proler 1370 51.43 15.58

3 Battelle 935 28.05 14.01

4 Thermochem 935 32.34 13.75

Therefore, the average cost / MW for gasification technology is Rs 14.53 Crores.

MSW gasification projects presently promoted in India (Chennai, Mumbai Projects) involveCapital investment of Rs 12.12 and 11.42 Crores per MW which is 15 to 20 % less compareto the average cost of similar projects estimated by NREL,USA.


MWH Addendum 2- 2

2. A detailed cost breakup of MSW biomethanation project coming up at Lucknow wasreviewed in an effort to ascertain the cost of major steps – MSW Preparation / Upgradation,Biomethnation and Power generation. The cost of pretreatment steps could not beapportioned since most costs other than the main equipment like Civil, Mechanical, Piping,Instrumentation etc., are given for the total project.

3. In view of the cost estimates illustrated above, the capital cost included in Table 16.1 and16.2 of the Technical Memorandum on WTE Technologies for MSW gasification projectscan be considered to be reliable.

4. The data in Table 16.1 for Biomethnation projects at Lucknow and Incineration project atHyderabad has been revised and details of the Vijayawada project has been included based oninputs received from MNES for these projects.


MWH Addendum 1 - 1

Figure 15.3: Mass Balance Diagram – Biomethanation Technology - Capacity 500 TPD (Thermophillic High Solids Dry Basis)

Note : Organic Fraction of MSW 36 % (Wet basis)

Conveyor

Steam 171

Exhaust Gas

52500 Nm3/d Biogas

DewateringUnit

MagneticSeparation

Trommel Screen Conveyor Ballisticseparator

Flare

HomogenisingDrum

(>180 mm)

50(Landfill / Recyclable)

146

40-180mm63 TPD(Landfilling / Recyclable)

1 (Recyclable)

Gas Storage(500 m3)

Dual Fuel Engine Power(5.0 MW)

3753760

Digester feedHydraulic Unit Mixing Unit

300(<40mm)

83 to (Landfill)

300

Con

veyo

r

Conveyor

496

ManualInspection


500

MSW

83

Waste Heat Recovery

Air

200

175

10

Centrifuge

Recirculation 3290

Wastewater

165 m3/D

ETP To Disposal

Sew

age/

Fre

sh W

ater

210

VibratingScreen

<12mm

170Aerobic Maturation Compost 125

>12mm40 Recyclable AIR+EXCESS HEAT FROM HEAT RECOVERY

299

Units: TPD

Water205 m3/day

Air

POWER GENERATION

ANAEROBIC DIGESTION

POST -TREATMENT

PRE -TREATMENT


Digester4 x 5540 m3


MWH Addendum 1 -2



1516

BOILER WATER TREATMENT

MSW PROCESSINGINERT

REMOVALPLUG SCREW

FEEDER GASIFICATION GAS COOLING

POWER GENERATION

INERT LANDFILL

10 11 13 12 14 62 21 23 25

1

2 4 7 20 2430

5

3

8

9

RAW WATER

(WASTE HEAT RECOVERY)

EXHAUST

RECYCLE


MWH Addendum 1-3



301498

82

Landfill8240-180 mm

146

Conveyor

Stack

Ash25

Power(6.2 MW)

ConveyorMagneticSeparator

Trommel Screen Ballisticseparator

>180 mm

50 (Landfilling / Recyclable)

(Recyclable)1

<40mm - 302

ManualInspection


500MSW

RDF INCINERATION/POWER

POST TREATMENT

PRE TREATMENT

Screw Press

118 m3/DWastewater

PelletiserRDF Pellets183

(CV 4000 kcal / kg)

Fluidized BedIncinerator/Boiler(70 % efficiency)

Steam Turbine(25 % efficiency)

MultipleCyclonesESPScrubber

HomogenizingDrum 64

(Landfill/Recycling)

302

UNITS -TPD


MWH Addendum 1 -4

Revised Section 15.3

A summary of Power generation potential utilizing MSW by different technologies is given inTable 15.4

Table 15.4 Summary of Energy Generation Potential of MSW WTE technologies

S.No Technology Energy Generation Potential

(MW/100 TPD Unsorted MSW)

1 Biomethanation 1

2 Gasification 2

3 Incineration of RDF 1.2

4 Landfill with Gas Recovery 0.4

Note: Organic Fraction of MSW is equivalent to 36 % (Wet Basis)

Power generation potential of Indian MSW is 1 MW/100 TPD. This is comparable to the potential of 1.1 to1.2 MW/100 TPD unsorted MSW considered abroad for biomethanation process.

Generally, gasification of MSW leads to 70-80 % of the energy inherent in the feedstock to be recovered asenergy in the product (gas, oil or solid). The net energy output of a gasification plant will be 2.0 MW per100 tonnes of unsorted MSW processed.

The use of RDF pellets, derived from MSW, has the potential to generate upto 1.24 MW electricity per 100TPD of unsorted MSW.

Power generation potential for LFG will be 0.4 MW per 100 TPD unsorted MSW.

A sewage treatment plant (capacity 10 MLD) has the potential to generate 1,050 Nm3/day of biogas, whichin turn can be used to generate 150 kW power. This plant also has a potential to save upto 53 kW powercompared to conventional activated sludge process.