The Biomass energy

8/6/2019 The Biomass energy

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Biomass Energy Page 1

1.INTRODUCTIONToday we face a serious problem of depletion of essential resources, despite the fact that

most humans have little access to them. Depletion of resources has played a role in the

collapse of past civilizations and now threatens to lead to the collapse of global society as a

whole. It is possible; however, adopt measures leading to sustainable use of resources. Not

all are simple measures, of course, but it is urgent to begin to implement, as claimed by the

Worldwatch Institute, with a mobilization and in times of war.

The depletion of many resources vital to our species-a result of dilapidation or destruction,

the result of predatory behavior consciously or unconsciously guided by the pursuit of

private benefits in the short term is one of the most troubling problems of the current

situation planetary emergencies

In other words, we face a serious problem of depletion of essential resources, although most

human beings have little access to them. Depletion of resources has played a role, although

not exclusive to the collapse of past civilizations and now threatens to drive the collapse of

global society as a whole (Diamond, 2006). And what are the key resources whose

depletion is posing problems?

In recent years, environmentalists and policymakers have struggled toevaluate the merits of

various biomass resources. This has posed an enormous challenge, in part, because biomass

brings together a host of environmental disciplines, including air, water, land-use, climate,

and energy. Since few people have expertise in all of these areas, the full range of

environmental impacts both positive and negative are not as readily apparent for

biomass as they are for solar, wind, or traditional fossil resources. As a result,

Sufficient, reliable sources of energy are a necessity for

industrialized nations. Energy is used for heating,cooking, transportation and manufacturing. Energy can

be generally classified as non-renewable and renewable.

Over 85% of the energy used in the world is from non-

renewable supplies. Most developed nations are

dependent on non-renewable energy sources such as

fossil fuels (coal and oil) and nuclear power. These

sources are called non-renewable because they cannot

be renewed or regenerated quickly enough to keep pace

with their use. Some sources of energy are renewable or

potentially renewable. Examples of renewable energy

sources are: solar, geothermal, hydroelectric, biomass,

and wind. Renewable energy sources are more

commonly by used in developing nations.


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envi nment l l e and small approach the topic of biomass with exceeding

caution despite the factthat biomass has the potentialto be one ofthe few carbon-neutral

and renewable energy resources thatis available on demand and has large-scale,

commercially viable applications.

Bioenergy is the conversion of biomass resources such as agricultural and forest residues,

organic municipal waste and energy crops into useful energy carriers including heat,electricity and transport fuels. Forthousands of years firewood was the traditional source of

heat for domestic purposes - local heating and food preparation - and this is stillthe case in

many parts ofthe world. Today, the availability of biomass-derived solid fuels in clean and

convenient forms (e.g. chi ps, pellets and bri uettes) and modern combustion equipment

have created renewed interest in the use of solid biofuels for domestic heating. For the

commercial and industrial sectors, available equipment allows the efficient production of

heat from biofuels on a larger scale. The EU target is to achieve some 2.6 exajoules (or

1018 joules) of biomass-derived heat annually by 2010.

Biomass electricity generation, or biopower, is a multi-stage process that converts non-

fossil fuel-derived organic material into electricity. Biomass can also be used to produce

fuels biofuels that can be used in vehicles. Because the vegetation thatis the base for all

biomass can be regrown, biopower and biofuels can be renewable. This means that

biopower and biofuels can help reduce our dependency on fossil fuels and nuclear power. If

the biomass is regrown, then it will sequester all ofthe carbon dioxide released when the

biomass is burned. This means that biopower and biofuels can hel p reduce the risks of

climate change. Furthermore, since biomass can be stored and burned when needed,

biopower can be available on demand, unlike wind and solar which are only available when

the wind blows and the sun shines. A 1997 Energy Innovations report from a group ofenvironmental organi ations forecasts that by 2030 with proper incentives, biomass could

provide more than half of all renewable energy in our economy and over 15% of all our

energy needs.

The greatest challenge to policies intended to promote biomass is targeting them toward the

environmentally preferable forms of biomass. To shed light on this question, a coalition of

major environmental groups have crafted and endorsed a statutory definition that maximi es

the clean and renewable energy potential of biomass projects. By adopting this definition,

states have an opportunity to hel p shape the future of biomass industry and ensure that

biomass technology is implemented in a way that maximi es its clean and renewablepotential.


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2.OVERVIEWBiomass is defined as any organic matterthatis available on a renewable or recurring basis.

It includes all plants and plant derived materials, including agricultural crops and trees,

wood and wood residues, grasses, aquatic plants, animal manure, municipal residues, and

other residue materials. Plants (on land or in water) use the light energy from the sun to

convert water and carbon dioxide to carbohydrates, fats, and proteins along with small

amounts of minerals. The carbohydrate component includes cellulose and hemi-cellulose

fi bers which gives strength to plant structures and lignin which binds the fibers together.

Some plants store starches and fats (oils) in seeds or roots and simple sugars can be found in

planttissues.

Biomass energy is derived from five distinct energy sources: garbage, wood, waste, landfill

gases, and alcohol fuels. Wood energy is derived both from direct use of harvested wood as

a fuel and from wood waste streams. The largest source of energy from wood is pulping

liquor or blackliquor, a waste product from processes ofthe pulp, paper and paperboard

industry. Waste energy is the second-largest source of biomass energy. The main

contributors of waste energy are municipal solid waste (MSW), manufacturing waste, and

landfill gas. Biomass alcohol fuel, or ethanol, is derived primarily from sugarcane and corn.

It can be used directly as a fuel or as an additive to gasoline.

In 2009, biomass production contributed 3.9 quadrillion Btu of energy to the 73.1

quadrillion Btu of energy produced in the United States or about 5.3% of total energy

production. Since a substantial portion of U.S. energy is imported, the more commonly

quoted figure is that biomass consumption amounted to 3.9 quadrillion Btu of energy ofthe

94.7 quadrillion Btu of energy consumed in the United States in 2009 or about 4.1%. Atpresent, wood resources contribute most to the biomass resources consumed and most of

thatis used in the generation of electricity and industrial process heat and steam.

However, the contribution of biofuels has nearly trippled since 2005 and now accounts for

about 40% of all biomass consumed. While most biofuels feedstocks are currently starches,

oils and fats derrived from the agricultural sector, whole plants and plant residues will soon

be an important feedstock for cellulosic biofuels. Algae are being developed as a source of

both oil and cellulosic feedstocks. The industrial sector (primarily the wood products

industry) used about 2.0 quadrillion Btu in 2009. The residential and commercial sectors

consume 0.05 quadrillion Btu of biomass; however, this figure may understate consumptionin these sectors due to unreported consumption, such as home heating by wood collected on

private property. The use of biomass fuels such as ethanol and biodiesel by the

transportation sectoris now at about 0.9 quadrillion Btu. This is less than the total amount

of biofuels produced because some liquid biofuels are used by other sources.

Biomass, in addition to being convertible into energy carriers, can also be converted into

biomaterials and biochemicals. The simultaneous production of bioenergy, biomaterials and


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biochemicals takes place in biorefineries. In a biorefinery, analogous to a petroleum

refinery, biomass feedstocks are converted into energy, fuels or other products using a range

of thermochemical and biochemical processes. Some of these techniques are already at a

stage of commercial development while others require further research and technological

development.

To stimulate progress in this direction, the Department of Energys (DOE) BiomassProgram began awarding cost-sharing contracts in 2007 to companies forthe development

of integrated biorefineries using cellulosic biomass. As of December 2010, there were 6

commercial biorefineries, 12 pilot biorefineries, 9 demonstration biorefineries and 2

research and development biorefineries. The names, locations and details of these

biorefineries are available on an interactive map produced by DOE's Biomass Program.

With the passage ofthe 2009 several programs that provide incentives forthe development

of advanced biofuels using cellulosic biomass.


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3.THE BIOENERGY CYCLE

Bioenergy is produced in a cycle. Sustainable use of natural energy mimics the

Earth's seasonal variations and minimizes the emission of pollutants into the air, rivers and

oceans. Most of the carbon to create it is taken from the atmosphere and later returned to the

atmosphere. The nutrients to create it are taken from the soil and later returned to the soil.

The residues from one part of the cycle form the inputs to the next stage of the cycle.

Carbon dioxide (CO2) is withdrawn from the atmosphere by the process of plant growth

(photosynthesis) and converted into vegetation biomass (trees, grasses, and other crops).

Harvested biomass, together with forestry and crop residues, can be converted into building

materials, paper, fuels, food, animal feed and other products such as plant-derived

chemicals (waxes, cleaners, etc.). Some crops may be grown for ecological purposes such

as filtering agricultural run-off, soil stabilization, and providing habitat for animals as well

as bioenergy. The solid biomass processing facility (represented by the factory building at

the bottom left) may also generate process heat and electric power. As more efficient

bioenergy technologies are developed, fossil fuel inputs will be reduced. Organic by-

products and minerals from the processing facility may be returned to the land where the


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biomass grew, thereby recycling some of the nutrients such as potassium and phosphorus

that were used for plant growth.

Selected residues from the town may be combined with forestry and crop residues, animal

wastes, and biomass crops to provide the feedstocks for a different type of biomass

processing (represented by the factory at the top right). This new biomass processing

facility (or biorefinery) could make a range of productsfuels, chemicals, new bio-basedmaterials, and electric power. Animal feed could be an important co-product of some

processes. Such biomass processing facilities would use efficient methods to minimi e

waste streams and would recycle nutrients and organic materials to the land, thereby helping

to close the cycle.

Biomass products (food, materials, and energy) used by the human population are

represented by the town at the bottom ofthe diagram. The residues from the town (scrap

paper and lumber, municipal refuse, sewage, etc.) are subject to materials and energy

recovery, and some may be directly recycled into new products.

Throughoutthe cycle, carbon dioxide from biomass is released backinto the atmosphere

from the processing plants and from the urban and rural communitieswith little or no net

addition of carbon to the atmosphere. Ifthe growing of bioenergy crops is optimi ed to add

humus to the soil, there may even be some net sequestration orlong-term fixation of carbon

dioxide into soil organic matter. The energy to drive the cycle and provide for the human

population comes from the sun, and will continue for many generations at a stable cost, and

without depletion of resources.


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4.SOURCES OF BIOMASSImportant sources of biomass and their characteristics are given here;

A. Crop residue and farm wastes: The straw of cereals and pulses, stalks and seed coats

of oil seeds, stalks and sticks of fibre crops, pulp and wastes of plantation crops, peelings,

pulp and stalks of fruits and vegetables and other wastes like sugarcane trash, rice husk,

molasses, coconut shells etc. comes under this category. Most of the crop residues have

higher ash content and mainly constitutes carbon, oxygen and hydrogen. Volatile matter

content is 60-75%. The agricultural residues are hygroscopic in nature. Ash content varies

from 0.5 to 2.8 per cent.

B. Industrial wastes: These wastes include wastes from paper mills, chemical mills etc. for

eg., paper wastes, plastic wastes, textile wastes, gas, oil, paraffins, cotton seeds and fibres,

bagasse etc. Plastic and rubber wastes have good calorific value.

C. Forest wastes: Logs, chips bark and leaves together constitute forest wastes. Sawdust is

the forest based industry waste. Forest products are also used as a. domestic fuel in many

developing countries.

D. Logging residues: Tree tops, small stems and roots removed from a standard logging

operation and broken debris generally considered as logging residues. It contains 40-50%

moisture, 50% carbon, 40% oxygen and nitrogen 5%.

E. Residues of wood product industries: Bark, knots, sawdust etc. are obtained from

wood product industry. Moisture content of these residues is around 20% with 67% volatile

matter and 11 % organic carbon.


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F. Resi es from pulp and paper industries: The bark and blackliquor produced in pulp

and paper factories can be used as major source of energy in the paper industry. Moisture

content varies from 5-10% with organic. carbon 8-11 per cent.

G. Muni ipal solid wastes: Generally municipal solid wastes refer to a mixture of

domestic, small construction and demolition wastes left out within a community.

Composition of municipal solid wastes is given in a Table 1. It shows the heterogenic nature

ofthese waste mixtures.

Table 1 :Composition of municipal solid wastes

Sl.No ComponentPercentage

(weight)

1 Paper 41

2 Metals 8.2

3 Glass, Stones, Ceramics 11.2

4 Plastic, rubber 4.9

5 Garbage, yard wastes 24

6 Miscellaneous 10.7

Total 100%

H. Muni ipal sewage sludges: The sludges contain 95% water, and 5% organic matter and

nutrients as the main constituents. These can be utili ed for the production of methane

through anaerobic digestion.

I. Animal wastes: The moisture content ofthe manures ranges from 60 to 85 percent. The

nitrogen varies from 0.3 to 0.9 %, phosphorus 0.05-0.1 % and potassium 0.12 to 0.8%

Available statistics indicates production of 1300 million tonnes of dung annually from all

types of animals. Ofthe total produced, 84% is of cow and buffalo dung and 13% goat and

sheep droppings. Dung is used as a fuelin the form of cakes and biogas.

Availability of biomass resources in India along with their coal equivalentis shown in Table

2.


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Table 2. Major biomass resources in India

Sl.No BiomassAvailability

(Tones/Yr.)

Coal equivalent

(Tones/Yr.)

Agricultural residues

1 Rice straw 9 58.4

2 Rice husk 19.9 15.7

3 Jute sticks 2.5 2.3

4 Wheat straw 50.5 37.5

5 Cattle dung 1,335.00 128

Agro-industrial bi-products

1 Bagasse 28.1 22.4

2 Molasses 2.1 0.8

3 Oil seed cakes 6.7 0.9

4 Saw dust 2 3.4

Forest products

1 Mahua flowers 1 0.4

2 Leaves, tops etc. 3.3 3

The different processes that are followed in India to make these wastes into a useful fuel are

discussed in the below article.


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5.BIOENERGY CONVERSION

So, Bioenergy conversion processes are;

I. Biomass Direct combustionII. Biomass Gasification

III. Pyrolisis LiquefactionIV. Anerobic DigestionV. Fermentation


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Biomass Direct Combustion:

Giant King Grass is suitable as a fuel for direct combustion (burning) in 100% biomass

electricity-generating power plants. Today, biomass power plants are fueled by agricultural

and forestry waste such as corn stover, wheat straw, rice husks and wood waste. The price

of agricultural waste has increased dramatically in China and India due to market demand,

and in many areas, growing Giant King Grass as a dedicated energy crop is less expensive

and more reliable than using waste. Agricultural waste is seasonal, because it is only

available after the food crop such as corn is harvested. The corn stover must be gathered

over long distances because the yield is quite low, then dried, baled, stored and utilized as

fuel until the next agricultural waste crop is available. Reliability, consistency and cost of

biomass fuel are the major issues facing biomass power plants today. A dedicated Giant

King Grass plantation co-located with a power plant is a cost effective and reliable solution

to producing clean electricity.


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Direct Combustion-Overview

DP CleanTech 30MW Biomass Electric Power Plant Suitable for Giant King Grass

Giant King Grass has been analyzed by DP CleanTech which has built and operates dozens

of biomass power plants in China and Europe. They conclude that Giant King Grass has

energy content, physical properties and ash properties very similar to corn stoverthattheyuse routinely as a fuel. Other potential customers have analyzed Giant King Grass and have

come to the same conclusion. VIASPACE Green Energy is pursuing several opportunities

for co-located Giant King Grass plantations and biomass power plants. The fast-growing

nature and proven, dependable energy characteristics of Giant King Grass allows power

plants to run 24 hours a day, seven days a week withoutinterruption or variable output due

to availability orinconsistent performance ofthe fuel.

Direct combustion (or "direct-fired") systems burn biomass in boilers to produce high

pressure steam. The steam turns a turbine connected to a generator-the same kind of steam-

electric generator used in fossil fuel power plants. As the turbine rotates, the generatorturns, and electricity is produced. This is the simplest and oldest way to generate electricity

from biomass. To increase the energy-producing efficiency of direct combustion, power

plants also operate cogeneration facilities, which capture waste heat and "secondary" steam

and use it to heat buildings and provide steam and heat for industrial processes such as

ethanol production or drying of chemical and wood products.

Agricultural waste and Giant King Grass have different properties than coal and require a

different boilertechnology. Biomass power plants are usually 10 to 30 MW in size which is

much smaller than coal power plants at 500 to 2000 MW. Most of the world's biomass

power plants use direct combustion to produce renewable and low carbon electricity.Existing coal power plants can be readily modified to replace up to 20% oftheir coal with

biomass pellets, buttheir boilertechnology cannot accommodate 100% biomass.

Corn stover bales at DP CleanTech power plant. Baling is only necessary ifthe fuel needs

to be

transported over long distances and stored or stored for several months. The bales are

broken

up before entering the boiler. Direct combustion power plants have a much lower capital

investment than solar power, and equipment is widely available. By using high yielding

Giant King Grass, the cost of electricity is much cheaperthan solar electricity. Furthermore,

biomass can produce low carbon electricity 24 hours a day which is needed for "base

power" applications.


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Biomass Gasification:

When biomass is heated with no oxygen or only about one-third the oxygen needed for

efficient combustion (amount of oxygen and other conditions determine if biomass gasifies

or pyrolyzes), it gasifies to a mixture of carbon monoxide and hydrogensynthesis gas or

syngas.

Combustion is a function of the mixture of oxygen with the hydrocarbon fuel. Gaseous fuels

mix with oxygen more easily than liquid fuels, which in turn mix more easily than solid

fuels. Syngas therefore inherently burns more efficiently and cleanly than the solid biomass

from which it was made. Biomass gasification can thus improve the efficiency of large-

scale biomass power facilities such as those for forest industry residues and specialized

facilities such as black liquor recovery boilers of the pulp and paper industryboth major

sources of biomass power. Like natural gas, syngas can also be burned in gas turbines, a

more efficient electrical generation technology than steam boilers to which solid biomass

and fossil fuels are limited.

Most electrical generation systems are relatively inefficient, losing half to two-thirds of the

energy as waste heat. If that heat can be used for an industrial process, space heating, or

another purpose, efficiency can be greatly increased. Small modular biopower systems are

more easily used for such "cogeneration" than most large-scale electrical generation.

Just as syngas mixes more readily with oxygen for combustion, it also mixes more readilywith chemical catalysts than solid fuels do, greatly enhancing its ability to be converted to

other valuable fuels, chemicals and materials. The Fischer-Tropsch process converts syngas

to liquid fuels needed for transportation. The water-gas shift process converts syngas to

more concentrated hydrogen for fuel cells. A variety of other catalytic processes can turn

syngas into a myriad of chemicals or other potential fuels or products.


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Pyrolysis Liquefaction:

Pyrolysis and Other Thermal Processing

Solid biomass can be liquefied by pyrolysis, hydrothermal liquefaction, or other

thermochemical technologies. Pyrolysis and gasification are related processes of heating

with limited oxygen. Conditions for producing pyrolysis oil are more likely to include

virtually no oxygen. Pyrolysis oil or other thermochemically-derived biomass liquids can be

used directly as fuel, but also hold great promise as platform intermediates for production of

high-value chemicals and materials.

Pyrolysis

Fast pyrolysis is a thermal decomposition process that occurs at moderate temperatures with

a high heat transfer rate to the biomass particles and a short hot vapor residence time in the

reaction zone. Several reactor configurations have been shown to assure this condition and

to achieve yields of liquid product as high as 75% based on the starting dry biomass weight

. They include bubbling fluid beds, circulating and transported beds, cyclonic reactors, and

ablative reactors.

Fast pyrolysis of biomass produces a liquid product, pyrolysis oil or bio-oil that can be

readily stored and transported. Pyrolysis oil is a renewable liquid fuel and can also be used

for production of chemicals. Fast pyrolysis has now achieved a commercial success for production of chemicals and is being actively developed for producing liquid fuels.

Pyrolysis oil has been successfully tested in engines, turbines and boilers, and been

upgraded to high quality hydrocarbon fuels although at a presently unacceptable energetic

and financial cost.


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In the 1990s several fast pyrolysis technologies reached near-commercial status. Six

circulating fluidized bed plants have been constructed by Ensyn Technologies, with the

largest having a nominal capacity of 50 t/day operated forRed Arrow Products Co., Inc. in

Wisconsin. DynaMotive (Vancouver, Canada) demonstrated the bubbling fluidized bed

process at 10 t/day of biomass and is scaling up the plant to 100 t/day. BTG (The

Netherlands) operates a rotary cone reactor system at 5 t/day and is proposing to scale the

plant up to 50 t/d. Fortum has a 12 t/day pilot plantin Finland. The yields and properties of

the generated liquid product, bio-oil, depend on the feedstock, the process type and

conditions, and the product collection efficiency.

Biomass Program researchers use both vortex (cyclonic) and fluidized bed reactors for

pyrolyzing biomass. The fluidized bed reactor ofthe Thermochemical Users Facility atthe

NationalRenewable Energy Laboratory is a 1.8 m high cylindrical vessel of 20 cm diameter

in the lower (fluidization) zone, expanded to 36 cm diameter in the freeboard section. Itis

equipped in a perforated gas distribution plate and an internal cyclone to retain entrained

bed media (typically sand). The reactor is heated electrically and can operate at

temperatures up to 700C at a throughput of 15-20 kg/h of biomass.

Recently, a catalytic steam reformer was coupled to the pyrolysis/gasification system. Like

the pyrolyzer, the reformeris an externally heated fluidized bed reactorthat will be used to

produce hydrogen from pyrolysis gas and vapors generated in the first stage ofthe process

and to clean the gas from tars.

Biomass Program micro-scale pyrolysis systems include externally heated different types

reactors coupled to the molecular-beam mass-spectrometer (MBMS). These systems are

very efficienttools, especially for studying mechanisms ofthermal and catalytic processes

and to optimize process conditions for different products from variety of feedstocks. For

example, the ongoing research sponsored by Philip Morris resulted in understanding the

chemical processes of biopolymer pyrolysis and oxidation leading to aromatic hydrocarbon

formation.


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Anaerobic Digestion:

Anaerobic digestion and regenerative thermal oxidiser component of Lbeck mechanical

biological treatment plant in Germany, 2007

Anaerobic digestion is a series of processes in which microorganisms break down

biodegradable material in the absence of oxygen, used for industrial or domestic purposes tomanage waste and/or to release energy.

The digestion process begins with bacterial hydrolysis of the input materials in order to

break down insoluble organic polymers such as carbohydrates and make them available for

other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon

dioxide, hydrogen, ammonia, and organic acids. Acetogenic bacteria then convert these

resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and

carbon dioxide. Finally, methanogens convert these products to methane and carbon

dioxide.

It is used as part of the process to treat biodegradable waste and sewage sludgeAs part of anintegrated waste management system, anaerobic digestion reduces the emission of landfill

gas into the atmosphere. Anaerobic digesters can also be fed with purpose grown energy

crops such as maize.

Anaerobic digestion is widely used as a source of renewable energy. The process produces a

biogas, comprising of methane and carbon dioxide. This biogas can be used directly as

cooking fuel, in combined heat and power gas engines or upgraded to natural gas quality


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biomethane. The utilisation of biogas as a fuel helps to replace fossil fuels. The nutrient-rich

digestate thatis also produced can be used as fertilizer.

The technical expertise required to maintain industrial scale anaerobic digesters coupled

with high capital costs and low process efficiencies had limited the level of its industrial

application as a waste treatment technology. Anaerobic digestion facilities have, however,

been recognized by the United Nations Development Programme as one ofthe most usefuldecentralized sources of energy supply, as they are less capital intensive than large power

plants.


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Fermentation:

Fermentation is the biochemical process that converts sugars into ethanol (alcohol).

Transformation of sugars into alcohols by fermentation is a common practice. Fermentation

is carried out by a group of living organisms: yeasts or bacteria. Ethyl alcohol, commonly

known as alcohol is one of the most important and popular industrial fermented products. It

is a liquid fuel, and can be used as an alternative to automobile fuels. The sugar enriched

materials like cane sugar, beet sugar, fruit sugar, potato, com, rice or any other crop of high

sugar contents can be used as substrates mainly, along with starchy and ligno-cellulosic

materials.

In contrast to biogas production, fermentation takes place in the presence of air and is,

therefore, a process of aerobic digestion. Ethanol producers use specific types of enzymes to

convert starch crops such as corn, wheat and barley to fermentable sugars.Some crops, such

as sugar-cane and sugar beets, naturally contain fermentable sugars.

In the dry mill process, grain is first ground into flour and then processed without separation

of the starch. Wet milling is more common. After the grain is cleaned, it is steeped and thenground to remove the germ. Further grinding, washing and filtering steps separate the fiber

and gluten. The starch that remains after these separation steps is then broken down into

fermentable sugars by the addition of enzymes in the liquefaction and saccharification

stages. To produce ethanol, yeast is added to a slurry (or "mash"), which is a solution of

fermentable sugars and water. The yeast ferments the sugars, producing a solution called

beer.


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The beer solution contains about 10-percent to 12-percent ethanol. The rate of the

conversion process depends on the amount of waterin the slurry and its acidity, temperature

and oxygen content. Up to a third of the original dry weight of the feedstock leaves the

fermentation process as carbon dioxide. The solids that remain afterthe mash has fermented

still contain nutrients suitable for use as livestock feed. Distilling the beer produces a

solution of 80-percent to 95-percent ethanol. Producers can use several methods of

dehydration to purify the ethanol solution furtherto 100-percent (200-proof) alcohol for use

as a motor fuel.

Following are the types of substrates used for alcohol production;

1. Sugary materials:Examples of sugary materials like sugarcane and its biproducts (bagasse, molasses)

and sugarbeet, fruit juice, sweet sorghum, sweet-potatoes etc. Sugarcane molasses is

largely being used in many countries for alcohol production. The yield of ethanolis

directly proportionalto the amount of sugar present.

2. Starchy materials:Tapioca, maize, wheat, barley, oat, sorghum, rice and potatoes are the starchy

materials that are used in ethanol production. It has been estimated that 11.7 kg of

corn starch can be converted into about 7 liters of ethanol.

3. Lignocellulosic materials:The sources of cellulose and lignocellulosic materials are the agricultural wastes and

wood. On the basis oftechnology available today, about 409 litres of ethanol can be

produced from one tonne oflignocellulose.


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6.MUNICIPAL SOLID WASTE (MSW)

Electricity can be produced by burning "municipal solid waste" (MSW) as a fuel. MSW

power plants, also called waste to energy (WTE) plants, are designed to dispose of MSW

and to produce electricity as a byproduct of the incinerator operation.

The term MSW describes the stream of solid waste ("trash" or "garbage") generated by

households and apartments, commercial establishments, industries and institutions. MSW

consists of everyday items such as product packaging, grass clippings, furniture, clothing,

bottles, food scraps, newspapers, appliances, paint and batteries. It does not include

medical, commercial and industrial hazardous or radioactive wastes, which must be treatedseparately.

MSW is managed by a combination of disposal in landfill sites, recycling, and incineration.

MSW incinerators often produce electricity in WTE plants. The US Environmental

Protection Agency (EPA) recommends, "The most environmentally sound management of

MSW is achieved when these approaches are implemented according to EPA's preferred

Municipal solid waste (MSW), commonly

known as trash or garbage, is a waste type

consisting of everyday items we consume and

discard. It predominantly includes foodwastes, yard wastes, containers and product

packaging, and other miscellaneous inorganic

wastes from residential, commercial,

institutional, and industrial sources. Examples

of inorganic wastes are appliances,

newspapers, clothing, food scrapes, boxes,

disposable tableware, office and classroom

paper, furniture, wood pallets, rubber tires,

and cafeteria wastes. Municipal solid waste

does not include industrial wastes, agricultural

wastes, and sewage sludge. The collection is

performed by the municipality within a given

area. They are in either solid or semisolid

form. The term residual waste relates to waste

left from household sources containing

materials that have not been separated out or

sent for reprocessing. Following are the

different types of wastes.


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order: source reduction first, recycling and composting second, and disposal in landfills or

waste combustors last.

Incineration is one of the waste treatment technologies that involve the combustion of

Municipal Solid Waste (MSW) without any pre-treatment (also called mass burning). Massburning has been in practice in developed countries for more than 100 years. More than 600

mass burning plants are operating around the world. Until 2000, much importance was not

given to the management of MSW in Asia and Africa. But, once CDM activities began, theproject developers started paying attention to MSW projects for the benefit of revenue from

CER sales which would make the project feasible.

Volume reduction of MSW for about 90% is possible with incineration plants, thereby

resulting in considerable land saving, as land will not be required to dispose of the 90%MSW. Only few countries in Asia have a long history of proper management of MSW using

incineration power plants. As of now, in Singapore, 4 power plant of sizes ranging from 30

MW to 80 MW are in operation (for more than 25 years) and one more plant is undercommissioning. A 2.5 MW plant is in operation in Phuket, Thailand.

The lower heating value of MSW varies considerably from country to country depending on

several factors. In general, if the economic situation is better, then the heating value will behigher. For the mass burn facilities, the minimum calorific value requirement is 7 MJ/kg on

an annual average basis.

In MSW mass burn system there is no pre-treatment except the removal of visible bulk

items. However, some of the wastes such as construction debris, earth, concrete, stones,


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chemical waste, explosive or highly flammable waste, carbon fibres, insulation materials,

Polyvinyl Chloride (PVC) etc., are not suitable for mass burn. It is also advisable to

separate biodegradable wastes from MSW to use in digesters so that biogas resulting fromthe digester can be used to generate power using gas engines.

MSW plants generally have limitations in the usage of steam cycle and the plant designconcept is different from biomass combustion system. Due to the level of complexity indesign and lower demand for such plants in developing countries, there are only limited

suppliers available in Asia. Though several suppliers may claim thatthey have the technical

know-how, it is worthwhile to do a due-diligence on the suppliers capability. Theequipment suppliers need more knowledge in combustion to burn MSW than to burn anyother kinds of fuels. The power plant should be designed with more flexibility and plenty of

margins. Generally, the excess air requirementis high.

With the use of modern technologies, itis also possible to minimise water pollution, odour

and noise problems. It is also possible to recover ferrous metals from the ash which

provides additional revenue.

Implementing MSW projects are more time consuming than biomass power plants as very

careful preparatory work are needed forthe incineration plants. Without proper preparation,the chances of failure for such plants are high. While we have visited several successful

MSW plants that are in operation for more than 10-20 years, we have also come across

several failure plants which were sold as scrap. Hence, project developers should payadequate attention and do the necessary preparatory works before implementing these

projects. It may also be worthwhile to engage qualified experts to study all modern concepts

and innovative technologies. Butthe technology selection should be done ca refully.

Although MSW plants are eligible underClean DevelopmentMechanism, there are certain

restrictions in selection oftechnology and usage ofMSW. Therefore, the project developer

should not neglect these aspects while developing the projects to getCDMCERrevenue.The potential forincineration plants in developing countries is high in the near future.


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7.ENVIRONMENTAL ISSUESBiomass technologies are friendlier to the environment than conventional energy

technologies, which rely on fossil fuels. Fossil fuels contribute significantly to many ofthe

environmental problems we face today greenhouse gases, air pollution, and water and

soil contamination. Biomass technologies could hel p us break our conventional pattern of

energy use to improve the quality of our environment.

Air Quality

Biomass alternatives can reduce the emission of nitrogen oxides, sulfur dioxides, and other

air pollutants associated with fossil fuel use.

Global Climate Change

Increased emissions of greenhouse gases from use of fossil fuels, especially carbon dioxide,

has created an enhanced greenhouse effect known as global climate change or global

warming. Biomass technologies produce very low or no amount of carbon dioxideemissions.

Soil Conservation

Soil conservation issues associated with biomass production include soil erosion control,

nutrient retention, carbon sequestration, and stabilization of riverbanks.

Water Conservation

Biomass technology life cycles may have impacts on watershed stability, groundwater

quality, surface water runoff and quality, and local water use for crop irrigation and/or

conversion facility needs.

Biodiversity and Habitat Change

Biodiversity is the genetic and species diversity ofliving things in a defined area or region.

Altered land use to supportincreased biomass production may result in changes in habitat

and levels of biodiversity.


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8.CONCLUSION ANDFINDINGSThere is an enormous untapped biomass potential, particularly in improved utilization of

existing residues, and forest and other land resources, and in higher plant productivity.

Modernization of bioenergy production and use could bring substantial social and economic

benefits to both rural and urban areas. As Pasztor and Kristoferson (1990, p. 28) putit, if

biomass energy systems are well managed, they can form part of a matrix of energy supply

which is environmentally sound and also contributes to sustainable development. If

biomass is to make any significant energy contribution to development however, it must be

produced in greater quantities. It must also provide efficient, sustainable, economically

justifiable and environmentally-sound energy systems whilst ensuring that other more

traditional modes of production and uses also are efficient and sustainable.

Itis expected that demand for biomass will rise considerably in the future, because of: (a)

population growth, particularly in developing countries; (b) grea ter use in the industrialized

countries due partly to environmental considerations; and (c) technological developmentswhich could allow eitherthe production of new orimproved biomass fuels, orthe improved

conversion of biofuels into more efficient energy carriers thus stimulating demand for

feedstock. But biomass energy still faces many barriers - economic, social, institutional and

technical. It is a large and varied source of energy at very uneven stages of development,

both with respectto scale and technological requirements. Enhanced biomass availability on

a sustainable basis will require support and development of new biomass systems.

Application of modern biomass energy technologies in many developing countries will

usually also depend strongly on foreign finance, because of the capital and other

requirements of many modernized renewable energies (Grubb, 1990). However, in the caseof the more traditional and also less capital-intensive technologies, innovation and

adaptations, local skills and entrepreneurs can play a leading role. Biomass production and

use, in an economic and sustainable manner, should thus be seen as an opportunity for

entrepreneurs of all descriptions especially since biomass is so widely distributed and used

throughoutthe world.

Many attempts have been made to introduce new energy technologies, but in most cases,

factors external to the technology seem to have played a greater role with respect to

acceptability than the technology itself. This is particularly true with respectto economics.

It can be argued that one ofthe major barriers to the commercialization of renewable-energy

technologies is that current energy markets in most cases ignore and/or do not pay the social

and environmental costs and risks associated with fossil fuel use. This is especially relevant

to biomass energy which has many environmental and social benefits. If externalities

such as employment, import substitution, energy security, environment and so on are

considered, then the economics change usually in favour ofthe biomass systems. Social and

land-use policies must also be given high priority.


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Programmes which are currently commercial, such as ethanol and electricity production,

can be analysed in both developing and developed countries and some general conclusions

can be drawn. The Brazilian ethanol case demonstrates the need for a clear government

commitment, the vulnerability of such large programmes to short-term market fluctuations

and the inherent difficulty of long-term energy planning. In Zimbabwe, the State played

largely a regulatory role to create the acceptable market conditions forthe ethanol projectto

succeed, leaving the funding entirely to the private sector. The success ofthe Pura biogas

project in India and the failure ofthe gasification projects in the Philippines highlight the

importance of social factors and long-term commitment in successful energy and

development projects.

Finally, from the results ofthe analysis of biomass energy projects in developing countries

it can be concluded thatthe requirements for successful biomass projects depend mainly on

the careful consideration of local socioeconomic factors, maximum participation and

control by local people from the outset (including initiation and planning), the generatio n of

short-term local benefits within a longer-term context, and economic viability. It is ofparamount importance to take a long-term view thatincludes sustainable development and

environmental accountability, whilst allowing for flexible aims, replicability and multiple

benefits.

Documents

The Biomass energy