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Evaluating Alternative Waste Management Strategies for Hakea Prison

Report Submitted to the Department of Corrective Services

Xian Fang Lou & Jaya Nair

Environmental Technology Centre, Murdoch University, Western Australia 6150

August 2009

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TABLE OF CONTENTS 1.0 Introduction …………………………………………………………. 2

2.0 Current waste management strategy …………………………….. 2

3.0 Alternative waste management strategies ………………………. 2

3.1 Amount and composition of Hakea Prison waste stream … 3

3.2 Chook Pen………………………………………………….. 3

3.3 Composting …………………………………………………. 4

3.3.1 Windrows composting …………………………… 4

3.3.2 Aerated pile composting ………………………… 5

3.3.3 Aerated bin composting …………………………. 5

3.4 Vermicomposting …………………………………………... 6

3.5 Combination of composting and vermicomposting…….. 6

3.6 Anaerobic digester …………………………………………. 7

4.0 Economic Analyses……………………………………………….. 14

5.0 Conclusion and Recommendations……………………………… 14

6.0 References ………………………………………………………… 15

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1.0 Introduction The majority of wastes generated in Australia are directed to landfill which has significant adverse environmental and economical impacts. Landfills emit large amount of greenhouse gas emissions which accelerate global warming, and causes potential groundwater contamination due to the leachate from the decomposition of wastes in an anaerobic condition. In addition, in a landfill, decomposition is slow and the waste materials in a landfill will take a long time to degrade, and some, not at all. With an increasing population and increasing affluence of the people in Australia, consumerism is increasing which leads to more waste generation. This increasing generation of waste demands increasing the current capacity of landfills. The sustainable strategy therefore is to divert waste from landfills and consider management of waste at the source of its generation. This need has been recognized by the Western Australian government and is expressed in the form of the WA Zero Waste Strategy. This strategy not only promotes alternative waste management strategies such as recycling, composting, anaerobic digestion etc, but also promotes the idea of reducing and preventing the production of waste in the first place. For the treatment of putrescible waste onsite, there are a couple of waste management strategies that can be deployed, some of which offer higher suitability and feasibility than others. Suitability of each waste management strategy is assessed by two main criteria: technical and economic feasibility. Presence of any social benefits will be an additional bonus contributing to the possible selection of a particular waste management strategy. The objectives of this report are to evaluate the current waste status of Hakea Prison and to provide options for alternative waste management strategies suitable for Hakea Prison.

2.0 Current waste management strategy Hakea Prison accommodates around 820 inmates in any given time which is similar to the capacity of a suburban lifestyle village. The current waste management strategy of the Hakea Prison was assessed through a visit by Dr Jaya Nair and Xian Lou from the Environmental Technology Centre. It was explained by the prison authorities that currently, Hakea Prison has a recycling program implemented onsite which divert some recyclable wastes from landfill. Cardboard is collected by Amcor, shredded paper by a paper recycling company. Attempts are made to collect plastics and metals to make it available for recycling. The present recycling program has reduced the use of 12 skip bins of 2 cu m capacity to 10 skip bins daily. The bins containing recyclable wastes and putrescible wastes are collected daily by council trucks and disposed of in the local landfill.

3.0 Alternative waste management strategies Having recognized the limitations of landfills, Hakea Prison is currently considering the adaptation of alternative strategies for waste management. The applicability and suitability of alternative waste treatment option will depend on the amount and composition of the waste stream generated by Hakea Prison, therefore assessing

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Putresible wasteNon putrescible

waste

Food waste

Wood waste

Green waste

1364 kg; (68%) 637 kg; (32%)

1225 kg; 89.8%

43 kg; 3.15%

96 kg; 7.04%

the amount and composition of waste generated is important to identify alternative waste treatment options. 3.1 Amount and composition of Hakea Prison waste stream During the site visit, potential sources of putrescible waste suitable for onsite waste management were identified. These included food waste from the kitchen, saw dust and wood waste from the wood workshop, green waste from the vegetable gardens and lawn clippings. It was estimated that approximately 68.2% of daily waste stream directed to the landfill are putrescible waste. The putrescible waste is made up of mostly food waste (approximately 89.9% of total putrescible waste) followed by wood waste and green waste (see Figure 1). The break down of the amount and composition of waste generated onsite can be seen in Table 1. This significant amount of putrescible waste offers the opportunity of certain onsite waste management options, each with their own advantages and disadvantages. These will be discussed in detail in following sections. Suitable alternative waste management strategies identified for Hakea Prison are composting, vermicomposting and anaerobic digestion.

3.2. Chook pen Fresh and uncontaminated food scraps from the food preparation area can be separately collected and can be used by a chicken coop. This will reduce the waste needed to be composted or handled otherwise through the treatment process. The chicken pen waste can be used in the garden. However it requires every day attention in feeding and maintaining the chook pen. This could be around 200 kg/day. This will use up vegetable scraps, provide egg and meat and chook poo can be used in the garden as fertiliser.

Figure 1: Amount and composition of daily waste generated at Hakea Prison

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Chook pen in Bridgewater lifestyle village

3.3 Composting Composting is described as the accelerate decomposition of organic waste in the presence of oxygen. This process occurs through a thermophilic and mesophilic stage where the materials are cured and converted to a stabilised material the compost. There are essentially three types of composting technology: windrows, aerated piles/bins and in vessel composting (Figure 2). The quantity of organic waste that can be treated through the composting process are kitchen waste (1300 kg), sawdust (100kg), garden waste (50 kg). However the proportion or the compost mixture will be based on the 50:50 ratio of kitchen waste to all other materials as sources of carbon. Therefore another 1000 kg of material can be utilised in the compost mixture daily such as grass clippings and paper waste (1000kg). 3.3.1 Windrow composting Windrows composting consists of putrescible waste stockpiled into long narrow or heap piles, which are aerated by natural/passive air movement. Windrows composting is the easiest and cheapest out of the three types of composting as it requires no forced aeration. However manual aeration of the stockpile is essential to ensure that the waste maintains its aerobic conditions. This means that the waste will take a longer time to degrade, and is characterised with a long retention time of 3-6 months. This leads to a need for large space area to stockpile the waste while it degrades.

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3.3.2 Aerated pile composting Aerated pile compositing is similar to that of windrows but air is forced into the stockpiles to aerate the compost profile. The advantages and disadvantages are similar to that of windrows composting but for the following differences. The provision of forced air supply will increase the capital cost and operational cost significantly. However, retention time of the composting process will be reduced from 3-6 months to 3-5 weeks (with 1 month curing), allowing for a more efficient waste treatment which means lesser space required to operate, as compared to windrows composting. This process also is less labour intensive than windrow composting. 3.3.3 Aerated bin composting In aerated bin composting, putrescible waste (the premixed waste to the right proportion) is placed in sealed bins, and air is provided to each bin to ensure that aerobic conditions are maintained. Similar to aerated piles, the capital and operation cost will be higher than in windrows due to the provision of air supply. Unlike both windrows and aerated piles, aerated bin composting occurs in a sealed container. This means that odour and vector attraction will not be an issue as well as very clean operation because of the process occurring in a confined space. Due to the increased amount of forced aeration within each bin, the retention is once again reduced to 2-3 weeks (with 2 months curing), which is more efficient than windrows and aerated piles. Aerated bins will also take up less space in comparison to compost pile. In addition, since turning of the compost piles are not required; this remains a viable option for Hakea Prison to adopt. There has been evidence of the successful implementation of bin composting in a correction facility similar in capacity to Hakea Prison (Sherman-Huntoon undated). Windrow composting generally is the simplest and cheapest to implement and in-vessel being the most complex and expensive technology however is labour intensive. Due to the resources available at Hakea Prison, only windrows composting will be evaluated. The cost and technology required for in-vessel composting is not feasible at the scale of Hakea Prison. As labour is not a limiting factor in the prison, windrow composting is most suitable for the prison. Figure 2: Composting activities can be undertaken in various forms, windrows composting (left), aerated pile composting (middle) and bin composting (right).

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3.4 Vermicomposting Vermicomposting is a form of aerobic composting where composting worms and microbes facilitate the decomposition of waste. Unlike composting, vermicomposting does not involve manual turning, the worms turn, aerate and convert the waste into the final product the vermicast a rich fertilizer. Vermicomposting can occur in either open systems, similar to that of windrows composting, or in reactors (in bins/containers) (Figure 3). Vermicomposting is ideally done in a closed system to minimize odour and vector attraction issues. Furthermore, worms prefer a warm, moist and dark environment, which are more effectively provided in a closed system. Vermicomposting requires larger space than windrow composting as the farms can only be ideally to a maximum of 1 mt height with feeding area only 30 cm on the top layer. Unlike forced aeration composting, vermicomposting is cheaper and simpler to operate, as aeration is provided by the worms and no manual handling is required other than feeding. In addition, vermicomposting require a shorter retention time as compared to composting (1-2 months). Despite the relatively simple operation to the vermicomposting, it remains more sensitive than composting due to the special requirements of the earthworms. Over watering of over feeding may upset the activity and environment of the earthworms causing earthworm mortality. The major drawback will be adjusting the moisture content, pH and possible chances of purification of the food waste if the proportion is not quite right. The large space requirement compared to other processes is also a drawback Figure 3: Vermicomposting system

Nonetheless, it is suggested that vermicomposting is a suitable alternative waste management strategy that could be considered for adoption at Hakea Prison. Such a system has also been implemented successfully in a correction facility similar in capacity to Hakea Prison (Sherman-Huntoon in US-undated). 3.5. Combining Composting and Vermicomposting The Environmental Technology Centre has researched and proved that a combination of composting and vermicomposting is a more effective organic waste management strategy than either of it by itself. A precomposting of organic waste through windrow composting followed by vermicomposting will produce a highly stabilised end product in half the time as composting or vermicomposting by itself. The pH and moisture maintenance is easy through this combination of technologies

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and the space requirement is also considerably reduced (Nair et al., 2006; Nair and Anda, 2007) This is most economically efficient if the composting and vermicomposting setups can be made by the inmates themselves. This process will provide more job opportunities and a better product for the vegetable garden.

3.6 Anaerobic digestion (AD) Anaerobic digestion is the accelerated decomposition of waste in the absence of oxygen. Organic material is fed into an air tight digester where the decomposition of waste can occur either at mesophilic or thermophilic conditions. In the absence of oxygen, biogas (methane and carbon dioxide), water, stabilized product and effluent are formed as the end product (Figure 4). Due to the high cost involved in operating a thermophilic anaerobic digester, only mesophilic anaerobic digester will be recommended for implementation at Hakea Prison. The waste materials that can be treated are the same materials however will require about the same quantity of water to process the waste. Figure 4: Anaerobic digestor at ETC (left) and produces biogas (middle) and effluent (right) that can be used as a fuel and fertilizer respectively

Advantages of anaerobic digestion

1. Minimal environmental footprint Anaerobic digester emits methane and carbon dioxide, (biogas), and captures

the biogas efficiently, preventing its release into the atmosphere. In addition, the biogas produced can be used as a form of energy such as direct gas for gas stove, hot water system and electricity generation, creating the potential of carbon offsets. Onsite anaerobic digester offers a net reduction in greenhouse gas emissions due to potential energy recovery.

2. Offers opportunity for energy recovery Should sufficient biogas be produced, there is the potential of electricity being

produced to run operational activities in the facility. Preliminary evaluation of

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the amount and composition of waste generated by Hakea Prison suggests that considerable amounts of biogas is produced daily, allowing for 30, 120L water heating units to be heated continuously for 14.12 hours/day, or approximately 1211.60KWh/day.

3. Short retention time and space saving (1 month)

The retention time is as short as 20 days. This implies that anaerobic digestion is a relatively efficient operation and will require a smaller working area as compared to composting for waste stabilization. As space is a limiting factor in Hakea Prison, this is a noteworthy bonus to the anaerobic digester.

4. No odour or vector issues Unlike certain composting and landfilling activities, anaerobic digestor contains the waste in an air tight container, eliminating issues concerning vector attraction, dust and odour issues.

5. Production of fertilizer The effluent produced from AD can be used as a high quality fertilizer. The digestion process increases the solubility of the nutrients, facilitating improved nutrients update by plants. Provision of fertilizer also reduces the cost and need of having to purchase fertilizer off-site. If the fertiliser produced is in excess of what can be locally used in the prison, it can be either given out to market gardens or disposed into the sewage system.

6. Easy and cheap to operate and maintain

Once the conditions of the anaerobic digester have been established, the operation and maintenance of the digester will be relatively simple and straightforward. Unlike forced aerated composting once the anaerobic digester is established, there will be minimal additional cost incurrence. The digester will only require the input of feed and maintain the digester at the specified condition with a maximum of 3 inmates and a supervisor at one time.

7. Possibly more cost effective in the long term Due to the cost savings from diverting waste from landfills, the reduction of council services, the energy saved from the utilization of energy recovery and the provision of fertilizer, the payback period for the digester will be shorter than composting activities and could possibly be more cost effective in the long run.

Disadvantages 1. High initial start up cost

The start up cost of an anaerobic digester is relatively high as compared to passive composting due to the need for system components such as food pulper, reactor, biogas and effluent tank. Furthermore, should the biogas be utilized for energy recovery, additional infrastructure such as the retrofitting of gas pipes to the current system, biogas generator, valves, etc, will be required. This would inevitable incurred a significant setup cost.

2. Needs regular monitoring and maintenance of digester performance

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In order to maintain an efficient environment for maximum waste degradation and biogas production, the pH, temperature, biogas production and biogas composition will have to be monitored regularly. Should there be any deviation from the optimal operating conditions; corrective actions should be imposed immediately. However it is manageable.

3. There is a risk of the natural gas being made available onsite as pointed out by the prison authorities due to the high security requirement of Hakea prison.

Advantages of onsite composting

1. Environmentally friendly Onsite composting eliminates the need for the transportation of waste offsite saving on transport related infrastructure and transport emissions. In addition, composting activities, especially passive composting requires minimal energy consumption for its daily operations and hence reduces the need for fossil fuel resulting in reduced emissions. Composting is also an aerobic process which eradicates the generation and emission of potent greenhouse gas – methane.

2. Labour intensive Composting activity may involve as many or as little steps as desired, dependent on the type of composting technique and retention time. As of any organic waste treatment, composting requires the separation of putrescible waste from non-putrescible waste, may require some coarse shredding. Besides sorting, labour is involved in bringing the waste, mixing them in right proportion, stockpiling and periodic manual turning of the stockpile. This supports the desired trend in Hakea Prison to accommodate job opportunities for increasing numbers of inmates.

3. Provide training and education Inmates allocated to build, operate and maintain the composting facility onsite will be provided basic training in occupational health and safety and waste management. This will go towards the provision of education and training that may help in the rehabilitation of inmates. Inmates may also be allocated to help build certain aspects of the composter such as partitions for aerated pile composting. This will provide training in basic building and construction. Furthermore, the presence of an onsite waste management facility can be used to provide a form of environmental education and increased awareness for staff members and inmates alike.

4. Easy and cheap to maintain Aerobic composting is relatively easy to operate and maintain. The cost of aerobic composting varies widely with the technology employed. Passive/windrows composting will be the cheapest and little infrastructure is needed. Significant cost incurrence starts to occur when forced aeration to maintain an aerobic condition is introduced such as in aerated pile composting and aerated bin composting. The provision of oxygen would however allow for a shorter retention time, and hence less required space. The choice of composting techniques will be made based on a balance between the cost and space resources.

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5. Production of mulch and fertilizer

Following aerobic decomposition after the specified retention time, the waste will have stabilized to produce compost. Compost contains essential plant nutrients and can be used as mulch to help the soil retain its nutrients and water, and provide nutrients to the soil when it breaks down. The availability of compost onsite will help the prison vegetable garden and reduces the cost and need of having to purchase fertilizer off-site. It can be expected that a daily production of 1 ton of compost is possible which may be in excess to the local need. It can be a saleable end product.

Disadvantages

1. May requires large area for operation Although the volume of waste to be treated is similar, the area taken up by composing will be significantly larger than anaerobic digestion as the stockpile height for composting is limited by the oxygen availability (Figure 5). In addition, open composting system will require more area as buffer zones to screen out odour and vector attraction issues. Due to the space limitation of Hakea Prison, certain composting activities, such as passive composting, may not be viable. Figure 5: Graphical comparison of the larger area needed by composting (left) due to lower height requirement than anaerobic digesters (right)

2. Possible odour and vector attraction Open composting of food waste may produce odours and could attract vectors if not properly maintained. This will be an important consideration as vector attraction may harbour diseases which may pose a health and safety risk. The health and safety aspect can be partially addressed by the creation on buffer zones but will require more land ideally take up the space in the vegetable garden zone. This can be overcome by covering the stockpile, but air will have to be introduced to the system to maintain an aerobic environment through turning the pile regularly. Correct mixing with carbon sources as the wood shavings/sawdust and maintaining the moisture level of the compost mixture.

Area taken = 300m2 Area taken = 60m

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3. Operating cost Forced aeration technique applied to stockpiles will incur a high operating cost. This is however not applicable to passive composting as in windrow composting. However would ideally need a front loader to mix the pile.

4. Labour intensive The stockpile needs to be prepared by premixing the waste materials in right proportion to establish the correct Carbon and Nitrogen ratio for effective composting. This is followed by regular turning of the pile, and in the end sieving the compost to get the best quality compost.

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Waste management option

Advantages Disadvantages

Landfilling

1. Straightforward and convenient

2. No infrastructure needed

1. Various adverse environmental impacts

2. Use of valuable land 3. Encourages waste

production 4. Operating cost

Windrows composting

1. Environmentally friendly 2. Labour intensive-

advantage to the prison 3. Easy and cheap to

maintain 4. Increased security 5. Cost saving in the long

run 6. Production of fertilizer

1. Requires a lot of space

2. Require initial set-up cost

3. Possible odour and vector attraction

7. Need for source separation of waste

4. Long retention time (3-6 months)

5. Only less than 5% meat possible

Aerated pile composting

1. Environmentally friendly 2. Labour intensive 3. Increased safety 4. Production of fertilizer 5. Requires less space

than windrows

1. Requires large area of space

2. Require initial set-up cost

3. Possible odour and vector attraction

4. Need for source separation of waste

5. Long retention time compared to anaerobic digestion (3-5 weeks)

6. Expensive to maintain 7. Due to aeration pipe,

may not be suitable for food waste

8. Only less than 5% meat possible

Bin composting 1. Environmentally friendly 2. Increased security 3. Production of fertilizer 4. Requires less space

than windrows and

1. Requires large amount of space

2. Require initial set-up cost

3. Need for source

Table 2: Summary of advantages and disadvantage of feasible alternative organic waste treatment strategies for Hakea Prison

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aerated pile composting 5. No odour or vector

attraction 6. Most efficient

composting activity

separation of waste 4. Expensive to maintain 5. Only less than 5%

meat possible

Vermicomposting 1. Environmentally friendly 2. Production of fertilizer 3. Requires more space

than windrows and aerated pile composting

4. No odour or vector attraction (if bins are used)

5. Difficult to maintain the optimum condition for the process using food waste

1. Meat waste not suitable

2. Need for source separation of waste

3. Require initial set-up cost

4. Long retention time compared to anaerobic digester (1-2 months)

5. Require considerable space for bins

Combined Thermocomposting and Vermicomposting

1. Environmentally friendly 2. Less process time than

individual process 3. Better end product than

both technologies separate

4. Easier to maintain the optimum conditions

5. Less retention time required

1. Not ideal with high amount of meat > 20%

2. Takes space for both systems

3. Labour intensive 4. Maintenance intensive

Anaerobic digestion

1. Environmentally friendly 2. Short retention time (1

month) 3. No odour or vector

issues 4. Does not require much

space 5. Offers opportunity for

energy recovery 6. Production of fertilizer 7. Easy and cheap to

operate and maintain 8. Possibly more cost

effective in the long term

1. High initial set-up cost

2. Needs monitoring and maintenance of digester performance

3. Production of methane gas onsite due to the particular aspect of a high security prison.

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4. Economic Analyses

The following analyses on the economic feasibility of each method are only approximate and

it will vary with the contractors, the inkind contribution from inmates in the construction of

the facility and energy recovery period.

Chook pen

100 chooks ($20/ chook) =2000

Pen Delivered to site + 100 x 2sqm/chook = 200 sqm chook pen with concrete pad

roof area 50 sqm= (200sqm x $100/sqm + 50 sqm x $500 sqm) = $45,000

Total expense- $47000

Income: 100 chooks - @ 250eggs/chook/year =25000 eggs/year @40c/egg =

$10,000/year

Payback time ~ 5years

Composting Bays

5 Concrete Bays $15000 X5 = $75000/

Income: Compost 500 cu m @$ 30/cu.m = $15000/annum

Payback time= 5 years

Anaerobic Digestor 10 cubic Mt capacity Digestor + pulper+ effluent storage tank = $80000 The costs with energy conversion depend on the utilisation method such as gas

water heater or generator. The cost of this will have to be incorporated.

Pay back time depends on the energy utilisation method.

5.0 Conclusion and Recommendation

After assessing advantages and disadvantages of the three possible technologies for implementation in Hakea Prison, the following recommendations are made. Current waste generation characteristics of Hakea Prison displayed approximately 68% of daily organic waste production has the potential for diversion from landfills by utilizing alternative waste management strategies. Windrows, aerated piles, bin

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composting, vermicomposting and anaerobic digestion have been analysed for their application in Hakea Prison. Anaerobic digestion is the most efficient technology as it is a technology that can convert waste to energy. This is the latest technology that has been accepted as the future for waste management. The biggest limitation to this process is the initial capital cost. The low footprint and the low running cost for onsite small scale biogas plant make it ideal for implementation in the prison. If the case of security in terms of production of methane gas onsite can be effectively overcome, this is the best option. Alternatively due to the availability of labour and skills in the prison, a combination of composting and vermicomposting will be the cheapest option. However it requires a large area and constant care and maintenance of the process. Inmates can be trained in the process which will provide a social benefit out of this project.

6.0 References

1. Jaya Nair, Vanja Sekiozoic and Martin Anda (2006). Effect of precomposting on vermicomposting of kitchen waste, Bioresource Technology, 97(16):2091-2095.

2. Nair, J and Anda, M (2007) Onsite Waste Management in an Urban Village- Treatment of Kitchen Waste through Composting and vermicomposting to minimize waste generation submitted to the Department of Environment and Conservation, Waste Management Board, Western Australia.