GEOG 419: Research in Environmental Geography

Large-scale composting options for YVR : cost analysis 2012

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UNIVERSITY OF BRITISH COLUMBIA Large-Scale Composting Options for YVR Cost Analysis  Natalia Pisarek  April 28, 2012  Report prepared at the request of The Vancouver Airport Authority, in partial fulfillment of UBC Geog 419: Research in Environmental Geography, for Dr.  David Brownstein   1  Table of Contents CONTENT PAGE NUMBER 1.0 EXECUTIVE SUMMARY  2  2.0 METHODS AND MATERIALS  3  3.0 COMPOSTING BASICS 3  4.0 COST IMPLICATIONS 4  5.0 METHODS/TECHNOLOGIES 5.1 Windrows 5.2 Covered Aerated Static Piles 5.3 Ag-Bag 5.4 In-Vessel Rotating Drum 5.5. Anaerobic Composting 5.6 Vermicomposting 5.7 Off-site Diversion 5 5 8 12 13 15 16 17    6.0 CONCLUSIONS AND RECOMMENDATIONS 18 REFERENCES  20   2  1.0 EXECUTIVE SUMMARY Metro Vancouver has established a mandate to divert 70% of its waste stream from the landfill by 2015 (Richmond Soil & Fibre, 2012). Vancouver International Airport (YVR) has several options fordiverting a significant portion of itswaste stream to a composting process. The airport’s waste stream currently consists of approximately 1,600 tonnes of organic material annually at the two main terminals and its satellite locations (MJ Waste Solutions 2011). YVR also generates about 150,000 kilograms ofwood scraps annually which may be used as bulking material (Vancouver Airport Authority 2011b). This report will assume a maximum composting scenario of about 1,600 tonnes per year. Therefore therecommended technologies will reflect this capacity. The research question explored in this reportcan be divided into two main questions. First, what are appropriate composting technologies for the airport, and second what are the associated costs? Six on- site technologies were evaluated, as well as an off-site diversion option.  The following composting systems were assessed:  Turned windrows  Covered aerated static  piles (C ASP)  Ag-Bag  In-vessel rotating drum  Anaerobic Digestion  Vermicomposting *The science of vermicomposting will not be explored in this report; it is only necessary to know that vermicomposting refers to composting using live worm species. The research found that the most suitable options are Ag-Bag and in-vessel technologies. The latter is much more expensive but provides the greatest degree of control over the process, including odour and vector management.Turned windrows are one of the cheapest options but present potential odour and vector problem. Covered aerated static piles and vermicomposting are the poorest options because of the very high capital investment required. These complex options are difficult to justify at the scale proposed for YVR (about 1, 6000 tonnes annually).Anaerobic digestion is feasible for the airport but this is also an expensive and complex system. Off-site diversion is inexpensive and simple in the short-term, but is not a competitive option in light of ongoing operational costs. It is important to note that all the options require outdoor storage or curing. A comparative table of advantages and disadvantages is provided at the end of this report. 3  2.0 MATERIALS AND METHODS  Academic literature, industry literature and government literature were referred to throughout the research process. Academic articles contain little economic information - industry-related texts such as manufacturer brochures and manufacturer websites were often more relevant. Direct correspondence with company representatives also generated a lot of important data. Finally, it is important to address a semantic issue.There is an important distinction between the ton and the tonne. The former is a metric measure referring to 1,000 kg and the latter is an equivalent to about 2,000 lbs. Both the ton and the tonne are presented in this report because data was collected from a variety of sources. Care has been taken to highlight a ton versus a tonne measure but only when it is significant. For example, when comparing a 1, 6000 tonne operation to a 40,000 ton operation the difference is trivial because 1, 6000 tonnes is still much less than the approximately 36,000 tonnes converted. This conversion does not add meaning to the discussion in which it is contextualized and therefore is omitted. 3.0 COMPOSTING BASICS There are many benefits of composting. First, composting diverts waste streams from landfills. The finished compost can also be used as a sustainable landscaping product, replacing fertilizers for example. A composting system also generates opportunities to teach the public about responsible waste management. Compost can also be sold for revenue; however BC legislation must be kept in mind. Finally, composting is not often a “for-profit” venture. Rather, it should be viewed as an investment toward responsible and sustainable environmental management. Aerobic composting is much more common in North America and requires the presence of oxygen. Aerobic conditions are achieved through static aeration (e.g. perforated pipes) or through mechanical turning or agitation (e.g. turned windrows, rotating drums). Anaerobic composting, more often referred to as anaerobic digestion, occurs in the absence of oxygen and produces biogases such as methane. Anaerobic digestion is more common in Europe and Asia and is often done at the mega-scale. Anaerobic digestion allows for the capture of biogases for the purpose of harvesting energy. This technology has not been widely proven locally or at the mid-scale.  All composting systems can be broken down into the following steps: raw material storage, mixing (and related: bulking, shredding, grinding), active composting, curing and screening for quality. Raw material storage refers to both the collection of organics in small bins and the storage of large 4  amounts of raw organics before it is fed into a composting system. Mixing, bulking, shredding and grinding all refer to a preparation process to achieve appropriate C: N ratios, moisture content, porosity, particle size and pH (Shaub& Leonard 1997). If feedstock is carefully adjusted the process is more efficient and there are fewer odour concerns (Shaub& Leonard 1997). Curing is when finished compost is left out to stabilize – this process generally requires about 3 months. Finally, screening for quality is required if compost is intended for sale. Organic materials need to be prepared to obtain optimal chemical and physical attributes before composting. C: N ratio is particularly important. Carbon and nitrogen are sometimes classified as “brown” and “green” materials. Food scraps are “green” materials, meaning that they have generally high nitrogen contents. In order for composting to occur there must be an adequate amount of carbon in the mix. Many materials can be used as bulking agents, such as wood scraps (Cornell Waste Management2005). Odour control is an important component to consider for any composting system. The full extent of odour control systems was beyond the scope of research to explore. Some preliminary suggestions can be derived from this report but it is not exhaustive. Research has shown that bio- filtration systems are very common and widely proven (Schlegelmilch 2005). Bio-filtration is a method of de-odorizing by pushing air through porous organic materials such as woodchips which absorb odours and release purified air. 4.0 COST IMPLICATIONS  Costs of composting are highly variable and greatly depend on the scale as well as the technology. Costs can be divided into three main categories: capital, operational and labour. Labour costs are essentially a subset of operational costs but are dealt with separately because they determine a large proportion of operational costs (Haaren, 2009). In general, costs increase with increasing technology. Below is a table listing common costs of composting for on-site operations.     5  Capital Operational Labour  Research and development  Attorney fees  Accountant fees  Engineering fees  Financing costs  Permits  Site development  Equipment purchase  Insurance  Fuel and lubricants  Equipment amortization  Electricity  Water  Equipment parts  Trucking  Bulking materials  Compliance testing   Wages  Benefits  Training  Number of people   5.0COMPOSTING METHODS/TECHNOLOGIES 5.1Turned Windrows  Windrow composting is an open-air systems requiring mechanical turning to ensure aerobic conditions.  Windrow composting is very common globally (Haaren 2009). Windrows are long, narrow piles about 2 to 3 meters high, 3 to 5 meters wide and up to 100 meters long (Haaren 2009). This design allows high temperatures to be maintained and some oxygen to circulate through the system. Windrows are most often turned with a specialized turning machine. This releases heat and exposes anaerobic pockets to oxygen. These turners are usually equipped with watering attachments to maintain optimum moisture levels.  Turned Windrows (Vancouver Composting Facility 2012)  6  The Vancouver Landfill Composting Facility is a local example, though at a much larger scale. This facility processes about 50,000 tonnes annually andcites a capital cost of $2.5 million, including site development. Capital costs include the following:  1.8 hectare paved surface, electric grinding plant (in- feed hopper, in-feed conveyor, screen, metal detector, 400-hp fixed hammer hog, and out-feed conveyor), 2 front-end loaders, excavator, 2 trommel screens. A figure of $77,000 was provided for the front-end loader, keeping in mind that YVR would only need of these machines. Another estimate for windrow equipment alone, excluding site development, is about $800,000 (Epstein 2011).There is a degree of variability since more sophisticated windrow systems require greater initial investment. For example, preparation of a site by paving is a substantial cost but not necessary for the composting process itself. However, paving prevents run-off from being absorbed by the land (Haaren 2009). The operational cost at the Vancouver facility was $48.69 per tonne in 2010 (City of Vancouver 2010). This figure is subject to a degree of variability as the cost per tonne in 2009 and 2008 were $38.10 and $44.54 respectively (City of Vancouver 2009 and 2008).  A graduate thesis published by Columbia University estimates that open-air windrow composting costs $22 per ton including capital investment (Haaren 2009). Operational costs were estimated at about $12 per ton annually (Haaren 2009).These figures were based on a 44,000 ton per year operation.Additional figures from operations across the U.S. include the following range: $6.5 per ton for 2,000 tons per year, $8 per ton for 17,000 tons per year, $12 per ton for 22,000 tons per year. It is possible to assume that operational costs for YVR (at 1,600 tonnes annually) will be found on the lower end of this range. Given the compost stream at YVR and the above figures a figure of $8 to $10 per tonne is realistic. At the risk of over-generalizing this translates into a range of $10,400 to $78,000 for annual operational costs for YVR. It is important to remember thatcapital costs will not differ substantially because they are largely a function of the technology (e.g. related equipment and labour demand) rather than scale (e.g. amount composted). Therefore, if capital investment is included the first few years of operational costs the figure will be higher. 7   Windrow Operational Costs (Haaren 2009)  Windrow composting is one of the least expensive options but has a much higher turn-over period - 6 months compared to 8 weeks for some of the other technologies.Finally, composting can generate undesirable emissions and odours due to imperfect aeration and material composition. Windrow composing is particularly susceptible to odour and vector problems since it is an entirely outdoor operation. It should also be kept in mind that the Vancouver facility composts primarily yard wastes and not food scraps. This is a very important distinction because food scraps are more likely to generate odorous compounds and to attract vectors such as rodents and birds (Haaren 2009). In fact, a windrow operation in Niagara Falls, Ontario had to temporarily shut down because composting food scraps resulted in significant odours (Haaren 2009; Clean Washington Center 1997). A minimum 300 m buffer zone is recommended for windrows (Clean Washington Center 1997). A table detailing the methane potential of yard scraps versus food scraps is provided below.  8   Methane Potential (Yoshida 2012) Technologies that are schematically related include: turnedstatic piles, aerated static piles (without cover), and aerated windrows (perforated pipes along windrow lengths).  5.2Covered Aerated Static Piles (CASP)  Covered aerated static piles are an open composting system which processes raw materials in large piles. This system is much more technologically complex than traditional windrows or piles. Two companies have been identified which provide the appropriate technology: Harvest Power Energy and Gore-Cover. In fact, Richmond Soil & Fiber operates a CASP system designed by Harvest Power Energy. The Harvest Power CASP system operates a pipe and fan “negative aeration system” for odour control and covers piles in a saw dust and cedar mix to ensure the appropriate temperature is maintained; this cedar cover also aids odour management. A similar technology called Gore-Cover (related to the textile manufacturer Gore-Tex) consists of a concrete foundation with horizontal perforated pipes through which air flows upward into the organics pile. The entire pile is covered by a special membrane cloth that keeps vapors and moisture contained while allowing the passage of nitrogen, carbon dioxide and unused oxygen (Haaren 2009). This system also maintains appropriate moisture and oxygen levels. Both Harvest Power CASP and Gore-Cover include a bio-filtration system for additional odour control. It has been estimated that the electricity used for air circulating the perforated pipes and for the monitoring of the system is about 0.75 kWh per ton (Haaren 2009).Additional electricity is used for screens and biofilters. Therefore, electricity usage is estimated at about 3.3 kWh per ton. CASP systems are more sophisticated and provide a greater degree of control but also require a lot of space. Below is a graph comparing space requirements between traditional windrows and Gore-Cover. 9   Space Requirements Gore-Cover versus Windrow (Haaren 2009)    Harvest Power CASP Cells (Harvest Power Energy, 2012)   The estimated cost for a 44,000 ton per year Gore-Cover facility is about $7 million. A local distributer from NetZero Waste estimated that a 4,000 tonne per year facility would require about $1.6 to $1.7 million. The Gore-cover itself costs $75,000 and is expected to last about 6 years. Some of the 10  capital costs associated with this technology will be similar to turned windrows, such as purchase o front-end loader or excavator and paving. It was not possible to obtain a quote from Harvest Power Energy but it is clear that an investment in the degree of hundreds of thousands dollars or more should be expected.  Labour is the largest category of operational costs, followed by repairs and maintenance (Haaren 2009). Research into the Gore system has found that total operational costs for fuels and supplies is about $50,000 and $20,000 for electricity for a 44,000 ton per year operation (Haaren 2009). Operational costs for this system have been estimated at $42 per ton, though at a much larger scale of operations (Haaren, 2009); operational costs at YVR would be lower given the projected scale of operations. Costs for a CASP system are calculated by the number of pile “units” required. A 44,000 ton per year operation would require 16 pile units (Haaren 2009). The local Gore-Cover distributor estimates that YVR would need three piles – one for storage, one for active composting and one for curing. It is safe to assume that a Harvest Power system would also require at least 2 piles since they are schematically similar. Also, since we know that Gore-Covers last 6 years and cost $75,000 each it is possible to extrapolate a replacement cost of $225,000 every 6 years. Finally, this technology is best applied at larger scales. Though it is possible to apply this technology for 1, 6000 tonnes per year, the cost implications will be significant. It is obvious that a reduced number of pile units indicate a reduced cost as compared to a much larger facility. However, the cost of site development and equipment purchase cannot be scaled down in the same manner. An advantage of CASP over windrows is that the turn-over period is relatively rapid - about 8 weeks of active composting (Haaren 2009). Ultimately, “with respect to cost and complexity of operation, [covered] aerated static piles are situated somewhere between windrows and the in-vessel technologies” (Haaren 2009, p.8). 11   Harvest Power CASP Cells (Harvest Power Energy 2012)   Gore-Cover CASP Cells (Haaren 2009)   12  5.3 Ag-Bag Ag-Bag composting is an enclosed version of windrow composting. Processing is done outdoors but is considered “enclosed” because raw materials are contained within a plastic silage bag during composting. This system also uses perforated pipes to ensure proper aeration. This system offers in-bag odour control and some degree of vector control.  Ag-Bag Technology (Assam 2010)  The cost estimates for this technology are “true” since these figures were calculated for YVR by a local distributor. This system is relatively easy and cost-effective to operate since a specialized bagging machine prepares the material for composting and only a single operator is required. The turn-over period is also relatively rapid at 8 weeks from bagging to finished compost, not including curing time. This bagging machine, the CT-5, costs approximately $25,000 new but may be purchased much cheaper used. $5,000 was the estimate provided for a used CT-5 machine (Pacific Forage Bags Supply 2012). Ten fans are also required to maintain the aeration pipes at $600 each. Therefore capital costs are estimated at about $31,000 if new equipment is purchased. The operational costs include fuel, purchase of the plastic composting bags and labour. The local distributor estimates that YVR would need one bag per week cumulating at about 46 bags per year. Assuming a 1:1 organics to bulking material ratio increases the input to about 3,000 tonnes annually and an operating cost of about $25,000 for the bags alone – about $7 per tonne. It is important to stress that this figure does not include fuel, maintenance and labour costs. However, the labour demand is relatively low. Space requirements are also relatively low. Finally, the plastic bags used in this process are not reusable, but they are recyclable.  13  5.4 In-Vessel Rotating Drum This system is a true “enclosed” process since raw materials are processed entirely within an automated machine called a rotating drum. Food waste is suitable for processing within rotating drums because these systems offer a high degree of odour control including bio-filtration. Conditions are monitored inside the vessel and turning mechanically degrades material. Moreover, the turn-over period is rapidrequiring only up to 1 week of active composting (Haaren 2009).Total annual water consumption for washing the composter and the collection bins was estimated to be 58.0 cubic meters per year (Aleksin 2007).  UBC In-Vessel (University Building Operations) A Wright Environmental (WEMI) drum with a 5 tonne daily capacity is operated at the University of British Columbia. Capital costs for the machine and related equipment was $1.2 million according to UBC operations. This figure includes site development, paving and equipment purchase. The WEMI drum was also evaluated by the University of Toronto. The capital costs were estimated at $1.2 million. Their report found that the composter itself cost $765,000, comprising 69% of capital costs (Rasanu 2008). Operational costs at UBC are about $300,000 annually. Of this total $40,000 is required to maintain the equipment, including parts. $160,000, or 53%, of this total is devoted to labour. UBC employs 4 people to run this system – 2 to operate the equipment and an additional 2 to collect organics in trucks. UBC only composts about 400 to 500 tonnes of material annually which results in a very high operational cost of $750 per tonne. UBC figures are higher than other examples found in the literature which cite the following range of operational costs:  $100 to 280 per ton and $188 to $250 per 14  ton (Haaren 2009; Shammas &Wang 2007). An industry average of several facilities is $130 per ton (Haaren 2009). It should be noted that the very high cost per tonne for UBC operations is a function of low throughput of only about 500 tonnes per year. If UBC operational figures are calculated for YVR’s 1,600 tonnes per year the operational cost would be closer to $188 per tonne. The University of Toronto estimated operational costs of $140,000. Labour was the largest component, comprising 65% of total operational costs (Rosanu 2008). A detailed breakdown of capital and operational costs for the University of Toronto scenario are provided below.Figures from UBC Operations and estimates by the University of Toronto and are reasonable comparisons for YVR given that the scale of operations is very similar.   University of Toronto In-vessel Cost Breakdown (Rasanu2008)  15  5.5 Anaerobic Digestion Anaerobic Digestion (AD)is the degradation of raw materials in the absence of oxygen. AD is rarely referred to as “composting” but for simplicity this term will be used for AD in the discussion. AD generates a lot of biogas that can be harvested for energy. Anaerobic digestion has been proven in Europe and Asia but is not as common in North America (Haaren 2009). Anaerobic digestion is also commonly done at the mega-scale. The organics stream at YVR is much smaller than most manufacturers of anaerobic digesters can accommodate. However, a Canadian company called CHFour Biogas is able to build a digester at the appropriate scale of 100 to 250 meters cubed. The capital cost of this machine is about $200,000 and does not include pumps and generators required to transform captured energy into electricity. A CHFour representative estimated that a complete system, with generation capacity, would cost in the range of $200,000 to $500,000; the digester would comprise about 50% of this cost. This total does not include site development, paving and the purchase of loading equipment such as an excavator which may be needed to fed organics into the digester.Additionally, this capital estimate does not include an odour control system. Taking all of these elements into consideration it is clear that an investment of $1 million is a reasonable estimate. Operational costs were estimated at about $20,000 annually just to maintain and operate the equipment. This does not include labour costs which can comprise over half of operational costs (Haaren 2009). It is estimated that only 1 person and 1.5 hours of labour would be needed to operate an AD facility of this size. However, this figure omits labour required to deliver organics to the AD site.  Fuel and electricity costs are also omitted from this $20,000. It is clear that this figure is much too low and not realistic. Assuming that an AD system and in-vessel aerobic system will have similar labour requirements it is possible to use UBC as a proxy. According to CHFour the labour load is about half that of UBC so a figure of $80,000 is a reasonable estimate for AD labour costs. Moreover, UBC cites a total of $300,000 annual costs. This includes machine maintenance, labour and “other”. Maintenance and labour account for $200,000, so $100,000 is the cost of fuel, electricity, water and insurance. It can be assumed that an AD facility will also procure these “other” costs. Therefore, it should be expected that annual operations should cost at least $200,000.  Space requirements for the digester itself are not great but additional space may be required to store materials before in-feeding and to store finished compost. It may be necessary to construct a building to house these materials which would procure an additional cost.The electricity potential of AD 16  is substrate dependent but the CHFour representative estimated that no more than 50 kW annually in a “best-case” scenario at this scale. Finally, this was the only company identified capable of accommodating YVR scale of operations. AD has not been widely proven in North America but is beginning to expand. Most current AD applications are manure composting on dairy farms. To truly assess the potential of this technology YVR would need to conduct a study to determine the biogas potential of its organics stream. 5.6 Vermicomposting Vermicomposting is generally very difficult to implement on a large-scale and is therefore not common. Small-scale worm composting is relatively inexpensive but becomes costly as throughout is increased. The vermicomposting method identified must be enclosed in a building. The only exception is the storage of raw organics before they are fed into the system. Vermicomposting can also be done outdoors in windrows or piles, but with the anticipation that such a system may cause problems at an airport,only enclosed vermicomposting systems are considered. There is only one high-profile example of large-scale vermicomposting in North America. This is the facility at Charlotte-Douglas Airport in North Carolina. The vermicomposting technology implemented at Charlotte-Douglas is a two-step method which first processes raw organics in an in-vessel drum and then feeds this initial compost into a vermicomposting system developed by Sustainable Agricultural Technologies. Technically any composting method is appropriate for the pre-worm step but an enclosed drum is desirable because it processes organics very rapidly. The reasoning behind this procedure is explained below.  Industrial Composting Unit (Sustainable Agricultural Technologies) 17  The system at the airport cost $1.1 million in capital investments, including an in-vessel drumby DTEnvironmental as well as the vermicomposting units. The cost of worms is negligible at about $6,000 for 300lbs. of worms (BioCycle 2011). Each vermicomposting unit has a daily capacity of about 300kilograms and costs$45,230(Sustainable Agricultural Technologies, 2012). Since YVR generates 4,000 kilograms daily about 10 to 13 vermicomposting units would be required. This would require a capital investment of about $450,000 to $587,990 for 10 to 13 units, respectively. This is in addition to the costs of an in-vessel system.  Therefore, the entire system would cost about $1.7 million. The vermicomposting unitsare not labour intensive to operate since they do not require turning or extended monitoring. It is estimated that 1 to 2 people could monitor 10 to 15 units. The cost of supplying bedding for the worms should also be considered. Appropriate materials include: finished compost, shredded cardboard or newspaper, shredded leaves and non-cedar sawdust (Sustainable Agriculture Technologies 2012). The construction wood-waste stream may be suitable and omit external costs for bedding. Sustainable Agricultural Technologies did not provide a quote for operational costs. The costs of an in-vessel system at this scale are known and since labour and maintenance costs for the vermicomposting units would overlap with the in-vessel costs, it can be estimated that this method would cost about $300,000 to operate. Curing is required post-vessel composting but the vermicomposting units are a “flow-down” system that allows for collection of finished compost from the bottom of the units (Sustainable Agricultural Technologies 2012). This method requires two steps because worm cultures cannot process post-consumer organics. Additionally these worm cultures cannot process meat, dairy, oil or salt. Vermicomposting produces the highest quality compost (Sustainable Agricultural Technologies 2012). This is the reason why Charlotte- Douglas is willing to go to such great lengths. Ultimately, if compost is not intended for sale the additional costs of vermicomposting are unjustified. 5.7 Off-Site Diversion Capital costs for off-site diversion are minimal and include the purchase of containers to collect raw materials and development of signage. Operational costs include training and ongoing labour costs for container maintenance and possible sorting. YVR’s current waste contract includes organics diversion. The full details of this waste contract are not provided butit is known that YVR will be charged less if a portion of its waste streamis diverted from landfills. YVR can potentially divert half of their total annual tonnage. A company representative reported that Richmond Soil & Fibre charges about $55 to $60 per 18  tonne deposited. At a scale of about 4 tonnes daily this would mean about $220 to $240 per day; this is about $88,000 annually. A table comparing costs of the different systems outlined in section 5 is provided below. TECHNOLOGY  CAPITAL COSTS  OPERATIONAL COSTS WINDROWS   $800,000*Equipment only  $8 to $10 per tonne  $128,000 to $160,000 annually  CASP  $1 to $2 million  $42 per tonne* High estimate  $67,200 annually  AG-BAG  $31,000*Equipment only  $7 per tonne* Labour excluded  $11,200 annually  ROTATING DRUM  $1.2 million  $188 per tonne*Proxy  $300,800 annually  AD  $200,000 to $500,000*Equipment only $1 million  $125 to $188 per tonne*Proxy  $200,000 to $300,800 annually VERMICOMPOSTING  $1.7 million  $188 per tonne*Proxy  $300,800 annually  OFF-SITE DIVERSION  n/a $55 to $60 per tonne*Tipping fee only  $88,000 to $96,000 annually Table – Estimated Cost Comparison for Different Composting Technologies Sources not included here due to lack of space  6.0 CONCLUSIONS AND RECOMMENDATIONS  The simplest and least expensive option in the short-term is off-site diversion, but this method is not recommended since operational costs mimic those of on-site operations. Additionally, there are non-monetary benefits of on-site composting such as greater process control, sustainable landscaping options and potential for sale of compost for revenue.The recommended technology is the Ag-Bag system due to low costs, ease of operation, relatively rapid turn-over period and odour control.The in- vessel system has high operational costs but requires relatively little space, offers high odour and vector control and processes material very rapidly. Turned windrows are relatively simple to operate and have low operational costs but capital costs are substantial for site development and equipment purchase. In 19  addition, odours and vectors are difficult to control with windrow composting. CASP cells are technically feasible at the projected scale but this technology is not recommended given high capital costs and increased system complexity which would increase labour costs. The CASP system also has substantially higher space requirements. The least suitable options are AD and vermicomposting because the very high capital investment required is unjustified at the scale being considered; less costly and less complex systems can meet the airport’s waste management needs. Vermicomposting should only be considered if an in-vessel system is selected and the compost is intended for sale. Additionally, YVR would need to research the biogas potential of its organics stream to fully assess the true benefit of an Anaerobic Digestion system.  ADVANTAGES DISADVANTAGES OPEN WINDROWS  Low operational costs  Odour problems  Vector problems  Slower rate COVERED ARATED PILES  Faster rate  Odours controlled  Efficient  Large capital investment  High operating costs AG-BAG  Efficient  Easy to operate  Relatively low cost  Ongoing purchase of silage bags IN-VESSEL ROTATING DRUM  High degree of control  Contained system  High odour and vector control  Lower quality compost  High capital costs  High ongoing operational costs ANAEROBIC DIGESTION  Energy harvesting  Reduced climate change impact  High capital costs  High operational costs  Low electricity output at this scale VERMICOMPOSTING  High quality compost  Two-step process  High operational costs OFF-SITE DIVERSION  Very few capital costs  High operational costs  20  This report has not dealt with other important issues relating to composting such as legislative demands, detailed bulking requirements, leachatesand CO2 output. Preliminary research has found that CO2 emissions will be similar for windrows and CASP cells but that ammonia emissions are much higher during windrow composting (Haaren 2009).Researchhas also shown that windrows have the worst effect on the environment because the process is not contained (Haaren 2009). Ag-Bag and in-vessel technology will also release carbon into the atmosphere. Anaerobic Digestion has the lowest climate change impact because it captures climate warming gases. The effect of carbon emissions related to transport is a separate issue but transport is a minor contributor to climate warming emissions compared to emissions from biodegradation (Haaren 2009). Other environmentalconsiderations include electricityand fuel demand.Additional research should look into the appropriate number and distribution of collection bins inside the terminals and satellite locations to ensure optimal collection. This includes determining the optimal pick-up route.Costs associated with setting up collection bins on- site are common to all of the technologies. Procedures for selling of compost were beyond the scope of research and omitted.  7.0 REFERENCES Ag-Bag Environmental.(2002). Composting made simple with Ag-Bag Environmental’sEcoPod Technology. Aleksin, S., Guest, G., and Ng, C. 2007. The Compost System at the University of British Columbia.University of British Columbia.(Accessed April 3, 2012). 1. Aslam, D. (2010, April ). The science behind in-vessel composting. Paper presented at 25th annual biocycle west coast conference , San Diego, CA. BC Advisory Committee on Anaerobic Digestion.(Accessed April 3, 2012).<>. BioCycle.Composting Roundup: Vermicomposting at international airport.(2011, December).BioCycle , 14. 21  Bonhotal , J., Schwarz, M., &Feinland, G. (2011). In-vessel composting options for medium-scale food waste generators .BioCycle ,March , 49-53. 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