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Comparison of end of life options for waste paper towel at the University of British Columbia Deere, Brendan; Yang, Qifeng; Bahrami, Nazani Apr 20, 2013

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UBC Social Ecological Economic Development Studies (SEEDS) Student Report       Comparison of End of Life Options for Waste Paper Towel at the University of British Columbia Brendan Deere, Qifeng Yang, Nazani Bahrami  University of British Columbia CHBE 484 April 20, 2013           Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report”.  Comparison of End of Life Options for Waste Paper Towel at the University of British Columbia   Br e n d a n D e e r e  , Q i f e n g Y a n g  , N a z a n i n B a h r a m i     Acknowledgements  We would like to express our appreciation to Brenda Sawada for her support and insight into this project. We would also like to recognize the UBC Department of Alternative Energy and the Department of Municipal services for their cooperation.   Executive Summary  In this paper, three paper towel disposal options were evaluated – landfill, compost and gasification (Nexterra Plant). The seed office would like to find that if it is feasible that UBC collects the paper towel waste and sends it to Nexterra Plant to produce syngas. Below is the summarized of the findings. Economy: $0.073/kgPT landfill, $0.079/kg compost, and -0.062 gasification; thus, gasification is economic feasible. Environement: 1.882kgCO2/kg PT landfill, 0.7577 kgCO2/kg PT, and 1.15kg CO2/kg PT; thus, the compost option is the most environmental- friendly option. Social impact: 9.243 kg/year/mg/m3,5.85 kg/year/mg/m3,and  332 kg/year/mg/m3; thus, the composting option also has the lowest health impact. Based on the finding, the compost option is the best based on the overall consideration in this paper; however, the gasification gives economic savings; even though it is not as environmental-friendly as the compost option, it is feasible.               i Table of Contents  Acknowledgements .......................................................................................................................... i Executive Summary ......................................................................................................................... i Table of Figures ............................................................................................................................. iii Table of Tables .............................................................................................................................. iii 1.0 Introduction ............................................................................................................................... 1  1.1 Background ........................................................................................................................... 1  1.2 Scope ..................................................................................................................................... 1  1.3 Functional Unit...................................................................................................................... 2  2.0 End of Life Options .................................................................................................................. 2  2.1 Landfill .................................................................................................................................. 2  2.2 Composting ........................................................................................................................... 3  2.3 Gasification ........................................................................................................................... 4  3.0 Comparison ............................................................................................................................... 5  3.1 Economy................................................................................................................................ 5  3.1.1 Landfill ........................................................................................................................... 6  3.1.2 Compost.......................................................................................................................... 6  3.1.3 Gasification..................................................................................................................... 6  3.1.4 Summary of Disposal Economics................................................................................... 7  3.2 Environment ...................................................................................................................... 8  3.2.1 Landfill ........................................................................................................................... 8  3.2.2 Compost.......................................................................................................................... 8  3.2.3 Gasification..................................................................................................................... 8  3.2.4 Summary of Environmental Impacts .............................................................................. 9  3.3 Society ................................................................................................................................. 10    ii 3.3.1 Landfill ......................................................................................................................... 10  3.3.2 Compost........................................................................................................................ 10  3.3.3 Gasification................................................................................................................... 10  3.3.4 Summary of Social Impacts.......................................................................................... 11  4.0 Recommendations ................................................................................................................... 11  5.0 Conclusion .............................................................................................................................. 11  6.0 Bibliography ........................................................................................................................... 12  Appendices.................................................................................................................................... 13  Appendix A: Calculations ......................................................................................................... 13       Table of Figures  System Boundary Diagram ............................................................................................................. 2  Landfill System Diagram ................................................................................................................ 3  Compost System Diagram .............................................................................................................. 4  Gasification System Diagram ......................................................................................................... 5    Table of Tables  Table 1: Composition of landfill biogas ......................................................................................... 3  Table 2: Economics of the UBC Nexterra Plant ............................................................................. 6  Table 3: Summary of disposal economics ...................................................................................... 7  Table 4: Emission Factors for Diesel Fuel...................................................................................... 9  Table 5: Summary of disposal emissions........................................................................................ 9  Table 6: Summary of global warming impacts ............................................................................. 11  Table 7: Summary of disposal health impacts .............................................................................. 11          iii 1.0 Introduction   1.1 Background  UBC currently purchases 2.82 km2 of White Swan Long Roll paper towel (PT) per year. This is approximately 70.5 tons. It can be assumed that the quantity of paper towel disposed of is directly proportional to the quantity of paper towel purchased (SEEDS paper). The paper towel is purchased from Kruger and is 100% recycled fiber and 88% post-consumer fiber (Kruger 2013). This brand is FSC and Ecologo certified making it an excellent environmental choice for UBC. Currently, the UBC compost program only accepts food services paper towel waste and sanitary paper towels are sent to a landfill 17 km from the university. UBC Operates an in-vessel compost unit and a biomass gasifier (Nexterra) both of which could be suitable for sanitary paper towel disposal. This study will explore these options relative to sending the waste paper towel to landfill. The end of life options will be evaluated from economic, environmental and health impact perspectives. Finally this study will recommend the best disposal process with relative to the assessment parameters.  1.2 Scope  The purpose of this report is to compare three disposal options for paper towels and recommend the best strategy to manage waste paper towel. This analysis focuses of the transportation of waste paper towel to the disposal sites and the disposal process. It excludes all procurement activities and the use of the disposal process products (if any). This study also excludes the offset credits from the production consumer fertilizers and wood pellets Figure 1: System Boundary Diagram illustrates the system boundaries that are within the scope of this study.                       1   Figure 1: System Boundary Diagram    This study assumes that the manufacturing and acquisition of paper towel is the same regardless of the waste disposal method. End of life options will be compared based on their carbon equivalent emissions and on the cost or savings associated with implementation.    1.3 Functional Unit  The comparison categories will be compared on a per-kilogram of paper towel basis to be able to compare between processes. The functional units for this project will be KgPT.   2.0 End of Life Options   2.1 Landfill  Landfilling is the do-nothing option. The waste is sent to a landfill for disposal by decomposition. Anaerobic bacteria consume the waste and break the organic matter into cellulose, amino acids, and sugars. Methane (CH4) and carbon dioxide (CO2) are produced by the process. Although this process produces greenhouse gasses, landfilling also stores a fraction of     2 the gasses when organic waste is not fully decomposed. On-site biogas contains methane, carbon dioxide nitrogen and oxygen as shown in Table 1: Composition of landfill biogas.  Table 1: Composition of landfill biogas  Composition of on-site biogas Percentage Methane (CH4) 41% Carbon dioxide (CO2) 34% Nitrogen (N2) 22% Oxygen (O2) 3% (U.S.EPA, 2008).    This study will evaluate the impacts associated with sending waste paper towel produced at UBC to the Ecowaste landfill located 22 km away from the university. Figure 2: Landfill System Diagram describes the path of the paper towel as it is sent to landfill.     Figure 2: Landfill System Diagram     2.2 Composting  Composting is the aerobic digestion of organic matter. In a solid waste facility or composting machine, the organic matter must be mixed with water, exposed to air and mixed. Given enough time, the organic matter starts to break down. The time required for the organic   3 matter to decompose is dependent on the composting vessel used. The aerobic digestion of organic matter produces CO2 and CH4. Composting of waste paper towel is beneficial because it can improve the nutrient quality and destruct pathogen, and reduce the production of odor.  UBC municipal services do not currently compost sanitary paper towel. This analysis considers off-site composting at the Harvest power 17 km from the university. Transportation of the waste to the facility will incur monetary and GHG emission costs. Figure 3 summarized the composting process considered.    Figure 3: Compost System Diagram     2.3 Gasification  The Nexterra plant at UBC uses an updraft gasification unit to produce syngas from biomass. In the gasification unit, the feedstock is subjected to drying, pyrolysis and is reduced to ash. Pyrolysis is the conversion of a carbonaceous solid to a combustible gas. This reaction takes place in a low oxygen environment producing CO2, CO, H2, CH4 and H2O. Contaminants such as ash particles and tars are also formed but can be removed with further processing (Belgiorno 2002). This process produces syngas which is separated into two streams. The first is injected into an oxidizer where the reaction energy can be collected by a boiler to produce steam and hot water. The second stream is cleaned with a thermal cracking process to remove tars; then fed into a natural gas combustion engine to generate electricity. Flue gas containing CO, CO2, H2O, and  4 NOx is emitted by this process. Gasification is considered to be more environmentally friendly than incineration because corrosive contaminants can be more easily removed. Syngas has a higher energy density than raw feedstock and is therefore economically preferable to incineration (RMS Ross Corporation 2013). Paper towel used as a fuel source would travel a distance of 10 km while being collected. This was estimated based on the distance a single vehicle must travel to visit the major buildings on campus. Figure 4: Gasification System Diagram summarizes the path of the paper towel during the gasification process.        Figure 4: Gasification System Diagram      3.0 Comparison   3.1 Economy  The three considered processes incur transportation and operational costs. This section assumes that transportation was done by a front loading diesel waste disposal vehicle with a paper towel capacity of 1815 kg and a fuel efficiency of 0.2 l/km. The disposal costs associated with each process are explored in the following sections.         5 3.1.1 Landfill  As shown in Table3, the total cost of Landfill is $0.073/kgPT; this cost includes the transportation cost and landfill rates. To calculate the transportation cost, students assumed a light truck is used to transport the waste, and roundtrip is required for transportation of the waste. With the distance, students could calculate the number trips, which gave the fuel cost; the cost of landfill was found by the rate of the waste; the rate of the waste is $63/ton. In short, the cost is higher than the Nexterra plant and lower than the composting site; however, one can see that the cost of landfilling is close to the cost of composting.  3.1.2 Compost  The method to calculate the transportation cost for compost is basically the same of the one of landfill; since the distance from UBC to the compost facility is longer than to landfill, it would have a higher transportation cost. To calculate, students used the horsepower of the composting machine to estimate the electricity, which is the main the cost of the process. In this part, some uncertainties exist because some hidden costs were uncovered; however, it shows that the cost of the composting is already the highest; thus, conclusion could be drawn at this point; composting option is the most expensive of the three.  3.1.3 Gasification  The UBC Nexterra plant economics are summarized in Table 2: Economics of the UBC Nexterra Plant:  Table 2: Economics of the UBC Nexterra Plant  Cost CAD$/year Start up 27,000,0001 Fuel 800,0002 Operators 600,0002 Maintenance 200,0002 Total 1,600,000 $/ GJ 8.27 1The Ubyssey 2012 2Interview with Jeff Giffon   Neglecting the cost of the initial investment the operational cost per year is 1.6 million  dollars. The Nexterra plant consumes 13 thousand tons of woodchips annually. The specific heat  6 of wood is 14.89  MJ/kg. From this it can be calculated that the energy cost of biomass gasification at UBC is $8.27/ GJ. The price of natural gas is approximately $8/ GJ. Despite this, UBC Nexterra projects a savings of $ 850,000/year in natural gas costs (Staley 2012). Given that the paper towel would be disposed of regardless of the nature of the disposal, the cost of purchasing the PT can be neglected and gasifying paper towel can actually provide a savings to the Nexterra plant. Gasifying paper towel would offset 1043 GJ of the plant’s energy demand annually. This is a savings of $4,310 per year or $0.061/kgPT in The disposal vehicle would require 39 trips and 78 l of fuel to move the annual quantity  of waste paper towel. The current price of diesel fuel is $1.40/l Therefore the cost of transporting the paper towel to the gasification centre is $109/year. Using paper towel as biomass at Nexterra also offsets the transport of 70 tons of woodchips from Cloverdale Fuel in Langley (120 km round trip) would offset 8 woodchip shipments (kcxi.com). This results in a $235.2/year savings in fuel costs or $0.0033/kgPT.  3.1.4 Summary of Disposal Economics  Table 3: Summary of disposal economics shows that disposal by gasification yields the greatest economic advantage. Gasifying waste paper towel would save on fuel costs for transportation and for the Nexterra plant. However, the savings are almost negligible; $4,310/year.   Table 3: Summary of disposal economics  Process Landfill Compost Gasification  (CAD$/kgPT) (CAD$/kgPT) (CAD$/kgPT) Transportation 0.01 0.002 -0.001 Disposal 0.063 0.077 -0.061 Total 0.073 0.079 -0.062              7 3.2 Environment     3.2.1 Landfill  Landfill is the worst option based on the concerns of environment because it produces the largest amount of CO2 comparing with the other two options. To calculate the production of CO2, given UBC purchased 9500 cases of paper towel from Kruger, which had a total weight of 70.5 ton. The area of an individual paper towel is 20 cm2; with this value, the weight of paper towel is found. Then, the total number of each pull can be calculated. The reason to calculate the total number of pull because each pull of paper towel produced 10g CO2. Then the amount of CO2 can be calculated. Landfill also produces CH4; thus, it has the highest global warming impact of the three options.  3.2.2 Compost  The compost option produces the least amount of CO2 of the three options; based on the environmental concern, this option seems the best because it produces less CO2 and CH4; even though CH4 is not compared here, the compost option indeed produces less methane. Some uncertainties occur here because the contaminated paper towel could not be composted due to the health reasons. Contamination of the paper towel has been neglected in the rest  of this study  3.2.3 Gasification  Paper towel is primarily composed of cellulose. For this study it was assumed that the specific energy of paper towel is approximately that of wood (14.89  MJ/kg). The density of paper towel was shown to be 0.025 kg/m2 (see appendices). Therefore the energy density of paper towel assuming a constant thickness is calculated to be 0.37  MJ/m2. UBC can extract 678 GJ/year from the gasification of paper towel.  The Energy Department at Sao Paulo State University showed that for syngas produced using eucalyptus biomass with a moisture content of 20% the total carbon equivalent emission factor is 0.080228 kgCO2/ MJproduced. This indicates that gasifying waste paper towel at UBC would produce 83.7 tons of CO2 equivalent gasses per year or 1.19 kgCO2/kgPT.    8 As shown above, the paper towel will travel 10 km during the collection process. For consistency of comparison it will be assumed that the PT will be transported by the same vehicle that would bring the waste to landfill. In practice this vehicle could be replaced with light capacity biodiesel or electric vehicle from the municipal services fleet. Table 4: Emission Factors for Diesel Fuel from Environment Canada shows the emission factors for diesel fuel. These values result in 217 kgCO2 emissions per year. This is 0.0031 kgCO2/kgPT. Gasifying paper towel would also offset 7 shipments of fuel from the Cloverdale Fuel  facility in Langley. This would result in an emissions savings of 469 kgco2 per year or 0.0067 kgCO2/kgPT.   Table 4: Emission Factors for Diesel Fuel   CO2 (g/L) CH4 (g/L) N02 (g/L) Diesel 2663 0.133 0.4    3.2.4 Summary of Environmental Impacts  Table 5: Summary of disposal emissions compares the carbon equivalent emissions from each of the three considered processes. From an emissions perspective it is clear that a compost facility equipped with emission recovery is the best option offering GHG reduction of 60%.  Table 5: Summary of disposal emissions  Process Landfill Compost Gasification  (kgCO2/kgPT) (kgCO2/kgPT) (kgCO2/kgPT) Transportation 0.013 0.01 -0.004 Disposal 1.869 0.7477 1.19 Total 1.882 0.7577 1.15    Global warming Impact(tons CO2 equivalent) Nexterra 83.19 Composting 52.7 Landfilling 3468   9 Table6: Global warming impact     3.3 Society   3.3.1 Landfill  According to Table 7, this option has the highest health impact because it produces CH4 and CO2. Students used the course note to calculate these values. The threshold limit values are provided in the course notes. The total production of emissions were found and shown in the sections above; thus, the toxicity index and health impact could be calculated.  3.3.2 Compost  As shown in Table7, composting has the lowest health impact, which is considered the best option based on this value. This value is important for the workers and people around the facility. Bothe the compost option and gasification have low values; however, the gasification option is still 36% higher than that of the composting option.  3.3.3 Gasification  Jeff Giffon, Head of Alternative Energy at UBC believes that dry paper towel could be introduces to the current feedstock provided there were no harmful additives. Chlorine would be particularly harmful to the process as it would be converted to hydro chloric acid (HCL) and damage the oxidizer and turbines. The UBC Nexterra plant is not equipped with the wet scrubber process required to remove the HCl from the syngas. Although the paper towel purchased by UBC is FSC and Ecologo certified; neither certification mandates the use of chlorine free processes. For this reason the sanitary waste could not be processed by the UBC Nexterra plant without further evaluation of the chlorine content of the paper towel and the feasibility of adding a wet scrubber to the Nexterra process. Operators at the plant are reluctant to modify the process at the moment as it is still undergoing trials (Giffon 2013).           10 3.3.4 Summary of Social Impacts  Table 7: Summary of disposal health impacts indicates that landfilling has a high health impact when compared with alternatives. Based on this data, landfilling is not considered as a good option for disposal. The best disposal option relative to health impacts is composting.  Table 7: Summary of disposal health impacts   Health Impact Nexterra 9.243 Composting 5.85 Landfilling 332    4.0 Recommendations  Biomass gasification showed the greatest potential from both an economic and greenhouse gas emission perspective, however the UBC plant is not equipped to process the harmful acidic by-products that would form as a result of the bleach used to white the paper towel.  Although UBC compost does not currently accept waste sanitary paper towel, this was shown to also be beneficial in terms of greenhouse gas reduction. This would result in a reduction of 78 tons of GHG gasses annually at a cost of $5,500/year. This study recommends that UBC explore the opportunity of composting waste sanitary paper towel as part of their greenhouse gas reduction initiative.   5.0 Conclusion  This study compared the possible end of life options for the waste sanitary paper towel at the University of British Columbia. It was shows that, although gasification of the paper towel resulted in an economic savings and a GHG reduction of 70 tons/year, the plant does not have the capacity to accept the current brand of paper towel as a fuel. Based on this fact it was concluded that composting is the most viable option for the end of life disposal of waste sanitary paper towel. This would result in a GHG reduction of 55 tons per year. The UBC compost   11 program does not currently accept waste sanitary paper towel. The waste would therefore need to be shipped off campus to a nearby compost facility. More important GHG reductions could be achieved if gasification were a viable option or the UBC compost program allowed sanitary paper towel into the process.   6.0 Bibliography  Beck-Friis, B, S Smars, H Jonsson, and H Kirchmann. "Gaseous Emissions of Carbon Dioxide, Ammonia and Nitrous Oxide   Belgiorno, V, G De Foe, C Della Rocca, and R.M.A Napoli. "Energy from gasification of solid wastes." Waste Management 23 (2003): 1-15. Web. 8 Apr. 2013.  Boloy, R, J Silveira, C Tuna, C Coronado, and J Antunes. "Ecological impacts from syngas burning in internal combustion engine: Technical and economic aspects." Renewable and Sustainable Energy Reviews 15 (2001): 5194-201. Web. 8 Apr. 2013.  Brennek, H, L Gardner, and S Song. "Streamlined LCA of Paper Towel End of Life Options for UBC SEEDS." (2012). Web. 8  Apr. 2013.   Dornburg, V, and A Faaij. "E ciency and economy of wood-rÿed biomass energy systems in relation  to scale regarding heat and power generation using combustion and gasicÿation technologies."  Biomass and Bioenergy 21 (2001): 91-108. Web. 8 Apr. 2013.  Eitzer, B. "Emission of Volatile Organic Chemicals from Municipal Solid Waste Failities." Environment  Science and  Technology29 (1995): 896-902. Web. 8 Apr. 2013.   Ekinci, K, H.M. Keener, and D.L. Elwell. "Composting Short Paper Fiber with Broiler Litter Additives." Compost Science and  Utilisation 8.2 (2000): 160-72. Web. 8 Apr. 2013.   Foley, B.J., and L.R. Cooperband. "Paper Mill Residuals and Compost Effects on Soil Carbon and Physical Properties."Journal of Environmental Quality 31 (2002): 2086-95. Web. 8 Apr. 2013.  from Organic Household Waste in a Compost Reactor under Di!erent Temperature Regimes." Journal of Agricultural  Engineering Resources 78.4 (2001): 423-30. Web. 8 Apr. 2013.   Gallardo-lara, F, and R Nogales. "Effect of the Application of Town Refuse Compost on the Soil-Plant System: A Review."Biological Wastes 19 (1987): 35-62. Web. 8 Apr. 2013.  Kurkela, E, P Stahlberg, P Simell, and J Leppalahti. "Updraft Gasification of Peat and Biomass." Biomass 19 (1989): 37-46. Web.  8 Apr. 2013.   Power Hearth. RMS-Ross Corporation, 2013. Web. 8 Apr. 2013.   Staley, R. "Gasificatio Redux." L’ACTUALITÉ CHIMIQUE CANADIENNE (2012). Web. 8 Apr. 2013.   Whitty, K, H Zhang, and E Eddings. "Emissions from Syngas Combustion." Combustion Science and Technology 180.6 (2008):  1117-36. Web. 8 Apr. 2013.  12 Appendices   Appendix A: Calculations   A.1 Gasification Emissions  Assumptions    Wood, paper towel and eucalyptus leaves have similar composition  Specific energy of wood is 14.89  MJ/kg  Emission factor for gasification of eucalyptus leaves is 0.080228 kgCO2/ MJ  UBC orders 70.5 tons of paper towel annually with an area of (from Kruger website)     Energy Content    Greenhouse Gas emitted       A.2 Gasification Economics  Assumptions:    Cost of wood is $800,000/year  Nexterra uses 13,000 tons/year  Specific heat of wood is 14.89  MJ/kg   13  Paper towel produces 1043 GJ annually    Cost of Energy     Savings   Paper towel would offset 1043 GJ   Cost of wood (by same calculation as above) is $4.13/ GJ    CO2 production of transportation:   Landfill(22km)   22km*0.621 mile/km = 13.6mile   Light truck fuel economy: 7mile/gallon   136 mile / 7mile/gallon = 1.95 gallon required.   Round trip: 1.95*2= 3.905 gallon=17.73L diesel required   17.73L*2.68kg diesel/ kg = 47.51 kg CO2   Paper towel weight: 70500kg. About 20 times of transporting 47.51*20/ 70500 = 0.015kgCO2/kgPT           14 Compost(17km)   17km*0.621miel/km=10.563 mile   Same truck   10.563/7 = 1.51 gallon diesel   Round trip = 1.51*2=3.01 gallon = 13.638 L diesel required   13.638 L * 2.68 kg/L = 36.55kg CO2   36.55*20/70500 = 0.01036 kgCO2/kg PT         CO2 production   Annual CO2production:   Landfill: 9500 cases purchased=70500 kg of paper towel   10 g CO2 produced per paper towel goes to landfill   Each pull of paper towel: 20cm*20cm   Paper density: 134g/m2   Each paper towel weight:   134g/m2/(0.2*0.2)m2=5.36 g   Total CO2 produced: (70500kg/0.00536kg)*0.01kg=131775.7 kgCO2/year   Landfill: 131775.7kg/70500 kg=1.869 kgCO2/Kg paper towel Composting: CO2 is found to be 2.5 times less than landfill production. Thus, Total CO2 produced=137892.02 kg    15 Composting=0.747 kgCO2/kg paper towel   COST:   Composting: machine horsepower:200,000KWh/year Electricity=0.07$/KWh Cost=200,000KWh/year*0.07$/KWh=$14000/year Capacity: 5 tonnes/day*365=1825 tonnes/year =1825000kg/year   ($14000/1825000)*(70500) =$5408/year   5408/70500=$0.077/kg Paper towel   Landfill: ($63/tonnes*70500kg)/ (1000kg*70500kg) =$0.063/kg paper towel   Total environmental impact   CO2 e=∑(GHG*GWPi)   CO2 e: emissions in carbon dioxide equivalents   GHGi: emissions of GHG pollutant   GWPi: GWP of GHG pollutant “i”   N: number of GHG emitted from the source   NOTE:In this LCA only main emission sources are considered.   Nexterra plant: (1.18kg CO2/Kg pt)*(70500/1000)=83.19tonnes CO2 equivalent   Composting: 0.7477*(70500/1000)=52.71285tonnes CO2 equivalent   Landfilling: ((1.869*70500)+(1.869*70500*0.41/0.34))/((1000))=3468.5 CO2 eq   According to EPA CO2:CH4   34%:41%    16 Human health risk assessment:   TLV(mg/m3)   CO2 :90001/TLV=0.00111   CH4:500 --1/TLV=0.002   Health impact or toxicity potential=∑Ei/TLVi   Ei-emission rate   Nexterra plant: health impact=(83190/9000)=9.24kg/year/mg/m3   Composting: Health impact=(52712.85/9000)=5.857kg/year/mg/m3   Landfill: Health impact=(131764.5/9000)+(158892.49/500)=332kg/year/mg/m3                                         17 

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