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An assessment of GHG emissions of two organic waste processing options for UBC Chen, Xinyi; Hamdy, Hany McRea; Wells, Ralph 2014-05-16

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 UBC Social Ecological Economic Development Studies (SEEDS) Student ReportHany McRae Hamdy, Ralph Wells, Xinyi ChenAn assessment of GHG emissions of two organic waste processing options for UBCCEEN 523May 16, 201410001657University of British Columbia 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”.  A UBC SEEDS ProjectCEEN 523 Term PaperXinyi ChenHany McRea HamdyRalph WellsMay 16, 2014An assessment of GHG emissions oftwo organic waste processingoptions for UBCiTABLE OF CONTENTSExecutive Summary................................................................................................................1Introduction ..........................................................................................................................2Project Objective......................................................................................................................... 2Option Descriptions .................................................................................................................... 2Project Scope .............................................................................................................................. 3Methods................................................................................................................................3Functional Unit............................................................................................................................ 3System Description ..................................................................................................................... 3Food Waste ................................................................................................................................. 4Emission Factors ...................................................................................................................... 4Transportation ............................................................................................................................ 5Emission Factors ...................................................................................................................... 6Electricity..................................................................................................................................... 6Global Warming Potential........................................................................................................... 7Combined Heat and Power (CHP) ............................................................................................... 7Results...................................................................................................................................8The UBC In-Vessel Composting System ...................................................................................... 8Harvest Power Anaerobic Digestion System:.............................................................................. 9System Emissions for Organic Waste Processing Options ........................................................ 10On-Campus Option ................................................................................................................ 10Off-Campus Option ................................................................................................................ 11Sensitivity Analysis .................................................................................................................... 12Discussion............................................................................................................................ 14Limitations and Future Work .................................................................................................... 14Conclusions ............................................................................................................................... 15Appendix 1: Equations ......................................................................................................... 16On-Campus Option.................................................................................................................... 16Off-Campus Option ................................................................................................................... 16Sensitivities ............................................................................................................................... 17Definition of Terms ................................................................................................................... 17Acknowledgements.............................................................................................................. 19References........................................................................................................................... 19iiTABLESTable 1.  Waste distribution among Metro Vancouver Facilities. ................................................... 4Table 2. Emission Factors for organic waste. .................................................................................. 5Table 3.  Distances and CNG consumption for transportation........................................................ 6Table 4. Emission factors for transportation fuels. ......................................................................... 6Table 5.  Emission factors for BC Hydro electricity production....................................................... 6Table 6. Global warming potentials for methane and nitrous oxide. ............................................. 7Table 7. CH4 Production values from Harvest Power. .................................................................... 7Table 8.  System CO2e emissions for on-campus and off-campus options. ................................. 10Table 9.  Sensitivity analysis results for transportation, electricity and rejection rate................. 13FIGURESFigure 1.  Mass flow and CO2e emissions from UBC In-vessel Compost System. ......................... 8Figure 2.  Mass flow and CO2e emissions for off-campus anaerobic digestion system. ................ 9Figure 3.  System CO2e emissions for on-campus and off-campus options. ................................ 10Figure 4.  Sensitivity analysis results for transportation, electricity and rejection rate................ 121EXECUTIVE SUMMARYIn our study, we evaluate two food waste processing options for the University of BritishColumbia for emissions of greenhouse gasses.  We considered an on-campus option based onthe existing UBC in-vessel aerobic composting system, and an off-campus option based on ananaerobic digestion system located in Richmond, BC that generates energy from biogas.We found that of the two options we considered, the off-campus anaerobic digestion optionhad net 52 tonnes lower CO2e emissions than the on-campus option based on the emissionfactors and assumptions we used.  We found that emissions from food waste diverted to landfillfor the on-campus option and carbon stored in soil from compost were the most significantfactors affecting emissions.  We further found that emissions related to transportation wereminor relative to other emissions as were emissions from electricity used for the on-campusfacility.We conclude that both options provide significant reductions relative to sending food waste toregional waste disposal facilities.  We recommend that UBC consider the benefits of including awaste sorting system to reduce or eliminate rejected food waste in any future processingoptions implemented by UBC.Further work could focus on completing energy and mass balances for the off-campus option,and determining associated emissions.  A full life cycle analysis could consider the fate of allcampus food waste (not just waste diverted to organic processing facilities) and evaluate arange of human health and environmental impact factors.2INTRODUCTIONAs University of British Columbia prepares to implement its Zero Waste Plan, organic wastediverted to composting is expected to triple over the next 3 – 5 years, increasing to 1300 tonnesannually by 2017 (SEEDS 2013). This expansion will likely exceed the capacity of UBC’s existingcompost system and this, along with operational issues, has led UBC to consider alternativeoptions including expansion of the existing system or sending some or all food scraps for off-campus processing (SEEDS 2013).Project ObjectiveThe objective of this project is to evaluate two organic waste processing options for UBC. Oneoption is based on the existing on-campus aerobic composting facility, the second option isbased on sending food waste off-campus to the Harvest Power biogas facility in Richmond, BC.Option DescriptionsThe on-campus option utilizes an ‘in-vessel’ fully-enclosed system which allows for a controlled,accelerated, aerobic composting process.  The UBC facility, the first of its kind at a Canadianuniversity, is capable of processing up to 5 tonnes/day and generates raw compost in 14 days(this excludes maturation time) 1. It includes a negative aeration biofiliter system.The off-campus option is a biogas and composting facility that is based on an anaerobicdigestion (AD) system that generates methane and other gasses.  It utilizes a high solids,mesophilic, multi-stage batch process to process food and landscaping organic waste2.  It alsoincludes an aerobic composting stage to process solids from the anaerobic stage and otherorganic waste. The aerobic stage includes a negative aeration biofiliter system.  The HarvestPower facility is capable of processing up to 30,000 tonnes/year and generating up to 2 MW ofpower through a combined heating and power(CHP) system2.The off-campus option also includes a proposed sorting facility operated by Earth Renu EnergyCorp, located on Annacis Island.  The sorting facility would remove contamination from UBCfood waste, ensuring food wasted delivered to the Harvest Power facility is nearlycontamination free.1 UBC in-vessel compost system description.2 Harvest Power biogas facility description.3Project ScopeThe focus of our evaluation is on greenhouse gas (GHG) emissions produced from processingfood waste for each option.  We consider emissions generated by the processing facilities and bytransportation required for the off-campus option and for transportation of food waste divertedto regional waste facilities due to contamination for the on-campus option.  We also considerbackground emissions from electricity consumed by the on-campus option.  Finally, we include apartial evaluation of CHP power production for the off-campus option but were not able toinclude a full energy balance evaluation for the off-campus option due to incomplete data.We focus on the food waste generated on the UBC Point Grey campus that is delivered tocompost facilities.  We do not consider the fate of campus food waste that is not diverted tocomposting and remains in the waste stream.Our study is a UBC Social Ecological Economic Development Studies (SEEDS)3 project that wasundertaken with support from the UBC Campus Sustainability Office.METHODSFunctional UnitFor our study, we defined our functional unit as mass of food waste, in metric tonnes, since thisis the unit of interest for UBC, and is common for the alternative systems under consideration aswell as for the waste stream.  In consultation with the project sponsor, we selected the mass offood waste expected to be diverted to compost in 2014, which is estimated to be 650 tonnes.Thus, our functional unit is defined as: 650 tonnes of UBC food waste.System DescriptionWe considered three sub-systems to be within the scope of our study.  The two organicsprocessing systems themselves (and waste disposal facilities for diverted food waste due tocontamination), the transportation between UBC and the organics processing facility for the off-campus option and to waste disposal facilities for diverted food waste.  We also consideredelectricity consumption at the organics processing systems. Methods for each system aredescribed in further detail below.3 SEEDS program description.4We did not consider the fate of UBC food waste that was not diverted to the organics processingsystems (i.e., campus food waste that is directly diverted to the waste stream).  We also did notconsider landscape organic waste (which is processed by UBC in a separate system), or barkmulch (which is processed in the same on-campus system as food waste) since the desire was tocompare emissions from the food waste component that is common to both systems.Food WasteThe food waste systems considered include the on-campus aerobic compost system, the off-campus anaerobic digestion and composting system, and landfill and waste-to-energy (WTE)options for diverted waste. For the mass flow of organic food waste, we assumed that 5% offood waste was non-organic contamination, and that due to contamination 20% of food wastewas diverted from organic processing stream to the waste stream4.  For food waste diverted tothe waste stream, we assumed waste was distributed among regional waste facilities based onreported distribution proportions (Table 1).Table 1.  Waste distribution among Metro Vancouver Facilities.5Facility Fraction (%)Vancouver Landfill 40Cache Creek Landfill 38Burnaby WTE 22For the off-campus option, it was assumed that food waste would be delivered to the EarthRenu Energy Corp. facility on Annacis Island, where the 5% non-organic contaminants would beremoved.  The uncontaminated food waste would then be delivered to the Harvest Power BCanaerobic digestion facility in Richmond BC.Emission FactorsCO2e emission factors for the food waste systems were obtained from multiple sources (Table2). We used local emission factors where available and were able to obtain BC specific factorsfor aerobic composting with negative aeration (we considered both the UBC in-vessel systemand the Harvest Power composting system to be negative aeration since they use bio-filtration4 Information provided by UBC Building Operations5 Metro Vancouver presentation.5systems). The compost sequestration factor was based on field studies undertaken by the USEnvironmental Protection Agency (USEPA 2006).Landfill emission factors were based on approved methodologies and data specific to BC landfills(CRA 2013; SSG 2013).  The emission factor for anaerobic digestion was based on theIntergovernmental Panel on Climate Change (IPCC) guidelines for national greenhouse gas(GHG) inventories (IPCC 2006).Table 2. Emission Factors for organic waste.Emission FactorType MTCO2e/MT SourceCompost (Negative Aeration) 0.087 CAR (2013) and GCC (2011)Compost Carbon Storage -0.20 USEPA (2006)Anaerobic Digestion 0.028 IPCC (2006)Vancouver Landfill 1.54 SSG (2013) and CRA (2009)Cache Creek Landfill 0.68 SSG (2013) and CRA (2009)Burnaby WTE 0.08 USEPA (2006)TransportationTransportation was only considered for off-campus transport of food waste (to the off-campusfacility and to regional waste disposal facilities).  On-campus transportation of food waste (fromcollection bins to the on-campus processing facility) was not considered, since this was expectedto be the same for each system considered.Distances to the off campus sorting and anaerobic digestion facilities and regional wastefacilities were determined from Google Maps (Table 3). Based on information provided by theproject sponsor, fuel efficiency was assumed to be 40 litre/100km and truck capacity wasassumed to be 16 tonnes.  We assumed one delivery per week for trips from UBC to the off-campus facility and fractional trips for waste to regional waste facilities. For CNG fueled trucks,we used an external, NRC sponsored, calculator to determine the fuel consumption of thevehicles over the distances of each listed route (Table 3; NRC 2012).6Table 3.  Distances and CNG consumption for transportation.DestinationDistance(km)CNGFuel/Trip(m3) DescriptionEarth Renu (Annacis Isand) 62 27 sorting Facility (organics from UBC)Harvest Power (Richmond) 20 9 A.D. facility (organics from Earth Renu)Vancouver Landfill 53 23 waste from UBCCache Creek Landfill 724 314 waste from UBCBurnaby WTE 48 21 waste from UBCUBC 50 22 soil delivery from Harvest PowerEmission FactorsWe obtained emissions factors for transportation fuels considered in our study that are basedon BC government guidelines (Table 4).Table 4. Emission factors for transportation fuels.Emission FactorFuel Type CO2e SourceDiesel 2.60 kg/litre BCMoF (2012)Compressed Natural Gas 2.16 kg/m3 BCMoF (2012)ElectricityBC Hydro electricity used to provide power to organics processing facilities is a backgroundemission source in our study.  We obtained a BC government emission factor for BC Hydroelectrical energy production and an emission factor that accounts for BC Hydro power imports(Table 5).Table 5. Emission factors for BC Hydro electricity production.Emission FactorElectricity Source MTCO2e/GWH SourceBC Hydro 25 BCMoF (2012)BC Hydro 84 Dowlatabadi (2011)7Global Warming PotentialWe used recently released global warming potential (GWP) values for methane and nitrousoxide (Table 6; IPCC 2013).  We adjusted emission factors that were based on 2007 IPCCemission factors (IPCC 2007).Table 6. Global warming potentials for methane and nitrous oxide.GWP ConversionGHG 2013 2007 Factor1 SourceCH4 28 25 1.12 IPCC (2013, 2007)N20 265 298 0.89 IPCC (2013, 2007)1Used to update emission factors that were based on 2007 GWPs.Combined Heat and Power (CHP)To estimate the annual energy output of the combined heat and power unit, we firstdetermined the annual methane production volume from the anaerobic digester using theannual mass of organic material digested and the biogas generation rates and methaneconcentrations obtained from Harvest Power (Table 7). Using a using a high heating value of39.1 MJ/m3 for natural gas and an overall efficiency of 75%, the total energy output from theCHP unit was estimated using a low volume, low concentration scenario and high volume, highconcentration scenario.Table 7. CH4 Production values from Harvest Power.LowValueHighValueBiogas Generation (m3/tonne) 50 90CH4 Content of Biogas (% by vol) 65% 75%8RESULTSThe UBC In-Vessel Composting SystemWe determined mass flows and component emissions for the on-campus system, diagramedbelow (Figure 1). The mass input to the on-campus system is 650 tonnes per year. Sorting atthe facility results in an estimated 20% of the material diverted to disposal due to 5% inorganiccontaminants . The rejected matter is transported to regional waste facilities at located inDelta(40%), Cache Creek(38%), and the Burnaby WTE center(22%). All mature compost fromorganics processing is utilized as soil for UBC landscaping.Figure 1.  Mass flow and CO2e emissions from UBC In-vessel Compost System. Red representstransportation emissions, green represents background electricity emissions, yellow arecomposting and disposal emissions and grey represents net carbon stored in soil.Post-ConsumerOrganic Waste(650 Tonnes)Sorting ofO-WasteWasteContaminatedWith Inorganics(130 Tonnes)Separated OrganicWaste (520 Tonnes)TransportIn-VesselComposterMatureCompostUBCLandscapingSoilAmendmentDisposalElectricity200,000 KWh5 MTCO2e1.95MTCO2e(Diesel)45MTCO2e97MTCO2e- 105MTCO2eCarbonStorage9Harvest Power Anaerobic Digestion System:We determined mass flows and component emissions for the off-campus system, diagrammedbelow (Figure 2). The mass input to the off-campus system is 650 tonnes per year. Food wastefirst goes the Earth Renu facility for sorting of inorganic waste (estimated 5%) anduncontaminated organics then goes to Harvest Power for anaerobic digestion. After the ADprocess, 50% of the organic mass then goes to the turned windrow for composting.  Theproduced mature compost then is transported to UBC to be utilized as landscaping soil.Figure 2.  Mass flow and CO2e emissions for off-campus anaerobic digestion system. Redrepresents transportation emissions, green represents estimated power production, yelloware emissions from anaerobic digestion and composting, and grey represents net carbonstored in soil.OrganicWaste(650t)Earth RenuSorting ofO-WasteSeparatedOrganic Waste(618t)AnaerobicDigester DigestateTransportMature CompostBiogasCHPHeatTransportWTEInorganicWaste(32t)Turned Windrow(309t)ElectricityElectricityTransport toUBC3.35MTCO2e(Diesel)0.80MTCO2e(Diesel)1.04MTCO2e(Diesel)160-340MWH 17MTCO2e27MTCO2e- 62MTCO2eCarbonStorage10System Emissions for Organic Waste Processing OptionsOn-Campus OptionWe determined the emissions from the composting system using the described on-campusoption and mass flows. The largest individual source of emissions was from the disposal of therejected matter which is responsible for 97 MTCO2e annually (Figure 3; Table 8). Theseemissions are from the rejected 20% of the total mass, primarily due to the organic massdisposed of in regional landfills.Figure 3.  System CO2e emissions for on-campus and off-campus options.Table 8. System CO2e emissions for on-campus and off-campus options.Options TransportationDisposal/AnaerobicDigestion1 CompostingCarbonStorage Total2On-Campus 1.9 97 45 -104 39Off-Campus 5.2 17 27 -62 -131Disposal emissions from on-campus option, AD emissions from off-campus option.2Total does not include 5 MTCO2e electricity emissions for on campus options.From the established route distances, disposal truck capacities and fuel efficiencies,transportation was found to only produce 1.9 MTCO2e/year on-campus and 5.2 MTCO2e/yearfor the off-campus option. This figure indicates that the emissions from transportation are thesmallest in magnitude of any of the contributing factors addressed in this study.We found that the contribution from grid-electricity consumption was similarly small inmagnitude. Using the BC Hydro stated carbon intensity of its electricity and the stated annual11electricity consumption of the In-Vessel Composter, the annual emissions were determined tobe 5.0 MTCO2e.The emissions from the composting of the 80% of the total mass retained on campus was splitinto two components; the emissions released during composting and the carbon stored in thecompost mass. The methane and nitrous oxide emissions from the composting process werefound to contribute 45 MTCO2e/year, coming from 520 tonnes of mass disposed. Beyond theprocess emissions, the composted material was calculated to have sequestered 104 MTCO2e,based on the EPA carbon flux figures.We found that total annual emissions were 39 MTCO2e for the on-campus option. This figuredid not include emissions from electricity for reasons outlined in the on-campus option.Off-Campus OptionWe determined emissions for the off-campus option using the outlined methodology for thesystem and the distances and emissions factors obtained for this option (Figure 3; Table 8). Sincenone of the organic material was rejected, there was no waste disposal category in the on-campus option. All of the organic matter delivered to Harvest Power, 95% of the total mass, wasassumed to be processed in the anaerobic digester, the emissions from which, were determinedto be 17 MTCO2e/year.For the emissions from transportation, since the trucks were assumed to be the same as theones used in the on-campus option, the fuel efficiencies and capacities were not changed. Fromthe trip distances and mass transported, the emissions were found to be 5.2 MTCO2e/year.Since no values for electricity consumption at Harvest Power could be obtained, emissions fromelectricity could not be calculated. For the sake of consistency, the total annual emissions fromthe off-campus and on-campus options were calculated excluding the emissions from electricity.For the mass composted in the turned windrow after being processed in the anaerobic digester,the same composting emission and storage factors were used as in the on-campus option. Fromthe mass composted at Harvest Power, we determined that the annual emissions were 27MTCO2e and the carbon mass stored in the composted material was 62 MTCO2e.12Sensitivity AnalysisWe considered the impact of switching the fuel of the disposal trucks from diesel to compressednatural gas to assess the sensitivity of emissions to transportation fuel. For the on-campusoption, switching fuels resulted in a decrease in emissions of 0.19 MTCO2e/year, a 9.9%reduction (Figure 4; Table 9). Similarly, switching fuels for the on-campus option reduced annualemissions by 0.47 MTCO2e or 9.0%.We also studied the response of emission rates to the carbon intensity of grid electricity for itscontribution to the on-campus option’s emissions. Using the BCHydro carbon intensity of 25tonnes/GWH, the annual emissions from the In-Vessel Composter were calculated to be 5.0MTCO2e. When the alternative carbon intensity for grid electricity  of 84 tonnes/GWH wasutilized, the annual emissions from consumed electricity were found to be 17 MTCO2e (Figure 4;Table 9).With 20% of the total mass being diverted for disposal, the total emissions of the on-campusoption were 39 MTCO2e/year. When we analyzed the on-campus option with a reduceddiversion rate of 5%, the total annual emissions decreased to -71 MTCO2e (Figure 4; Table 9).This difference reflected a reduction of the disposal emissions, a decrease of the transportationemissions, an increase of the compost emissions and an increase of the stored carbon in thecompost material associated with composting all of the organic material on campusFigure 4.  Sensitivity analysis results for transportation, electricity and rejection rate.13Table 9.  Sensitivity analysis results for transportation, electricity and rejection rate (MTCO2e).FuelElectricityFactor Rejection RateOptions Diesel CNGBCGov PICS 20% 5%Transportation (UBC) 1.9 1.8 - - - -Transportation (HP) 5.2 4.7 - - - -Electricity (UBC) - - 5 17 - -Rejection Rate (UBC) - - - - 39 -7114DISCUSSIONWe found that of the two options we considered, the off-campus anaerobic digestion optionhad lower GHG emissions based on the emission factors and assumptions we used:  from anannual input of 650 tonnes of food waste, the off-campus option generated - 13 tonnes of CO2eemissions compared to 39 tonnes CO2e emitted for the on campus option, a net difference of52 tonnes CO2e.We determined that the highest emission source in the system we evaluated was from rejectedwaste sent to regional waste facilities from the on-campus option (97 tonnes CO2e).  This wasdue to emissions from the Vancouver and Cache Creek landfills (WTE had a relatively smallemission factor compared to landfill emission factors). The single most impactful factor wascarbon stored in soils generated from compost (- 104 tonnes CO2e for the on-campus option).Finally, we found that transportation related emissions made up a relatively small proportion ofour results.From our sensitivity analysis, we learned that reducing rejected food waste due tocontamination for the on-campus option has a significant impact on emissions (resulting in achange from 39 tonnes emitted to -71 tonnes stored, a net difference of 110 tonnes CO2e).  Wealso found that considering an alternative emission factor for background electricity emissions,that considered emissions from BC power imports, had a relatively small  impact on emissions(we note that emissions from background electricity were reported on but not included in totalsbecause we were unable to determine energy consumption emissions for the off-campusoptions).  Finally we determined that considering an alternative fuel source for transportation(compressed natural gas) had negligible impacts on our results.Limitations and Future WorkFuture work should focus on completing the full energy balance for the off-campus option,which was were not evaluated in our study.  Electricity and heat generated from the CHP systemat Harvest Power would offset emissions from grid electricity and fossil fuel based natural gas,and need to be considered to determine the net emissions related to energy consumption andproduction.Additional work to complete the mass balance for the off-campus option should also bepursued.  We estimated mass flow from the AD to composting system based on an estimate15from the literature and we did not consider emissions (or emission offsets) associated withother outputs from the AD system such as liquid fertilizers or liquid wastes not recycled or sentto the compost system.In our review of literature we noted that some recent estimates for CO2e emissions from ADsystems were an order of two or three times higher than the IPCC (2006) factor we used in thisstudy (Phong 2012; DHV 2010). Since we could not relate the cited factors to the type of ADsystem employed by Harvest Power, we did not use them in our study.  These results, however,suggest that GHG emission factors for AD warrant further consideration and review in futurestudies.Finally, while we limited our scope to one environmental impact type, and did not evaluate thefull system, we note that our evaluation could be expanded to consider a full life cycle analysis(LCA), that includes the fate of campus food waste not diverted to processing facilities should beconsidered, along with a full range of environmental impacts, including human health, localsmog impacts and local ecosystem impacts.ConclusionsBased on our preliminary findings, we conclude that both the on-campus and off-campusoptions would provide significant emission reductions compared to emissions from food wastedelivered to a regional waste facility.  We recommend that UBC further evaluate the energybalance, mass flows and end products for the Harvest Power option, and consider a full range ofenvironmental impacts for both systems.  Finally, we recommend that UBC consider the benefitsof including a waste sorting system to reduce or eliminate rejected food waste in any futureprocessing options implemented by UBC.16APPENDIX 1: EQUATIONSOn-Campus OptionDisposalmsite = mtotal*(rrejection – rinorganic)*rsite (1)Cdisposal = msite*csite (2)Disposal TransportationCtransport = dsite*fdiesel*cdiesel*msite/mcapacity (3)ElectricityCelectricity = Eelectricty*celectricity (4)Composting (emissions)mcompost = mtotal*(1-rrejection) (5)Ccompost = mcompost*(ccomp,CH4 + ccomp,N2O) (6)Composting (storage)Scompost = mcompost*scompost (7)Off-Campus OptionTransportationmorganic = mtotal*(1-rinorganic) (8)(To Earth Renu)Ctrans,ER = tER*dER*fdiesel*cdiesel (9)(To Harvest Power)Ctrans,HP = dHP*fdiesel*cdiesel*morganic/mcapacity (10)(To UBC)Ctrans,UBC = dUBC*fdiesel*cdiesel*roundup(rAD,compost*morganic/mcapacity) (11)Anaerobic DigestionCAD = morganic*cAD (12)Composting (emissions)mAD,compost = morganic*rAD,compost (13)CAD,compost = mAD,compost*(ccomp,CH4 + ccomp,N2O) (14)Composting (storage)SAD,coompost = mAD,compost*scompost (15)Annual CH4 Generation in Anaerobic DigesterVCH4 = morganic*vbiogas*rCH4 (16)Annual Energy Output from CHP unitECHP = VCH4*HHVCH4*ηCHP (17)17SensitivitiesTransportation (CNG)For all transportation equations, substitute (FCNG*cCNG) for ( dsite*fdiesel*cdiesel) (18)Definition of TermsCAD = emissions from anaerobic digestion (MTCO2e/year)cAD = emission factor for anaerobic digestion (MTCO2e/tonne)CAD,compost = emissions from composting in off-campus option (MTCO2e/year)cCNG = emission factor for compressed natural gas (MTCO2e/m3)Ccompost = emissions from composting in on-campus option (MTCO2e/year)ccomp,CH4 = emission factor for CH4 emissions from composting (MTCO2e/tonne)ccomp,N2O = emission factor for N2O emissions from composting (MTCO2e/tonne)cdiesel = emissions factor for diesel fuel (MTCO2e/L)Cdisposal =  emissions from specific waste disposal site (MTCO2e/year)Celectricity = emissions from grid electricity consumption (MTCO2e/year)celectricity = carbon intensity of grid electricity (MTCO2e/GWH)csite = emissions factor for organic matter at specific waste disposal site (MTCO2e/tonne)Ctransport = emissions from transportation to specific waste disposal site (MTCO2e/year)Ctrans,ER = emissions from transportation from UBC to Earth Renu (MTCO2e/year)Ctrans,HP = emissions from transportation from Earth Renu to Harvest Power (MTCO2e/year)Ctrans,UBC = emissions from transportation from Harvest Power to UBC (MTCO2e/year)dER = round-trip distance from UBC to Earth Renu (km)dHP = round-trip distance from Earth Renu to Harvest Power (km)dUBC = round-trip distance from Harvest Power to UBC (km)dsite = round-trip distance from UBC to specific waste disposal site (km)ECHP = total thermal and electrical energy produced by combined heat and power generator (MJ/year)Eelectricty = electrical energy consumption (GWH/year)FCNG = compressed natural gas consumed on a single round-trip route of a specific distance (m3)fdiesel = fuel consumption rate of diesel vehicle (L/100km)HHVCH4 = high heating value of methane (MJ/m3)mAD,compost = organic mass composted in off-campus option (tonne/year)mcapacity = mass capacity of disposal vehicles (tonne)mcompost = organic mass composted in on-campus option (tonne/year)morganic = organic mass in waste stream (tonne/year)msite = organic mass disposed of at specific waste disposal site (tonne/year)mtotal = total mass of waste stream (tonne/year)18ηCHP = overall efficiency of combined heat and power generator based on HHV (%)rAD,compost = rate of organic mass composted in off-campus option (%)rCH4 =  methane content of biogas by volume (%)rinorganic = rate of inorganic mass in waste stream (%)roundup( ) = round value in parenthesis up to nearest integerrrejection = rejection rate of waste stream (%)rsite = rate of total rejected waste diverted to specific waste disposal site (%)SAD,coompost = carbon stored in compost in off-campus option (MTCO2e/year)Scompost = carbon stored in compost in on-campus option (MTCO2e/year)scompost = carbon storage factor for composted material (MTCO2e/tonne)tER = number of vehicle trips to Earth Renu from UBC (1/year)vbiogas = biogas production from anaerobic digestion of organic mass (m3/tonne)VCH4 = volume of methane produced from anaerobic digestion (m3/year)19ACKNOWLEDGEMENTSWe are grateful to Bud Fraser and Liska Richer of the UBC Campus Sustainability Office forsupport and project coordination.  We thank Anthony Lau, Farhang Nesvanderani and Xiaotao Bifor helpful comments and providing data sources.  Geoff Hill and Francina Sole-Mauri of HarvestPower BC provided data helpful to the project.REFERENCESBCMOF (British Columbia Ministry of Environment).  2012. 2012 BC Best Practices Methodologyfor Quantifying Greenhouse Gas Emissions. Victoria, B.C.http://www.env.gov.bc.ca/cas/mitigation/pdfs/BC-Best-Practices-Methodology-for-Quantifying-Greenhouse-Gas-Emissions.pdfCAR (Climate Action Reserve.) 2013.  Organic Waste Processing Project Protocol (Version 1.1).Los Angeles CA. http://www.climateactionreserve.org/wp-content/uploads/2012/02/Organic_Waste_Composting_Project_Protocol_V1.0_Package_020312.pdfCRA (Conestoga-Rovers & Associates Ltd.) 2009.  Landfill Gas Generation Assessment ProcedureGuidance Report.  Report prepared for BC Ministry of Environment. Victoria B.C.http://www.env.gov.bc.ca/epd/codes/landfill_gas/pdf/lg-assessment.pdfDHV.  2010. Update of emission factors for N2O and CH4 for composting, anaerobic digestionand waste incineration Amersfoort, The Netherlands.http://www.agentschapnl.nl/sites/default/files/2013/10/DHV2010%20-%20Update%20emission%20factors%20N2O%20and%20CH4%20for%20Waste.pdfDowlatabadi, H. 2011.  Briefing Note 2011-: Lifecycle analysis of GHG intensity in BC’s energysources.  Pacific Institute for Climate Solutions (PICS).  Victoria, BC.http://pics.uvic.ca/sites/default/files/uploads/publications/Lifecycle%20analysis%20of%20GHG%20intensity%20in%20BC%27s%20energy%20sources%20.pdfGCC (Green Communities Committee).  2011. Becoming Carbon Neutral: A Guidebook for LocalGovernments in British Columbia.http://www.toolkit.bc.ca/sites/default/files/CNLG%20Final%20July%202011_0.pdfIPCC (Intergovernmental Panel on Climate Change).  2013. Chapter 8: Anthropogenic andNatural Radiative Forcing - Final Draft Underlying Scientific-Technical Assessment. In:Working Group I Contribution to the IPCC Fifth Assessment Report (AR5), Climate Change2013: The Physical Science Basis. In Press. Cambridge University Press, Cambridge, UnitedKingdom and New York, NY, USA.20http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter08.pdfIPCC (Intergovernmental Panel on Climate Change). 2007.  Chapter 2: Changes in AtmosphericConstituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis.Contribution of Working Group I to the Fourth Assessment Report of the IntergovernmentalPanel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and NewYork, NY, USA. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf.IPCC (Intergovernmental Panel on Climate Change).  2006. 2006 IPCC Guidelines for NationalGreenhouse Gas Inventories, Prepared by the National Greenhouse Gas InventoriesProgramme, Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds). Published:IGES, Japan. http://www.ipcc-nggip.iges.or.jp/public/2006gl/index.html.NRC(Natural Resource Canada). 2012. Go with Natural Gas Use in the Canadian TransportationSector-Deployment Roadmap Implementation Committee.http://www.gowithnaturalgas.ca/others/cngva-calculators/Phong, N.T.  2012. Greenhouse Gas Emissions from Composting and Anaerobic Digestion Plants.Doctoral Thesis. Rheinische Friedrich-Wilhelms-University.  Bonn, Germany.http://hss.ulb.uni-bonn.de/2012/3002/3002.pdfSEEDS (Social, Ecological, Economic Development Studies).  2013.  Project Description Form: TheFuture of Organic Waste at UBC.  UBC Campus Sustainability Office, Vancouver, BC.SSG (Sustainability Solutions Group).  2013.  UTown@UBC Community Energy and EmissionsPlan. Report prepared for the University of British Columbia.  Vancouver, BC.USEPA (United States Environmental Protection Agency).  2006. Chapter 4: Composting in SolidWaste Management and Greenhouse Gases: A Life-Cycle Assessment of Emissions and Sinks;3rd Edition. http://epa.gov/climatechange/wycd/waste/downloads/chapter4.pdf.USEPA (United States Environmental Protection Agency).  2006.  Chapter 5: Combustion in SolidWaste Management and Greenhouse Gases: A Life-Cycle Assessment of Emissions and Sinks;3rd Edition. http://epa.gov/climatechange/wycd/waste/downloads/chapter5.pdf.USEPACHPP (United States Environmental Protection Agency Combined Heat & PowerPartnership). 2008. Catalogue of CHP Technologies.http://www.epa.gov/chp/documents/catalog_chptech_full.pdf

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