... Carbondioxide(CO2)isabsorbedby land and vegetation through theprocessofphotosynthesis.Thenet emissions arenegative(sequestration) and substantial,offsettingapproximately884MMTCO2E,orapproximately13%oftotal emissions in2006.114Thecarbonsequestration and storageprovidedby land canbepreservedthoughsustainable land management practices, and canbeenhancedbyrestorationof land, suchasreforestationofcontaminated land. The emissions estimateforthe land basedcarbonsinkisgivenbytheInventory.Specifically,Chapter7, Land Use, Land UseChange, and Forestry,providesanassessmentofthenetGHGfluxresultingfromtheuses and changesin land types and forestsintheU.S.,includingnet emissions fromforestlandremainingforestland,croplandremainingcropland, land converted to cropland,grasslandremaininggrassland, land converted to grassland,settlementsremainingsettlements,landfillyardtrimmings, and ... Opportunities to Reduce Greenhouse Gas Emissions through Materials and Land Management Practices September2009APPENDIXATECHNICALSUPPORTFOR OPPORTUNITIES TO REDUCE GREENHOUSE GAS EMISSIONS THROUGH MATERIALS AND LAND MANAGEMENT PRACTICES Thisappendixprovidesadescriptionofthemethodologiesused to developthesystems‐basedpiechartofU.S. greenhouse gas (GHG) emissions showing materials and land management (FiguresES‐1 and 2 through 5in Opportunities to Reduce Greenhouse Gas Emissions through Materials and Land Management Practices) ,aswellasthemethodologiessupportingthetotaltechnicalpotentialscenarios and theGHGemissionreductionsthatcouldbeachieved through materials and land management activities.SECTIONA‐1METHODOLOGYFORCREATINGTHESYSTEMSPIECHARTS(FIGURESES‐1 AND 2 THROUGH 4)Asdescribedin Opportunities to Reduce Greenhouse Gas Emissions through Materials and Land Management Practices (the“maintext”),Figure1wasderivedfromtheInventoryofU.S. Greenhouse Gas Emissions and Sinks:1990‐2006(“theInventory”).85TheInventorycomprehensivelyquantifiesthecountry’sprimaryanthropogenicsources and sinksofGHG emissions basedonacommon and consistentmethodologythatenablesparties to theUnitedNationsFrameworkConventiononClimateChange(UNFCCC) to comparetherelativecontributionofdifferentemissionsources and GHGs to climatechange.Inaddition to reporting emissions bythestandardcategoriessetbytheIntergovernmentalPanelonClimateChange(IPCC)methodology,theInventorypresents emissions allocated to theeconomicsectorswheretheyareemitted.86ThisisthebasisofFigure1,with34%of emissions comingfromElectricPowerIndustrysources,28%fromTransportationsources,19%fromIndustrialsources,8%fromAgriculturesources,6%fromCommercialsources, and 5%fromResidentialsources.87Acollectionofsourcesworkingtogether to fulfillacommonneedistermeda“system.” To betterunderstand and describetheconnectionsbetween materials and land management and climatechange,thispaperpresentsa“systems‐based”perspective.Ratherthancategorizing emissions according to thesectorwheretheyareemitted, emissions arecategorizedaccording to theneeddrivingthose emissions. TherearemanypossiblecategorizationsofGHG emissions bysystem,butthesystemsherearechosen to examinetheroleof materials management and land management. Figures2 through 5showthesame2006GHG emissions asFigure1,butreallocatethe emissions bysystem,demonstratinghowmuchoftheU.S.GHG emissions areassociatedwith materials and land management practices. Thesystemsperspectiveallowsconsiderationofmitigationoptionsthatarenotasevidentinthesector‐basedview.Byconsideringthe practices thatcontribute to the emissions, notthephysical emissions source,wecanseewherechangesin practices upstreamhavethemostpotential to reduce ... Ton=Timeperiodoftransition,defaultis1yearforcarbonlossesAlthoughthisequationissimilartotheequationusedtoestimatecarbonlossesinDOM(seebelow),itisnotinaccordancewiththe2006IPCCGuidelines.Theguidelinesrecommendagreaterdegreeofdisaggregationoflandusedatabyclimateandsoiltype.Theequationaboverepresentsasimplificationofthevariabilityofcarboncontentsinsoilthatexistsonregionalandnationalscales.Thesoilcarbonstockfortheoldlandusecategory(Cso)wasbasedoninformationfordifferentecosystemtypespresentedinthe2000IPCCreportonLandUse,LanduseChange,andForestry.117Thesoilcarbonstockforthenewlandusecategoryofsettlements(Csn)wasbasedonafractionofCso.Forforestlandandgrassland,thefractionwas0.5andforcropland,thefractionwas0.8.GuoandGifford(2002)observedthatlandusechangesofforestlandtocroplandandpasturelandtocroplandresultedinsoilcarbondecreasesof42 %and5 9%,respectively.118Theestimateforthisprojectassumesthattheconversionofforestlandorgrasslandtourbanlandisequivalenttoaconversiontocropland(boremoveexistingvegetationandcausesignificantsoildisturbance);therefore,GuoandGiffordsworksupportsthiseffortsestimationofa50%lossassociatedwiththisconversion.Itisestimatedthatsoilsunderforestsorgrasslandswillloseapproximately50%oftheoriginalorganiccarbonwhenthelandisconvertedtodevelopedland.Theselossesareaconsequenceofboththeremovalofsurfacesoils (to providesuitablebuildingfoundation)andnaturaloxidationwhenthesoilisgradedfollowingremovalofthevegetativecover.Lossesfromcroplandsareonlyexpectedtobe20%becausethesesoilsalreadyundergoperiodictillageandthemajorityofnaturaloxidationwillalreadyhaveoccurred.AliteraturereviewforthisprojectdidnotidentifyotherstudiescomparabletoGuoandGifford(2002)thatestimatedsoilcarbonlossesassociatedwithconvertingcroplandtourbanland.Therefore,the20%soilcarbonlossestimatefordevelopmentofcroplandintourbanlandisbasedonbestprofessionaljudgment.th...