Economic Consequences of Increasing Polymer Conten

RESEARCHKeywordsautomobiledismantlersgoalprogrammingpolymersrecyclingshreddersAddresscorrespondenceto:JacquelineA.lsaacsDepartmentofMechanical,Industrial,andManufacturingEngineering334SnellEngineeringCenterNortheasternUniversity360HuntingtonAvenueBoston,MA02115,[e-mail](EOL)vehicledisposal.Withincreas-inguseoflightermaterialstoenhancefueleconomythesteel-dominatedcontentofautomobilesischangingtoincludeagreaterfractionofpolymers.Inlightofimpendingregulationsforvehicledisposal,variousalternativesforremanufacturingandreuseofcomponentsandmaterialdisposalareunderin-vestigation.Forexample,ifshredderoperationsareusedtoreclaimmetallicmaterials,thentheextentofdisassemblywillsignificantlyaffectproftabilityaswellastheenvironmentUsinggoalprogramming,weexplorechangestothecur-rentUS.vehiclerecyclinginfrastructurefortheireffectsondismantlerandshredderproftabilities.Toinvestigatetheef-fectoflightweightingontheprofrtabilrtyoftherecyclingin-frastructure,twospecificvehicledesignsarecompared:asteelunibodyandapolymer-intensivevehicle.Othersce-nariosexaminetheoutcomesformandatingremovalofpolymermaterialsduringdisassemblyandforincreasingthedisposalcostofscrappolymertothatofhazardouswaste.Theresultsindicatethat,ifproperlycontrolled,thecurrentautomobilerecyclinginfrastructureintheUnitedStatescanremaineconomicallyviablewhileitimproveswithrespecttoenvironmentalconsiderations.Alternatively,implementa-tionofcertainpoliciesthatreduceprofitabilitycouldcausedisastrousconsequences,resultingintheeconomiccol-t~lapseoftheinfrastructure.journalofIndustrialEcology191RESEARCHIntroductionTheautomobileanditsassociatedindustrieshaveenjoyedsignificantgrowthasaresultofeverincreasingworldwidedemand.Althoughover75%ofthematerialsinend-of-life(EOL)vehiclesarecurrentlyreusedorrecycledintheUnitedStates,thereisaconcernthatlandfillspaceisbeingrapidlyconsumed(Brooke1991).Inaddition,thereisgrowingpressuretoreduceenergyusagebyimprovingfueleconomythroughtheuseoflightweightmaterials,andbyusingrecycledmaterialsformanufactureofthesevehicles.'Regulationsarebecomingmorestrin-gent(Berry1991),sometimesrequiringmanu-facturerstouserecycledmaterialsintheirproducts(ChynowethandRotman1993).Inaddition,consumerawarenessoftheenviron-mentandrecyclingregulationshaveputpres-sureonmanyautomobilemanufacturersandtheirsuppliers,forcingthemtotakeresponsibil-ityforthedisposalofEOLvehicles.Somemanu-facturersareaddingdisposalcoststothesellingpriceoftheirproducts.IntheUnitedStatestwoindustriescomprisethecurrentpost-useprocessinginfrastructureforEOLvehicles:dismantlingandshredding.TheextenttowhichagivenEOLvehicleisdis-mantledpriortoshreddingishighlydependentontheprofitabilityofremovingvaluablepartsandothermaterials.Shreddersprocessthere-mainingvehicleforitsvaluablemetallicscrap.Withthechangingmaterialsmixinnewautomo-biledesigns(usinglightweightmaterials),andpossiblenewrequirementsandregulationsfordisposalandtreatment,dismantlersandshred-dersarefacedwithuncertaintiesregardingtheprofitabilityoftheirbusinesses.Itis,however,inthepublicinterestthatadaptationstotheexist-ingEOLautomobileprocessinginfrastructuremaintainitsfunctionalityandprofitability.With-outprofitabilityinprocessingEOLvehicles,therecouldbeareversiontothesituationthatoccurredintheUnitedStatespriortotheestab-lishmentoftherecyclinginfrastructureinthe1970s:theproliferationofjunkcars,whichledtodecreasesinpropertyvalues(Fieldetal.1994).Inthisarticle,wepresentamodeloftheU.S.automobilerecyclinginfrastructurethatusesgoalprogrammingtotrackandanalyzematerialsstreamsandprofitabilitiesforalternativepro-cessingscenarios.Optimalquantitiesofdisas-sembledmaterials(priortoshredding)aredeterminedtomaintainpreferredlevelsofprof-itabilityforboththedisassemblerandtheshred-der.Thetwovehicledesignsfocusonmaterialsinaspecificclass,thatis,plaincarbonsteelsorpolymercomposites.Thefirstdesignreflectsmaterialsusedinastandardsteelunibodyve-hicle,whiletheothertypifiesapolymer-inten-sivevehicle,basedonbodypanelsubstitutioninaunibodydesign.Foreachofthesetwovehicledesigns,thesystemmodelgeneratesinformationregardingtheprofitabilityoftherecyclinginfia-structure.Abasecaseforthesteelunibodyde-signsimulatescurrentinfrastructureconditions.Variouscasesdemonstratetheconsequencesfordisassemblerandshredderprofitabilitieswith(1)increasingpolymercontentinthevehicledesign,(2)increasingthequantityofpolymermaterialsremovedfromtheEOLvehicle,and(3)increasingdisposalcostsforpolymers.LightweightVehiclesEnvironmentalregulationsoverthepasttwodecadeshavedramaticallyinfluencedthedesignandmanufactureoftheautomobile.In