LifeCycleAssessmentofHandDryingSystems

September19,2011CommissionedbyDyson,Inc.PreparedbyMaterialsSystemsLaboratoryMassachusettsInstituteofTechnologyTrishaMontalboJeremyGregoryRandolphKirchain

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Contents1 Introduction..........................................................................................................................................52 Goalandscope......................................................................................................................................62.1 Goals.............................................................................................................................................62.2 Scope.............................................................................................................................................62.2.1 Functionalunit......................................................................................................................72.2.2 Systemboundary..................................................................................................................82.2.3 Cutoffcriteria.....................................................................................................................11

3 Lifecycleinventoryanalysis................................................................................................................113.1 Billofactivities............................................................................................................................123.1.1 Production:materialsandmanufacturing..........................................................................143.1.2 Use......................................................................................................................................163.1.3 Endoflife............................................................................................................................183.1.4 Transportation....................................................................................................................193.1.5 Dataquality:sensitivityanalysis.........................................................................................19

3.2 Unitprocessinventorydata........................................................................................................203.3 Uncertaintyanalyses...................................................................................................................21

4 Lifecycleimpactassessment..............................................................................................................224.1 Lifecycleimpactassessmentmethodologies.............................................................................224.1.1 Globalwarmingpotential...................................................................................................234.1.2 IMPACT2002+.....................................................................................................................234.1.3 Cumulativeenergydemand................................................................................................244.1.4 Waterconsumptionandlandoccupation..........................................................................25

4.2 Baselineanalysis.........................................................................................................................254.2.1 Resultsbyimpactassessmentmethodology......................................................................254.2.2 Endpointcategorynormalization........................................................................................324.2.3 Rankordercomparison.......................................................................................................33

4.3 Additionalproductlifecycles......................................................................................................334.4 Contributionanalysisforindividualproducts.............................................................................344.4.1 Dryers..................................................................................................................................344.4.2 Cottonrolltowels................................................................................................................37

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4.4.3 Papertowels.......................................................................................................................395 Lifecycleinterpretation......................................................................................................................405.1 Sensitivityanalysis......................................................................................................................415.1.1 Lifetimeusage.....................................................................................................................415.1.2 Manufacturingstageelectricgridmix................................................................................425.1.3 Usephaseelectricgridmix.................................................................................................435.1.4 Useintensity.......................................................................................................................445.1.5 Endoflifescenario.............................................................................................................455.1.6 Dryerelectronicsunitprocess............................................................................................465.1.7 Cottonrolltowelreuses......................................................................................................485.1.8 Pulpmanufacturingprocess...............................................................................................485.1.9 Papertowelmass................................................................................................................495.1.10 Allocationofrecycledcontent............................................................................................505.1.11 Manufacturinglocation.......................................................................................................515.1.12 Uselocation(regionalvariation).........................................................................................52

5.2 Uncertaintyanalyses...................................................................................................................545.2.1 Scenariouncertainty...........................................................................................................545.2.2 Billofactivitiesuncertaintyanalysis...................................................................................61

6 Conclusions.........................................................................................................................................656.1 Keydriversofenvironmentalimpact..........................................................................................656.1.1 Handdryers.........................................................................................................................656.1.2 Cottonrolltowels................................................................................................................656.1.3 Papertowels.......................................................................................................................66

6.2 Sensitivityofresultstoscenariosanddataquality....................................................................666.3 Comparativeassessmentofproductenvironmentalimpact.....................................................676.4 Recommendationsforreducingdryingsystemenvironmentalimpact.....................................686.5 Studylimitations.........................................................................................................................69

7 References..........................................................................................................................................708 Criticalreview.....................................................................................................................................73A Appendices..........................................................................................................................................73A.1 Handdryingsystembillsofactivities.........................................................................................73A.1.1 Energyconsumptioncalculationsfordryerusestage........................................................78

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A.2 Modifiedunitprocessdata.........................................................................................................78A.3 Unitprocessimpactandquality.................................................................................................85A.3.1 Statisticaltests....................................................................................................................85

A.4 Allocationofrecycledcontent....................................................................................................95A.5 NSFP335Protocol.......................................................................................................................96A.6 Comparisonwithexistingstudies...............................................................................................96A.6.1 Dryers..................................................................................................................................96A.6.2 Cottonrolltowels................................................................................................................97A.6.3 Papertowels.......................................................................................................................98

A.7 Supplementalanalyses.............................................................................................................102A.7.1 Warehousing.....................................................................................................................102A.7.2 Regionalvariation:secondarylocations...........................................................................102

A.8 Evaluation.................................................................................................................................107A.8.1 Completenesscheck.........................................................................................................107A.8.2 Sensitivitycheck................................................................................................................108A.8.3 Consistencycheck.............................................................................................................112

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1 IntroductionThequestionoftheenvironmentalimplicationsofthehanddryerversuspapertowelisfacedbymanypeople,asevidencedbyitscoverageinthemedia[15].Assuch,thereareanumberofstudiesthattargetthisparticularquestion,includingastreamlinedlifecycleassessmentconductedforAirdriLtd.andBobrickWashroomEquipmentthatcomparesastandardwarmairdryertopapertowels[6],ahanddryertowelcomparisonproducedbyMyClimateandcommissionedbyDysoninSwitzerland[7],acomparisonbetweencottonrolltowelsandpapertowelscommissionedbyVendor[8],andsomecalculationsmadebytheClimateConservancyforSalon[9].MorecomprehensivelifecycleassessmentsthatcomplywiththeISO14040and14044lifecycleassessmentstandards[10,11]arealsoavailable.TheseincludeastudyfortheEuropeanTextileServicesAssociation(ETSA)thatalsocomparescottonrolltowelstopapertowels[12],anotherinvestigatingmultipletypesoftissueproductsforKimberlyClark[13],andathirdforExcelDryerthatcomparesitsXLERATORhanddryertoastandardwarmairdryerandpapertowels[14].DysonhasalsoconductedalifecycleassessmentofitsDysonAirbladehanddryerinaccordancewiththePAS2050standard[15]inordertoobtainaCarbonReductionLabelfromtheCarbonTrust[16].Amongallthesestudies,onlytheonebyMyClimate[7]comparesalltypesofdryingsystemsahighspeedhandsindryerrepresentedbytheDysonAirbladehanddryer,astandardwarmairdryer,cottonrolltowels,andpapertowels(seeFigure1forimagesofthesedifferentdryingsystems).Itdoesnotincludethehandsundervariantofhighspeeddryers,however.Bycontrast,thereportconductedforExcelDryer[14]includesahighspeedhandsunderdryertheXLERATORhanddryerbutthendoesnotconsiderahighspeedhandsindryerorcottonrolltowels.Andbecauseofthestudiesdifferingfunctionalunits,assumptions,anddata,lifecycleassessmentoutcomescannotbeeasilycompared.Dysoncommissionedthisstudyasameansofaddressingthisgap.Thegoalofthisanalysisistoevaluateandcomparethevarioushanddryingsystemsincludingbothvariantsofhighspeedhanddryersfromthedifferentstudiesbyplacingthesystemsonaconsistentbasis.Lifecycleassessment(LCA)[17,18]isusedtoconductthisstudy.LCAisacomprehensiveframeworkwithalevelofdetailthatrequiresastrictadherencetoaconsistentmethodology.ThismethodologyisarticulatedintheInternationalOrganizationforStandardizationssetofLCAstandardsthatarepartofitsISO14000environmentalmanagementseries.AlifecycleassessmentthatfollowstheLCAstandardsISO14040and14044[10,11]containsfourmainsteps:

Goalandscopedefinitionarticulatestheobjectives,functionalunitunderconsideration,andregionalandtemporalboundariesoftheassessment.

Inventoryanalysisentailsthequantificationofenergy,water,andmaterialresourcerequirements,andemissionstoair,land,andwaterforallunitprocesseswithinthelifecycle.

Impactassessmentevaluatesthehumanandecologicaleffectsoftheresourceconsumptionandemissionstotheenvironmentassociatedwiththelifecycle.

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Interpretationofresultsincludesanevaluationoftheimpactassessmentresultswithinthecontextofthelimitations,uncertainty,andassumptionsintheinventorydataandscope.

Acriticalreviewbyapanelofexpertsisalsorequiredforstudieswheretheresultsareintendedtosupportcomparativeassertionsthatwillbedisclosedtothepublic.ThisstudyhasbeenconductedinaccordancewiththerequirementsoftheISOstandards14040and14044,includingthecriticalreview.Thecontentinthisreportisgroupedintothesamefourareasoutlinedinthestandards,followedbyconclusions,asummaryofthecriticalreview,andappendices.

2 Goalandscope2.1 GoalsTheoverallgoalofthisstudyistocomparethelifecycleenvironmentalimpactofseveralhanddryingsystemsusingaconsistentbasis.Specificgoalsareto:

1) Evaluatehowhanddryingsystemsimpacttheenvironmentunderdifferentmanufacturingandusescenarios.

2) Identifyimpactdriversandwaystotargetthosefactors.3) Informproductdesigndecisions.

ThisstudywascommissionedbyDysonanditisexpectedthattheresultswillbeusedtosupportcomparativeassertionsthataredisclosedtothepublic.Thereporthastwoaudiences.Thefirstaudienceisanyinterestedpartywhowishestounderstandthedata,assumptions,andmethodologiesusedtocalculatelifecycleenvironmentalimpactforthehanddryingsystems.ThesecondaudienceistheDysonengineerswhoareinterestedinunderstandingthedriversofenvironmentalimpactforthehanddryingsystems.2.2 ScopeThesevensystemsfordryinghandsevaluatedinthisreportinclude:

1) ADysonAirbladehanddryerwithanaluminumcover(ahighspeedhandsindryer)2) ADysonAirbladehanddryerwithaplasticcover(ahighspeedhandsindryer)3) AnExcelXLERATORhanddryer(ahighspeedhandsunderdryer)4) Agenericstandardwarmairhanddryer(ahandsunderdryer)5) Genericcottonrolltowels6) Genericpapertowelsmanufacturedfromvirgincontent7) Genericpapertowelsmanufacturedfrom100%recycledcontent

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Inadditiontothedryersandtowels,packagingisconsideredinallcases,aswellasdispensersinthecaseofthetowelsystemsandawastebinandbinlinersforthepapertowelsystems(Table1).

Figure1Dryingsystemsincludedinthisstudy(lefttoright):DysonAirbladehanddryerwithaplastic

cover,ExcelXLERATORhanddryer,genericstandardwarmairhanddryer,genericcottonrolltowelsanddispenser,andpapertowelsanddispenser.Note:picturesarenotshownwithaconsistentrelativescale.

Table1Additionalproductlifecyclesincludedinhanddryerortowelsystems.

Dryingsystem Packaging Dispenser Wastebin BinlinersAirbladedryer,aluminum Airbladedryer,plastic XLERATORdryer Standarddryer Cottonrolltowels Papertowels,virgin Papertowels,100%recycled

2.2.1 FunctionalunitAsinglepairofdryhandsrepresentsthefunctionalunit.Thecorrespondingreferenceflowsthereforeincludetheallocatedfractionofahanddryerorthenumberofcottonorpapertowelsassociatedwithdryingthatpairofhands(Table2).Forthehanddryers,dryisdefinedbytheNSFProtocolP335[19],whichsetsforthastandardfordryeroperationandhygiene,therebyprovidingaconsistentbasisfordeterminingusetimes.Althoughhygieneispartoftheprotocolandisanotherpurposeofthesystemsthatisofinteresttothescientificcommunity(e.g.[2024]),itisnotconsideredinthisanalysis.Sincehanddryersclearlydrymorethanonepairofhandsovertheirlifetime,theirimpacthastobeallocatedacrossallthesepairsofhands.Thesameholdstrueforthecottonrolltowels,toweldispensers,wastebin,binliners,andpackagingusedbytheseproducts.Allocationisaccomplishedbyassumingdryershavea5yearlifespan(giventhe5yearwarrantiesonthehighspeeddryers[25,26]),overwhichtheydry350,000pairsofhands[27]equaltoapproximately1,350pairsofhandsaweek.Therefore,1/350,000or2.86106oftheimpactofadryerisallocatedtothefunctionalunit.Thesame

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assumptionsareusedforthetoweldispensers,wastebin,andpackaging.Theeffectofdryerlifetimeusageonenvironmentalimpactisinvestigatedinthesensitivityanalysis.Binlinersandcottonrolltowelsarealsousedformultiplepairsofdryhandsbutdonotlastthefull350,000uses.Thereforetheyrequiretheirownallocationstrategies.Iffivebinlinersareconsumedeachweekoneforeachworkday[6]eachlinerwillcorrespondto,onaverage,270pairsofdryhands.Consequently,1/270or0.0037binlinersareallocatedtothefunctionalunit.Althoughwastebinsandbinlinerscanalsobeusedforthedisposalofotherobjects,theirimpactsarefullyallocatedtopapertowels,whichrepresentsaworstcasescenarioforthepapertowels.Additionally,thepresenceofpapertowelswillincreasetheneedtochangetheliners.Likewise,thefactthatcottontowelscanbelaunderedandreusedanaverageof103times[12]beforetheyaredisposedhastobetakenintoaccountwhencalculatingthefractionofatowelrequiredtofulfillthefunctionalunit.Noallocationisnecessaryforpapertowels.

Table2Correspondingdryingsystemreferenceflowgivenafunctionalunitofdryingonepairofhands.

Dryingsystem ReferenceflowHanddryers 2.8610

6dryerandpackagingElectricitytodryonepairofhands

Cottonrolltowels9.71103cottontowelandpackaginga2.86106cottontoweldispenserLaundrytowashatowel

Papertowels2towelsandpackagingb2.86106papertoweldispenser2.86106wastebin3.7102binliner

(a)Assumingonecottonrolltowelpullperdry(b)Assumingtwopapertowelsperdry.

2.2.2 SystemboundaryTheanalysisincludesalllifecyclestages,fromcradletograve,alongwithtransportationbetweeneachstage.ThesestagesandtheircorrespondinglocationsareshowninFigure2forthehanddryer,cottonrolltowel,andpapertowelsystems.TheUnitedStatesistheprimaryregionoffocusfortheuseoftheproductsinthisstudy,althoughscenariosinvolvingseveralotherregionsthroughouttheworldhavebeenevaluatedinthesensitivityanalyses.Inordertoputthehanddryingsystemsonequalfootingfromasupplychainstandpointandtomaketheanalysisstrictlyacomparisonbetweentheperformanceoftheproductsystemsratherthanbetweenspecificsupplychainscenarios,allsystems,withtheexceptionofpapertowels,areassumedtobemanufacturedinChinaandusedintheUnitedStates.Chinaisacommonlocationforthemanufacturingoftechnologyproducts;itisalsoareasonableassumptionforthemanufactureofcottonrolltowels(see[12]).Papertowels,ontheotherhand,areassumedtobebothmanufacturedandusedintheUnitedStatesbecausethisrepresentstheindustrystandardforaproductthatisusedinalocationwheretherawmaterialsareplentifulatacompetitivepriceandtheproductionisnotlaborintensive.

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Figure2Handdryer,cottonrolltowel,andpapertowellifecyclestagesandcorrespondinglocations

assumptionsforthebaselinescenario.

Material1

Material2

MaterialN

Papertowellifecyclestages

Baselinelocation

Materials Manufacturing Use Endoflife

Distributioncenter

Manufacturingfacility Washrooms Wastefacility

Transport(road)

Transport(road)

Transport(road)

KansasCity,KS,UnitedStates

KansasCity,KS,UnitedStates

Variouslocations,UnitedStates

100kmfromwashrooms

250kmfrommanufacturingfacility

Material1

Material2

MaterialN

Cottonrolltowellifecyclestages

Baselinelocation

Materials Manufacturing Use Endoflife

Distributioncenter

Manufacturingfacility Washrooms WastefacilityLaundry

Transport(road)

Transport(road)

Transport(road)

Transport(road)

Transport(ship,rail)

KansasCity,KS,UnitedStatesShanghai,China

Variouslocations,UnitedStates

100kmfromwashrooms

100kmfromwashrooms

250kmfrommanufacturingfacility

Material1

Material2

MaterialN

Dryerlifecyclestages

Baselinelocation

Materials Manufacturing Use Endoflife

Distributioncenter

Manufacturingfacility Washrooms Wastefacility

Transport(road)

Transport(road)

Transport(road)

Transport(ship,rail)

KansasCity,KS,UnitedStatesShanghai,China

Variouslocations,UnitedStates

100kmfromwashrooms

250kmfrommanufacturingfacility

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2.2.2.1 LifecyclestagesUpstreamprocessessuchastheminingoforeortheextractionandrefiningofpetroleumforvehiclefuelareincludedwithinsystemboundaries.Oncetheoreisextractedandrefinedintorawmaterials(thematerialsstageinFigure2),thematerialsaretransportedtoamanufacturingfacilitywheretheyareprocessedandassembledintofinishedproducts(themanufacturingstage).Onlytheenergyrequiredtomanufacturedryersortowelsisaccountedforinthecalculationofmanufacturingstageimpact.Capitalequipment(e.g.buildings,machines,etc.)usedbyDysonoranyoftheotherhanddryerortowelmanufacturingfirmsisnotincludedinthemanufacturingphaseoftheanalysisbecausethepublishedreportsondryerandtowelproductionthatservedassourcesofinventorydataforthisreportlikewisedonotincludecapitalequipmentintheprimaryproductionphase.Thisassumptionisreasonablegiventheexpectedsmallcontributionofauxiliaryelectricityandcapitalequipmenttotheoveralllifecycleburdenofthehanddryingsystems.Dataforcapitalequipmentupstreamofdryingsystemproduction,however,isincludedthroughuseoftheecoinventdatabaseforunitprocessinventorydata.Afterproduction,thedryersandcottonrolltowelsaretransportedfromChinatoadistributioncenterintheUS.Thepapertowelfacility,bycontrast,islocatedintheUSandisthereforeassumedtobecolocatedwithadistributioncenter,whicheliminatestheneedforacorrespondingtransportationstep.Althoughtransportationtoandfromthedistributioncenterisaccountedfor,theimpactduetothecenteritselfisnotincludedinthesystembecausetheburdensassociatedwithoperatingwarehousesaresmallincomparisonwiththeburdenofmanufacturing.ThisisbasedonroughcalculationsusingdatafromacasestudybyCarnegieMellonUniversity[28]thatindicatethatwarehousingwouldbeapproximately0.05%ofthetotalGWPfordryers,0.5%forcottonrolltowels,and3%forpapertowels(seeAppendixA.7.1).Theproductsarenexttransportedfromthedistributioncentertoawashroom,wheretheusestagetakesplace.Fordryers,theusestageimpactissolelyduetotheelectricityrequiredforoperation.Whilethestandarddryer,whichheatstheair,canpotentiallyaffectwashroomHVACperformance,thiseffectisnotconsideredintheanalysisduetothedifficultyofquantifyingsuchaneffect.Maintenanceofthedryersisalsoassumedtobebeyondthescopeofthisanalysisbecausemaintenanceistypicallyalabordrivenactivity,whichisnotincludedinthescopeofenvironmentalimpactassessment.Theusestageforthecottonrolltowelsencompassesnotonlytheuseofthetowelinsideawashroom,butalsoacleaningstepwhichtakesplaceatalaundryfacility.Consequently,cottonrolltowelshaveanadditionaltransportationsteptodeliverthemtoandfromthelaundry.Finally,attheendoflife,allproducttypesaretransportedtoanearbywastefacilitywheretheyareincineratedorsenttoalandfill.Withtheexceptionofthecardboardpackaging,thereisnoclearevidencethattheseproductsarecommonlyrecycledorinthecaseofcottonandpapertowels,compostedintheUS.2.2.2.2 AllocationofrecycledcontentSystemboundariesalsohavetobedefinedwhenaproductlifecycleispartofanopenlooprecyclingsystem,asisthecaseforthepapertowelsmanufacturedfromrecycledcontent.Insuchcases,

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allocationdecisionsfortherawmaterialproduction,recycling,andendoflifeburdensarenecessarybecausethepapertowelsystemcannotbeexpandedtoencompassallproductlifecyclesduetolackofknowledgeabouttheadditionalproducts.VariousallocationstrategiesaredescribedinAppendixA.4.Thecutoffmethod,whichassignstheburdenofrecyclingtotheproductlifecyclesthatuserecycledcontent(Figure36),ischosenforthebaseline.Sincepapertowelscanuserecycledcontentbutarerarelyrecycledthemselves(sameassumptionasintheKimberlyClarkstudy[13]),theyrepresentthefinalproductofanopenlooprecyclingsystemandareallocatedtheburdensfromrecyclingwastepaperandendoflifeinaccordancewiththeselectedstrategy.2.2.3 CutoffcriteriaInadditiontohanddryingsystemboundaries,thecutoffcriteria,orthepointatwhichinputoroutputflowsareexcludedfromtheanalysis,havetobedefinedforeachsystem.Thesecriteriacanbebasedonthemass,energy,orenvironmentalsignificanceoftheflows.InthecaseoftheDysonAirbladehanddryer,allpartsareaccountedfor,withthesmallerpartssuchasscrewsorfastenersaggregatedintoasinglepart[27].ThedataonwhichthisanalysisisbasedalsoincludedabreakdownoftheresistorsandothercomponentsontheDysonAirbladehanddryersprintedcircuitboard;thislevelofdetail,however,wasdeemedunnecessaryandthedatareaggregatedtocircuitboardlevel.TheXLERATORdryer,standarddryer,andpapertowellifecycleinventorieswereallbasedonthestudyforExcelDryer[14].Thisstudyincludedasmanycomponentsaspossiblegivenavailableinformation,andpredictedthatomittedpartswouldaccountforless1%oftotalimpact.Lastly,thecottonrolltowelswerebasedontheETSAstudy[12],whichexcludedprocessesthatconsistedoflessthan1%oftotalmassandenergybalance.Thenumberofprocessesexcluded,however,waslimitedsothattheyaccountedfornomorethan5%ofthetotalbalance.

3 LifecycleinventoryanalysisThissectiondetailsthedataandassumptionsusedtoconductalifecycleinventoryanalysisforeachhanddryingsystem.Thecompleteinventoryisgeneratedbycombiningbillofactivities1dataforeachsystemwithlifecycleinventorydataofrequiredunitprocessesfromexistingdatabases(Figure3).Wheneverpossible,datausedinthisstudywereobtainedfromexistingsources.Billofactivitiesdatasourcesandassumptionsforallhanddryingsystemsaredetailedbylifecyclestage.SomeoftheassumptionsarelaterevaluatedinthesensitivityanduncertaintyanalysestoassesstheireffectontheLCAresultsanddryingsystemcomparison.Thebillofactivitiesdatainformationisfollowedbyadescriptionofthelifecycleinventorydatausedbytheunitprocesses.Table3summarizestheassumptionsmadeforthebaselinescenario;detaileddataforeachhanddryingsystemcanbefoundinAppendixA.1.MuchofthedataforproductcompositionsandmanufacturingprocessesarederivedfromotherLCAstudiesonthesystems;whennecessary,assumptionsaremadeinordertoinsurethattheanalysesareconductedonaconsistentbasis(e.g.,productionoruselocation).1Billofactivitiesisdefinedtoincludematerialcomposition,productionrequirements,userequirements,andtransportationdistancesforaproductsystem.

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Inparticular,allproducts,withtheexceptionofpapertowels,areassumedtobemanufacturedinChina(seeFigure2),eventhoughthisisnotnecessarilythecaseforthedryersinreality(e.g.,theXLERATORdryerisproducedintheUS[14]andtheDysonAirbladehanddryerisproducedinMalaysia[27]).Theuseofaconsistentbasisformanufacturinglocationandtransportationdistancesismotivatedbyanobjectiveofthestudytocomparetheinfluenceofdifferentmanufacturingandusescenariosofthedifferenthanddryingsystems.Thisisonlymeaningfulifthesupplychainscenariosarethesameandplausibleforsimilarproducts.Chinaisahighlyplausiblelocationfortheproductionofhanddryersbecauseitisacommonlocationforthemanufacturingoftechnologicalproducts.Usingaconsistentbasisenablesacomparisonamongproductsthatisfocusedonproductattributesincludingmaterialcomposition,manufacturingprocess,andenergyconsumption,andnotonsupplychainconfiguration(whichisnotknownforallproducts).However,asensitivityanalysisonmanufacturinglocationisincludedtoexploretheimpactofthisassumption.Papertowelsaretheexceptiontothispractice:thisstudyassumesthatthepapertowelsareproducedandusedintheUSbecausethisistheindustrystandardforaproductthatisusedinalocationwheretherawmaterialsareplentifulatacompetitivepriceandtheproductionisnotlaborintensive.

Figure3Stepstoconvertbillofactivitiesdatatoenvironmentalimpact.

3.1 BillofactivitiesThebillsofactivitiesforeachproductsystemaredetailedinAppendixA.1.Theyarecombinedwithunitprocessinventorydatatoconstructdryingsystemlifecycleinventories.MostofthesedatawereobtainedfromcriticallyreviewedLCAsdatingfrom2006andlater.Withtheexceptionofthecottonrolltowelbillofactivities,dataareatmost10yearsold.DysonsupplieddataforitsDysonAirbladehanddryers[27].DatafortheXLERATORandstandarddryersweretakenfromtheExcelstudy[14],whichobtaineditsdatadirectlyfromExcelDryer,IncandinthecaseofthestandarddryerfromtheAirdristreamlinedLCA[6].CottonrolltoweldatawereobtainedfromtheETSAreport[12];thisstudyusedexistingliteraturefromthe1990sand2000sforcottonrolltowelproduction,butconducteditsownsurveyoflaundriestodevelopalaunderingprocessinventory.Finally,papertoweldatawerebasedonacombinationoftheExcel[14],KimberlyClark[13],andETSA[12]studies.TheExcelstudyalsoreliedontheKimberlyClarkreportforpapertoweldata,whereastheETSAstudyreliedona2001reportonthebestavailabletechniquesreportinthepulpandpaperindustry[29].

Billofactivitiesdata

Lifecycleinventoryanalysis Lifecycle

inventoryUnitprocessinventorydata

Environmentalimpact

Impactassessmentmethodology

Lifecycleimpactassessment

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Table3Assumptionsusedtogeneratehanddryingsystemlifecycleinventoriesforthebaselineanalysis.

DryingsystemAirblade(highspeed

handsindryer)XLERATOR(highspeed

handsunderdryer)Standard

warmairdryer Cottonrolltowels Papertowels

Functionalunit 1pairofdryhandsLifetimeusage 350,000pairsofdryhandsover5years[26,27]Mass(+manufacturingscrap)perdryerortowel

Al:14.8kg(1.43kg)Pl:9.9kg(2.16kg)[27]

9.4kg(1.12kg)[14] 6.4kg(0.9kg)[14] 16.2g(2.2g)[12] 1.98g(0.08g)[14]

Manufacturinglocation China China China China USManufacturingenergyperdryerortowel

146MJelectricity[27]

156MJelectricity[14]

156MJelectricity[14]

431kJelectricity507kJgas[12]

14.7kJelectricity24.4kJgas[14]

Uselocation US

Useintensity12sec@1,400W+0sec@0W+439sec@1W

20sec@1,500W+1.5sec@750W+429sec@1W

31sec@2,300W+1.5sec@1,150W+406sec@0.4W

1towel(pull)+laundry 2towels

Endoflifescenario76.7%ofcardboardrecycled19%ofremainingwasteincineratedwithenergyrecovery81%ofremainingwastelandfilledwithmethanecaptureandconversiontoelectricity[30,31]

TransportationRawmaterialtoplantPlanttowarehouseWarehousetowashroomWashroomtolaundryandbackWashroomtowastefacility

250kmviatruck10,500kmviaoceanfreighter+2,600kmviafreighttrain+24kmviatruck(excl.papertowels)1,760kmviatruck100kmviatruck(cottontowelsonly)100kmviatruck

Additionallifecycles Packaging Packaging Packaging Packaging,dispenser Packaging,dispenser,wastebin,binlinersPackagingperdryerortowel 2.94kgcardboard[27]

0.27kgcardboard[14]

0.45kgcardboard[14] 0.08gpolyethylene 0.18gcardboard[14]

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3.1.1 Production:materialsandmanufacturingThisanalysisaccountsfortheimpactofmaterialproduction,includingupstreamimpactstartingfromoreextraction.Dryermaterialsareconservativelyassumedtobemanufacturedfromvirgincontent.Theyarethentransported250kmfromtheirrespectiveproductionorstoragefacilitytothemanufacturingplantwheredryerortowelmanufacturingtakesplace.Twohundredfiftykilometerswaschosenasanintermediatedistancebetweenthe750kmbyroadassumedinAirdriandExcelstudies[6,14],andthe30kmusedinthereportforCarbonTrust[27].Withtheexceptionofthepapertowelsystems,allmaterialsproductionandmanufacturingtakesplaceinChina(seediscussionatthebeginningofSection3abouttheuseofaconsistentbasis);consequently,theChineseaveragegridmix,alongwithChineseemissionfactorswhenavailable,isassumedfortheproductionofelectricity.Papertowels,bycontrast,areassumedtobemanufacturedintheUSandthusrelyontheUSgrid(seediscussioninSection3).Oncetheproductsarefinished,theyarethenshippedtoadistributioncenterintheUSandfromtheretoawashroom.AlltransportationstepsinthisanalysisareconsolidatedintoaseparatelifecyclestageandsummarizedinSection3.1.4.MaterialsandmanufacturingdataforthealuminumandtheplasticDysonAirbladehanddryerswereprovidedbyDysonandarebasedonthefirmsanalysisforitsCarbonReductionLabelthroughtheCarbonTrust[27].Melamineisassumedforthebulkmoldingcompound.Materialsdataforthedryersaccountfora9.7%anda22%scraprateforthealuminumandplasticdryers,respectively,whichrepresentstheworstcasescenarioformaterialloss.Capitalequipmentusedindryermanufactureisnotincluded(inaccordancewiththesystemboundaries,detailedinSection2.2.2.1).CorrespondingdatafortheXLERATOR,thehighspeedhandsunderdryer,werebasedonthestudypreparedforExcelDryer[14].TheExcelstudyusesagenericbillofactivitiesthatdoesnotrepresentanyoneXLERATORinExcelDryersproductline.Specifically,thereportassumesthattheXLERATORscoverisacombinationofthedryersthreeavailablecovers:stainlesssteel,plastic,andchromefinish.Thisassumptioniscarriedoverintothisstudybecausenoalternativedatawereavailablefortheindividualcovers.Thesamestudyisusedtoobtainproductiondataforastandardwarmairdryer(whichis,inturn,basedontheAirdriB709modelfromtheEnvironmentalResourcesManagementstudyconductedforAirdriLtd.andBobrickWashroomEquipment[6]).Forbothdryers,polypropyleneisassumedforunknownplastictypes,suchasthePlasticmixturelistedintheproductsbillsofmaterialsforthehousingretainerandmotorplastics.Thedryersalsocontainunspecifiedmass.Thismassisaccountedforwhencalculatingtransportationstageimpact,butisassumedtohavenoinfluenceonproductionstageimpact.Finally,a15%scrapratearoundtheaveragerateofthetwoDysonAirbladehanddryersisaddedtothematerialinputflowsofbothdryersinordertoensureanaccuratecomparison.ScrapvaluesinTable3,however,areslightlylessthan15%becausethescrapratewasnotappliedtoelectroniccomponentsorunspecifiedmass.ProductiondataforthecottonrolltowelswereobtainedfromtheOkInstitutreportfortheEuropeanTextileServicesAssociation[12].Theproductionofthesetowelsincludesproductionofcottonfibers,spinningandsizingoftheyarn,andweaving,desizing,andbleachingofthefabric.A10%weightlossisassumedinthespinningprocess[12],plusa2%lossinweaving[32].Thus,ittakes18.4gramsofcottonfiberstoproducethe16.2gramsofcottontowelthatrepresentonepulloftheroll[12].Thedispenser

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usedforthecottontowelsisbasedonthepapertoweldispenserintheExcelstudy,althoughnobatteriesorcircuitryassociatedwithautomaticpapertoweldispensersareincludedsincethetowelsarepresumablypulledbyhandfromtheroll.Papertowelsmanufacturedfrom100%virginandfrom100%recycledcontentareexaminedinthisanalysis.Theformerisassumedtousepulpmanufacturedviathesulfateorkraftpulpingprocess,thedominantpulpingprocessthataccountsfor80%oftheworldspulpproduction[33],andbleachedusingelementalchlorinefree(ECF)technology,themostcommonbleachingprocessforsulfatepulpintheUSasof2002[34].Thispulpisthentransported250km(adistanceconsistentwithrawmaterialtransportationdistancesforthehanddryers)fromitsrespectivefacilitytoanonintegratedmanufacturingplantwherethepapertowelsareproduced.VirginpapertowelmanufacturingdatawerebasedontheExcelDryer[14],KimberlyClark[13],andETSA[12]studies.Papertowelsmanufacturedfromrecycledcontentwerealsoassumedtobeproducedinanonintegratedplant.Insuchcases,marketdeinkedpulpwouldbetransportedtothisplantfromitsrespectivemanufacturingfacilityandusedasarawmaterialinpapertowelproduction.Billofactivitiesandinventorydatafordeinkedpulpmanufacturedfrom100%recycledcontent,however,wereunavailableevenamongthecriticallyreviewedLCAstudies.TheKimberlyClark[13]reportprovidesanincompleteinventory,whilethestudybyExcel[14]doesnotevenaccountfortheenvironmentalimpactfrompulpmanufacturing(thisisacknowledgedinthereport).AlthoughtheETSA[12]studyprovidesaninventoryfortissuemanufacturing,thisinventoryisforanintegratedplant(wherepulpandtissuearemanufacturedinacontinuousprocess)andassumesonly50%recycledcontentGiventhelackofavailabledata,thisstudymadesimplifyingassumptionsforthedeinkedpulpmanufacturingprocess.Specifically,theimpactassociatedwithmanufacturingdeinkedpulpwasassumedequaltothatassociatedwithmanufacturingECFbleachedsulfatepulp.Woodinthesulfatepulpprocess,however,wasreplacedwith1.5kgofwastepaper[12].Thissubstitutionaddresseskeydifferencesinrawmaterialacquisition,butitmayleavesomeprocessesinthepulpingstepthatarerequiredonlyforvirginmaterialproduction(suchaswoodchipping).Whiletheseassumptionsintroduceuncertaintytotheresults(moresothantheresultsofpapertowelsmanufacturedfromvirgincontent),theuncertaintycannotbequantifiedduetolackofactualinventorydataforpapertowels.Amoredetailedstudyonrecycledpapertowelsisrecommended;sincenosuchstudycurrentlyexists,papertowelresultsfromthisstudywerecomparedwithresultsfromtheotherLCAsinAppendixA.6.3toensurethisstudysassumptionswerereasonableInbothcases,pulpandtissueweremanufacturedinthesamecountrywheretheusestagetakesplace(seediscussioninSection3).Additionally,thisassumptionisconsistentwiththeKimberlyClarkstudy.Papertowelshaveafinalproductmassof1.98g;a3.85%manufacturinglossisaccountedforinrawmaterialrequirements[13,14].Themanufacturingplantisalsoassumedtobeiscolocatedwithadistributioncenter,thuseliminatingtheneedfortransportationbetweenmanufacturingplantandwarehouse.Thisisareasonableassumptionbecausetheimpactofanytransportbetweentheplantandthedistributioncenterwouldbeminisculeincomparisonwiththeimpactoftransportingthehanddryersandcottonrolltowelsover13,000kmfromChinatotheirrespectivedistributioncenters.

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Theresultsforthepapertowelscontainingrecycledcontentarepresentedusingthecutoffallocationapproach,whichisdetailedinAppendixA.4.Thisallocationschemewasselectedforthebaselineanalysisbecauseitonlyaccountsfortheburdensdirectlyassociatedwiththeproductionanddisposaloftherecycledcontenttowels.Papertowelsarenotrecycled(sameassumptionastheKimberlyClarkstudy[13])andthereforerepresentthefinalproductlifecycleinanopenlooprecyclingsystem.Thus,followingthecutoffallocationscheme,papertowelsmanufacturedfrom100%recycledcontentareassignedthefullburdenfromrecyclingwastepaperbackintopulp,andthefullburdenfromendoflife.Inadditiontothetowellifecycle,lifecyclesforadispenser,wastebin,andbinlinersareincludedintheassessmentofpapertowelhanddryingsystems.Thedispenseristhesameasthatusedforthecottontowels;thewastebinisassumedtobeentirelycomposedofsteel,andthebinlinersfrompolyethylene.3.1.2 UseIdeally,billofactivitiesdatafortheusephasewouldincludedetailsofwashroomvisitorusagepatternsforeachhanddryingsystemhowlongtheyspentoperatingeachdryerorhowmanytowelstheyusedafterwashinghands.Suchdatawouldalsocoverthesignificantvariationinthewaypeopledrytheirhandsduetodifferencesinhandsizes,inpreferencesaboutacceptabledryness,andinwillingnesstospendtimedryinghands.However,therealityisthattherearenoexistingdatasourcescapturingthiswidevariation,noristhereacommonmethodfordetermininghanddrynessacrossallthedifferentdryingsystems.Whilethisstudyhasnotattemptedtoaddressthisgap,theauthorshavenonethelessmadeeveryefforttocharacterizedryingsystemuseintensityusingthebestavailabledataandaconsistentbasisforcomparison.Useintensityrepresentstheamountofresourceseachhanddryingsystemrequirestodryapairofhands.Forhanddryers,thisisrelatedtothetimeusersspendoperatingthedryers.Handdryerdrytimeshavebeenincorporatedintothestudyintwoways:(1)measuredaccordingtoastandardthatdefineswhenhandsaredryand(2)reportedbydryermanufacturers(Table4).Toensureaconsistent,scientificbasiswhencomparinghanddryers,thisstudyadoptsmeasureddrytimesasitsprimarybaseline.ThesetimesweremeasuredaccordingtotheNSFProtocolP335[19](seeAppendixA.5),whichdefineshygienicallydryhandshashavinglessthan0.1gramsofmoistureremainingafterdrying.NSFprotocolmeasurementswereperformedbyDyson.ManufacturerreporteddrytimesareusedasasecondarybaselineforsomeanalysesinSection4.1.Thesereporteddrytimeswereobtainedfromdryerspecificationstakenfrommanufacturerswebsites.NeitherExcelDryernorthestandarddryermanufacturers,however,providedocumentationonhowtheyarrivedattheirdryersrespectivedrytimesorwhattheirbasiswasfordryness.Variationinuseintensityisalsoevaluatedinordertoassesstheconsequencesofdifferinguserpreferencesandthus,differingusagepatterns.Forinstance,usersmayprefertoholdtheirhandsintheairstreamuntiladesireddrynessisachievedreferredtoasdryingdrivenusageinthisreport.Thedrytimesfordryingdrivenusagearedefinedas50%belowto25%abovethemeasuredbaselinedrytimes(asdefinedbytheNSFProtocolP335).Alternatively,usersmayprefertowaitthesamelengthoftimefortheirhandstodry,regardlessofdryertype,beforeleavingreferredtoastimedrivenusage.

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Dryingdrivenusageisassessedinasensitivityanalysis(seeSection5.1.4)andbothdryingandtimedrivenusagepatternsareassessedintheuncertaintyanalysis(seeSection0).

Table4Measuredandreporteddrytimesforhanddryers.

Dryer MeasuredNSFP335forUS ReportedAirblade 12sec[27] 12sec[35]XLERATOR 20sec[27] 12sec[14]Standarddryer 31sec[27] 30sec[6]

Oncedrytimeisdetermined,itisthenmultipliedbythedryersinuseratedpowertoarriveattheenergyconsumedduringoperation.Inuseenergyconsumption,though,isonlypartofadryerstotalenergyrequirementasdryersalsoconsumeenergyevenwhennotactivelydryinghands.Inadditiontodrytime,boththeXLERATORandthestandarddryersareassumedtohavea1.5secondspindowntimeathalfpower[14];theDysonAirbladehanddryer,bycontrast,usesadigitalmotoranddoesnotconsumepowerduringspindown[27].Alldryersarealsoassumedtohavesensorsthatrequireenergywheninstandbymode.TheXLERATORisassumedtohavethesame1WstandbypowerconsumptionastheDysonAirbladehanddryer[35],whereasthestandarddryerislowerat0.4W[36].Timespentonstandbyiscalculatedbysubtractingthetotaluseandspindowntimefor350,000pairsofhandsfromthetotaltimeinthe5yeardryerlifespan.Thistotalstandbytimeisthennormalizedbythe350,000usesandmultipliedbystandbypowerrating.Fromhere,spindownandstandbyenergyconsumptionsareaddedtoadryersinuseenergyconsumptiontoarriveatthetotalenergyallocatedtodryingapairofhands.TheUSaverageelectricgridmixisusedwhenassessingtheenvironmentalimpactofthisenergy.Table5summarizesdryerpowerconsumption,alongwithspindownandstandbytimes;additionaldetailsforcalculatingdryerenergyconsumptioncanbefoundinAppendixA.1.1.

Table5Dryerpowerconsumptionduringuse,spindown,andstandby.

Inuse Spindown Standby Power Time Power Power TimeAirblade 1,400W[35] 0sec 0W[27] 1W[35] 439secXLERATOR 1,500W[25] 1.5sec[14] 750W[14] 1W 429secStandarddryer 2,300W[27] 1.5sec[14] 1,150W 0.4W[36] 418secTheuseintensityofthecottonrolltoweldryingsystemisrepresentedbyonepullonacottontowelrollperfunctionalunit,equaltotheETSAstudysassumption[12].Whiletheinwashroomuseofcottonrolltowelsdoesnothaveanimpact,launderingthetowelsdoes.ThelaunderingprocessisalsobasedontheETSAstudy[12].Usedtowelsaretransported50kmfromthewashroomtothelaundry,wherethey

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arewashedandthermallydisinfectedbeforebeingpackagedinplasticfilmandreturnedtothewashroom.Unlikethehanddryers,thereisnoequivalentprotocolfordeterminingthenumberofpapertowelsrequiredtoachieveaspecificlevelofdryness.Thus,thepapertowelbaselineassumesauseintensityoftwotowelsperfunctionalunitbasedonobservationaldatafromaUniversityofFloridastudy[37].AspartoftheUFstudy,researchersobservedthelengthoftimepublicwashroomuserswashedtheirhandsandthenumberofpapertowelstheytooktodrytheirhands.Papertowelusagevariedbetweenoneandseventowels,withanaverageof2.1towelsperuser.ItshouldbenotedthatthetwopapertoweluseintensityassumptionisconsistentwithseveralotherLCAstudies(seeTable40),anoteworthyexceptionbeingtheKimberlyClarkStudy,whichassumes1.5papertowels.However,noneofthestudiesprovidesanyrigorousjustificationforthenumberofpapertowelsused,includingKimberlyClark.Thus,thedatafromtheUFstudyisusedasthebasisforthenumberofpapertowelsinthisstudy.Anotherconsiderationisthattheexactnumberofpapertowelswilllikelydependontowelmass,whichvariesamongthedifferentstudiessurveyed.Bothuseintensityandtowelmassarelaterexploredinasensitivityanalysis(seeSections5.1.4and5.1.9).Sincepapertowels,packaging,dispensers,thewastebin,andbinlinersdonotrequireanyenergyduringuse,theythereforehavetoimpactinthisstage.3.1.3 EndoflifeOncethehanddryersortowelsarenolongerinuse,theproductsaretransported100kmtoawastefacility,consistentwith[27],anddisposedaccordingtoUSaveragewasteandrecyclingfractionsfrom2008[30].Thus,76.7%ofcardboardpackagingisrecoveredforrecycling;eachkilogramofcardboardisassumedtodisplace0.78kgofnewcardboard(estimatedbasedon[12]).Nineteenpercentoftheremainingcardboardandallotherwasteisincinerated,withtheremaining81%senttothelandfill.Bothenergyrecoveryfromincinerationandmethanecapturefromlandfillemissionsareconsideredinthebaselinescenario.Incinerationenergyrecoveryisassumedtoproduce0.65kWhofelectricityperkilogramofwasteincinerated[38].Sincethis0.65kWhrepresentstheavoidedproductionofelectricity,eachdryingsystemiscreditedwith0.632gCO2eqperkilogramofwasteincineratedtheemissionsassociatedwithproducing0.65kWhofelectricitygiventheUSaveragegridmix.Methanecapturedfromlandfillemissionsisalsoassumedtobeburnedwithenergyrecoverytoproduceelectricity.AdditionaldetailsandreferencesforthisprocesscanbefoundinAppendixA.2Asidefromtherecyclingofcardboardpackaging,nootherrecyclingisassumedtotakeplace.Whilehanddryerscanberecycled(andindeedarerequiredtoberecycledinEuropeperthewasteelectricalandelectronicequipmentdirective[39]),thereisnoclearevidencethatthisiscommonpracticeintheUS.PapertowelrecyclingisalsopossibleasnotedbyKimberlyClark[40],althoughtheirLCAstudy[13]assumesthatthepapertowelsarenotrecoveredafterdisposal.Likethehanddryers,thereisnostrongevidencethatrecyclingpapertowelsiscommonpracticeintheUS;composting,however,isgainingground(e.g.[41,42])andisthusaddressedinthesensitivityanalysis(seeSection5.1.5).Cottontowelsarenotrecycled,butcanpotentiallybereusedasindustrialcleaningcloths[12](althoughthisscenarioisnotconsideredinthisanalysis).

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3.1.4 TransportationTransportationtakesplacebetweeneachofthelifecyclestages.Distancesareeithertakenfromliterature,orestimatedaccordingtoproduction,use,andendoflifelocations.Table6liststhedistanceandvehicletypeforeachtransportationstep.Vehicletypesarechosentomatchascloselyaspossibletothoseusedin[12,27].Somestepsarenotincludedinthepapertowellifecyclebecausethetowelsareassumedtobemanufacturedinthesamecountrywheretheyareusedandhaveamanufacturingfacilitycolocatedwiththeirwarehouse.Cottonrolltowelshavetheadditionalstepofbeingtransportedtoandfromthelaundry.

Table6Transportationvehiclesanddistancesforallproducts(unlessnotedotherwise).

What Towhere Distance Vehicle NotesRawmaterials Manufacturingplant 250km >16ttruck

Finishedproduct LongBeachport 10,500km[43] Oceanfreighter ExcludingpapertowelsFinishedproduct Warehouse 2,600km24kma

Freighttrain>32ttruck

Excludingpapertowels

Finishedproduct Washroom 1,760kmb >32ttruck

Dirty/cleantowels Laundry&back 100km[12] 3.57.5ttruck CottontowelsonlyUsedproduct Wastefacility 100km[27] 7.516ttruck

(a)Estimatedusing[27,44](b)EstimatedbyaveragingdrivingdistancesfromKansasCity,KStoNewYork,NY;LosAngeles,CA;andChicago,ILusing[44].

3.1.5 Dataquality:sensitivityanalysisNumerousassumptionsaremadeinthedefinitionofbillsofactivities.Asensitivityanalysisisusedtoexploretheextenttowhichvariabilityinthebaselinescenarioassumptions(detailedinSections3.1.1through3.1.4)affectstheenvironmentalimpactsofthehanddryingsystems.TheresultsofthesensitivityanalysisarepresentedinSection5.1.Theanalysisevaluatesarangeofscenariosthatdeviatefromthebaseline.Thebaselineassumptionsaddressedinclude(withbaselinevaluesshowninparentheses):

Lifetimeusage(350,000)numberofpairsofhandsdriedoverthe5yearproductlifespan. Manufacturingphaseelectricgridmix(ChinaorUSaveragemix)technologyportfoliothat

supplieselectricpowerfordryerandtowelproduction. Usephaseelectricgridmix(USaveragemix)technologyportfoliothatsupplieselectricpower

fordryerandtoweluse.

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Useintensity(variesbyproduct)lengthofdrytimefordryers,ornumberofpapertowelsorcottonrolltowelpullsrequiredtodryhands.

Endoflifescenario(19%incinerated,81%landfilledwithenergyrecovery)fractionofwasteincinerated,landfilled,recycled,orcomposted;energyrecoveryassumptionismaintainedthroughout.

Dryerelectronicsunitprocess(Electroniccomponent,active,unspecified)unitprocessinventorychosentorepresentthecontrolandopticsassembliesintheXLERATORandstandarddryers.

Cottonrolltowelreuses(103cycles)numberoftimescottonrolltowelscanbelaunderedandreusedbeforedisposal.

Papertowelmass(1.98g)massofvirginandrecycledcontentpapertowels. Pulpmanufacturingprocess(ECFbleachedsulfate)manufacturingprocessofpulpusedby

virginpapertowels. Endoflifeallocationmethodologyforrecycledcontentinpapertowels(cutoff)allocationof

theburdenofprimarymaterialproduction,recycling,andendoflifeprocesses. Manufacturinglocation(ChinaorUS)wheretheproductsaremanufactured;affects

productionelectricgridmixandtransportationdistances. Uselocation(US)wheretheproductsareused;affectstransportationdistances,electricgrid

mix,andendoflifescenario.3.2 UnitprocessinventorydataInadditiontothebillofactivitiesdata,unitprocessinventorydataarealsonecessarytogeneratealifecycleinventory.Aunitprocessisthesmallestelementconsideredinthelifecycleinventoryanalysisforwhichinputandoutputdataarequantified[11].Theinputsandoutputscanbeintermsofotherunitprocesses(e.g.,electricityorsteelproduction)orbasicsubstances(e.g.,mineralsorgaseousemissions).Theseunitinventoriesaretypicallyobtainedfromdatabasessuchasecoinvent[32]andUSLCI[45].Wheneverpossible,theunitprocessinventorydataforthelifecycleinventoriesaretakenfromtheecoinventDatabasev2.1[32].Themajorityofecoinventunitprocessesareusedwithoutmodification.Consequently,theyrepresentthedatabasesdefaultassumptionssuchastheinclusionofcapitalequipmentforrawmaterialsproduction,amixtureofcountryspecificemissionsfactorsforasinglecountryselectricityproductionowingtodataavailabilitylimitations,andtheuseofEuropeanfuelsandemissionsfactorsforroadtransportation.Inafewcases,though,ecoinventprocessdataismodifiedordataisadoptedfromexternalsourcesbecauseofalackofexistinginventorydata:

Galvanizedsteelcreatedusingecoinventdataforsteelandzinccoating

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Sheetsteelsheetcreatedusingecoinventdataforsteelandrolling Plasticmixturewithextrusioncreatedusingecoinventdataforpolypropyleneandextrusion Glassfiberreinforcedpolypropylenecreatedusingecoinventdataforglassfibersand

polypropylene Polycarbonate/acrylonitrilebutadienestyrenemixtureofthetwopolymers,basedon[27] CottonrolltowelmanufacturingadoptedfromtheETSAstudy[12];theseprocessesinclude

spinningthecottonfibersintoyarn,sizingtheyarn,weavingthetowels,anddesizing,scouring,andbleaching

CottontowellaunderingadoptedfromtheETSAstudy,whichliststhedetergent,energy,andwaterrequiredtowashthetowels

Pulpfromwastepaperamodifiedecoinventsulfatepulpingprocess(ECFbleached)inwhichwoodisreplacedwith1.5kgwastepaper(basedon[12])

Cardboardrecyclingcreatedusingecoinventdatawithanestimatedrecyclingratefrom[12] Incinerationwithenergyrecoverybasedonecoinventdatawithanestimatedelectricity

generationratefrom[38] Landfillwithmethanecapturebasedonecoinventdatawithestimatedmethanecaptureand

electricitygenerationratesfrom[46] CompostingbasedondatafromaEuropeanCommissionstudyonbiodegradableMSW[47]

BillsofactivitiesforthesemodifiedunitprocessesareincludedinAppendixA.2.Also,agenericecoinventunitprocess,Electroniccomponent,active,unspecified,thesameunitprocessasintheExcelstudy[14],isusedfortheXLERATORandstandarddryerelectroniccomponentsbecausespecificinformationisnotavailableforthesecomponents.3.3 UncertaintyanalysesUncertaintyanalysesareusedtoassesstheconsequencesofvariabilityoruncertaintyintheinputsonenvironmentalimpactresultsofthehanddryingsystems.Twotypesofuncertaintyanalysesareconductedinthisstudy.Thefirstaddressesvariabilityinthebaselinescenarioassumptions.Distributionsareassignedtoparameterssuchaslifetimeusage,electricgridmix,anduseintensity.AMonteCarlosimulationisthenemployedtogeneratescenariosgiventheparameterdistributionsandcalculatetheresultingenvironmentalimpactdistribution.Thesecondanalysisinvestigatesuncertaintyandvariabilityinthebillofactivitiesdata.Incomparisontothefirstanalysis,whichaddressesscenariolevelvariables(e.g.useintensity),thisanalysisfocusesonthequantityofeachunitprocessrequiredbyahanddryingsystem.Thisquantityisrelatedto,butnotthesameas,thescenariolevelvariables:forinstance,thebillofactivitiesdataincludehanddryeruse

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phaseelectricityconsumption,whichnotonlydependsonuseintensity,butalsoonthedryerspowerrating.Often,however,uncertaintydataisnotavailableorcannotbederivedfortheunitprocessquantitiesincludedinthebillofactivities.Apedigreematrixapproach[32]isthereforeemployedtotranslatequalitativeassessmentsofthedatasourcesintoquantifiableuncertaintycalculations.Aspartofthismethod,thebillofactivitiesdatasourcesarefirstevaluatedbasedonsixcharacteristics:reliability,completeness,temporalcorrelation,geographiccorrelation,furthertechnologicalcorrelation,andsamplesize.Oneoffivequalitylevelsthatdescribethedegreeofuncertaintyischosenforeachofthecharacteristicsbasedondescriptionsfoundin[32].Thesequalitylevelsare,inturn,eachassociatedwithanuncertaintyfactorthatquantifiestheiruncertainty(Table7).Lowerqualitylevelvaluesrepresenthigherconfidenceinthedataandthustranslatetosmalleruncertaintyfactors.Aseventhbasicuncertaintyfactorisalsoaddedaccordingtowhethertheprocessrepresentsaninputoroutputtothetechnosphereoremissions.Finally,uncertaintyfactorsareusedtocalculatethegeometricstandarddeviation(SDg)ofthebillofactivitiesdatausingthefollowingequation:

27262524232221 lnlnlnlnlnlnln UUUUUUUg eSD

Uxrepresenttheuncertaintyfactorsofthesixcharacteristicsplusthebasicuncertaintyfactor.ThepedigreematrixapproachisappliedtoeachelementinthebillofactivitiesandtheresultinggeometricstandarddeviationsenteredintoSimaPro,wheretheyareusedtoscalethedistributionmeans(representedbythebaselineunitprocessquantities).AMonteCarlosimulationisthenruntoassesstheconsequencesofdatasourcequalityonenvironmentalimpact.TheresultsarepresentedinSection5.2.2andqualitylevelsassignedtoeachprocessarelistedinAppendixA.3.

Table7Pedigreematrixuncertaintyfactors[32].

QualityLevel 1 2 3 4 5Reliability 1.00 1.05 1.10 1.20 1.50Completeness 1.00 1.02 1.05 1.10 1.20Temporalcorrelation 1.00 1.03 1.10 1.20 1.50Geographicalcorrelation 1.00 1.01 1.02 1.10Furthertechnologicalcorrelation 1.00 1.20 1.50 2.00Samplesize 1.00 1.02 1.05 1.10 1.20

4 Lifecycleimpactassessment4.1 LifecycleimpactassessmentmethodologiesTheenvironmentalimpactsassociatedwithalifecycleinventorycanbecalculatedusingalifecycleimpactassessment(LCIA)methodology.LCIAcalculationsinthisstudyhavebeenperformedusingthe

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SimaPro7softwarepackagefortheglobalwarmingpotential(GWP),IMPACT2002+,andcumulativeenergydemand(CED)methodologies.Resultsarealsopresentedforwateruse(anelementaryflow)andlandoccupation(amidpointcategoryintheIMPACT2002+methodology).Novaluechoicesorweightingareusedintheapplicationoftheseimpactassessmentmethodologies.Eachmethodologyisdescribedbelowalongwithajustificationforitsuse.4.1.1 GlobalwarmingpotentialGlobalwarmingpotential(GWP)[48]incorporatestheimpactofgaseousemissionsaccordingtotheirpotentialtocontributetoglobalwarmingbasedonthevaluespublishedin2007bytheIntergovernmentalPanelonClimateChange(IPCC).Theimpactsforallgaseousemissionsareevaluatedrelativetocarbondioxideusingcharacterizationfactorsthattranslatethemassofeachgasintoanequivalentmassofcarbondioxide(e.g.1kgCH4emittedintotheatmosphereisequivalentto25kgCO2[49]).Thesefactorsareinternationallyacceptedasameansofcharacterizinggreenhousegasemissions.ResourceconsumptionandliquidandsolidemissionsarenotincludedintheGWPmethodologybecausetheydonotdirectlycontributetoglobalwarming.Biogeniccarbondioxideandcarbonmonoxideflowsarealsonotincludedintheaccounting(unlesstheanalysisinvolvescarbonsequestration);biogenicmethane,however,isincluded2.Inthisreport,characterizationfactorsarebasedona100yeartimeframebecausetheyarethemostcommonlyusedfactorsinLCAstudies.GWPwasselectedasanLCIAmetricbecauseofitshighprofileintheassessmentofproductenvironmentalperformancefornumerousproducttypesacrosstheworldandparticularlyforenergyintensiveproducts.Furthermore,themetricisusedinvirtuallyallofthestudiesusedasreferencesforthisstudy.ForthesereasonsGWPisusedastheprimarymeansforcomparisonofenvironmentalimpact.4.1.2 IMPACT2002+IMPACT2002+[50]isadamageorientedmethodthatevaluatesenvironmentalimpactinfourendpointcategories:humanhealth,ecosystemquality,climatechange,andresources.Thesecategoriesarecalculatedfrom15midpointcategories(showninFigure4)which,inturn,havebeenadaptedfromIMPACT2002,Ecoindicator99,CML(CenterofEnvironmentalScience),andIPCC.DamagetoHumanHealthisinunitsofdisabilityadjustedlifeyears(DALY),implyingthatdifferentdisabilitiescausedbydiseasesareweighted.EcosystemQualityisreportedinunitsofpotentiallydisappearedfractionofplantspecies(PDFm2yr).ClimateChangeissimilartoGWPfromabove,butusescharacterizationfactorsbasedona500yeartimeframe.Finally,ResourcesincludesassessmentofmineralsandfossilfuelsinunitsofMJ.EachdamagecategorycanthenbenormalizedbyaverageEuropeanimpactsandweightedinordertoaggregateallimpactsintoasinglevaluewhichhastheunitsofpoints,where1000pointsrepresentstheaverageenvironmentalimpactofaEuropeaninoneyear.Weightingisnotusedinthisstudy.

2AconsequenceofbiogeniccarbonnotbeingincludedintheIPCCstandardforthisstudyisthatitmayobscuretheimpactofseveralcriticalassumptionsregardingcarbonneutralityofpulpingliquorcombustionduringproductionofsulfatepulpforvirgincontentpapertowels.Italsoneglectstheforestryimpactsforpapertowels.However,thisstudyfollowstheIPCCmethod,whichdoesnotincludebiogeniccarbonasitrepresentsthescientificconsensusoncarbonaccounting.

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Amultiindicatorimpactassessmentmethodwassoughtthatcouldcalculateotherimportantimpactsbeyondglobalwarmingsuchashumanhealthandecosystemquality.IMPACT2002+wasselectedbecauseitisaninternationallyacceptedmethodforLCIAthatincludescharacterizationmodelsfromseveralwellrespectedLCIAmethodologies.Furthermore,ithasbeenusedinanotherkeyhanddryingstudy(theExcelstudy[14]).ThisstudyincludesresultsfromIMPACT2002+midpointcategoriesintabularformat,butmostofthegraphicalresultsarepresentedforthehumanhealthandecosystemqualityendpointcategoriestofacilitateaclearandsimplecomparisonofenvironmentalimpactwithinthesecategories.Theothertwoendpointcategories,climatechangeandresources,arenotincludedinthisstudybecausetheyareverysimilar(althoughnotidentical)toGWPandcumulativeenergydemand(describedbelow),andthereforeareconsideredredundant.

Figure4The15midpointcategoriesandfourendpointcategoriesofIMPACT2002+.

AlimitationofapplyingtheIMPACT2002+methodologyisthatitisfocusedonaEuropeancontext,whereasthefocusofthisstudyistheUnitedStates.However,thisassumptionisacceptablegiventhatmultipleregionsoutsidetheUSwillbeevaluatedinsensitivityanalysesanditisnotconstructivetousedifferentLCIAmethodsforeachregion(particularlywhentheymaynotbeavailableforallregions).Furthermore,IMPACT2002+hasbeendeemedtobecurrentlymoreinternationallyacceptedthanUSspecificmethodssuchasTRACI.4.1.3 CumulativeenergydemandCumulativeenergydemand(CED)[48]includesalldirectandindirectenergyconsumptionassociatedwithadefinedsetofunitprocesses.Itdoesnotdirectlyaccountfortheimpactofrawmaterialconsumptionoremissionstotheenvironment.ValuesforCEDaremeasuredintermsofenergy(e.g.

Lifecycleinventoryresults

CarcinogensNoncarcinogens

RespiratoryinorganicsIonizingradiation

OzonelayerdepletionRespiratoryorganicsAquaticecotoxicity

TerrestrialecotoxicityTerrestrialacid/nutriLandoccupation

AquaticacidificationAquaticeutrophication

GlobalwarmingNonrenewableenergyMineralextraction

EcosystemQuality

Humanhealth

ClimateChange

Resources

MidpointCategories EndpointCategories

25

joules).ItisimportanttonotethatCEDisaproxymetricforenvironmentalimpactandthus,itisnotaformalimpactassessmentmethod,althoughitiscommonlyreferredtoassuchandwillbeinthisreport.LikeGWPandIMPACT2002+,CEDisawidelyacceptedmethodology.CEDwasselectedasanLCIAmethodologyforthisstudybecauseenergyconsumptionisoftentheprimarydriverofenvironmentalimpactforelectricityintensiveproductssuchashanddryers.Furthermore,thepublicisfamiliarwithenergyasaproxymetricofenvironmentalimpactbecauseoftheextensivemarketingaroundenergyconsumptionofconsumerproducts.Cumulativeenergydemandisanextensionofthistypeofthinkingtotheentireproductlifecycleandthus,isanaturalmetricforuseinthisstudy.4.1.4 WaterconsumptionandlandoccupationWaterconsumptioniscalculatedasanelementaryflowinthelifecycleinventoryandlandoccupationisamidpointcategoryintheIMPACT2002+methodology.Theyareincludedasimpactassessmentmetricsbecausetheyareparticularlyrelevanttoassessmentsofproductsmadefromnaturalresources(suchaspaper).Asidefrompresentationofresults,however,theyarenotfurtherassessed.Waterconsumption,inparticular,isnotaLCIAmethodology,butratherasummationofwateruse(includingturbineflows)thatiscalculateddirectlyfromdryingsystemlifecycleinventories.4.2 Baselineanalysis4.2.1 ResultsbyimpactassessmentmethodologyFigure5showstheresultingGWP,brokendownbylifecyclestage,associatedwithdryingonepairofhands.BothmeasuredandreporteddrytimesareincludedinFigure5aandb,respectively.Inbothcases,thetwoDysonAirbladehanddryersystemsareassociatedwiththelowestGWPsofallthehanddryingsystems,followedbytheXLERATORsystem.Thestandarddryersystem,ontheotherhand,isassociatedwiththehighest.Sinceeachdryerdriesupto350,000pairsofhandsoveritslifespan,theimpactfromtheproductionandendoflifestagesallocatedtoeachpairofdryhandsisverysmall;consequently,dryerimpactisdominatedbyuseanddryerswithsimilardrytimes(andpowerratings)willhavesimilarimpacts.Cottonrolltowelsystemimpactisalsodominatedbyuse,whichisdrivenbythewashingofthetowels.Bycontrast,materialsandmanufacturinghavethelargestimpactforpapertowels.Despitethedifferentmanufacturingprocesses,thereisminimaldifferencebetweenthevirginandtherecycledpapertowelsbecausetheythisstudyassumestheyusethesametissuemanufacturingprocess,andpulpproducedfromwastepaperhasnearlythesameGWPaspulpproducedwithvirginwood.ItisdifficulttoassessexactlyhowthisassumptionimpactstheresultsbecausetheKimberlyClarkstudycalculatesat30%increaseinGWPimpactforrecycledpapertowelsovervirginpapertowels[13],whereasthePaperTaskForce[58]notedina1995reportonprintingpaperthatdeinkedpulpproductionconsumeslessenergyandmorebleachingchemicalsthanbleachedkraftpulpproduction.AconsistencycheckisperformedinAppendix8A.6A.6,whichcomparestheGWPresultsinFigure5withresultsfromliterature.Thecheckindicatesthatthereisvariationinotherpublishedresultsofpapertowelimpacts,buttheoutcomesinthisstudyaresimilartothosecalculatedintheKimberlyClarkstudy.Improvedinventorydataonrecycledpapertowelswouldhelptoclarifythesediscrepanciesamongstudies.

26

IMPACT2002+results,calculatedusingmeasuredandreporteddrytimes,arepresentedinFigure6.Onlyhumanhealthandecosystemqualityareincludedbecausetheothertwoendpointcategories,climatechangeandresources,aremaderedundantbythisreportsuseofGWPandCED.Additionally,midpointcategoryoutputs,usedinthecalculationoftheendpoints,areincludedinTable8.Intheseresults,theimpactsoftheDysonAirbladehanddryersaregenerallylowerthanthoseoftheotherdryingsystems:onlythecottonrolltowelsareassociatedwithlowerimpactsinthecarcinogen,ionizingradiation,andmineralextractionmidpointcategories.Roughlyspeaking,DysonAirbladehanddryerimpactsarefollowedbytheXLERATORandcottonrolltowelimpacts,andthenbythestandarddryerandpapertowelimpacts;theexactorderofthesystemswillultimatelydependonthemidpointcategory.

27

Figure5Globalwarmingpotentialassociatedwithdryingasinglepairofhands.

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Figure6Impactassociatedwithdryingasinglepairofhandsbasedonimpact2002+endpointshumanhealthandecosystemquality.(a)and(c)arecalculatedusingmeasureddrytimes(inaccordancewiththeNSFProtocol)and(b)and(d)arecalculatedusingmanufacturerreporteddrytimes.

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Airblade,aluminum

Airblade,plastic

XLERATOR Standarddryer

Cottonrolltowels

Papertowels,virgin

Papertowels,100%

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E

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s

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q

u

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EndofLifeUse

Transportation

Manufacturing

Materials

(c)Measureddrytimes

100

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30

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60

70

80

90

100

Airblade,aluminum

Airblade,plastic

XLERATOR Standarddryer

Cottonrolltowels

Papertowels,virgin

Papertowels,100%

recycled

E

c

o

s

y

s

t

e

m

q

u

a

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i

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y

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P

D

F

.

c

m

2

.

y

r

]

EndofLifeUse

Transportation

Manufacturing

Materials

(d)Reporteddrytimes

29

Table8Impact2002+midpointcategoryresultsforeachdryingsystem(givenmeasureddrytimes).

IMPACT2002+midpointcategories Units

Airblade,aluminum

Airblade,plastic XLERATOR

Standarddryer

Cottonrolltowels

Papertowels,virgin

Papertowels,

100%recy.Endpt.Category

Carcinogens gC2H3Cleq 0.277 0.272 0.486 1.111 0.205 0.525 0.525 HHNoncarcinogens gC2H3Cleq 0.102 0.090 0.189 0.386 0.145 0.454 0.457 HHRespiratoryinorganics gPM2.5eq 3.63103 3.45103 6.33103 0.0135 8.16103 0.0126 0.0128 HHIonizingradiation BqC14eq 0.127 0.119 0.239 0.521 0.104 0.291 0.290 HHOzonelayerdepletion gCFC11eq 1.43107 1.24107 2.68107 5.38107 1.03106 1.18106 1.21106 HHRespiratoryorganics gC2H4eq 6.02104 5.81104 1.11103 2.27103 3.31103 4.38103 4.09103 HHAquaticecotoxicity gTEGwater 486 462 1135 2197 935 1619 1628 EQTerrestrialecotoxicity gTEGsoil 118 113 243 484 290 410 417 EQTerrestrialacid/nutri gSO2eq 0.0757 0.0725 0.136 0.293 0.221 0.291 0.298 EQLandoccupation cm2org.arable 0.102 0.094 0.227 0.478 22.1 45.0 21.1 EQAquaticacidification gSO2eq 0.0308 0.0297 0.0551 0.1210 0.0499 0.0812 0.0822 Aquaticeutrophication gPO4Plim 2.66104 2.45104 2.28103 2.80103 2.03103 4.05103 4.06103 Globalwarming gCO2eq 4.44 4.19 7.85 17.2 10.2 14.6 14.8 CCNonrenewableenergy kJprimary 72.1 69.2 130 285 171 245 247 REMineralextraction kJsurplus 0.162 0.137 0.170 0.216 0.062 0.280 0.277 REEndpointcategories:HHhumanhealth;EQecosystemquality;CCclimatechange;REresources.

30

Figure7Cumulativeenergydemandassociatedwithdryingasinglepairofhands,assuming(a)measured

drytimesand(b)reporteddrytimes.

100

0

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400

500

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Airblade,plastic

XLERATOR Standarddryer

Cottonrolltowels

Papertowels,virgin

Papertowels,100%

recycled

Cumulativee

nergyd

eman

d[kJ

eq] EndofLife

Use

Transportation

Manufacturing

Materials

(a)Measureddrytimes

100

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XLERATOR Standarddryer

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nergyd

eman

d[kJ

eq] EndofLife

Use

Transportation

Manufacturing

Materials

(b)Reporteddrytimes

31

Figure8Waterconsumptionassociatedwithdryingasinglepairofhands(calculatedfromlifecycle

inventoriesbasedonmeasureddrytimes).

Figure9Landoccupation(IMPACT2002+midpoint)associatedwithdryingasinglepairofhands

(calculatedbasedonmeasureddrytimes).

100

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XLERATOR Standarddryer

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incl.tu

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[L]EndofLifeUse

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32

CEDresults,alsocalculatedusingmeasuredandreporteddrytimes,arepresentedinFigure7.Again,thehighspeeddryersystemsareshowntohavethelowestimpacts,andthepapertowelandthestandarddryersystemsthehighest,withthecottonrolltowelsystemfallingsomewhereinbetween.InthecaseofCED,virginpapertowelshavethehigherimpactbecausethemethodologyaccountsfortheenergyembodiedinvirginwood.ResultsfromwaterconsumptionandlandoccupationareshowninFigures8and9,respectively,formeasureddrytimesonly.Waterconsumptioniscalculateddirectlyfromthelifecycleinventories,andlandoccupationisamidpointcategorywithinIMPACT2002+andcontributestotheecosystemqualityendpointcategory.4.2.2 EndpointcategorynormalizationSomeLCIAmethodologies,inparticularthoseconcerningmultipleissuessuchasIMPACT2002+,haveanadditionalnormalizationstepinwhichtheresultsofendpointcategoriesaredividedbyafactorbeforebeingweightedandcombinedintoasinglescore.InthecaseofIMPACT2002+,thedamageassessmentsarenormalizedbydividingtheimpactbythetotalimpactofallsubstanceswithinaspecificcategorythatapersonlivinginEuropeisexposedtooveroneyear[50].ThisnormalizationenablesacomparisonofthefourendpointcategoriessoonecanseewhichhavethegreatesteffectonanaverageEuropean.Figure10showstheresultsofthisnormalizationforthetwoendpointcategoriesinFigure6aswellasfortheotherendpointcategories,climatechangeandresources.Theresultsindicatethathumanhealth,climatechange,andresourceshaveapproximatelythesamerelativeimpactwhiletheimpactofecosystemqualityismuchless.

Figure10IMPACT2002+endpointcategoriesafternormalizationofresultsgivenmeasureddrytimes.

0.0

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IMPA

CT20

02+

endp

oint

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s[10

6pts]

HumanHealthEcosystemQualityClimateChangeResources

33

4.2.3 RankordercomparisonDryingsystembaselineresultsformeasureddrytimesarecomparedinTable9byrankorderingthesystems.(Rankorderformeasureddrytimesisslightlydifferentforthehumanhealthandwaterconsumptionimpactcategories.)Systemsareassignedthesamerankifthedifferencebetweentheirimpactsiswithin10%ofthesmallerofthetwonumbers.TheplasticDysonAirbladehanddryerhasthelowestimpactforallofthemetrics,followedbythealuminumDysonAirbladehanddryerandtheXLERATORdryerforallmetricsexceptwaterconsumption,wheretheimpactofthecottonrolltowelsisessentiallyequivalenttothatoftheplasticDysonAirblade.Thus,therankorderofthetopthreeproductsisnearlyindependentofthemethodusedtocalculateimpact.Therankorderofthestandarddryerandthetowels,however,ismorestronglydependentontheimpactassessmentmethod,althoughafewgeneralizationscanbemade:thestandarddryerandvirginpapertowelsystemsarealmostconsistentlyassociatedwiththehighestimpact,regardlessofimpactassessmentmethod;assuch,cottonrolltowelimpactisalwayslessthanvirginpapertowelimpact,asisthatoftherecycledpapertowels.Thesignificanceofthedifferencebetweendryingsystemenvironmentalimpactvaluesislaterevaluatedinthescenariouncertaintyanalysis(Section5.2.1)andthebillofactivitiesuncertaintyanalysis(Section5.2.2)

Table9Rankorderofenvironmentalimpactoftheproductsusingthebaselinescenarioandmeasureddrytimesforalloftheimpactassessmentmetrics(1=lowestimpact,7=highestimpact).

Productsystem

Globalwarmingpotential

Humanhealth

Ecosystemquality

Cumulativeenergydemand

Waterconsumption

Landoccupation

Airblade,aluminum 1 1 1 1 3 1Airblade,plastic 1 1 1 1 1 1

XLERATOR 3 3 3 3 4 3

Standarddryer 7 7 4 6 7 4Cottonrolltowels 4 3 6 4 1 6

Papertowels,virgin 5 5 7 7 5 7

Papertowels,100%recy. 5 5 4 5 5 5

4.3 AdditionalproductlifecyclesEachdryingsystemiscomprisedofmultipleproductsthatarerequiredtofulfillafunctionalunit(seeTable1).Globalwarmingpotentialandotherimpactresultscanthereforebebrokendownnotonlybylifecyclestage,butalsobythesedifferentproducts.Figure11showstheportionofeachdryingsystemsGWPattributedtoeachoftheseproducts.Fordryers,theonlyotherproductispackaging,

34

whichaccountsforaverysmallfractionoftotalimpact.SlightlymoreoftowelGWPsareassociatedwithpackaging,dispensers,wastebins,andbinliners,butthemajorityoftheimpactisstillduetothetowelsthemselves.

Figure11GWPofhanddryingsystems,brokendownbyproduct.

4.4 ContributionanalysisforindividualproductsThissectionincludesacloserlookattheenvironmentalimpactofthedifferenthanddryingsystems,specificallythecontributionstoanddriversofthatimpact.4.4.1 DryersAscanbeseenfromFigure5,thematerials,manufacturing,transportation,andendoflifestagesofhanddryerscompriseasmallfractionofthetotalimpactassociatedwithdryingonepairofhandsaround4%to13%ofGWPwhencalculatedusingmeasureddrytimes.Consequently,alteringtheassumptionsrelatedtotheselifecyclestages,suchasaccountingforscraplossinXLERATORandstandarddryerproductionorlocatingproductioninChina,willhaveminimalaffectonthefinalimpactresults.Nonetheless,itisstillimportanttomorecloselyevaluatethesestagesmaterialsandmanufacturinginparticularastheyaremuchhigherthantheothertwobecausetheyarecollectivelyresponsibleforasmuchas283kgCO2eqbeforetheirimpactsareallocatedamongthe350,000handdryingsthattakeplaceduringadryerslifetime.Additionalevaluationwillalsohelptoinformproductdesigndecisions.Theproduction(i.e.materialsandmanufacturing)stageGWP,beforeallocationamonglifetimeuses,isbrokendowninFigure12forthealuminumandplasticDysonAirbladehanddryers,andinFigures13and14fortheXLERATORandstandarddryers,respectively.AscanbeseenfromFigure12,over75%oftheimpactisduetothreeprocesses:electricity,steelsheet,andaluminumorPC/ABS.Thesteel

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35

sheetandaluminumorPC/ABSdominateimpactbecauseoftheirhighmassesrelativetothoseofotherdryercomponents:aluminumandPC/ABSareusedforthedryercoversandsteelsheetforthedryerbackplateplus,inthecaseoftheplasticdryer,reinforcementbrackets.Electricity,ontheotherhand,dominatesbecausethedryerisassumedtobemanufacturedinChinaandthereforeusesacarbonintensivegridmix.Theremainingcomponents,whichformthedryermotor,ducts,electronics,andsoforth,arelessthan25%ofproductionimpact.

Figure12Breakdownofproduction(materials&manufacturing)phaseGWPfor(a)aluminumand(b)

plasticDysonAirbladehanddryers.

OverhalftheproductionGWPsoftheXLERATORandstandarddryersareduetothedryerscontrolandopticsassemblies(Figures13and14).Theseassemblies,however,accountforlessthan3%ofdryermass(seeTable19intheAppendix).GiventheiroutsizedimpactinproportiontotheirmassesaswellasrelativetoDysonAirbladehanddryerresults(theDysonAirbladehanddryerscircuitboards,bycontrast,accountforlessthan2%ofproductionGWP),thereisanopportunitytotakeacloserlookatthematerialsandmanufacturingprocessesthatgointoproducingtheseassemblies.Specifically,moreinformationabouttheassembliesintheXLERATORandstandarddryersisneededbecausetheirinventoriesarecurrentlymodeledwithagenericunitprocessfromecoinvent,Electroniccomponent,active,unspecified,whichmaynotaccuratelyrepresentthem;bycontrast,moredetailsareknownabouttheDysonAirbladehanddryerselectroniccomponentsandamorespecificunitprocess,Printedwiringboard,throughhole,leadfreesurface,isused.TheuseofthegenericecoinventprocesstomodeltheelectronicsoftheXLERATORandstandarddryersisexaminedmorecloselyinSection5.1.6aspartofthesensitivityanalysis.ElectricityusedinmanufacturingtheXLERATORandthestandarddryersrepresentsthesecondlargestcontributorstotheproductionstageGWP,consistentwiththechartsinFigure12.SincetheXLERATOR

AluminumElectricity

Steelsheet

Melamine

PkgingGFRP

PS PP

Other

(a)AluminumAirbladeProductionGWP:

191kgCO2 eq/dryer

PC/ABS

Electricity

Steelsheet

Melamine

Pkging

GFRP PSPP

Other

(b)PlasticAirbladeProductionGWP:

113kgCO2 eq/dryer

36

coverisassumedtobeacombinationofthedryersthreedifferentcoversstainlesssteel,plastic,andchromefinishnoonematerialdominatesbymass.

Figure13BreakdownofproductionphaseGWPfortheXLERATORdryer.

Figure14BreakdownofproductionphaseGWPforastandarddryer.

Control,optics

assembly

Electricity

Steel

GFRP

Naturalgas

Zinc

Other

ProductionGWP:275kgCO2 eq/dryer

Control,optics

assembly

Electricity

Steel

Aluminum

Naturalgas Zinc Other

ProductionGWP:271kgCO2 eq/dryer

37

Asnotedearlier,alteringtheassumptionsrelatedtotheproduction,transportation,andendoflifestageswillhaveminimalaffectonthetotalGWPassociatedwithdryingonepairofhandswithahanddryer.Assumptionsrelatedtotheusephase,however,cansignificantlychangeGWPbecausetheusephasedominatestotalimpact.Usephaseimpactisdrivenentirelybyelectricityconsumption,mostofwhichoccurswhenthedryerisinuseratherthanwhenitisspinningdownoronstandby(Figure15).Thesensitivityanalysis(Section5.1)includesanassessmentofuseintensity,whichdefineshowlonguserswaittodrytheirhandsandtherebyaffectsusestageGWP;powerconsumptionisconsideredfixedforthisstudy.

Figure15BreakdownofdryerusestageGWP.

4.4.2 CottonrolltowelsLikedryers,cottonrolltowelshavetheirproduction,transportation,andendoflifestageimpactsallocatedacrossmultipleuses.Forcottonrolltowels,thisisthe103times[12]theycanbereusedbeforedisposal.Producingtheequivalentofonepullonacottontowelroll,however,stillemits253gCO2eq.Thebreakdownofcottonrolltowelproduction(Figure16)showsthatweavingaccountsforalargefractionofGWPonaccountofitsenergyrequirements,whereassizing,theadditionofstarchtoyarntofacilitateweaving,islessthan1%ofthetotal.OverhalfofthetotalGWPassociatedwithusingacottonrolltoweltodryapairofhands,though,isduetotheusestagespecificallylaunderingthetowels(Figure5).Withinthisprocess,thenaturalgasrequiredtoheatthewaterandthermallydisinfectthetowelscontributesthemosttousephaseimpact(Figure17);transportationtoandfromlaundryfacilitiesisnotincludedinthefigure.

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38

Figure16GWPbreakdownofproducingtheequivalentofonepullonacottontowelroll.

Figure17GWPbreakdownofwashingcottonrolltowel(usestageimpact).

Cottonfibers

Spinning

Sizing

Weaving

Desizing/scouring/bleaching

ProductionGWP:253gCO2 eq/pull

Naturalgas

Electricity

Soap

Sewage

WashingGWP:6.78gCO2 eq/pull/use

39

4.4.3 PapertowelsPapertowelscontributethemosttosystemimpactintheirrespectivehanddryingsystems:asFigure11shows,packaging,dispensers,wastebins,andbinlinersaccountforlessthan10%oftotalGWP.Mostofthisimpact,inturn,canbeattributedtopulpproductionandtowelmanufacturing(Figure5).TheresultsinFigures59indicatethatpapertowelswithrecycledcontenthavealowerimpactthanvirginpapertowelsforfourofthesixmetrics.Theextentofthedifferenceinimpactdependsonthemetric:inthecaseofGWP,humanhealth,andwaterconsumption,thedifferencebetweentheimpactsofthetwosystemsislessthan10%;thisisreflectedinthedryingsystemrankingsinTable9wherebothpapertowelsystemsareassignedthesamerank.Thisconclusion,naturally,issubjecttopulpingprocessdataandtheassumptionthattherecycledpulpingprocessisthesameasthevirginpulpingprocess.Theconclusioncouldpotentiallychangeifprocessesotherthansulfatepulpareusedandifinventorydataonarecycledpulpingprocesswereused.Thedifferencebetweenthetwosystemsismorepronouncedforecosystemquality,CED,andlandoccupation.VirginpapertowelshaveahigherCEDbecausethemetricaccountsfortheenergyembodiedinthewood.Likewise,thisneedforwoodcontributestothelandoccupationmetric,whichitselfispartoftheecosystemqualitycalculationintheIMPACT2002+LCIAmethodology(see[50]).Figures18and19respectivelybreakdowntheGWPandCEDassociatedwithpapertowelproductionintopulpmanufacturingandtheprocessesrequiredtoproducepapertowelsfrompulp.Pulpmanufacturingisinturnbrokendownintotheimpactduetowoodorwastepaperandthemanufacturingprocess.Asthechartsshow,theGWPbreakdownsofbothpapertoweltypesareverysimilar,partlybecausetheGWPLCIAmethodologydoesnotaccountforbiogeniccarbonembodiedinthewood.Therenewableenergycontentinthepaper(analogoustobiogeniccarbon),however,isaccountedforintheCEDLCIAmethodology:theenergyembodiedinthewoodusedinmanufacturingvirginpulpincreasesthepulpscontributiontoCEDaswellastheoverallimpact(seeFigure7).

40

Figure18GWPbreakdownofpapertowelproductionfrom(a)virginand(b)recycledcontent.

Figure19CEDbreakdownofpapertowelproductionfrom(a)virginand(b)recycledcontent.

5 LifecycleinterpretationThelifecycleinterpretationsectionfocusesonunderstandingthelifecycleimpactassessmentresultswithinthecontextoftheanalysislimitations,uncertainty,andassumptions.Thisisaccomplishedwith

Wood

Pulpmfg

Electricity

Naturalgas

Sewage

(a) VirgincontentProductionGWP:

5.96gCO2eq/towel

Wastepaper

Pulpmfg

Electricity

Naturalgas

Sewage

(b) RecycledcontentProductionGWP:

6.08gCO2eq/towel

Wood

Pulpmfg

Electricity

Naturalgas

Sewage

(a) VirgincontentProductionCED:197kJ/towel

Wastepaper

Pulpmfg

Electricity

Naturalgas

Sewage

(b) RecycledcontentProductionCED:103kJ/towel

41

sensitivityanduncertaintyanalyses.Theformerevaluatesvariabilityinbaselinescenarioassumptions,oneparameteratatime,whilethelatterexploressimultaneousvariationofparametersaswellasaddressesuncertaintyinthebillofactivitiesdata.ApedigreematrixandMonteCarlosimulationarerespectivelyusedtoquantifyandtopropagateuncertaintiesintheanalysis.5.1 SensitivityanalysisOnescenarioalonecannotaccountforthewiderangeofusagepatternsorotherparametersthatcanaffectenvironmentalimpact.Sensitivityanalysesarethereforeconductedtoaddressthevariabilityinthebaselinescenariosassumptions.Assumptionsaddressedinclude:

Lifetimeusage Manufacturingphaseelectricgridmix Usephaseelectricgridmix Useintensity Endoflifescenario Dryerelectronicsunitprocess Cottonrolltowelreuses Papertowelmass Pulpmanufacturingprocess Endoflifeallocationmethodologyforrecycledcontentinpapertowels Manufacturinglocation Uselocation

Intheseanalyses,thehanddryingsystemGWPsarecomparedunderdifferentscenariostoassesstherobustnessoftheobservationinSection4.2thathighspeeddryershavethelowestimpactofallthesystems.Theseanalysesarealsousedtoevaluatehowdifferentfactorsaffecteachsystemsenvironmentalburdenandwhichofthosefactorsmatterthemost.Theresultsindicatethatelectricgridmixanduseintensity(Sections5.1.25.1.4)exertthelargestinfluenceondryingsystemGWP.Later,aMonteCarlosimulation(Section5.2.1)isusedtoevaluatetheuncertaintysurroundingthebaselinescenarioassumptions.DryerimpactiscalculatedassumingmeasureddrytimeasassessedwiththeNSFProtocolP335.5.1.1 LifetimeusageThebaselinescenarioassumesalifetimeusageof350,000pairsofhandsdriedovera5yeartimeframe[26,27].Theactualnumberofuses,however,couldbehigherorlower,dependingonwashroom

42

traffic:forinstance,theExcelstudyassumes260,000pairsofhandsaredriedover10years[14].Figure20illustratestheeffectofbothlowerandhigherusageoverthe5yeartimeframe.Increasingusagereducesimpactbecausetheproductionandendoflifeburdensofthedryer(ordispenser,packaging,etc.)arespreadovermorepairsofhands.ForthealuminumDysonAirbladehanddryersystem,anincreaseinusageto450,000resultsinalessthan4%decreaseinimpact;thischangeisevenlowerfortheothersystemsaslittleas0.4%forthecottonrolltowelsystem.Thus,changinglifetimeusagealoneisnotsufficienttofavoreithercottonorpapertowelsoverthehighspeedhanddryers.

Figure20EffectofproductlifetimeusageondryingsystemGWP.

5.1.2 ManufacturingstageelectricgridmixThisnextsensitivityanalysisinvestigatestheconsequencesofalteringthemanufacturingstageelectricgridmixbyassessingdryingsystemGWPgiventwohypotheticalextremes:acarbonintensiveallcoalgridandagreenerallhydropowergrid.Ahypotheticalallnucleargridisalsoaddedforcomparison.Theanalysisaccountsfortheassumptionthatpapertowelsaremanufacturedinadifferentlocationfromdryersandcottonrolltowelsbyassumingthehypotheticalgridmixesusetechnologiesappropriateforeachdryingsystemsmanufacturinglocation.Thatis,thehypotheticalallcoalgridfordryerproductionassumesChinesetechnologyandtherebyassociatedemissionsfactorswhereastheallcoalgridforpapertowelmanufacturingassumesUStechnology.AsseenfromtheresultsinFigure21,alteringthemanufacturingstagegridmixminimallyaffectsdryerGWPbecausethisstageaccountsforaverysmallfractionofoverallenvironmentalimpact(seeFigure5).Theoppositeistrueofpapertowels,whichderivethemajorityoftheirimpactfrommaterialsandmanufacturing.Theuseofagreenergrid,however,cannotcompletelyeliminatepapertowelemissionsbecausesomeoftheemissionsarederivedfromthepulpingprocess,aswellasfromnaturalgasusedintissuemanufacturing(seeFigure18).Cottonrolltowelsfallsomewhereinbetweenthesetwoextremes

0

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Airblade,aluminum

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recycled

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alwa

rmingp

oten

tial[g

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becausewhiletheirproductionaccountsforalargerfractionofGWPcomparedtothedryers,over50%ofimpactisduetotheusestage.

Figure21EffectofalteringmanufacturingphasegridmixondryingsystemGWP.

5.1.3 UsephaseelectricgridmixInadditiontothemanufacturingstageelectricgridmixanalysis,ausestagegridmixanalysisisalsoconducted.Thelatterisaccomplishedinsimilarfashionwithhypotheticalallcoal,allhydropower,andallnucleargridsusedtoassesstheconsequencesofvaryinggridmixondryingsystemGWP.SinceusestageisassumedtotakeplaceintheUS,allhypotheticalgridsassumeUStechnologyandemissionsfactors.Onlytheimpactsofdryerandcottonrolltowelsystemsareaffected:theimpactsofthepapertowelsystemsdonotchangeasnousestageelectricityconsumptionisassociatedwiththosesystems.TheeffectofthedifferentgridsisshowninFigure22.SincetheUSreliesoncoalforaround45%ofitsgrid[51],thebaselineisalreadycarbonintensive.Thus,GWPincreasesonaverage53%forthehighspeeddryerswhentheyarerunonanallcoalgrid.Bycontrast,hydropowerandnucleargridsaremuchlesscarbonintensive,whichallowsdryerimpacttodecre