生物CCUS供应链中的碳核算—确定科学和政策的关键问题(英)-IEAVIP专享VIP免费

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Carbon accounting in Bio-CCUS

supply chains – identifying key issues

for science and policy

IEA Bioenergy Task 45

IEA Bioenergy Task 40

February 2022

xxxx: xx

IEA Bioenergy: Task XX

Month Year

xxxx: xx

ISBN 979-12-80907-05-9

Published by IEA Bioenergy

The IEA Bioenergy Technology Collaboration Programme (TCP) is organised under the auspices of the International Energy Agency (IEA) but is functionally and legally autonomous.

Views, findings and publications of the IEA Bioenergy TCP do not necessarily represent the views or policies of the IEA Secretariat or its individual member countries

The IEA Bioenergy Technology Collaboration Programme (TCP) is organised under the auspices of the International Energy Agency (IEA) but is functionally and legally autonomous.

Carbon accounting across Bio-CCUS supply chains

– identifying key issues for science and policy

By: Olle Olsson1, Nabil Abdalla2, Silvana Bürck2 & Horst Fehrenbach2

1 SEI (Stockholm Environment Institute)

2 ifeu (The Institute for Energy and Environmental Research)

Title of publication

Subtitle of publication

Authors and / or acknowledgements here

Edited by

IEA Bioenergy: Task 45 & Task 40

February 2022

Summary

Having just a few years ago been a topic primarily featured in future-oriented energy system

and climate models, Bio-CCUS (bioenergy with carbon capture and utilization or storage), is

increasingly becoming a matter of on-the-ground deployment. However, while the

technological aspects of capture, utilization and storage of biogenic CO2 are rather well-

understood and have in many cases already been used in commercial settings, there are still

substantial gaps on the policy and governance side. Particularly important aspects here are

carbon accounting, how to quantify the climate impact of Bio-CCUS systems and how to include

these elements in policy frameworks. In this report, we review key issues to focus on and discuss

different options for how these could be addressed from a scientific as well as from a policy

perspective. Importantly though, while upstream feedstock supply chains are a key factor in

total life cycle emissions accounting, there is already a large literature on carbon accounting

in biomass supply chains in general. As we do not expect feedstock supply chains for bio-CCUS

differ from biomass supply chains in general, this report only briefly touches upon upstream

aspects.

While it is common for CCU and CCS systems – be they based on biogenic or fossil CO2 - to be

jointly discussed as (bio-) CCUS, there are important differences between the two. This pertains

to post-capture CO2 accounting, as well as policy systems and business models. For Bio-CCS,

analysis of post-capture CO2 flows should be fairly straightforward, as the CO2 is to be

permanently stored and immobilized in geological formations. This is assuming avoidance of

e.g., leakages in transport and storage as well as the minimization of use of fossil energy for

CO2 transport. The major policy challenge around Bio-CCS concerns how to design policy

frameworks to incentivize carbon dioxide removal (CDR), also referred to as negative emissions.

A key question is if, or to what extent, policy frameworks for carbon dioxide removal should be

integrated into existing systems for emission reductions – such as the EU emissions trading

system – or whether there should be specific ring-fenced systems for CDR.

Analysis of the post-capture CO2 flows for Bio-CCU is more complicated than for Bio-CCS. CO2

can be utilized for a wide range of purposes, including as feedstock for many different products,

which means that there are great many cases to analyze to understand the net climate impact

in detail. This concerns aspects such as the process efficiency, the kinds of energy used and

what existing product the Bio-CCU product could be replacing. In addition, a very important

issue that has thus far not received sufficient attention is how to factor in the variation in CO2

storage permanence between different CCU products, i.e., for how long time CO2 used in a

product stays away from the atmosphere. This can vary from less than a year for a fuel or a

chemical, via decades for non-packaging plastics and up to possibly centuries in the case of

some building materials. Given the growing interest in (bio-)CCU projects, it is essential to find

approaches to a) quantify how the climate impact of CCU products depends on CO2 storage

permanence and b) how these aspects can be integrated into policy frameworks. To this end,

we suggest to draw inspiration from similar frameworks, such as the UNFCCC accounting

framework for Harvested Wood Products. However, there is a clear and urgent need for more

research into this. To ensure that Bio-CCUS systems can fulfil their potential to mitigate climate

change, it is key to strike a balance between properly understanding the full picture of their

climate impacts and finding reasonably straightforward means how to include these aspects in

policy frameworks.

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CarbonaccountinginBio-CCUSsupplychains–identifyingkeyissuesforscienceandpolicyIEABioenergyTask45IEABioenergyTask40February2022xxxx:xxIEABioenergy:TaskXXMonthYearxxxx:xxCopyright©2022IEABioenergy.AllrightsReservedISBN979-12-80907-05-9PublishedbyIEABioenergyTheIEABioenergyTechnologyCollaborationProgramme(TCP)isorganisedundertheauspicesoftheInternationalEnergyAgency(IEA)butisfunctionallyandlegallyautonomous.Views,findingsandpublicationsoftheIEABioenergyTCPdonotnecessarilyrepresenttheviewsorpoliciesoftheIEASecretariatoritsindividualmembercountriesCarbonaccountingacrossBio-CCUSsupplychains–identifyingkeyissuesforscienceandpolicyBy:OlleOlsson1,NabilAbdalla2,SilvanaBürck2&HorstFehrenbach21SEI(StockholmEnvironmentInstitute)2ifeu(TheInstituteforEnergyandEnvironmentalResearch)TitleofpublicationSubtitleofpublicationAuthorsand/oracknowledgementshereEditedbyIEABioenergy:Task45&Task40February20221SummaryHavingjustafewyearsagobeenatopicprimarilyfeaturedinfuture-orientedenergysystemandclimatemodels,Bio-CCUS(bioenergywithcarboncaptureandutilizationorstorage),isincreasinglybecomingamatterofon-the-grounddeployment.However,whilethetechnologicalaspectsofcapture,utilizationandstorageofbiogenicCO2areratherwell-understoodandhaveinmanycasesalreadybeenusedincommercialsettings,therearestillsubstantialgapsonthepolicyandgovernanceside.Particularlyimportantaspectsherearecarbonaccounting,howtoquantifytheclimateimpactofBio-CCUSsystemsandhowtoincludetheseelementsinpolicyframeworks.Inthisreport,wereviewkeyissuestofocusonanddiscussdifferentoptionsforhowthesecouldbeaddressedfromascientificaswellasfromapolicyperspective.Importantlythough,whileupstreamfeedstocksupplychainsareakeyfactorintotallifecycleemissionsaccounting,thereisalreadyalargeliteratureoncarbonaccountinginbiomasssupplychainsingeneral.Aswedonotexpectfeedstocksupplychainsforbio-CCUSdifferfrombiomasssupplychainsingeneral,thisreportonlybrieflytouchesuponupstreamaspects.WhileitiscommonforCCUandCCSsystems–betheybasedonbiogenicorfossilCO2-tobejointlydiscussedas(bio-)CCUS,thereareimportantdifferencesbetweenthetwo.Thispertainstopost-captureCO2accounting,aswellaspolicysystemsandbusinessmodels.ForBio-CCS,analysisofpost-captureCO2flowsshouldbefairlystraightforward,astheCO2istobepermanentlystoredandimmobilizedingeologicalformations.Thisisassumingavoidanceofe.g.,leakagesintransportandstorageaswellastheminimizationofuseoffossilenergyforCO2transport.ThemajorpolicychallengearoundBio-CCSconcernshowtodesignpolicyframeworkstoincentivizecarbondioxideremoval(CDR),alsoreferredtoasnegativeemissions.Akeyquestionisif,ortowhatextent,policyframeworksforcarbondioxideremovalshouldbeintegratedintoexistingsystemsforemissionreductions–suchastheEUemissionstradingsystem–orwhetherthereshouldbespecificring-fencedsystemsforCDR.Analysisofthepost-captureCO2flowsforBio-CCUismorecomplicatedthanforBio-CCS.CO2canbeutilizedforawiderangeofpurposes,includingasfeedstockformanydifferentproducts,whichmeansthattherearegreatmanycasestoanalyzetounderstandthenetclimateimpactindetail.Thisconcernsaspectssuchastheprocessefficiency,thekindsofenergyusedandwhatexistingproducttheBio-CCUproductcouldbereplacing.Inaddition,averyimportantissuethathasthusfarnotreceivedsufficientattentionishowtofactorinthevariationinCO2storagepermanencebetweendifferentCCUproducts,i.e.,forhowlongtimeCO2usedinaproductstaysawayfromtheatmosphere.Thiscanvaryfromlessthanayearforafuelorachemical,viadecadesfornon-packagingplasticsanduptopossiblycenturiesinthecaseofsomebuildingmaterials.Giventhegrowinginterestin(bio-)CCUprojects,itisessentialtofindapproachestoa)quantifyhowtheclimateimpactofCCUproductsdependsonCO2storagepermanenceandb)howtheseaspectscanbeintegratedintopolicyframeworks.Tothisend,wesuggesttodrawinspirationfromsimilarframeworks,suchastheUNFCCCaccountingframeworkforHarvestedWoodProducts.However,thereisaclearandurgentneedformoreresearchintothis.ToensurethatBio-CCUSsystemscanfulfiltheirpotentialtomitigateclimatechange,itiskeytostrikeabalancebetweenproperlyunderstandingthefullpictureoftheirclimateimpactsandfindingreasonablystraightforwardmeanshowtoincludetheseaspectsinpolicyframeworks.2AcknowledgmentsThisreportisacomponentoftheIEABioenergyinter-taskproject“DeploymentofBio-CCS/UValueChains”.WewouldliketothankNiclasScottBentsen,AnnetteCowie,UweFritsche,KatiKoponenandStefanMajerforveryvaluablecommentsanddiscussionsoverthedevelopmentofthisreport.Allremainingerrorsoromissionsaretheresponsibilityoftheauthors.3Index1Introduction........................................................................................52CO2flowsinBio-CCUSsystems–anoverview.................................................72.1CapturingBiogenicCO2...........................................................................72.2EmissionsfromTransport&storageofCO2....................................................82.3Bio-CCSasanegativeemissionstechnology...................................................92.4ClimateimpactofBio-CCU.....................................................................102.4.1TypesofEmissions........................................................................102.4.2Trendsovertime..........................................................................132.4.3CO2storagepermanence.................................................................142.4.4Keydeterminantsofoverallclimateimpact..........................................163IntegratingBio-CCUScarbonaccountinginpolicyframeworks...........................173.1Bio-CCSCO2governance........................................................................173.2PolicyintegrationofBio-CCU..................................................................183.2.1PracticalandMethodologicalChallengesofBio-CCUAccounting..................183.2.2Existingexamplesofcarbonaccountingacrossbordersandsectors..............193.2.3PossibilitiesofPolicyIntegration.......................................................214Discussion.........................................................................................234.1Bio-CCUandnegativeemissions–aquestionoftime......................................234.2UseofparallelstonavigatetheBio-CCUgovernanceconundrum.......................254.3Nextstepsandfurtherresearch...............................................................254AbbreviationsAFOLUAgriculture,ForestryandOtherLandUseBio-CCUS/BECCYSCaptureandstorageorutilizationofbiogenicCO2CCS/CCUCarboncaptureandstorage/carboncaptureandutilizationCDMCleanDevelopmentMechanismCDRCarbonDioxideRemovalCORSIACarbonOffsettingandReductionSchemeforInternationalAviationDACDirectAirCaptureETSEmissionsTradingSystemEOR/EGREnhancedOil/GasRecoveryGWPGlobalWarmingPotentialHWPHarvestedWoodProductsLCALifeCycleAssessmentNDCNationallyDeterminedContributionNETNegativeEmissionsTechnologyNIRNationalInventoryReportP2X/PtXPower-to-XPVPhotovoltaicsR&DDDResearchanddevelopment,demonstration&deploymentREDRenewableEnergyDirective51IntroductionInordertorealizetheambitionofthe2015Parisagreementtolimitglobalwarmingto1.5°C,globalCO2emissionsneedtoreachnet-zerobyaround2050(IPCC2018).ThisisclearlyahighlyambitiousandverychallengingtargetdespiterapiddevelopmentsindeploymentofkeytechnologieslikesolarPV,windpowerandelectrificationofroadtransport.Carbondioxideremoval(CDR)-sometimesalsoreferredtoasNegativeEmissionsTechnologiesorNETs-isanadditionaltoolthatcanbedrawnupontoenablethenet-zerotargeteveninthepresenceofresidualgreenhousegas(GHG)emissions.AmongthedifferentsolutionsthatcanenableCDR,bioenergywithcarboncaptureandstorage(Bio-CCSorBECCUS)hasbeenoneofthosemostdiscussedintheresearchliterature(e.g.,AndersonandPeters2016;vanVuurenetal.2017;Hecketal.2018).Muchofthediscussionintheliteraturehastakenaverylong-termperspectiveontheissueandhasbeendedicatedtoaddressingthepotentialbroadersustainabilityimpactsfrombroaddeploymentofBio-CCS(IPCC2018;Hanssonetal.2021).However,inthelightoftheincreasinginterestinCDRfrompolicymakers,itishightimetoalsoinvestigateaspectspertainingtothepracticalitiesofactualnear-termdeploymentofBio-CCSsystemsandvaluechains.InparallelwiththegrowingpoliticalandresearchinterestinBio-CCS,therehasbeenasimilarriseofinterestincaptureandutilizationofbiogenicCO2fordifferentpurposes,includingasfeedstockforproductionofmaterials,chemicalsorfuels.ThisiscommonlyreferredtoasBio-CCUorBECCUandthetwoareoftenjointlyreferredtoasBio-CCUSorBECCUS(Textbox1).Bio-CCUSsystemscanbeimplementedinabroadrangeofcontexts,includingbutnotlimitedtosectorsthatalreadyusesubstantialamountsofbiomassasfuelorfeedstock,suchasheat&powergeneration,pulp&papermillsorbiogasproduction(Olssonetal.2020)1.However,eventhoughthereissubstantialphysicalandtechnologicalpotential,therearestillplentyofquestionsremainingwhenitcomestooperationalizingfullBio-CCUSvaluechains.WhiletherearerelativelymatureCO2capturetechnologies,Bio-CCStransportation&storageinfrastructuresarestillinearlystagesofdevelopment,andthesamegoesforBio-CCUproductmarkets.ItisstillnotclearhowbusinessmodelsshouldbedesignedtomakeforeconomicallyviableBio-CCUSvaluechains.Textbox1.OnabbreviationsrelatedtocaptureofbiogenicCO2NoteonabbreviationsCaptureandstorageorutilizationofbiogenicCO2issometimesabbreviatedas“BECCS/U”,sometimesas“BECCUS”andsometimesas“Bio-CCUS”.Thereisnotyetrealconsensusastowhichispreferred.However,thelatterhastheadvantagethatitdoesnotexcludecaptureofbiogenicCO2thatoriginatesfromprocesseswhereenergygenerationisnottheprimarygoal.Examplesofthisincludefermentationintheproductionofbioethanolorupgradingofbiogastobiomethane.1Whilethepotentialvolumestobecapturedfromexistingbiomass-usingfacilitiesaresmallrelativetothoseenvisionedinIAMs,theyshouldnotbedismissed.Forexample,addingCCStobiogenicCO2pointsourcesintheglobalpulp&papersectorcouldenablemorethan130milliontonnesofcarbondioxideremoval(Kuparinenetal.2019).6Furtherdevelopmentandscalingofbio-CCUSwillrequirepolicysupport,whichwilllogicallybelinkedtopotentialcontributiontoclimatechangemitigation.However,developingandimplementingsuchpoliciesmayturnouttobequitechallenging,forseveralreasons.Firstly,quantificationofbiomass-basedlifecycleGHGemissionsisalreadyquitecomplicated,ashasbecomeclearovertherecentdecadeasthemeritsofdifferentbiomass-basedenergycarriershavebeendiscussedacrossabroadrangeofpolicycontexts(Searchingeretal.2008;Berndesetal.2013;LamersandJunginger2013).Tothisalreadyintricateanalysisshallnowalsobeincorporatedananalysisoftheclimateimpactsrelatedtocapture,utilizationand/orstorageofCO2.Secondly,evenwithcomprehensiveandtransparentmethodsbywhichBio-CCUSlifecycleGHGbalancescanbedeveloped,akeyremainingquestionishowtoimplementthesemethodsinpolicyframeworks.Therewillbeaneedtofindabalancebetweena)acknowledgingtheheterogeneityacrossdifferentvaluechains,andb)avoidingoverlycomplicatedlegalspecificationsthatarecostlytoadminister.Inaddition,itwillbecrucialtofindwaystoallocateburdensandbenefitsappropriatelyincaseswherecapturedcarbonistransferredacrossBio-CCUSsupplychains,notonlybetweensectors(e.g.,agriculture/forestry>industry->airtransportasmightbethecasewithaBio-CCUaviationfuel)butbetweenjurisdictionsaswell.Inthisreport,wereviewthechallengesaroundaccountingfortheclimateeffectsofBio-CCSandBio-CCUsupplychainsanddiscusskeyissuesthatneedtobeaddressedtoprepareasoundscientificandlegallyfunctionalfoundationforpoliticalgovernanceofBio-CCUS.ItisimportanttoemphasizethatBio-CCUScanbeimplementedinmanydifferentcontextsandsectors.Thismeansthattherecanbesubstantialvariationsintermsoftheactualdetailsofcarbonaccountingandclimateimpact,andwedonotstrivetoprovidedetailanalysisforeachcontext.Rather,ourambitionistogiveamoreprincipaloverviewofsomeparticularlyimportantgeneralissues.Thereportisstructuredasfollows.Insection2,weprovideanoverviewofkeyissuesthatneedtobeconsideredwhenquantifyingGHGemissionsacrossBio-CCUSsupplychains.Insection3,wediscusshowtoapplythesescientificfindingswithinagovernancecontext.Section4,finally,concludeswithadiscussion,somerecommendationsforpolicymakersandresearchers,andsuggestionsforfurtherresearch.2CO2flowsinBio-CCUSsystems–anoverviewThisreporttakesasitsstartingpointBio-CCUS/BECCUSasajointconcept,acknowledgingthattheBio-CCSandBio-CCUvaluechainshavemanyjointcomponentsandthatinnovationprocesseswilllikelycross-fertilizebetweenthem(Olssonetal.2020).Atthesametime,Bio-CCSandBio-CCUarequitedistinctwhenitcomestotheirCO2flows(seeFigure1),theirclimatechangemitigationpotentialandhowthisshouldbegoverned.Forthisreason,thissectionreviewstheBio-CCSandBio-CCUperspectivesinturn.Figure1.ConceptualillustrationofthecarbonflowsrelatedtoBio-CCSandBio-CCU.BC=Biomasscombustion&FC=Fossilfuelcombustion.FigurebyLappeenrantaUniversityofTechnology(Olssonetal.2020)Anotherkeyaspectthatthereadershouldbeawareofisthatwedonotdwellatanylengthonupstreamfeedstocksupplychainemissions.WhilethesearehighlyimportantfortotallifecycleemissionsofBio-CCUSsystems(e.g.,Terlouwetal.2021),weassumethatBio-CCUSfeedstocksupplychainswillnotdifferfrombioenergyfeedstocksupplychainsingeneral.Asthereisalreadyalargebodyofliteratureonthegreenhousegasbalancesandclimatechangeimpactsofbioenergysupplychainsingeneral(e.g,Creutzigetal.2015;Cowieetal.2021;IEABioenergy2021),wewillfocusonthelaterstagesofBio-CCUSsupplychain.Inotherwords,onecouldframeourfocushereinasa“gate-to-grave”(Bio-CCS)orpossibly“gate-to-cradle”(Bio-CCU)analysis,aswecenterourdiscussiononflowsofbiogenicCO2eitherindifferentformsofproducts(Bio-CCU)oronthewaytolong-termstorage(Bio-CCS).2.1CAPTURINGBIOGENICCO2AgeneralaspecttokeepinmindwhendiscussingtechnologicalaspectsofBio-CCSandBio-CCUistoseethemassub-categoriesofCCSandCCUingeneral.TheCO2capturestageinfluencestheoverallclimateimpactoftheBio-CCUSsupplychainpredominantlythroughthecaptureratesandtheenergyneededfortheprocess.Thecaptureratescanvarysubstantiallybetweenprocessesandcontext,dependingone.g.,thenumberofpointsourcesataspecificfacility.IfmostoftheCO2emissionsfromafacilityareconcentratedatonesource,thismakesforlowercostsofcapturewhereasifemissionsaredistributedacrossseveraldifferentpointsources,highcaptureratescanbecomeprohibitivelyexpensive(Olssonetal.2020).Asfortheenergyneededforcapture,thehighertheenergyefficiency–i.e.,thelowertheenergypenaltyoftheprocess-andthelowertheGHGfootprintoftheenergyusedforcapture,thebettertheoverallCO2balanceofthecapturestage.AsisillustratedinFigure2,thereisgreatheterogeneitybetweendifferentsectorsandprocesseswhenitcomestotheenergydemandsofCO2capture.AnimportantaspecttoemphasizehereisthatwhethertheCO2tobecapturedisbiogenicorfossilisinitselftypicallynotaprimaryfactorindeterminingtheenergydemand.Figure2.OverviewofenergyneedsforCO2captureindifferentprocesses.DatafromvonderAssenetal(2016).SomekeyaspectstobementionedwhenitcomestothingsthatdeterminetheclimateimpactofthecapturestageincludeCO2concentrationinthegasstreaminquestion,theavailabilityofprocessheaton-site(e.g,Olssonetal.2020)andiftheheatusedforthecaptureprocesscanberecoveredafterwards(Bisinellaetal.2021).Forexample,bioethanolproductionfacilitiestypicallyhaveveryhighlyconcentratedCO2streamsresultingfromfermentationprocesses,andthesecanbecapturedatlowenergyexpense.ThesamegoesforbiogasupgradingprocessesthatalreadyhaveCO2separationasoneofitsprocessstages.Pulp&papermillshaveonlymodestlyconcentratedCO2streamsbuttend,ontheotherhand,tobeverylargefacilitiesandwithgoodon-sitesupplyofprocessheat(vonderAssenetal.2016).Foralltheseprocesses,however,itisimportanttoemphasizethatthereisalotofcurrentR&DactivityarounddevelopingmoreefficientcaptureprocesseswithimportantanalysestobedonearoundhowbesttointegrateCO2captureasacomponentofoverallplantoperationandenergysystems(Creutzigetal.2019).2.2EMISSIONSFROMTRANSPORT&STORAGEOFCO2IftheCO2capturedistobesequesteredingeologicalformationsforlong-termstorage,itwillinmanycasesbetransportedalongdistance.CO2canbetransportedbylandintrucksorbyrailway,butforlongerdistancesandlargervolumes,pipelinesandshiptransportarethetwomostviablealternatives(Kjärstadetal.2016).TheemissionsfromtheenergyneededtotransportCO2variesdependingonthemodeoftransportusedaswellasthetransportdistance,buttendtobefairlysmall,amountingto10-25kgCO2pertonneCO2transportedfordistancesupto1000kmusingpipelineorshiptransport(Bisinellaetal.2021).Emissionsfromshiptransportaremainlyafunctionofthetypeofenergyandtheship’sfuelefficiency.Consequently,lowertransportdistances,moreefficientenginesandincreaseduseoflow-carbonfuelscanhelpreduceemissionsfromthispartofthesupplychain.NotealsothatthereareprojectsinvestigatingthepossibilityofinstallingCCSequipmentonships,i.e.,capturingCO2fromtheship’senginesforonboardstorage(Roussanaly2021).Therearealsoembeddedemissionsresultingfromconstructionoftransport&storageinfrastructure.Therehas–tothebestofourknowledge–notbeenanyanalysesdoneonhowsuchemissionsaffecttheoverallbalanceofBio-CCSprojects,butCuéllar-Franca&Azapagic(2015)analyzeafossil-basedCCSsupplychainandfindthatemissionsarisingfrominfrastructureconstructionplayonlyamarginalroleintheoverallbalance.ThisisaconclusionthatreasonablyshouldextendtoBio-CCSprojectsaswell(Bennettetal.2019).AsforthepermanentstoragestageoftheCCSsupplychain,anaccidentorsomesortoffailurecouldresultinemissions.Thismeansthatcarefulsiteselectionandconstructionofthestoragefacilityisessential,asisreliablemonitoringtechniques(Gholamietal.2021).PublicconcernaroundthesafetyofCO2storageisDirectaircaptureNaturalgascombinedcycleRefineriesCoalpowerIntegratedpulp&papermillMarketpulpIronandsteelCementIntegratedgasificationcombinedcycleGasprocessingH2production0123456020406080100GJ/tonneCO2CO2concentration(%)alsoacentralissueandanimportantfactorwhye.g.,keyCO2storagesitesinEuropearelikelytobelocatedoffshore.2.3BIO-CCSASANEGATIVEEMISSIONSTECHNOLOGYInsection2.1,wenotedthatfromatechnologicalperspective,Bio-CCSshouldbeseenasasub-categoryofCCStechnologiesmoregenerally.Similarly,fromagovernanceperspective,Bio-CCSshouldbeseenasasub-categoryoftheportfoliooftechnologiesusedforcarbondioxideremoval(CDR),alsoreferredtoasnegativeemissionstechnologies(NETs).CDR/NETscomeinmanyformsandcanbecategorizedasa)nature-basedsolutionslikeafforestation,reforestation,oceanfertilizationandenhancedweathering,b)purelytechnology-basedsolutions,wheredirectaircapture(DAC)isreallytheonlyavailableoption,andc)technologiesthatstraddleboththe“nature”and“technology”spheresinthesensethattheirpotentialtoremoveCO2fromtheatmosphereisheavilyreliantonmanagementandprocesschoicesinthebiosphereaswellasinthe“technosphere”.ThislattercategoryiswhereBio-CCSresides,togetherwithe.g.,biocharsystems.CO2flowsinnatureaswellasinhuman-engineeredsystemscanbequitecomplicatedanditisimportanttoproperlyunderstandthekindsofdemandsthatshouldbeplaceduponaspecificsolutiontoqualifyasanegativeemissionorcarbondioxideremovaltechnology.Tanzer&Ramírez(2019,p.1216)arguethatfourkeycriterianeedtobefulfilledinordertoachievecarbondioxideremoval/negativeemissions:1.Greenhousegasesarephysicallyremovedfromtheatmosphere.2.Theremovedgasesarestoredoutoftheatmosphereinamannerintendedtobepermanent2.3.Upstreamanddownstreamgreenhousegasemissionsassociatedwiththeremovalandstorageprocess,suchasbiomassorigin,energyuse,gasfate,andco-productfate,arecomprehensivelyestimatedandincludedintheemissionbalance.4.Thetotalquantityofatmosphericgreenhousegasesremovedandpermanentlystoredisgreaterthanthetotalquantityofgreenhousegasesemittedtotheatmospherethroughoutthefullsupplychain.ForBio-CCSsystems,criterion1isfulfilledinthesensethatphotosynthesizingplantsremoveCO2fromtheatmospheretoproduceplantbiomass.Insystemswithouthumaninterference,thecarbonwouldeventuallyreturntotheatmosphereintheformofCO2oncetheplantdiesanddecomposes.Criterion2isfulfilledforBio-CCSasCO2capturedaspartofBio-CCSsystemsaredestinedforlong-term/permanentgeologicalstorage.Criteria3and4arerelatedandshouldbefulfilledforBio-CCS,consideringtheaspectsthatwerediscussedundersection2.1and2.2,i.e.,highcapturerates,lowenergy-relatedCO2footprintfromcaptureandtransportandsustainablefeedstock.2Thequestionofhowtodefine„permanent“inthiscontextiscentral.Wediscussthisinmoredetailin2.4and3.2.2.4CLIMATEIMPACTOFBIO-CCUIncontrasttoBio-CCS,Bio-CCUvaluechainsfollowadifferentlogicwiththemainpurposebeingtousecarbondioxideasinputtogeneratevalueviatheprovisionofproductse.g.,fuels,chemicalsorplastics.However,inordertodothis,thereisneedofadditionalvalorization,followingonthecapturestage.Thisadditionalvalorizationmightcomewithadditionalprocessesinvolved(suchastheproductionofhydrogenforfuels),whichsubsequentlyleadtoadditionalclimateimpacts.Therefore,anoverviewoftheclimateimpactofBio-CCUwillbegivenherewithparticularfocusonsourcesofemissions,supplychainprocessesandstoragepermanence.2.4.1TypesofEmissionsThreekeyaspectsarecrucialwhenitcomestoemissionsrelatedtoBio-CCU.Firstly,andaswasdiscussedinsection2.1,CO2qualityintermsofconcentration,asthisiskeyforenergydemandforcapture.Secondly,supplychainemissionsincludingthosethatariseduringtheproductionofadditionalinputsneededforCCUvalorization,suchashydrogen.Thirdly,emissions3arisewhentheCO2-derivedproductreachesitsendoflifeandiseitherenergeticallyrecoveredordecomposed,i.e.,providedthatnoadditionalcascadingtakesplace4.2.4.1.1OriginofCO2TheenergydemandandpossibleassociatedemissionimpactsfromCO2capturingwerecoveredinsection2.1andareassumedtobethesameforBio-CCUvaluechainsasforBio-CCS.Havingsaidthis,thegradeofpurityofthecapturedCO2,whichdependsontheprocessandtechnologyinvolved,canbecrucialforthesubsequentutilization.WorthnotingisthatdifferentgradesofpurityarerequiredfordifferentCCUapplications.Mineralization,forexample,canmakeuseoflowpurityCO2(Zimmermanetal.2018),whereasthefoodandbeverageindustryrequireshighpurityCO2(Naims2016).2.4.1.2EmissionswithindifferentutilizationpathsThereisaverywiderangeofCCUstudiesavailableandthegeneralutilizationroutesareindependentofthecarbonorigin–beitbiogenicCO2orfossilCO2.Intermsofcategorizationofthedifferentroutestomakeiteasiertonavigatetheavailableoptions,afewdifferentapproacheshavebeensuggested.Forexample,BioenergyEurope(2019)distinguishbetweenfourmainutilizationpaths:mineralization,chemicalconversion,biologicalconversionanddirectutilization(Figure3).ThisoverviewislargelyalignedwithAl-Mamoorietal.(2017),whocategorizetheroutesintoa)enhancedoil/gasrecovery(EOR/EGR),b)fuelsproduction,c)chemicalsproductionandd)non-geologicstorageofCO2(mineralization).However,Al-Mamoorietal.(2017)alsoadddesalinationandpotablewaterproductionasanadditionalCCUpathbyusingCO2totransformbrinetowater.3ParticularattentionshouldbegiventoCH4emissionsrelatedtotheend-of-lifephase,asCH4contributestoclimatechangeinotherdimensionsthanCO2.4Forexample,throughrecyclingofplasticsproducedviaBio-CCU.Figure3.CO2utilizationpathways.FigureadaptedfromBioenergyEurope(2018)ThisbroadvarietyofCCUoptionsleadstodifferentrequirementsintermsoffeedstock-especiallyenergyorhydrogen-whichinturnareassociatedwithemissions.WhereasdirectutilizationofCO2(inthecaseofe.g.,enhancedoilrecoveryorcarbonationofbeverages)doesnotrequireadditionalinputs,theproductionofcarbonatesviamineralizationrequirescalcium/magnesium-richfeedstock.Similarly,chemicalconversiontofuelorchemicalsrequiresenergyandhydrogen.Consequently,eachCO2utilizationpathhasadifferentenvironmentalimpact,whichneedstobeanalyzedinalifecycleassessment.Thereby,nationalorregionalconditionsinbackgroundsystemsandlogisticsneedtobeconsidered,aswellasthetimedimension(seesection2.4.3).ToassesstheclimateimpactsofsuchBio-CCU-products,theiradditionalrequirementsintermsoffeedstock,energyandhydrogenneedtobeconsideredthoroughly.Provisionofthesecomewithemissions,which,dependingonthebackgroundsystemathand,caneitherresultinbenefitsordrawbacks,comparedtoconventionalnon-Bio-CCUproductsystems.Hence,suchmulti-inputs(e.g.,severaladditionalinputs)shouldbelimitedasmuchaspossible,especiallyfossil-basedinputs,and/ormadeavailableinarenewablewayinordertoreduceassociatedemissions.Consideringtherenewableenergysystem,particularattentionshouldbegiventoalternativeusesoftheenergy(conflictofuse)andimpactsofnon-renewablecomponentssuchascriticalminerals.2.4.1.3EmissionswithintheproductionchainTakingtheentireproductionchainintoaccount,emissionsarisefromCO2capture,CO2transportationandalsofromtheprovisionofadditionalinputs,suchashydrogen.Inthecontextofelectrofuels,theoriginofCO2andenergycanbeconsideredthemainsustainabilityissues(Philibert2018).Consequently,alifecycleapproachisrequired,aswellasacomparisonwithanalternative(Bennettetal.2014).Therefore,itiscrucialtodetermineallemissionsoccurringwithintheproductionchain,butalsoCarbondioxide(CO2)MineralisationChemicalconversionBiologicalconversionDirectutilizationCommoditiesFuels&chemicalsPolymersMethaneMethanolFormicacidSynthesisgasMTBEDMEOlefinsFormaldehydeGasolineEthanolMethanol…DieselGasolineOlefinsConstructionmaterials(concrete,aggregates)Precipitatedcalciumcarbonates(PCC)GreenhousesAlgaecultivationBiologicalmethanationFood&beveragesIndustrialgasRefrigerantsWorkingfluidSolventspHcontrolEnhancedoil&gasrecoveryEnhancedcoalbedmethanerecoveryPolycarbonatesPolyolsUrea+H2+H2+N2(CH4)(CH3OH)(HCOOH)(CO+H2)takeintoaccountthecontributingassociatedproductsystems,suchasenergyprovision.Figure4fromBennetetal.(2014)providesaframeworkforassessingemissionsforanLCAapproachthatwillbedescribedbriefly.UpstreamemissionscomprisetheemissionsassociatedwiththecaptureoftheCO2thatwillbefurtherutilized.UtilizationemissionsoriginatefromtheprocessofutilizingCO2,i.e.,thevalorizationoftheCO2.Emissionsoccurringwithintheprovisionofadditionalmaterialandenergyinputareincludedinthispart.Furtheremissionsassociatedwiththemanufacturingofproducts,transportationanddistributionarepartofthedownstreamemissions.Dependingonthespecificcase,upstreamemissionscanvaryfromnegligibletosubstantial.Excludingfeedstocksupplychainemissions,upstreamemissionsaremostlyassociatedwiththecaptureoftheCO2,collectionandtransportation.Asmentionedinchapter2.2,emissionsrelatedtotransportationmightvaryandcanhavehighimpactsontheoverallclimateassessment.Similarly,highcontributionstotheoverallclimateimpactcanberelatedtotheprovisionofCO2fromlowconcentrationCO2streams,asinthiscasehighenergyinputsarerequired.Mainemissionsourcestypicallyoccurwithintheutilizationphase.Here,additionalexpensesintermsof,e.g.,processenergy-electricityaswellasheat-arerequiredtoprocesstheCO2.Assuch,especiallyintermsofelectricity-basedpathssuchasPtXfuelsandunlessverylow-emissionelectricityisused,theutilizationphasecontributesmosttotheoverallclimateimpact(Liebichetal.2020).Besideselectricity,hydrogenandheatareoftenrequiredinlargeamounts,especiallyinthecaseoffuelproduction.Botharecurrentlybasedmainlyonfossilsources,whichmeansthatdecarbonizationoftheseinputsiscrucialtoenableaCCUproductwithlowlifecycleemissions.Similarlytoupstreamemissions,downstreamemissionsplayaratherminorrole,astheyareassociatedwithtransportationanddistribution.However,end-of-lifeemissionscanplayasignificantroleinthecontextofcarbonaccountingifanenergeticutilizationorrecoverytakesplacewithoutsubsequentCCSorcascadinguse(subsequentCCU).WhereastheseemissionsneedtobeaccountedforinthecaseoffossilCO2,theyusuallycanbeomittedinthecaseofCO2originatingfrombiogenicsources,astheseshouldhavealreadybeenaccountedforatthepointofbiomassharvest.Figure4:EmissionswithinCCU(Bennettetal.2014)2.4.1.4HydrogenprovisionFrequently,hydrogenisrequiredasanadditionalinputinordertomanufactureCCUproducts.Currently,hydrogenoriginatesmainlyfromnaturalgassteamreforming,buthydrogencanalsobeproducedbywaterelectrolysis,biomassorbioenergycarrierssuchasbiomethane(IRENA2020;Autenriethetal.2021).Electrolysisisaveryenergy-intenseprocedure,althoughthereareongoingR&Deffortsaimedatreducingtheenergydemand.Inhydrogen-basedpathways,electricityforhydrogenproductionplaysthemainroleregardingtheglobalwarmingpotentialofthederivedCCUproduct(Liebichetal.2020).InordertominimizeclimateimpactsofBio-CCU,energyforelectrolysisshouldthusonlyoriginatefromsourceswithverylowGHGemissions.Duetotheintermittencyofwind&solarandthefactthatlimitedrenewableenergyneedstobeavailableforothersectorsaswell,hydrogenproductioncouldtakeplacewhenrenewableenergygenerationexceedsdemandorwhenremainingthermalproductionisunderutilized(Bennettetal.2014).This,however,woulddrasticallyincreasethehydrogengenerationcosts,aggravatingthefactthat,besidesenergyavailability,thehighcostofhydrogensupplyisamaineconomicchallenge(Kärkietal.2020)5.TheroleofhydrogenisthuscrucialintheentireclimateimpactofCCUproducts.Hence,ideally,onlyso-calledgreenhydrogen,generatedbyrenewableenergies(HorngandKalis2020),shouldbeconsideredinthemanufactureofanyBio-CCUSproduct.However,aquestionarisesifthereisenoughhydrogenleftforBio-CCU,consideringothercompetingdemandoflimitedrenewableelectricityandH2.2.4.1.5EnergyprovisionBesidestheprovisionofelectricityforhydrogenproduction,thegeneralprovisionofenergyintermsofelectricityandheatplaysasignificantrole.Liebichetal.(2020)investigatedtheenvironmentalimpactoftheproductionofPtXfuels,suchasFischer-Tropschfuels,methanol,syntheticnaturalgas,biomethaneandhydrogen.TheydemonstratethattheprovisionofelectricitycontributesmostlytotheoverallGWPandthattheuseofrenewableenergieshaspositiveclimateimpacts,comparedtotheirconventionalreference.Therefore,analogoustohydrogen,ideally,onlyrenewableenergiesshouldbeutilizedinBio-CCUSproductionchains.2.4.2TrendsovertimeForaholisticassessmentoftheclimateimpactsofCCUitiscrucialtoconsidertheimpactsbothnowandinthefuture,takingintoaccounttrendsintechnologicaldevelopments,includingperspectivesonfutureenergysystems.Inthecontextoftechnologicaldevelopment,Dairaniehetal.(2016)conductedamarketanalysisandinvestigatedkeypotentialsandbarriersofalargevarietyofCCUproductsoverthecomingdecades6.TheresultsdemonstratethatprogresshasbeenmadeinthedomainofCCUproductsandtheirscalabilityandthatcurrentmarketsituationappearstobefavorableforfourprimarymarkets:a)buildingmaterials,b)chemicals,c)fuelsandd)polymers.FiveCCUproductsareforecasttocompriseamarketwithatotalvalueofoverUS$800billionby2030,therebyutilizing7billionmetrictonsofCO2perannum.Theseproductscompriseaggregates,fuels,concrete,methanolandpolymers.TomaximizethemarketsizeaswellastheCO2emissionreductionpotential,implementationofstrategicaction,suchaspoliticalaction,iscentral.AdditionalscenariodemonstrationwithaneconomicperspectivecanbefoundinNaims(2016).Forexample,inthelong-termscenario,itisassumedthatsyntheticfuelproductionincreases.TherequiredCO2isexpectedtobeavailablefromalargevarietyofprocesses.However,takingtheefficiencyofsyntheticfuelsintoaccount,SRU(2017)arguesthatsyntheticfuels-includingCCUfuels-shouldprimarilybeappliedinaviation,shippingandotherapplicationswhereelectrificationorothermeansofdecarbonizationwillbe5Itshouldhoweverbenotedthatmanyanalystsexpectelectrolysercoststodecreasesubstantiallyasmanufacturingscalesup(MaterialEconomics2020),whichisanimportantsteptowardsreducingcostsofgreenH2.Havingsaidthis,electricitycostsarethekeyparameterthatneedstobeaddressedtolowerthecosts.6Dairaniehetal.(2016)analyzeconventionalCCU,whichmeansthatthestudydoesnotexplicitlyfocusonbiogenicCO2.challengingorimpossible7.Consequently,thefutureimplementationofCCUdependsontechnologicaldevelopment,aswellasoverallpoliticaldevelopmentsinthisregard.Besidesthesetrendsintechnologies,developingfuelpricesneedtobeconsidered,astheymighthaveanimpactonthescaleupandimplementationofCCUtechnologiesingeneral(Al-Mamoorietal.2017).Furthermore,trendsinenergysystemsplayasignificantrole,asalotofenergyisrequiredformanyCCUoptions(chapter2.4.1.3)and,asdescribedinchapterError!Referencesourcenotfound.,theclimateimpactismostlyafunctionofthetypeofenergyprovision.WithaparticularviewtoGermany,Purretal.(2019)developedsixscenariosfornewpathwaystowardsresource-efficiencyandGHG-neutrality.Thesescenariosdescribedifferentrawmaterialconsumptionratesandenergysystems,whichmakeGHG-neutralityby2050possible.HighestGHGreductionandthusclimateimpactscanbeachievedbysubstitutingfossilelectricitygenerationbyrenewablepowergeneration.Theso-called“supremescenario”demonstratessuchapossiblepathway,focusingonthesubstitutionoffossilelectricity.SuchafuturedevelopmentmightbethebasisforfurtherCCUimplementation.AccordingtoBernathetal.(2017),renewableenergyisconsideredtheprimarykeyinordertoachievedecarbonizationandthatwindenergybecomesthemostimportantelectricityproviderinGermanyandEurope.ThistrendmightsupportCCUdevelopments,aspreviouslydescribed.OnaEuropeanlevel,thefuturescenariospresentedbytheEuropeanCommission(2018)implythatby2050,thelarge-scaleelectrificationoftheenergysystemwillsubstitutethefossil-basedenergysystembeyondjusttheelectricitysector.Consequently,therenewableenergysectorisconsideredtoplayasignificantrole,asitiscrucialtoachievenationalandEuropean-wideclimatechangemitigationgoals.AnimportantquestionforlargescaleBio-CCUimplementation(e.g.,theprovisionofBio-CCUfuelonlargescale)isthatitwillrequirecarbonsourcesthatmaybehardtocomebyinaworldwherecomprehensiveelectrificationtakesplaceandlimitedsustainablebiomassisrequiredformaterialutilizationratherthanenergyprovision.Inthiscontext,directaircapture(DAC)mightpotentiallyplayasignificantroleasameansofsupplyingcarbondioxideinthefuture.Hence,thetrendsofCCUtechnologydevelopmentandtheirefficiencyaswellastrendsinenergysystemsarenottheonlyaspectsthatneedtobeconsidered.Anentiretrendanalysisofsocietalandeconomicchangeneedstobeconductedtorevealsystemiceffectsfromhowsectorsmaychange.2.4.3CO2storagepermanenceWithrespecttoclimateimpactsofCCUasawhole,CO2storagepermanenceisofutmostimportance.Aspreviouslydescribed,CO2canbeutilizedandtherebystoredinalargevarietyofproducts.However,thetimecarbonwillbestoredintheseproductsvariessubstantiallyfromdaysorweekstocenturies(Bruhnetal.2016),asCO2canbere-emittedattheendoftheproduct’slifetime.Thecharacteristicsofthestoragesolutionsarecrucialintheoverallclimateimpactsofcarbonremovals,moresothantheactualremovaltechnology(Mitchell-LarsonandAllen2021).Fromasystemicpointofview,theissueofdelayedemissionsisparamount,asatemporalstoragecouldprovidesomemuch-neededbreathingroomforthetransformationofoursocietytowardsamoresustainablefuture.SeveralapproacheshavebeendevelopedinordertoaddressdelayedemissionsinLCA’sproperly(RamirezRamirezetal.2020;Zimmermannetal.2018).Bennetetal.(2014)distinguishbetweenutilizationswithpermanentstorageandutilizationswithsubsequentemissionsofCO2.TheformercomprisesEORandconsequentlyanyrelatedutilizationsuchasEGR,aswellasthedeploymentofmineralization.Theseutilizationsareconsideredtostorecarbon“permanently”.Storageincementcanlastfromdecadestocenturies(Bruhnetal.2016),whereas7Forexample,muchroadtransportationcouldbeelectrifieddirectlywithouthavingtousesyntheticfuels.utilizationswithsubsequentneartermemissionsareproductswhicharerathershortlived,suchasfuelsorplastics(Bennettetal.2014)thatstorecarbonfromdays/weeks(fuels)toyears(plastics)(Bruhnetal.2016).However,tothisday,theredoesnotexistageneraldefinitionofpermanenceinthecontextofcarbonstorage.Forexample,whenprocuringcarbondioxideremovalsolutions,thesoftwarecompanyStripedefinespermanentcarbonstoragetobe1000years(Orbuch2020).InthecontextofCCUanddelayedemissions,RamirezRamirezetal.(2020)proposea500-yearhorizon,meaningemissionswithinthistimewindowshouldbeaccountedfor,whereasemissionsoutsideofthisperiodshouldbeignored,undertheassumptionthatclimatechangebythispointintimeeitherhasbeenmanagedorhasgoneoutofcontrolcompletely.Atthesametime,theauthorssuggestthatGWP20andGWP100shouldbeused.Inthislight,intermediatestoragecanhelpmitigateclimatechangeandcouldassuchbeconsidered,whendiscussingmid-termclimatechangemitigationpolicies.Thiscouldeitherentailade-factosinkwithviewtothetimeframes2050and2100,respectively,ifcarbonretentiontimesexceedtheaforementioned,or,ontheotherhand,beincludedwithaproportionatedshareofitsGWP,correspondingtotheamountofradiativeforcingcarriedoutbytheyear2050/2100.WhereasRamirezRamirezetal.(2020)presentamongothersthe500-yearhorizonfordelayedemissions,theIPCCuses2100asthetimeframeforthereportingundertheParisAgreements(IPCC2021).Consequently,furtherdiscussionisrequiredinordertodefinepermanence(i)andinordertodecidehowtohandleutilizationswithastoragetimeofe.g.40yearsandsubsequentcrediting(ii).Besidesthis,thequestionofsubstitutionandallocationbetweensectorsandacrossborders(iii)remains,whichwillbefurtherdiscussedinchapter3.2.1.Inprinciple,aslongasCCUproductsdonotstorecarbonphysicallyonaverylongtimescale,theseoptionscannotbeconsideredtobenegativeemissiontechnologies.OnlyCCUproductswithpermanentstoragecanbeconsideredasdirectclimatechangemitigationmeasuresincontrasttoindirecteffects,e.g.thedisplacementoffossil-basedproductsviaCCU,takingintoaccountthatthecarbonstoragewillbemonitoredregularly,asitisthecaseforCCS(Bruhnetal.2016).ThisimpliesthatonlyBio-CCScanbeconsideredanoptionifnegativeemissionsistheobjective(Philibert2018).However,intermsofcarboncontentofaproduct,Bio-CCUcanbeconsideredasanet-zero-CO2compatibleoption(Gabriellietal.2020)andcouldhelpfaceoutfossilprimaryenergycarriersorproducts.ProvidedtheseCCUroutesachieveareductioninGHGemissions,theycouldverywellhelpbridgethegaptoafundamentallydecarbonizedeconomy.ComparisonoftwoproductsCumulativeCO2-Storage(Mio.tCO2)AnnualstoragerateinMio.tCO2Expectedlife-time1)Scenario/yearuntil2030until2040until2050Onaverage,considerationoftheentireobservationperiodCCU–plastics(long-lived)158316,8047316YearsCCU-mineralization265177,82,6DecadestocenturiesSource:Fehrenbachetal.(2021);1)Bruhnetal.(2016)Table1PotentialcumulativeCO2StorageinCCUoftwoexemplarycasesinGermanyThecomparisonoftwodifferentCCUproductsdemonstratestheimportanceoftheconsiderationoftheCO2storagepermanence8.TakinganannualcarbonstoragerateofeachCCUapplication(plasticsand8ThesestorageratesoriginatefromcalculationsoftheBio-CCUpotentialinGermany,unpublished.mineralization)intoaccountandmodellingthestoragepotentialforthenextdecades,theplasticsCCUdeploymentappearstostoremorecarbonthantheCCUmineralization.BesidesthefactthatbothCCU-productscannotbeproducedatthesamequantity(duetolimitedadditionalcalcium/magnesium-richfeedstockformineralization),thestoragepermanenceisnotconsideredhere,whichbringsthecarbonstorageoftheseproductsintoadifferentlight.Evenlong-livedplasticshavealife-timeshorterthanmineralizedbuildingmaterials,whereasmostofthetheoreticallystoredcarbonwillpracticallybere-emittedsubsequently.FollowingBennetetal.(2014),suchamineralizedbuildingmaterialcanbeconsideredapermanentstorage,contrarytoplastics.ThisexampledemonstratedthatthefactorstoragepermanenceneedstobeconsideredthoroughlyinadditiontoproductionquantitiesofdifferentCCUderivedproducts.Furthermore,thesubstitutioneffectsoffossilreferenceproductsneedtobeconsideredforbothapplicationsinordertoderiveaholisticestimationoftheclimateimpactofCCUplasticsandCCUmineralization.2.4.4KeydeterminantsofoverallclimateimpactInsummary,thekeyaspectsthatneedtobetakenintoconsiderationandthatcontributemostsignificantlytotheoverallclimateimpactofBio-CCUproductsarethus:i.theconcentrationandpurityofCO2tobefurtherutilized,ii.thenatureofutilization,e.g.,PtXwithhighenergydemandsvs.mineralizationandrespectivelowenergydemands,iii.theoriginofhydrogenandenergy,or–inotherterms–thebackgroundenergysystem,andiv.thestoragepermanence.Additionally,thedemandnowandinthefutureforsuchCO2-basedproductsaswellastheavailabilityofCO2sourcesinahypotheticaldecarbonizedeconomyneedtobetakenintoaccount.Bennetetal.(2014)analyzeCCUoptionsregardingtheirclimateimpact,comparedtoconventionalproductsystems.Basedonthis,theyproposethreecriteriathatarecrucialindeterminingthepotentialimpactonlimitingorreducinggreenhousegasemissions.Thesecriteriaextendthepreviouslymentionedaspectsandcomprise:•TheextentofCO2emissionreductionincomparisontoconventionaloptions:inordertofullyassessthereductionpotential,allemissionsintheupstream,utilizationanddownstreamsystemneedtobeconsideredandcomparedtoanalternativescenario.Regardingthealternativescenario,particularattentionshouldbedriventothefactthatina“Post-Paris-2015-World”afossilreferencescenariodoesnotcorrespondtothecurrentandfuturestateanymore.Consequently,thecomparisonshouldbedriventowardsascenariothat–forexample-includescurrentmitigationmeasuresaswell.•Coverofcostsbypotentialrevenue:Ideally,theCCUproducthasaspecificmarketpricethatentirelycoversallcostsduringtheproductionline.Inordertolowercosts,aswellasenergyrequirements,especiallyutilizationroutesthatdonotrequireCO2purificationshouldneedtobeconsidered.•Scalabilityoftheutilizationpath:TheCCUproductcanonlyhavesignificant(positive)climateimpacts,whentheproductionisscalableandthusthedemandforCO2ishighenoughtobemeaningfultomitigationoverall.Thisaspectincludesthedemandfromconsumerside,aswellasthesupplyofCO2fortheproductionphase.Finally,withregardto(i),Schwanetal.(2018)concludethatCCUcanonlybeconsideredasanoption,whenalotofrenewableenergyisavailableandwhenlessenergyisconsumedthanavailable.ThesecircumstancescouldpotentiallybemetintheMENA(MiddleEast&NorthAfrica)region.Inthecontextofrenewableenergy,thequestionaboutthemostappropriatedeploymentoflimitedrenewableenergyresourcesremains(Bennettetal.2014).3IntegratingBio-CCUScarbonaccountinginpolicyframeworksTherapidpaceatwhichBio-CCUShasgonefromconceptualdiscussionstodeploymentconsiderationshasmeantthatpolicyhavenotkeptupandmanyregulatoryframeworkscurrentlyinplacedonotincludeadequategovernanceprovisions.However,challengesofintegrationintoexistingstructureordevelopingnewstructuresdiffersomewhatbetweenBio-CCUandBio-CCS.ForBio-CCS,thechallengelargelyboilsdowntoanabsenceofpolicyframeworksrelatedtonegativeemissionsmorebroadly,whereasthechallengesrelatedtoBio-CCUaremorerelatedtosettingupaccountingframeworks.Acknowledgingthedifferentcharactersofthechallenges,wediscussthetwoseparatelybelow.3.1BIO-CCSCO2GOVERNANCEInthelastcoupleofyearsandfollowingonthecallsmadebye.g.,Anderson&Peters(2016)andvanVuurenetal.(2017)forintensifieddiscussionsaroundnegativeemissionspolicy,researcharoundnegativeemissionsgovernancehasdevelopedmarkedly.Havingsaidthat,thisdoesnotmeanthatallquestionsareresolved,quitethecontrary.Asithappens,thecomplicatednatureofnegativeemissionsconceptuallyaswellaspoliticallydoesnotlenditselfwelltoswiftimplementationinpolicy.AfirstquestiontobediscussedrelatestothemoralhazardproblemhighlightedbyAnderson&Peters(2016)andconcernstheextenttowhichnegativeemissionsshouldbeincentivizedrelativetoemissionreductions.Itisimportantthatnegativeemissionsarenotseenasanalternativetoemissionreductions,butratherasacomplementarymeasure(Cartonetal.2021)9.Principaldecisionsaroundthisquestionhaveimportantconsequencesforpolicydesign.Forexample,Rickelsetal.(2020)discusshownegativeemissionscouldbeintegratedintotheEUETSthroughasystemwherecompaniesareawardedfreeemissionallowances(EUAs)amountingtotheamountofCO2removedfromtheatmosphere.WhilethisapproachhasadvantagesinbeingarelativelyelegantwayofintegratingCDRintheEUETS,itdoesentailanimplicitrecognitionoftheequivalencebetweenemissionreductionsandcarbondioxideremovalthatiscriticizedbyCartonetal.(2021).Anotherquestionpertainingtoincentivizingnegativeemissionsiswhetherpolicymeasuresshouldbedirectedspecificallyatthecarbondioxideremovalassuchortowardsstimulatingdemandforgoodsproducedwithnegativeemissions.Forexample,afacilitythatgeneratesnegativeemissionsthroughBio-CCSwillalsoproduceothergoods,beitelectricity,heat,fuelsorindustrialproducts.Should,forexample,policyincentivesbetiedstrictlytothenegativeemissionsassuch,orshouldtherebeasystemthatincentivizesnegativeemission“products”,i.e.negativeemissionelectricity/heat/etc.(Rickelsetal.2020;Harris2021;Klementetal.2021)?Inaddition,therestillexistsomepracticalhurdles,whichcanprovequitechallenging.CCSprojects,regardlessofthecarbonorigin,oftenlacksocialacceptance(Elkerbout&Bryhn,2019)andarealsofearedtoprolongtheexistingcarbon-basedenergysystemandthushinderatransitiontorenewables10.Moreover,regulationinotherplacesisslowtoadapt.The1996LondonProtocoltotheConventiononthePreventionofMarinePollutionbyDumpingWastesandOtherMatterof1972(inthefollowingreferredtoastheLondonProtocol)prohibitedthetransboundarytransportofCO2forthespecificinjectionintosub-seabedformations(Garrett&McCoy,2013).OnlyasrecentlyasOctober2019,atthe41stLondonConvention,anamendmenttoarticle6oftheLondonProtocoldatingbackto2009wasadoptedinordertoallowforCO2exportsfortheabove-mentionedpurpose.Againstthebackgroundofthevastavailabilityofoffshorestoragesites(incontrasttothelimitedamountonshore),thisdevelopmentcouldprovequitesignificant(Elkerbout&Bryhn,2019).9Asimilarquestionpertainstowhetherornotnegativeemissionsshouldbering-fencedsothatitwouldnotbepossibletousenegativeemissionsgeneratedintheLULUCFsectortocompensateforresidualemissionsintheenergy,industryortransportsectors.10Aconceptreferredtoas„carbonlock-in“.3.2POLICYINTEGRATIONOFBIO-CCU3.2.1PracticalandMethodologicalChallengesofBio-CCUAccountingHistorically,carbondioxideasaprocessoutputhasbeentreatedlikeawastewithout(by)productstatusorvalue.Thisisnolongeristhecaseifsaidcarbondioxidegainsvaluebyusingitinanadjacentprocessasaninputforthepurposeof,e.g.,constitutingthecarbonsourceforahydrocarbon-basedfuel.Followingthis,anumberofquestionsarise.1)Whogetsthecreditfor“carbonrecycling”,or:howtoallocatetheburdenoftheemittedcarbon/carbondioxideattheendofitslifecycle?2)Howtoaddresscarbondioxidemovementbetweendifferentcountries?3)Howtohandlepotentialby-products?Questions1and2arerelated,butvaryinscope.Thefirstquestionaddressesthelinkingofmultipleproductsystemsonacompanylevel(e.g.,apowergenerationprocessandasubsequentproductionofPtXfuelsorbio-methaneproductionandsubsequentcarbonationofbeverages).Asageneralrule,CO2ofbiogenicoriginisconsideredtobeazero-sum-game,astheCO2wasfixedbyaplant.Itsemissionfartherdownstreamthusdoesnotcontributetoclimatechange,astheamountofCO2emittedcannotexceedtheamountofCO2fixedinthefirstplace.11However,thisonlyholdstrueforthelifecycleofthecarbonintotal.Fromtheviewpointofthecarbongenerating(first)processorproductsystem,itsproductisnolongerliableforthecarbonemission,ifasubsequentprocess(productsystem)canusethiscarbonasaninput.Thisconstitutesa“negative”emission,orremovalofatmosphericcarbonbecauseupuntilthispointinthevaluechainofthefirstproductsystem,onlycarbonsequestrationviabiomassgrowthhastakenplace,butnotacarbonreleasetotheenvironment.Fromtheviewpointofthesubsequent,carbonutilizingprocess,thecarbonwouldhaveenteredtheatmosphereanywayandisthustheresponsibilityofthefirst,CO2generatingprocess.Hence,thefirstproductsystemhastoreporttheCO2emissionintheendofthesecondproductsystem’svaluechain.Itiseasytoseethat,ifthereisnoprecautiontaken,theresultcouldbethatthisisaccountedforasanegativeemissionandnottherealzero-sum-game.Asasolution,allocationofburdens(orcredits)betweenbothlinkedproductsystemsisadvised.Asthisconstitutesarathernormativequestion,theauthorsrefrainfromadvisingonwhichallocationprocedureismostsuitableandrefertoFehrenbachetal.(2017)andRamirezRamirezetal.(2020)foramorein-detaildiscussion.ThefollowingFigure5illustratesanexampleoftwodistinctproductsystemsthatarelinkedviaCO2.Here,thefirstproductsystemisabiomassCHPplantwhichproducesbiogenicCO2.ThesecondproductsystemisagenericprocessthatvalorizesthissameCO2.Intheend,apermanentsequestrationofthecarbontakesplace(arrowtowardCCS).Thisconstitutesanegativeemissionandthusacarboncredit.However,insteadofafinalCCS,areleasetoatmosphereisalsoapplicableinthisexample(arrowtowardsCO2emission).Fehrenbachetal.(2017)findthreepossiblesolutionsforthecarboncrediting,asisreviewedbelow.If,however,noCCSattheendofthecarbonvaluechaintakesplace,theabove-mentionedprecautionisneeded,the“solutions”havetobeexpandedormodified:Solutions1a:IfthebiomassCHPplantcreditsitselfasacarbonsink,theCO2valorizationprocesshastoaccountfortheCO2emissionintheend.Solution2a:Thebioethanolplantdoesnotconsideritselfasinkandaccountsfor/reportstheCO2emission,thenthesubsequentCO2valorizingprocesshastobeawardedtheCO2creditorbonusinorderforthezero-sumequationtobecorrect.11NotethatthisholdsonlytrueforCO2orrathersubstanceswithequivalentGWP.If,forinstance,theCO2istransferredtoMethanewithadifferentGWP,thedeltaofGWPxAmountforbothspecieshastobeaccountedfor.Solution3b:Bothprocessessharetheburdensandcreditsviaanallocationmechanism,thenintotal,bothcreditsandburdenshavetoadduptozero.Figure5MultifunctionalproductsystemslinkedviaCO2(Fehrenbach,etal.,2017)ThesecondquestionfocusesoncarbonaccountingamongcountriesandreportingdutiesunderclimatechangemitigationinstrumentssuchastheUnitedNationsFrameworkConventiononClimateChange(UNFCCC).Thisfollowsaterritorialprinciple,meaningthateveryratifyingstatehastoreporttheemissionsthatariseonitsterritory.If,however,aCO2transportoraBio-CCUSvaluechainwithsubsequentexportacrossbordersareestablished,itisofutmostimportancethatnodoublecounting(informofaCO2creditornegativeemission,doubleinthesenseoftheexportingcountryaswellastheimportingcountrybothconsidertheamountofsequesteredCO2withintheproductathandfortheirrespectivecarbondioxidebudget)occurs,ifthecarbon-basedproductispermanent.If,ontheotherhand,theCCU-basedproductisshort-lived,itmustbeensuredthat–withrespecttothecarboncontentoftheproduct–thezero-sumgamestillapplies,i.e.,ithastobeavoidedthattheexportingcountrygainsanegativeemission,whereastheimportingcountrytreatsthecarboncontentoftheproductaszero,followingaccountingpracticesforbiogenicCO2.AsBio-CCUSconstitutesatechnicalparallelto‘natural’plant-basedproducts,itshouldthusbetreatedassuch(seesection3.2.2).ForasystemintegrationofBio-CCUS,both,forinlandaswellascross-bordertransportofCO2,thereremainsthequestionoftransportinfrastructure(Elkerbout&Bryhn,2019).WhilethediscussionofCO2transportforgeneralCCS/CCUprojectsfocusesonthebenefitsofconcentratedindustrialclusters,especiallybioenergyplantstothisdatearedecentralizedandwithregardtoGermany–Europe’smainconsumerofbioenergy12–heavilyso.13Althoughagasnetworkexists,theamountofCO2thatcouldbetransportedisverylimited,resultingintheneedforeitheraseparateadditionalpipelinenetworkwithcorrespondingexpendituresoralargescaleroadtransport,withaccompanyingemissions.3.2.2ExistingexamplesofcarbonaccountingacrossbordersandsectorsIfBio-CCSandBio-CCUSsystemsshouldconstituteapotentialemissionsinkofanysignificanceinthefuture,therehavetobeguidelines,methodologies,rulesorconventionsinplacethataretailoredespeciallyforthehandlingofCO2.WithviewtoemergingCO2markets,oneofthemostimportantquestionstobe12OthernotablesareFrance,ItalyandSweden,onaper-capitabasis,theScandinaviancountries,theBalticsandAustria(EUROSTAT2018a,2018b,https://publications.jrc.ec.europa.eu/repository/bitstream/JRC109354/biomass_4_energy_brief_online_1.pdf)13Thisholdsespeciallytrueforbiogasplants.addressedishowthemovementofCO2betweendifferentsectors,industriesandcountriesisregulated.Tothisdate,aninternationalcomprehensiveframeworkspecificallyforCO2doesnotexist.Thereisthusneedforadevelopmentofsuch.However,forBio-CCU,parallelstoalreadyexistingframeworkscanbedrawnduetotheapparentfunctionalequivalency.Below,wediscussthreeframeworksthatcouldprovideguidanceforthegovernanceofBio-CCU.3.2.2.1ReportingofHWP–HarvestedWoodProductsintheNationalInventoryReportsfollowingtheIPCC2006Guidelinesandthe2019Refinementtothe2006IPCCGuidelinesforNationalGreenhouseGasInventoriesReportingofHWPintheNationalInventoryReports(NIR)followthe2006IPCCGuidelinesforHWP.Generally,theguidelineprovidesfourdifferentapproaches14andaddressesthequestionofhowHWPcontributetowardstheAFOLUsectorassourcesorsinksofCO2.Althoughtheguidelineinits’entiretyfocusesonmanyissuesthatareirrelevantforBio-CCUS,someaspects,especiallyconcerningtheinternationaltradeandpermanenceofstorageofCO2couldprovideafirstbasisforacorrespondingregulationofBio-CCUS.InordertodeterminewhetherornotHWPconstituteacarbonsinkorsource,bothdomesticallyusedandexportedHWPareconsidered15butonly,iftheystemfrommanagedforests.However,here,thesystemboundaryandthustheresponsibilityofcarbonemissionsorremovals,respectively,isdependentontheapproachchosen.The“production”and“simple-decay”approachesconsidertheHWPproducingcountryasresponsibleforCO2emissionsorremovals,whereasthe“stock-change”and“atmospheric-flow”approachesburdenorcredittheconsumingcountry.WhileallapproachesinthemselvesconstituteviableoptionsinassessingHWPasCO2sourceorsinkonlytheformer–“production“and“simple-decay”arereallyinlinewiththegeneralideaoftheterritorialprincipleoftheNIR.Thecountryoforiginisthusresponsibleforeithertheemissionsorthecarbonremovalsofthesectorintotal.Inaddition,itwouldhardlyincentivizeBio-CCU(orotherCCUprojects,forthatmatter)toreporttheemissionsrelatedtotheenergyexpenditures(andothers)thatareneededforCCS/CCUifrelatedremovalsintheformofanexportedproductwouldbereportedwithinthecountryofdestiny(Umweltbundesamt,2020).Moreover,theIPCCGuidelinesontheonehandconsiderthedecayofHWPandthusachangeofthecarbonstorageovertime.Ontheotherhand,itdistinguishesbetweendifferentHWPcategorieswithspecificdecayfunctionsandHWPhalf-life.Inthisway,thechangingcarbonstockinHWP,andsubsequentlychangingfunctionascarbonsink,isdonejusticeconsideringthedifferencesincarbonretentionofdifferentproductcategories16.AnimplementationalongthesamelinesforBio-CCUproductswithdistinctproductcategoriesandindividualdecayfunctions/CO2releaseincombinationwithterritorialresponsibilityandreportingdutycouldconstituteafirststartingpointfortheregulatoryframingoftheaccountingofinternationalCO2trade.3.2.2.2CDM–CleandevelopmentmechanismandParisAgreementArt.6.4–internationalcarbontradingmarketsforemissionoffsetting.Establishedin2006,theCDMaspartoftheKyotoProtocolwasoneofthefirstglobalcarbonmarket/offsetschemesforthepurposeofclimatechangemitigation.Thegeneralideacouldbedescribedasfollows:Industrializedcountries(AnnexBcountries)investindevelopingnations(non-AnnexBcountries)onaprojectbasisinordertoachieveadditionalemissionreductionswhencomparedtothepathwayofthedevelopingcountrywithoutsuchaninvestment(baselinescenario).Thequantitiesofachievedemissionreductionsarebeingassessedandacorrespondingamountof“certifiedemissionreductions”(CER)generated.TheseCERscanthenbesoldtoAnnex-Bcountriesandcounttheretowardsthecountry’s14Forreferenceandadetaileddescription,theauthorsrefertoChapter12andAnnex12A.ofthe2019refinementtotheIPCC2006Guidelines15Inaddition,thecontributionofHWPinsolidwastedisposalsites(SWDP)ispossible.AsaparalleltoBio-CCUS,ifBio-CCUSderivedproductsarebeingdisposedofinSWDPswithoutoxidationtoCO2oranaerobicdegradationtoCH4toasignificantamount,thissinkoptioncouldbeincluded.TheIPCCGuideincludesthisoptionforHWPs,too.16Forexample,paperproductsonaveragehaveashorterlifespanandthuscarbonsequestrationfunctionwhencomparedwithsolidwoodproductssuchasfurniture.respectiveemissionreductiongoals.Thekeyaspecthereistheconceptofadditionality,andithastobeindisputablethattheemissionreductionwouldn’thaveoccurredwithouttheCDMinitiative.Inrealitythough,additionalityhasproventobecomeahighlycontroversialissue.Similarly,correctestimationoftheactualcontributionofindividualprojectshasbeenproblematicbecauseofanasymmetryininformationbetweenprojectparticipantsontheonesideandauthoritiesontheother(Cames,etal.,2016)17.HoweverdisputedtheCDMschemeintermsofrealandmeasurableclimatechangemitigationmayhavebeen,itcouldproveavaluablebasisforits’successorundertheParisAgreement(Camesetal.2016).Lessonslearnedintermsofenvironmentalintegrityandgeneralmarketdesigncouldthusbeimplemented.Theabove-mentionedsuccessoroftheCDM,Article6.4oftheParisAgreement,isstillundernegotiationanditremainstobeseenhowthiscarbonmarketwillshapeout.OnekeyprogressionfromtheCDM,however,constitutesthefactthatundertheParisAgreement,allparticipatingcountrieshavetofulfillNationallyDeterminedcontributions(NDCs)(Cames,etal.,2016).Thiscouldleadtoafundamentalreassessmentofpreviouspractices,asthehostcountrieswillnowhavetoachieveemissionreductionsthemselves,shrinkingtheopportunities/marketforthegenerationofCERs18.Moreover,thecountries’NDCwillhavetobeconsideredasthenewcounterfactualscenariowhendeterminingemissionreductionquantitiesintheformofCER,resultinginamoredynamicalbeitpotentiallycomplexassessment,comparedtotheCDM’sbusinessasusualcounterfactualscenario(Cames,etal.,2016).3.2.2.3CORSIA–Market-basedinitiativefortheaviationsectorInadditiontopolicy-basedcarbonmarkets,certainindustries,especiallytheoneswherearapiddecarbonizationisnoteasilyachievablecouldstarttheirowncarbon-offsettinginordertocommittoclimatemitigation.Asafirst,CORSIA(CarbonOffsettingandReductionSchemeforInternationalAviation)ismeanttostabilizetherapidlygrowingemissionsintheinternationalaviationsector(DEHST2020)19.Whereasnational-andinternationalairtravelwithintheEEA(theEU27plusIceland,LichtensteinandNorway)20iscoveredbytheETS,internationalaviationisexcludedthusfar,resultinginaneedofaschemelikeCORSIA21.Startingin2019,allaircraftoperatorsmonitortheiremissionsinordertodeterminethestatus-quowhichfunctionsasabaselinereferenceforfutureoffsets.Withthebeginningof2021,allparticipatingairlineswillhavetocompensatetheCO2emissions22thatexceedthebaselineoftheyears2019and2020minustheusageofsustainableaviationfuels(DEHST2020).Thecertificatestobepurchasedbytheairlineshavetofulfillanumberofrequirementsinlinewithothercarbonoffsetschemes,suchasadditionality(cf.section3.2.2.2)nodouble-countinginotherclimatechangemitigationinitiativesorregulationsandconsiderationofboth,socialandenvironmentalaspects.3.2.3PossibilitiesofPolicyIntegrationAgainstthebackgroundofcurrentclimatechangemitigationinstruments,Bio-CCUSapplicationandrelatedrecycling-and/orstorageapproachesforCO2onlyplayaverysubordinaterole.Nevertheless,asoutlinedabove,boththeIEAandtheEUenvisionBio-CCU/Stocontributesignificantlytowardsabelow2°Cgoalasakeyinstrumentinthetoolboxofdifferentapproaches.InordertohelpBio-CCUStechnologiestogainthenecessarymomentum,theregulatoryframeworkhastobeinplacefirst.Onaninternationallevel,countriesachievinganet-increaseintheircarbonstockviaBio-CCUSshouldbeeligibletoaccountforthisanalogoustohowHWParerepresentedasboth,anemissionsinkandsource,17Thecitedstudyconcludesthatthevastmajority(85%)ofinvestigatedprojectsundertheCDMwouldnotfulfilltheoutlinedcriteria.18Ontheotherhand,thiscouldalsosolvetheproblemofactualadditionalityasdiscussedinthecontextoftheCDM.19https://www.dehst.de/SharedDocs/downloads/DE/publikationen/Factsheet_CORSIA_EU_ETS.pdf?__blob=publicationFile&v=320SwitzerlandispartoftheEEA,butdoesnotparticipateinCORSIA.21Coveredareallcompaniesthatexceed10.000tCO2emissionsoninternationalflightswithplanesexceedingamaximumlift-offweightof5.7t.22Othernon-CO2relatedclimateeffectsofaviationtrafficarenotyetincluded,butaresubjecttofutureconsiderations,astheyposeasignificantclimatechangerisk.withintheNIR.Thisisonlycoherentwiththelogicofthereport,asenergyexpendituresandthelikeneededwithintheBio-CCU/Svaluechainalreadyareincludedandhavetobereported.IfBio-CCU-derivedproducts,however,donotleadtoanincreasedcarbonstock,forinstance,becausethecarbonstoragedurationislimited23,thecarboncontentcouldbehandledinanalogytootherbiogeniccarbonwithintheNIRbyassigningaGWPof0.Moreover,asBio-CCUSconstitutesapromisingoptionforbothadditionalityandemissionsavingscomparedtothebaseline,itcouldbeconsideredanidealprojectcategoryfortheCDMsuccessorandotherinternationalcarbonoffsettingschemes.WithviewtothemoreprogressiveandchallengingclimatechangemitigationgoalsofsupranationalinstitutionssuchastheEU,amoreregulativeapproachisthinkablewiththeREDandits’iterationsasthekeyinstrument.Inits’currentversion,theREDwithatimehorizonuntil2030definesontheonehandoverarchinggoals,suchastheshareofrenewablesinthedifferentsectors,forexample,butalsodefinesquotafordifferenttechnologiesorrawmaterials.Forinstance,theshareoffirst-generationbiofuelsiscapped,while,ontheotherhand,thereisaminimumquotaforadvancedbiofuelsthathastobeachieved.Asub-quotaforBio-CCU-derivedproductsinlinewithothersub-quotasconstitutesapossiblefirststep.Inaddition,multiplyingfactors24arepermittedwithintheREDinordertoincreasethecompetitivenessofindividualtechnologiesortohelpthemtoestablish.SinceBio-CCUisarathernewapproachfarfromlargescalemarketpenetrationorcompetitionwiththestatusquo,multiplyingfactorscouldbeconsidered.Another,moreindirectapproachwouldbetheimplementationofemissionreductiongoalsfordifferentsectors,withtheideaofthecombinationofchallengingemissionreductioncriteriaand(possible)highspecificemissionreductionpotential(withintoevennegativeemissionsifcarbonstorageisofpermanence)ofBio-CCUproductsresultinginarapiddevelopmentofaBio-CCUeconomy.BothapproachesareviableandcouldbeincludedinordertoreflectonthedifferentpathwaysofEUcountriesinthepast.Inanycase,itisparamounttoallBio-CCUSapproachesthata)sustainablebiomassfeedstockisutilized,resultinginb)realemissionreductions,andthatc)doublecountingisavoided.23Seesections2.4and4.24EverykWhofelectricityconsumedinthetransportsectorcanbemultipliedby3.If,say,thegoalistoachieveatleast100kWhelectricityconsumptioninyear202X,inrealityonewouldonlyrequire33kWhphysicallytofulfilltherequirements.4DiscussionWhilebothBio-CCUandBio-CCScanbeimportantpiecesinthepuzzleofgettingtheworldtonet-zeroGHGemissionsby2050,theirrolesareboundtobequitedifferent.Bio-CCSisclearlyameanstogeneratenegativeemissions,butwhetherornotthisisthecaseforBio-CCUisamoredifficultquestionwheretheanswerwillvarybetweencontextsandwheretheremaybeasubstantialgreyareadependingonthecarbonstoragepermanence.Regardless,Bio-CCUcanprovidesocietywithfuels,chemicalsandmaterialswithaverylowGHGfootprint-onethatwillalsotendtowardszeroaselectricitygenerationisincreasinglydecarbonized.ForbothBio-CCUandBio-CCShowever,itwillbecrucialtodevelopmechanismsandpracticesforhowtotrackCO2flowsacrosstherespectivesupplychainsaswellassetupgovernanceframeworksforhowtoaddresstheseissuesinpolicy.Inthisreport,wehaveoutlinedsomeoftheconceptsthatwillbeparticularlyimportanttothisend,withkeyissuessummarizedinTable2onthenextpage.4.1BIO-CCUANDNEGATIVEEMISSIONS–AQUESTIONOFTIMEThekeydifferencebetweenBio-CCUandBio-CCSintermsofclimatechangeimpactistime,asisillustratedinFigure6.ForBio-CCS,theCO2capturedisstoredpermanentlywhichshouldentailareductionofatmosphericCO2providedthatcaptureratesarehigh,asmallGHGfootprintoftheenergyusedforcaptureandtransportandlowupstreamfeedstockemissions.Figure6.TimelinetoillustrateindicativeCO2storagetimesforsomeBio-CCUSexamples.ForBio-CCU,manyapplicationscurrentlyunderdiscussionentailCO2beingre-releasedintotheatmospherefairlysoon,inmostcasestoorapidlytobeeffectiveintermsofeffectivelyreducingthewarmingeffectinthewaythatisthecaseiftheCO2ispermanentlystored.Whetheronechoosesthe500-yearlimitchosenasthecut-offpointforpermanencebyRamirezRamirezetal.(2020)orthe1000-yearlimitsetbyStripe(Orbuch2020)bothmaybecriticizedforarbitrariness,itcanstillbearguedthatmostBio-CCUapplicationsfailtomeetcriterion2–permanentstorage–accordingtotheframeworkdevelopedbyTanzer&Ramirez(2019).AllBio-CCUSBio-CCSAllBio-CCUShort-livedBio-CCU(e.g.,fuels)Mid-longlivedBio-CCU(e.g.,plastics)Long-livedBio-CCU(e.g.,constructionmaterials)KeyaspectsforCO2countingEnergyinput,UpstreamfeedstockemissionsDistancebetweenbiomassplantandgeologicalstorage?Carbonretentionovertime(e.g.decay);potentialsecondlifestage/handling;Accountingprinciples(e.g.avoidanceofdoublecounting);LCperformanceincomparisontoconventionalproducts(systems);ILUC/aLUCandsustainabilityofthesupplychain;Movementbetweensectors,trackingacrosssupplychains;LCperformanceincomparisontoconventionalproducts(systems);accountingprinciples(e.g.avoidanceofdoublecounting)Secondlife;CarbonretentionovertimeDecayfunctionCarbonretentionovertime(e.g.decay)KeyaspectsforpolicyConsiderationofconcentrationandpurityofCO2inrecommendations(avoidfurtherpurificationstepswherepossibleforenvironmentalandeconomicreasons);considerationofenergyandupstreamfeedstockinrecommendationsMoralhazardproblem?Emissionreductionsvsnegativeemissions:equivalenceorring-fencing?Accountingprinciples;LCperformance;Sustainabilityofthewholesupplychain;ILUC/aLUC;Considerationofend-useemissionsAdaptationtorecyclabilityIncentiviselong-livedBio-CCUratherthanshort-livedKeyopenquestionsTypeofbiomassinvolvedStoragepermanence/geologicalsecurityCut-offpoint(s)forlong-livedvs.short-lived(HWPvs0/500);Accountingprinciplesinspecificcases,e.g.sectorcoupling,CO2asaresourceTypeofhydrogenprovidedTypeofhydrogenprovidedsupplyofadditionalfeedstock?Marketsituation/access;supplyofadditionalfeedstock(calcium-richminerals…)Table2.Summaryofkeyissuesforresearchon,andgovernanceof,CO2flowsinBio-CCUSsupplychains.4.2PARALLELSASAGUIDETOBIO-CCUGOVERNANCE?TrackingCO2flowsinBio-CCSis–atleastifwerestrictourselvestothepost-capturepartsofthevaluechain-conceptuallyfairlystraightforward,asitisessentiallyaone-directionprocessfromcaptureviatransporttolong-termstorage.ForBio-CCU,however,keepingtrackofCO2canseemabitdauntingatfirstglance.OneapproachthatcanhelpstructurethinkingaroundthisquestionistoviewtheBio-CCUvaluechainasaparalleltothenaturalsystem,i.e.,whereCO2iscapturednotusingtechnologybutthroughphotosynthesis.Inotherwords,then,onecouldviewtheCO2capturefacilityasareallyfast-workingtreeandwithensuingdownstreamprocesses,betheyfuelsormaterials,asvariantsofbio-products.AfuelproducedfrombiogenicCO2canbeseenasformofbiofuelandaplasticproducedfrombiogenicCO2canbeseenasaformofbioplastic.Thekeydifferencefromtheperspectiveoflifecycleassessmentisthatthebiofeedstock(i.e.,theCO2)canbeassumedtobeapurewasteproduct,inthesensethatitsupstreamprocesssupplychainemissionsareassumedtobezero(Fagerströmetal.2021).Buildingonthisparallelcouldfacilitatetheuseofexistingframeworkssuchastheaccountingrulessetuparoundharvestedwoodproductsaswasdiscussedinsection3.2.2,althoughitwouldthenbenecessarytoadaptspecificsarounde.g.,assumedhalf-livesofproducts.AnotherusefulparallelwhenitcomestogovernancestructuresistherecentlyproposedProset–ProgressiveOffset-concept(Mitchell-LarsonandAllen2021).Thisisanapproachthatwouldallowjointincentivizationofdifferentcarbondioxideremovalsolutionsacrossawiderangeofcharacteristicswhenitcomestocost,technologicalmaturityandcarbonstoragepermanence.Asnotedinsection2.3,CDRsolutionscancomeinmanyvarieties.Some–likeafforestation–arecommerciallyavailableandinexpensivebutcomewithsubstantialuncertaintiesinthatitisaprocessthattakesplaceovermanyyearsandwherenaturaldisturbanceslikewildfiresquicklycanundodecadesofcarbonsequestration.Ontheoppositesideofthespectrum,directaircaptureandstorage(DACCS)canenablealmostinstantaneousremovalandlow-riskpermanentgeologicalstorageofatmosphericCO2,butisstillinearlystagesofcommercializationandordersofmagnitudemoreexpensive.UndertheProsetconcept,companieswantingtooffsettheiremissionscandosousingallCDRsolutionsofdifferentvariations,butforeveryyearthatpasses,themandatedshareofemissionsoffsetusingpermanentstorage(e.g.,DACCS)solutionswillhavetoincreaseattheexpenseofsub-permanentsolutionscharacterizedbyhighrisksofreversal(i.e.,re-releaseofcapturedCO2intotheatmosphere).ApplyingthisthinkingtoBio-CCUwouldmeanthatpolicyincentivesforproductswithshort-termCO2storagecouldbehighinaninitialstagebutthengraduallyphasedout,asfocusincreasinglyshiftstolonger-termstoragesolutions.ItisimportanttonotethoughthattheanalogueisnotperfectandmoreresearchisneededtoanalyzeexactlyifandhowtheProsetconceptcouldbeappliedto(BE)CCUcontexts.Asitturnsout,eventhoughtheissueofcarbonstoragepermanenceiscommontothetwoconcepts,therearealsoimportantdifferences.ThisincludestheneedtotakeintoaccounttheneedtomonitorandallocateresponsibilitiesasBio-CCUproductsmovegeographicallyaswellasbetweenactors.4.3NEXTSTEPSANDFURTHERRESEARCHThisreportshouldprimarilybeseenasascopingstudyofsomeoftheemergingissuesthatwillhavetobeaddressed,discussedandresolvedtomakesurethatBio-CCUandBio-CCScanliveuptotheirpotentialasclimatechangemitigationsolutions.Thereareseveralissuesthatneedtobeaddressedinthenear-termtoensurethatthepolicyandregulatoryworkkeepsinpacewithtechnologicaldevelopmentsanddemandsforprompton-the-grounddeployment.Keyremainingquestionsinclude:-IsthereaneedforspecificBio-CCULCAguidelinesinadditiontothosedevelopedforCCUbytheLCA4CCUinitiative?ThiscouldbeespeciallyimportantforB2Borcross-bordertrade&transportofCO2asaresourceperseorembeddedwithinproducts,e.g.aBio-CCUderivedPtXfuel.-HowtoaddresscasesthatincludenegativeemissionsthroughBio-CCSbutwheretotalprocessemissionsstillareabovezerobecauseofunavoidablefossilemissions?Animportantcasehereiscement,wherehalfoftheCO2emissionscancomenotfromfuelburningbutfromcalcinationoflimestone.ThismeanssothatevenwithCCSanduseofbiomassforprocessheat,itmaynotbepossibletoreachzeroorbelow-zeroemissions.-HowtoaddressstoragepermanenceofCO2inproductswithacarbonretentiontimeofdecadesoryears?HowtoaddressthecontributionofdelayedemissionsfromcascadinguseofCO2againstclimategoals,e.g.anintermediatestorageof–say–15years?Isthereneedforatwo-foldapproach,e.g.onerobustapproachforthepurposeofpracticalpolicyintegrationandamoredistinguishedapproachtobeusedin–say–LCA?-Howtofixtheconundrumofbiomass-to-energy-CCSandinverserelationshipofprocessefficiencyandnegativeGWP(inshort:aworseefficiencyrequiresmorebiomassperkWhandwithsubsequentCCS,achievesrespective‘better’negativeGWPsperkWh)?Finally,itisimportanttoemphasizethataholisticapproachfortheutilizationofbiomassresourcesindifferentsectorsisneeded.Thisincludestheconsiderationoflimitedrenewablesavailabilityandtransformationefficienciesonasupra-nationalscale.InordertoproperlyassesstheclimatechangemitigationpotentialsofBio-CCUS,itisparamounttoreflectontheavailabilityofsustainablysourcedbiomassacrossallsectors.ReferencesAl-MamooriA,KrishnamurthyA,RownaghiAA,RezaeiF.2017.CarbonCaptureandUtilizationUpdate.EnergyTechnol.5(6):834–849.https://doi.org/10.1002/ente.201600747AndersonK,PetersG.2016.Thetroublewithnegativeemissions.Science[Internet].[accessed2018Aug13]354(6309):182–183.https://doi.org/10.1126/science.aah4567vonderAssenN,MüllerLJ,SteingrubeA,VollP,BardowA.2016.SelectingCO2sourcesforCO2utilizationbyenvironmental-merit-ordercurves.Environmentalscience&technology.50(3):1093–1101.AutenriethC,BaganzA,BärK,BirthT,BumharterC.2021.StellungnahmeBMWi-ForschungsnetzwerkBioenergieBiomasseundBioenergiealsTeilderWasserstoffwirtschaft[Internet].[placeunknown];[accessed2021Oct4].https://www.energetische-biomassenutzung.de/fileadmin/media/6_Publikationen/Stellungnahmen/Stellungnahme_FNBioE_H2-BM_final.pdfBennettJA,MelaraAJ,ColosiLM,ClarensAF.2019.Lifecycleanalysisofpowercycleconfigurationsinbioenergywithcarboncaptureandstorage.ProcediaCIRP[Internet].[accessed2021Mar5]80:340–345.https://doi.org/10.1016/j.procir.2018.12.014BennettSJ,SchroederDJ,McCoyST.2014.TowardsaFrameworkforDiscussingandAssessingCO2UtilisationinaClimateContext.EnergyProcedia.63:7976–7992.https://doi.org/10.1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