Breaking the Biological Barriers to Celluloic Ethanol: A Joint Research Agenda

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DOE/SC-0095

BreakingtheBiologicalBarrierstoCellulosicEthanol: AJointResearchAgenda

AResearchRoadmapResultingfromthe

BiomasstoBiofuelsWorkshop December79,2005 Rockville,Maryland

WorkshopSponsoredbythe

U.S.DepartmentofEnergy

OfficeofEnergyEfficiency OfficeofScienceandRenewableEnergy OfficeofBiologicalandEnvironmentalResearchOfficeoftheBiomassProgram Genomics:GTLProgram

PublicationDate:June2006


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ExecutiveSummaryWell also fund additional research in cuttingedge methods of producingethanol, not just from corn, but from wood chips and stalks or switchgrass.

PresidentGeorgeW.Bush,StateoftheUnionAddress,January2006*

Arobustfusionoftheagricultural,industrialbiotechnology,andenergyindustriescancreateanewstrategicnationalcapabilityforenergyindependenceandclimateprotection.InhisStateofthe

UnionAddress(*Bush2006),PresidentGeorgeW.BushoutlinedtheAdvancedEnergyInitiative,whichseekstoreduceournationaldependenceonimportedoilbyacceleratingthedevelopmentofdomestic,renewablealternativestogasolineanddieselfuels.Tepresidenthassetanationalgoalofdevelopingcleaner,cheaper,andmorereliablealternative

energysourcestosubstantiallyreplaceoilimportsinthecomingyears.Fuelsderivedfromcellulosicbiomassthefibrous,woody,andgenerallyinedibleportionsofplantmatterofferonesuchalternativetoconventionalenergysourcesthatcandramaticallyimpactnationaleconomicgrowth,nationalenergysecurity,andenvironmentalgoals.Cellulosicbiomassisanattractiveenergyfeedstockbecauseitisanabundant,domestic,renewablesourcethatcanbeconvertedtoliquidtransportationfuels.

Tesefuelscanbeusedreadilybycurrent-generationvehiclesanddistributedthroughtheexistingtransportation-fuelinfrastructure.

TeBiomasstoBiofuelsWorkshop,heldDecember79,2005,wasconvenedbytheDepartmentofEnergysOfficeofBiologicalandEnvironmentalResearchintheOfficeofScience;andtheOfficeoftheBiomassProgramintheOfficeofEnergyEfficiencyandRenewableEnergy.

Tepurposewastodefinebarriersandchallengestoarapidexpansionofcellulosic-ethanolproductionanddeterminewaystospeedsolutionsthroughconcertedapplicationofmodernbiologytoolsaspartofajointresearchagenda.Althoughthefocuswasethanol,thescienceappliestoadditionalfuelsthatincludebiodieselandotherbioproductsorcoproductshavingcriticalrolesinanydeploymentscheme.

Tecorebarrieriscellulosic-biomassrecalcitrancetoprocessingtoethanol.Biomassiscomposedofnaturesmostreadyenergysource,sugars,buttheyarelockedinacomplexpolymercompositeexquisitelycreatedtoresistbiologicalandchemicaldegradation.Keytoenergizinganewbiofuel

industrybasedonconversionofcellulose(andhemicelluloses)toethanolistounderstandplantcell-wallchemicalandphysicalstructureshowtheyaresynthesizedandcanbedeconstructed.Withthisknowledge,innovativeenergycropsplantsspecificallydesignedforindustrialprocessingtobiofuelcanbedevelopedconcurrentlywithnewbiology-basedtreatmentandconversionmethods.Recentadvancesinscienceandtechnologicalcapabilities,especiallythosefromthenascentdisciplineofsystemsbiology,promisetoaccelerateandenhancethisdevelopment.Resultingtechnologies

*www.whitehouse.gov/stateoftheunion/2006/

BiofuelsJointRoadmap,June2006 OfficeofScienceandOfficeofEnergyEfficiencyandRenewableEnergy U.S.DepartmentofEnergy
http://www.whitehouse.gov/stateoftheunion/2006http://www.whitehouse.gov/stateoftheunion/2006


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Executive Summary

willcreateafundamentallynewprocessandbiorefineryparadigmthatwillenableanefficientandeconomicindustryforconvertingplantbiomasstoliquidfuels.Tesekeybarriersandsuggestedresearchstrategiestoaddressthemaredescribedinthisreport.

Astechnologiesmatureforaccomplishingthistask,thetechnicalstrategy

proceedsthroughthreephases:Intheresearchphase,within5years,anunderstandingofexistingfeedstocksmustbegainedtodevisesustainable,effective,andeconomicalmethodsfortheirharvest,deconstruction,andconversiontoethanol.Researchiscenteredonenzymaticbreakdownofcellulosicbiomasstocomponent5-and6-carbonsugarsandlignin,usingacombinationofthermochemicalandbiologicalprocesses,followedbycofermentationofsugarstospecifiedendproductssuchasethanol.Processeswillbeintegratedandconsolidatedtoreducecosts,improveefficacy,reducegenerationofandsensitivitytoinhibitors,andimproveoverall

yieldsandviabilityinbiorefineryenvironments.

Tetechnologydeploymentphase,within10years,willincludecreationof

anewgenerationofenergycropswithenhancedsustainability,yield,andcomposition,coupledwithprocessesforsimultaneousbreakdownofbiomasstosugarsandcofermentationofsugarsvianewbiologicalsystems.

Teseprocesseswillhaveenhancedsubstraterange,temperatureandinhibitortolerance,andthecapabilitytofunctionincomplexbiorefiningenvironmentsandovertimescalesthatareeconomicallyviable.

Tesystems-integrationphase,within15years,willincorporateconcurrentlyengineeredenergycropsandbiorefineriestailoredforspecificagroecosystems.Employingnewandimprovedenzymesforbreakingbiomassdowntosugarsaswellasrobustfermentationprocessesjointlyconsolidatedintoplantsormicrobes,thesehighlyintegratedsystemswill

accelerateandsimplifytheend-to-endproductionoffuelethanol.Inmanyways,thesefinal-phasetechnologieswillstrivetoapproachtheoreticalconversionlimits.Tenewgenerationofbiotechnologieswillspurengineeringofflexiblebiorefineriesoperableindifferentagriculturalregionsofthecountryandtheworld.

Tesuccessofthisprogramforeffectivelyconvertingcellulosicbiomasstoethanolwillbebasedoncouplingsophisticatedengineeringwithfundamentalbiologicalresearch.Tenewgenerationofbiologicalresearchsystemsbiologyisbuiltonthenationalinvestmentingenomics.Systemsbiologyinvolvesnewtechnologiesforincreasinglydetailedhigh-throughputanalysesandcomputingtomaketransparentthecomplexitiesofbiologyandallowpredictiveunderstandingandrationaldesign.Multidisciplinaryteamresearchapproacheswillacceleratescientificprogressanditstranslationtonewbiorefineryprocesses.Comprehensivesuitesoftechnologies,someinresearcherslaboratoriesandsomeconsolidatedinfacilities,willenhancetechnicalperformance,improveproductivity,andreducecoststoallowaffordableandtimelyprogresstowardthesegoals.Newresearchcapabilitiesandfacilitieswillserveasanengineforfundamentalresearch,technologydevelopment,andcommercialization.

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Contents

Executive Summary..............................................................................................................................................................................iii

Introduction.............................................................................................................................................................................................1

Joint Workshop Challenges Biofuel Science and Technology Communities.........................................................................................1

Americas Energy Challenges...................................................................................................................................................................2

ThePromiseofBiofuels.........................................................................................................................................................................2

A Growing Mandate for Biofuels: Policy, Legislative, and Other Drivers..............................................................................................3

Benefits of Biofuels..................................................................................................................................................................................5

NationalEnergySecurityBenefits.........................................................................................................................................................6

EconomicBenefits.................................................................................................................................................................................6

EnvironmentalBenefits.........................................................................................................................................................................7

Feasibility of Biofuels...............................................................................................................................................................................8

LandAvailability....................................................................................................................................................................................8

AgriculturalSustainabilityofBiomassProduction...............................................................................................................................12TodayFuelEthanolProductionfromCornGrain(StarchEthanol).....................................................................................................12

TomorrowBiorefineryConcepttoProduceFuelEthanolfromCellulosicBiomass.............................................................................13

Ethical,Legal,andSocialIssues(ELSI).................................................................................................................................................17

EERE OBP Platform for Integrated Biorefineries..................................................................................................................................17

DOE Office of Science Programs.............................................................................................................................................................19

Biomass to Biofuels Workshop: Creating a Common Research Agenda to Overcome Technology Barriers.....................................22

Cited References.....................................................................................................................................................................................24

Background Reading..............................................................................................................................................................................28

Technical Strategy: Development of a Viable Cellulosic Biomass to Biofuel Industry...................................................29Research Phase (within 5 years)............................................................................................................................................................29

FeedstockUseandOptimization..........................................................................................................................................................29

Deconstruction....................................................................................................................................................................................30

FermentationandRecovery.................................................................................................................................................................31

Technology Deployment Phase (within 10 years)................................................................................................................................32

Feedstocks...........................................................................................................................................................................................34

Deconstruction....................................................................................................................................................................................34

FermentationandRecovery.................................................................................................................................................................34

Systems Integration Phase (within 15 years).......................................................................................................................................34

IntegrationandConsolidation.............................................................................................................................................................35

SYSTEMS BIOLOGY TO OVERCOME BARRIERS TO CELLULOSIC ETHANOL................................................................................37

Lignocellulosic Biomass Characteristics.......................................................................................................................................39

Structure and Assembly of Cell Walls....................................................................................................................................................41

Factors in Recalcitrance of Lignocellulose Processing to Sugars.........................................................................................................44

PlantArchitecture...............................................................................................................................................................................45

Cell-WallArchitecture..........................................................................................................................................................................45



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CONTENTS

MolecularStructure.............................................................................................................................................................................45

Optimization of Plant Cell Walls............................................................................................................................................................47

UnderstandingCell-WallStructureandFunction.................................................................................................................................47

ControlofLigninSynthesisandStructure............................................................................................................................................49

Improved Methods, Tools, and Technologies........................................................................................................................................50Technical Milestones..............................................................................................................................................................................51


Feedstocksfor Biofuels.......................................................................................................................................................................57

Creation of a New Generation of Lignocellulosic Energy Crops...........................................................................................................60

MaximizingBiomassProductivity.......................................................................................................................................................61

TechnicalMilestones...........................................................................................................................................................................67

Ensuring Sustainability and Environmental Quality............................................................................................................................68


Model Systems for Energy Crops............................................................................................................................................................71


The Role of GTL Capabilities for Systems Biology .................................................................................................................................74

ProteinProductionCapabilities...........................................................................................................................................................74

MolecularMachinesCapabilities.........................................................................................................................................................75

ProteomicCapabilities.........................................................................................................................................................................75

CellularSystemCapabilities.................................................................................................................................................................75

DOEJointGenomeInstitute.................................................................................................................................................................76

OtherNeededCapabilities...................................................................................................................................................................76

Other Biofuel Opportunities: Development of High-Productivity Biodiesel Crops............................................................................77


For Further Reading...............................................................................................................................................................................81

Deconstructing Feedstocks to Sugars............................................................................................................................................85

Determining Fundamental Physical and Chemical Factors in the Recalcitrance of Lignocellulosic Biomass to Processing ...........86

ResearchGoals....................................................................................................................................................................................88


TheRoleofGTLandOBPFacilitiesandCapabilities.............................................................................................................................90

CrosscuttingTools,Technologies,andScience......................................................................................................................................91

Developing Better Enzymatic Systems for Biological Pretreatment: Ligninases and Hemicellulases.............................................91

ResearchGoals....................................................................................................................................................................................92


CrosscuttingTools,Technologies,andScience......................................................................................................................................97

Understanding the Molecular Machinery Underpinning Cellulose Saccharification: Cellulases and Cellulosomes .......................97

ResearchGoals....................................................................................................................................................................................98

TechnicalMilestones.........................................................................................................................................................................101

CrosscuttingTools,Technologies,andScience....................................................................................................................................103

TheRoleofGTLandOBPFacilitiesandCapabilities...........................................................................................................................104

Harvesting the Biochemical Potential of Microorganisms Through Metagenomics .......................................................................105

ResearchGoals..................................................................................................................................................................................106

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Characterizing Cell Walls Using High-Throughput Methods..............................................................................................................108



CrosscuttingTools,Technologies,andScience....................................................................................................................................112

Breakthrough, High-Payoff Opportunity: Simplifying the Bioconversion Process by Understanding Cell-WallDeconstruction Enzymes Expressed in Plants....................................................................................................................................113

ScientificChallengesandOpportunities............................................................................................................................................113

ResearchGoals..................................................................................................................................................................................113

References............................................................................................................................................................................................115

Cellulosome References.......................................................................................................................................................................117

CellulosomeReviews.........................................................................................................................................................................117

DesignerCellulosomes......................................................................................................................................................................117

Sugar Fermentation to Ethanol.....................................................................................................................................................119Optimizing Microbial Strains for Ethanol Production: Pushing the Limits of Biology.....................................................................122

ScienceChallengesandStrategy.......................................................................................................................................................124


TheRoleofGTLCapabilities...............................................................................................................................................................131

Advanced Microorganisms for Process Simplification.......................................................................................................................132

ScienceChallengesandStrategiesforProcessSimplification............................................................................................................135


TheRoleofGTLCapabilities...............................................................................................................................................................138

Enabling Microbiological Tools and Technologies that Must be Developed.....................................................................................138

Breakthrough, High-Payoff Opportunities.........................................................................................................................................140MicrobialCommunitiesforRobustEnergyProduction.......................................................................................................................140

Model-DrivenDesignofCellularBiocatalyticSystemsUsingSystemsBiology...................................................................................142

DirectBioproductionofEnergy-RichFuels.........................................................................................................................................147

OptimalStrains:FermentativeProductionof40%EthanolfromBiomassSugars..............................................................................149

AnAlternativeRouteforBiomasstoEthanol:MicrobialConversionofSyngas...................................................................................152

Cited References...................................................................................................................................................................................154

Crosscutting 21st Century Science, Technology, and Infrastructure for a New Generationof Biofuel Research............................................................................................................................................................................155

Opportunities and Challenges ............................................................................................................................................................155

Analytical Tools to Meet the Challenges of Biofuel Research............................................................................................................156Genomics..........................................................................................................................................................................................156

Transcriptomics:High-ThroughputExpressionAnalyses....................................................................................................................158

Proteomics........................................................................................................................................................................................158

Metabolomics...................................................................................................................................................................................159

GlycomicsandLignomics..................................................................................................................................................................160

Fluxomics..........................................................................................................................................................................................161

EnzymeStructureandFunction.........................................................................................................................................................162



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CONTENTS

Imaging Technologies..........................................................................................................................................................................163

ImagingNeedsforFeedstockResearch..............................................................................................................................................163

ImagingNeedsforMicrobialCommunitiesinDeconstructionandConversionofBiomasstoEthanol...............................................164

Microbial Cultivation............................................................................................................................................................................165

Data Infrastructure...............................................................................................................................................................................166Computational Modeling.....................................................................................................................................................................168

Modeling:GenomeSequenceAnalysis..............................................................................................................................................168

Modeling:Molecular.........................................................................................................................................................................170

Modeling:PathwaysandNetworks...................................................................................................................................................171

Modeling:BiorefineryProcess...........................................................................................................................................................171

Capability Suites for Bioenergy Research and Facility Infrastructure..............................................................................................172

DOEJointGenomeInstitute...............................................................................................................................................................173

ProductionandCharacterizationofProteinsandMolecularTags......................................................................................................173

CharacterizationandImagingofMolecularMachines......................................................................................................................175

AnalysisofGenomeExpression:TheOmics.......................................................................................................................................176

AnalysisandModelingofCellularSystems.......................................................................................................................................178

Cited References...................................................................................................................................................................................180

Bioprocess Systems Engineering and Economic Analysis.....................................................................................................181

Research Goals......................................................................................................................................................................................181

Milestones.........................................................................................................................................................................................182


APPENDICES.........................................................................................................................................................................................185

Appendix A. Provisions for Biofuels and Biobased Products in the Energy Policy Act of 2005..................................186

Appendix B. Workshop Participants.............................................................................................................................................188

Appendix C. Workshop Participant Biosketches......................................................................................................................192

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INTRODUCTION

Tecurrentapproachtointroducingbiofuelsreliesonanevolutionarybusinessandeconomicdriverforasteadybutmoderateentryintothemarket.echnologiesforimplementingthisnewindustryarebeingtestedeitherbyproducinghigher-valueproductsfromrenewables(suchaslacticacid)orasincrementaladditionstocurrentcorn-ethanolrefineries(suchastheconversionofresidualcorn-kernelfiberstoethanol).

Tisreportisaworkshop-producedroadmapforacceleratingcellulosicethanolresearch,helpingmakebiofuelspracticalandcost-competitiveby2012($1.07/galethanol)andofferingthepotentialtodisplaceupto30%ofthenationscurrentgasolineuseby2030.ItarguesthatrapidlyincorporatingnewsystemsbiologyapproachesviasignificantR&Dinvestmentwillspuruseofthesetechnologiesforexpandedprocessingofenergycropsandresidues.Furthermore,thisstrategywilldecreaseindustrialriskfromuseofafirst-of-a-kindtechnology,allowingfasterdeploymentwithimprovedmethods.Ultimately,theseapproachesfostersettingmoreaggressivegoalsforbiofuelsandenhancethestrategyssustainability.

AmericasEnergyChallengesTetripleenergy-relatedchallengesofthe21stCenturyareeconomicandenergygrowth,energysecurity,andclimateprotection.TeUnitedStatesimportsabout60%ofthepetroleumitconsumes,andthatdependencyisincreasing.*SincetheU.S.economyistiedsocloselytopetroleumproductsandoilimports,disruptionsinoilsuppliescanresultinsevereeconomicandsocialimpacts.Conventionaloilproductionwillpeakinthenearfuture,andtheresultingenergytransitionwillrequireaportfolioofresponses,includingunconventionalfossilresourcesandbiofuels.Environmentalqualityandclimatechangeduetoenergyemissionsareadditionalconcerns.AnnualU.S.transportationemissionsofthegreenhousegas(GHG)carbondioxide

(CO2)areprojectedtoincreasefromabout1.9billionmetrictonsin2004toabout2.7billionmetrictonsin2030(EIA2006).

ThePromiseofBiofuelsFuelsderivedfromcellulosicbiomass**thefibrous,woody,andgenerallyinedibleportionsofplantmatterofferanalternativetoconventionalenergysourcesthatsupportsnationaleconomicgrowth,nationalenergysecurity,andenvironmentalgoals.Cellulosicbiomassisanattractiveenergyfeedstockbecausesuppliesareabundantdomesticallyandglobally.Itisarenewablesourceofliquidtransportationfuelsthatcanbeusedreadilybycurrent-generationvehiclesanddistributedthroughtheexistingtranspor

tation-fuelinfrastructure.Ethanolfromcorngrainisanincreasinglyimportantadditivefuelsource,butithaslimitedgrowthpotentialasaprimarytransportationfuel.***TeU.S.starch-basedethanolindustry

willjumpstartagreatlyexpandedethanolindustrythatincludescellulosicethanolasamajortransportationfuel.

Celluloseandhemicelluloses,foundinplantcellwalls,aretheprimarycomponentofbiomassandthemostplentifulformofbiologicalmaterialonearth.Teyarepolysaccharidesmadeupofenergy-richsugarsthatcanbeconvertedtoethanol(seesidebar,UnderstandingBiomass,p.53).Current

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methodstobreakdownbiomassintosimplesugarsandconvertthemintoethanolareinefficientandconstitutethecorebarriertoproducingethanolatquantitiesandcostscompetitivewithgasoline.

Biologicalresearchisundergoingamajortransformation.Tesystemsbiologyparadigmbornofthegenomerevolutionandbasedonhigh-

throughputadvancedtechnologies,computationalmodeling,andscientific-teamapproachescanfacilitaterapidprogressandisareadilyapplicablemodelforbiofueltechnology.SystemsbiologyisthecoreoftheOBERGenomics:GLprogram,whosegoalistoachieveapredictiveunderstandingofthecomplexnetworkofinteractionsthatunderpinthebiologicalprocessesrelatedtobiofuelproduction.BiologicalchallengestowhichGLcanapplysystemsbiologyapproachesincludeenhancingtheproductivityofbiomasscropsoptimizedforindustrialprocessing,improvingenzymesystemsthatdeconstructplantcellwalls,andincreasingtheyieldofethanol-producingmicroorganisms.Systemsbiologytoolsandknowledgewillenablerationalengineeringofanewgenerationofbioenergysystemsmadeupofsustainableenergycropsforwidelyvaryingagroecosystemsandtai

loredindustrialprocesses.Tisresearchapproachwillencouragethecriticalfusionoftheagriculture,industrialbiotechnology,andenergysectors.

AGrowingMandateforBiofuels:Policy,Legislative,andOtherDrivers

Aprimarygoalofthepresidents2001NationalEnergyPolicy(NEP)istoincreaseU.S.energysupplies,incorporatingamorediversemixofdomesticresourcestosupportgrowthindemandandtoreducenationaldependenceonimportedoil(NEPDG2001).AEIacceleratesandexpandsonseveralpolicyandlegislativemandates(AEI2006).Itaimsto

reducethenationsrelianceonforeignoilintheneartermandprovidesa22%increaseinclean-energyresearchatDOEforFY2007,acceleratingprogressinrenewableenergy.

AccordingtoAEI,theUnitedStatesmustmovebeyondapetroleum-basedeconomyanddevisenewwaystopowerautomobiles.Tecountryneedstofacilitatedomestic,renewablealternativestogasolineanddieselfuels.Teadministrationwillaccelerateresearchincutting-edgemethodsofproducingsuchhomegrownrenewablebiobasedtransportationfuelsasethanolfromagriculturalandforestryfeedstocksincludingwoodchips,

*Gasolineanddieselconstituted98%ofdomestictransportationmotorfuelsin2004,withethanolfromcorngrainsupplyingmostoftheremaining2%.Annualgasoline

consumptionin2004wasabout139billiongallons,and3.4billiongallonsofethanolwereusedprimarilyasafuelextendertoboostgasolineoctanelevelsandimprovevehicleemissions.

**Cellulosicbiomass,alsocalledlignocellulosicbiomass,isacomplexcompositematerialconsistingprimarilyofcelluloseandhemicellulose(structuralcarbohydrates)bondedtolignininplantcellwalls.Forsimplification,weusethetermcellulosicbiomass.

***In2004,11%oftheU.S.cornharvestyielded3.4billiongallonsofethanol(NRDC2006),roughly1.7%ofthe2004fueldemand.TusifallcorngrainnowgrownintheUnitedStateswereconvertedtoethanol,itwouldsatisfyabout15%ofcurrenttransportationneeds.



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INTRODUCTION

stalks,andswitchgrass.AEIwouldfostertheearlycommercializationofadvancedbiofueltechnologies,enablingU.S.industrytoleadindeployingbiofuelsandchemicalsinternationally.

Achievingthegoalofdisplacing30%ofthenationscurrentgasolineuseby2030wouldrequireproductionlevelsequaltoroughly60billiongallonsa

year(Bgal/year)ofethanol(seeable1.Comparisonsof2004GasolineandEthanolEquivalents,thispage).Anannualsupplyofroughlyabilliondrytonsofbiomasswillbeneededtosupportthislevelofethanolproduction.

ArecentreportbytheU.S.DepartmentofAgriculture(USDA)andDOEfindspotentialtosustainablyharvestmorethan1.3billionmetrictonsofbiomassfromU.S.forestandagriculturallandsbymid-21stCentury(Perlacketal.2005).InvestmentsinR&Dandinfrastructureareneededtorealizethisfeedstockpotential.

TeU.S.EnergyPolicyActof2005(EPAct;AppendixA,Provisionsfor

BiofuelsandBiobasedProductsintheEnergyPolicyActof2005,p.186)hasestablishedaggressivenear-termtargetsforethanolproduction.Akeyprovisionrequiresmixing4Bgalofrenewablefuelwithgasolinein2006.

Tisrequirementincreasesannuallyto7.5Bgalofrenewablefuelby2012.For2013andbeyond,therequiredvolumewillincludeaminimumof250milliongallons(Mgal)ofcellulosicethanol.AnothersectionoftheEPActauthorizesfundsforanincentiveprogramtoensuretheannualproductionof1Bgalofcellulosicbiomass-basedfuelsby2015.Ethanolisthemostcommonbiofuelproducedfromcellulose,butotherpossiblebiofuelcompoundscanbeproducedaswell.

OtherimportantlegislativedriverssupportingbiofuelsaretheBiomassR&DActof2000anditleIXoftheFarmBill2002(U.S.Congress2000;U.S.

Congress2002).TeBiomassR&DActdirectedthedepartmentsofEnergyandAgriculturetointegratetheirbiomassR&DandestablishedtheBiomassResearchandDevelopmentechnicalAdvisoryCommittee(BAC),which

advisestheSecretaryofEnergyandtheSecretaryofAgricultureonstra-Table1.Comparisonsof2004GasolineandEthanolEquivalents

2004Gasoline

(billion gallons)

Ethanol Equivalents

(billion gallons)

U.S.consumption,2004 139 200

About60%fromimports 83 120

Requirements to displace 30% of 2004 U.S.consumption

42 60

Biomassrequirementsat80gal/ton 750Mton

Landrequirementsat10ton/acreand80gal/ton

75Macre

Numbersofrefineriesat100Mgal/refinery

600(eachrequiring160miles2netor125,000acres)

tegicplanningforbiomassR&D.Asaprecedenttothecurrentpresidentialinitiative,in2002BACsetagoalrequiringbiofuelstomeet20%ofU.S.transportationfuelconsumptionby2030aspartofitsvisionforbiomass

technologies(BAC2002).itleIXsupportsincreaseduseofbiobasedfuelsandproductsandincentivesandgrantsforbiofuelandbiorefineryR&D.

Inadditiontolegislativemandates,severalindependentstudieshaveacknowledgedthegreatpotentialofbiofuelsinachievingamorediversedomesticenergysupply(NCEP2004;Greeneetal.2004;Lovinsetal.2005).Growing



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supportfordevelopingbiomassasakeyenergyfeedstockiscomingfromavarietyofnationalandinternationalorganizations(GEC2005;AgEnergyWorkingGroup2004;IEA2004).Althoughthesereportsdifferintheamountsofgasolinethatcouldbereplacedbyethanolfrombiomass,theyallagreeonthreekeyissues:(1)Currenttrendsinenergyusearenotsustainableandareasecurityrisk;(2)Nosinglesolutionwillsecuretheenergyfutureadiverseportfolioofenergyoptionswillberequired;and(3)Biofuelscanbeasignificantpartofthetransportationsectorsenergysolution.

Initsevaluationofoptionsfordomesticproductionofmotorfuels,theNationalCommissiononEnergyPolicy(NCEP)recommendedcellulosicbiomassasanimportanttopicfornear-termfederalresearch,development,anddemonstrationandfoundthatcellulosicethanolhasthepotentialtomakeameaningfulcontributiontothenationstransportationfuelsupplyinthenexttwotothreedecades(NCEP2004).

TeNaturalResourcesDefenseCouncil(NRDC)hasprojectedthatanaggressiveplantodevelopcellulosicbiofuelsintheUnitedStatescouldproducetheequivalentofnearly7.9millionbarrelsofoilperdayby2050morethan50percentofourcurrenttotaloiluseinthetransportationsectorandmorethanthreetimesasmuchasweimportfromthePersianGulfalone(Greeneetal.2004).Tiscorrespondstoroughly100Bgal/yearethanol.NRDCalsorecommends$1.1billioninfundingbetween2006and2012forbiomassresearch,development,anddemonstrationwith45%ofthisfundingfocusedonovercomingbiomassrecalcitrancetoethanolprocessing.Tisleveloffundingisexpectedtostimulatearegularflowofadvancesneededtomakeethanolcost-competitivewithgasolineanddiesel.

AnindependentanalysisfromtheRockyMountainInstitutefoundthat

significantgainsinenergyefficiencyandthelarge-scaledisplacementofoilwithbiofuels,mainlycellulosicethanol,wouldbekeycomponentsofitsstrategytoreduceAmericanoildependenceoverthenextfewdecades(Lovinsetal.2005).

oillustratethewidespreadsupportforfuelethanol,theGovernorsEthanolCoalition,anorganizationdevotedtothepromotionandincreaseduseofethanol,nowincludes32memberstatesaswellasinternationalrepresentativesfromBrazil,Canada,Mexico,Sweden,andTailand.Inarecentreport,thecoalitioncalledforrapidexpansionofethanoltomeetatleast10%oftransportationfuelneedsassoonaspracticableandfordevelopmentoflignocellulosic-basedfuelsforexpansionbeyondthoselevels

(GEC2005).Teuseofethanol,particularlybiomass-derivedethanol,canproducesignificantsavingsincarbondioxideemissions.Tisapproachoffersano-regretspolicythatreducesthepotentialfuturerisksassociated

withclimatechangeandhastheaddedbenefitofeconomicdevelopment.

BenefitsofBiofuelsBiofuels,especiallycorn-derivedandcellulosicethanol,constitutetheonlyrenewableliquidtransportationfueloptionthatcanbeintegratedreadily

withpetroleum-basedfuels,fleets,andinfrastructure.Productionanduse



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INTRODUCTION

ofbiofuelscanprovidesubstantialbenefitstonationalenergysecurity,economicgrowth,andenvironmentalquality.

NationalEnergySecurityBenefitsNational security is linked to energy through the dependence of thiscountry and many others on imported oilmuch of it located in

politically troubled parts of the globe. As such, the potential for largescale failures in the global production and distribution system presentsa real threat. GovernorsEthanolCoalition(GEC2005)

odaytheUnitedStatesisdependentonoilfortransportation.Alternative,domesticallybased,andsustainablefuel-developmentstrategies,therefore,areessentialtoensuringnationalsecurity.Americaaccountsfor25%ofglobaloilconsumptionyetholdsonly3%oftheworldsknownoilreserves.About60%ofknownoilreservesarefoundinsensitiveand

volatileregionsoftheglobe.Increasingstrainonworldoilsupplyisexpectedasdevelopingcountriesbecomemoreindustrializedandusemoreenergy.AnystrategytoreduceU.S.relianceonimportedoilwillinvolveamixofenergytechnologiesincludingconservation.Biofuelsareanattractiveoptiontobepartofthatmixbecausebiomassisadomestic,secure,andabundantfeedstock.Globalavailabilityofbiomassfeedstocksalsowouldprovideaninternationalalternativetodependenceonanincreasinglystrainedoil-distributionsystemaswellasareadymarketforbiofuel-productiontechnologies.

EconomicBenefitsAbiofuelindustrywouldcreatejobsandensuregrowingenergysupplies

tosupportnationalandglobalprosperity.In2004,theethanolindustrycreated147,000jobsinallsectorsoftheeconomyandprovidedmorethan$2billionofadditionaltaxrevenuetofederal,state,andlocalgovernments(RFA2005).Conservativeprojectionsoffuturegrowthestimatetheadditionof10,000to20,000jobsforeverybilliongallonsofethanolproduction(Petrulis1993).

In2005theUnitedStatesspentmorethan$250billiononoilimports,andthetotaltradedeficithasgrowntomorethan$725billion(U.S.CommerceDept.2006).Oilimports,whichmakeup35%ofthetotal,couldriseto70%overthenext20years(EthanolAcrossAmerica2005).

Amongnationaleconomicbenefits,abiofuelindustrycouldrevitalize

strugglingruraleconomies.Bioenergycropsandagriculturalresiduescanprovidefarmerswithanimportantnewsourceofrevenueandreducerelianceongovernmentfundsforagriculturalsupport.Aneconomicanalysis

jointlysponsoredbyUSDAandDOEfoundthattheconversionofsomecroplandtobioenergycropscouldraisedepressedtraditionalcroppricesbyupto14%.Higherpricesfortraditionalcropsandnewrevenuefrombioenergycropscouldincreasenetfarmincomeby$6billionannually(DeLa

orreUgarte2003).



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Fig. 1. Reduced Carbon

Dioxide Emissions of Ethanol

from Biomass.Whencom

paredwithgasoline,ethanol

fromcellulosicbiomasscould

dramaticallyreduceemissionsofthegreenhousegas,carbon

dioxide(CO ).Althoughburn2

inggasolineandotherfossil

fuelsincreasesatmospheric

CO concentrations,thepho2

tosyntheticproductionofnew

biomasstakesupmostofthe

carbondioxidereleasedwhen

bioethanolisburned.[Source:

AdaptedfromORNL Review(www.ornl.gov/info/ornlreview/

v33_2_00/bioenergy.htm)]

EnvironmentalBenefits

ClimateChange

Whenfossilfuelsareconsumed,carbonsequesteredfromtheglobalcarboncycleformillionsofyearsisreleasedintotheatmosphere,whereitaccumulates.BiofuelconsumptioncanreleaseconsiderablylessCO

2,

dependingonhowitisproduced.TephotosyntheticproductionofnewgenerationsofbiomasstakesuptheCO releasedfrombiofuelproduction

2

anduse(seeFig.1.ReducedCarbonDioxideEmissionsofEthanolfromBiomass,thispage).Alife-cycleanalysisshowsfossilCO

2emissionsfrom

cellulosicethanoltobe85%lowerthanthosefromgasoline(Wang2005).Teseemissionsarisefromtheuseoffossilenergyinproducingcellulosicethanol.NonbiologicalsequestrationofCO

2producedbythefermentation

processcanmakethebiofuelenterprisenetcarbonnegative.

Arecentreport(Farrelletal.2006)findsthatethanolfromcellulosicbiomassreducessubstantiallybothGHGemissionsandnonrenewable

energyinputswhencomparedwithgasoline.Telowquantityoffossilfuelrequiredtoproducecellulosicethanol(andthusreducefossilGHGemissions)isduelargelytothreekeyfactors.Firstistheyieldofcellulosicbiomassperacre.Currentcorn-grainyieldsareabout4.5tons/acre.Starchis66%byweight,yielding3tonstoproduce416galofethanol,comparedtoanexperimentalyieldof10drytonsofbiomass/acreforswitchgrasshybridsinresearchenvironments(10drytonsatafuture

yieldof80gal/ton=800galethanol).Useofcorngrain,theremainingsolids(distillersdriedgrains),andstovercouldyieldethanolatroughly

http://www.ornl.gov/info/ornlreviewhttp://www.ornl.gov/info/ornlreview


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INTRODUCTION

700gal/acre.Currentyieldfornonenergy-cropbiomassresourcesisabout5drytons/acreandroughly65gal/ton.Tegoalforenergycropsis10tons/acreat80to100gal/tonduringimplementation.Second,perennialbiomasscropswilltakefarlessenergytoplantandcultivateandwillrequirelessnutrient,herbicide,andfertilizer.Tird,biomasscontainsligninandotherrecalcitrantresiduesthatcanbeburnedtoproduceheatorelectricityconsumedbytheethanol-productionprocess.

Energycropsrequireenergyinputsforproduction,transportation,andprocessingaviablebioenergyindustrywillrequireasubstantialpositiveenergybalance.Figure2.ComparisonofEnergyYieldswithEnergyExpenditures,thispage,comparesresultsforcellulosicandcornethanol,gasoline,andelectricity,demonstratingasubstantiallyhigheryieldforcellulosicethanol.Overtimeamaturebioenergyeconomywillsubstitutebiomass-derivedenergysourcesforfossilfuel,furtherreducingnetemissions.

Fig. 2. Comparison of Energy Yields with Energy Expendi

tures.Tefossilenergyreplacementratio(FER)compares

energyyieldfromfourenergysourceswiththeamountoffos-

silfuelusedtoproduceeachsource.Notethatthecellulosic

ethanolbiorefinerysprojectedyieldassumesfuturetechno-

logicalimprovementsinconversionefficienciesandadvances

thatmakeextensiveuseofabiomasscropsnoncellulosic

portionsforcogenerationofelectricity.SimilarassumptionswouldraisecornethanolsFERif,forexample,cornstover

weretoreplacecurrentnaturalgasusage.Tecornethanol

industry,alreadyproducingethanolasanimportantadditive

andfuelextender,isprovidingafoundationforexpansion

tocellulosicethanol.[Source:Figure,basedontheArgonne

NationalLaboratoryGREEmodel,isderivedfromBrink-

manetal.2005.Otherpapersthatsupportthisstudyinclude

Farrelletal.2006andHammerschlag2006.]

OtherEnvironmentalBenefitsPerennialgrassesandotherbioenergycropshavemanysignificantenvironmentalbenefitsovertraditionalrowcrops(seeFig.3.MiscanthusGrowthoveraSingleGrowingSeasoninIllinois,p.9).Perennialenergycropsprovideabetterenvironmentformore-diversewildlifehabitation.Teirextensiverootsystemsincreasenutrientcapture,improvesoilquality,sequestercarbon,andreduceerosion.Ethanol,whenusedasatransportationfuel,emitslesssulfur,carbonmonoxide,particulates,andGHGs

(Greeneetal.2004).

FeasibilityofBiofuelsTeUnitedStatescouldbenefitsubstantiallybyincreasingitsuseofdomestic,renewablefuelsinthetransportationsector,butcanbiofuelsbeproducedatthescaleneededtomakearealdifferenceintransportationconsumptionoffossilfuels?Morespecifically,isthereenoughlandtoprovidetheneededlarge-scalesupplyofbiomass,istheuseofbiofuelssustainableagriculturally,canbiofuels

becomecost-competitivewithgasoline,andiscellulosic-biofuelproductiontechnicallyfeasibleforenergy?Teshortanswertoallthesequestionsis

yes,andthissectionsummarizesrecentreportsthatsupportthisview.

LandAvailabilityAmajorfactorinfluencingtheextenttowhichbiofuelswillcontributetoAmericasenergyfutureistheamountoflandavailableforbiomassharvesting.



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Arebiomassresourcessufficienttomeetasignificantportionoftransportation-fuelconsumption,andhowwouldharvestingbiomassforenergyaffectcurrentagriculturalandforestrypractices?

In2005,astudyjointlysupportedbyDOEandUSDAexaminedwhetherlandresourcesintheUnitedStatesaresufficienttosustainproductionofover1billiondrytonsofbiomassannually,enoughtodisplace30%ormoreofthe

nationscurrentconsumptionofliquidtransportationfuels.Byassumingrelativelymodestchangesinagriculturalandforestrypractices,thisstudyprojectsthat1.366billiondrytonsofbiomasscouldbeavailableforlarge-scalebioenergyandbiorefineryindustriesbymid21stCenturywhilestillmeetingdemandforforestryproducts,food,andfiber(Perlacketal.2005)(seesidebar,ABillion-onAnnualSupplyofBiomass,p.10).Tissupplyofbiomasswouldbeasevenfoldincreaseoverthe190milliondrytonsofbiomassperyearcurrentlyusedforbioenergyandbioproducts.Mostofthisbiomassisburnedforenergy,withonly18milliondrytonsusedforbiofuels(primarilycorn-grainethanol)and6milliondrytonsusedforbioproducts.

Tebiomasspotentialdeterminedbythebillion-tonstudyisonescenariobasedonasetofconservativeassumptionsderivedfromcurrentpracticesandshouldnotbeconsideredanupperlimit.Crop-yieldincreasesassumedinthisstudyfollowbusiness-as-usualexpectations.Withmoreaggressivecommitmentstoresearchonimprovingenergycropsandproductivity,thebio

masspotentialcouldbemuchgreater.Energy-cropyieldisacriticalfactorinestimatinghowmuchlandwillbeneededforlarge-scalebiofuelproduction,andthisfactorcanbeinfluencedsignificantlybybiotechnologyandsystemsbiologystrategiesusedinmodernplantbreedingandbiomassprocessing.

Manypotentialenergycrops(e.g.,switchgrass,poplar,andwillow)areessentiallyunimprovedorhavebeenbredonlyrecentlyforbiomass,comparedtocornandothercommercialfoodcropsthathaveundergonesubstantialimprovementsinyield,diseaseresistance,andotheragronomictraits.Amorecompleteunderstandingofbiologicalsystemsand

Fig. 3.MiscanthusGrowth over

a Single Growing Season in

Illinois.Miscanthushasbeen

exploredextensivelyasapoten

tialenergycropinEuropeand

nowisbeingtestedintheUnited

States.Tescaleisinfeet.Tese

experimentsdemonstrateresults

thatarefeasibleindevelopment

ofenergycrops.[Imagesource:

S.Long,UniversityofIllinois]



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INTRODUCTION

ABillion-TonAnnualSupplyofBiomass:SummaryofPotentialForestandAgriculturalResources

I

n2005,astudyjointlysupportedbyDOEandUSDAexaminedwhetherlandresourcesintheUnitedStatesaresufficienttosustainproductionofover1billiondrytonsofbiomassannually,enoughtodisplace30%ormoreofthenationscurrentconsumptionofliquidtransportationfuels(Perlacketal.2005).

Assumingrelativelymodestchangesinagriculturalandforestrypractices,thisstudyprojectsthat1.366billiondrytonsofbiomass(368milliondrytonsfromforestand998milliondrytonsfromagriculture)couldbeavailableforlarge-scalebioenergyandbiorefineryindustriesbymid-21stCenturywhilestillmeetingdemandforforestryproducts,food,andfiber(seeFig.A.PotentialBiomassResources,below).Tissupplyofbiomass

wouldbeasevenfoldincreaseoverthe190milliondrytonsofbiomassperyearcurrentlyusedforbioenergyandbioproducts.Mostofthisbiomassisburnedforenergy,withonly18milliondrytonsusedforbiofuels(primarilycorn-grainethanol)and6milliondrytonsusedforbioproducts.

LandareaintheUnitedStatesisabout2billionacres,with33%forestlandsand46%agriculturallandsconsistingofgrasslandsorpasture(26%)andcroplands(20%).Oftheestimated368milliondrytonsofforestbiomass,142milliondrytonsalreadyareusedbytheforestproductsindustryforbioenergyandbioproducts.Severaldifferenttypesofbiomasswereconsideredinthisstudy.Residuesfromtheforestproductsindustry

includetreebark,woodchips,shavings,sawdust,miscellaneousscrapwood,andblackliquor,aby-productofpulpandpaperprocessing.Loggingandsite-clearingresiduesconsistmainlyofunmerchantabletreetopsandsmallbranchesthatcurrentlyareleftonsiteorburned.Forestthinninginvolvesremovingexcesswoodymaterialstoreducefirehazardsandimproveforesthealth.Fuelwoodincludesroundwoodorlogsburnedforspaceheatingorotherenergyuses.Urbanwoodresiduesconsistprimarilyofmunicipalsolidwaste(MSW,e.g.,organicfoodscraps,yardtrimmings,discardedfurniture,containers,andpackingmaterials)andconstructionanddemolitiondebris(seeableA.PotentialBiomassResources,thispage,andFig.B.BiomassAnalysisfortheBillion-onStudy,p.11).

Fig. A. Potential Biomass Resources: A otal of

More than 1.3 Billion Dry ons a Year from Agri-

cultural and Forest Resources.

Biomass ResourcesMillion

Dry Tons per Year

Forest Biomass

Forestproductsindustryresidues 145

Loggingandsite-clearingresidues 64

Forestthinning 60

Fuelwood 52

Urbanwoodresidues 47

Subtotal for Forest Resources 368

Agricultural Biomass

Annualcropresidues 428

Perennialcrops 377

Miscellaneousprocessresidues,manure 106

Grains 87

Subtotal for Agricultural Resources 998

Total Biomass Resource Potential 1366

TableA.PotentialBiomassResources



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Fig. B. Biomass Analysis for the Billionon Study[Source:Multi Year Program Plan, 20072012,OBP,EERE,

U.S.DOE(2005)]

Severalassumptionsweremadetoestimatepotentialforestbiomassavailability.Environmentallysensitiveareas,landswithoutroadaccess,andregionsreservedfornontimberuses(e.g.,parksandwilderness)wereexcluded,andequipment-recoverylimitationswereconsidered.Asannualforestgrowthisprojectedtocontinuetoexceedannualharvests,continuedexpansionofstandingforestinventoryisassumed.

Amongagriculturalbiomassresources,annualcropresiduesaremostlystemsandleaves(e.g.,cornstoverandwheatstraw)fromcorn,wheat,soybeans,andothercropsgrownforfoodandfiber.Perennialcropsconsideredinthestudyincludegrassesorfast-growingtreesgrownspecificallyforbioenergy.Grainprimarilyiscornusedforethanolproduction,andmiscellaneousprocessresiduesincludeMSWandotherby-productsofagriculturalresourceprocessing.

Atotalof448millionacresofagriculturallands,largelyactiveandidlecroplands,wereincludedinthisstudy;landsusedpermanentlyforpasturewerenotconsidered.Otherassumptionsforagriculturalbiomassresourcesincludea50%increaseincorn,wheat,andsmall-grainyield;doublingtheresidue-to-grainratioforsoybeans;recoveryof75%ofannualcropresidueswithmoreefficientharvestingtechnologies;managementofallcroplandwithno-tillmethods;55millionacresdedicatedtoproductionofperennialbioenergycrops;averagebiomassyieldforperennialgrassesandwoodyplantsestimatedat8drytonsperacre;conversionofallmanurenotusedforon-farmsoilimprovementtobiofuel;anduseofallotheravailableresidues.



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INTRODUCTION

applicationofthelatestbiotechnologicaladvanceswillacceleratethedevelopmentofnewbiomasscropshavingdesirableattributes.Teseattributesincludeincreasedyieldsandprocessability,optimalgrowthinspecificmicroclimates,betterpestresistance,efficientnutrientuse,andgreatertolerancetomoisturedeficitsandothersourcesofstress.Furthermore,manybiotechnologicaladvancesforgrowingbetterbiomasscropswillbeusedtoimprovefoodcrops,easingthepressureonlandareaneededtogrowfood.Jointdevelopmentofthesebiotechnologicaladvanceswithothercountrieswillhelpmoderatetheglobaldemandforcrudeoil.Inanidealizedfuturescenariowithgreaterper-acreproductivityinenergy,food,andfibercropsanddecreaseddemandfortransportationfuelsresultingfrommoreefficientvehicles,theUnitedStatescouldhavesufficientlandresourcestoproduceenoughbiomasstomeetallitstransportation-fuelneeds.

AgriculturalSustainabilityofBiomassProductionSustainablepracticesforgrowingandharvestingbiomassfromdedicatedcropswillbeessentialtothesuccessoflarge-scalebiofuelproduction.Capitalcostsofrefineriesandassociatedfacilitiestoconvertbiomasstofuelswillbeamortizedoverseveraldecades.Tesecapitalassetswillrequireasteadyannualsupplyofbiomassfromalargeproportionofsurroundingland.Terefore,athoroughunderstandingoftheconversionpathwayandofbiomassharvestingslong-termimpactsonsoilfertilityisneededtoensuresustainability.Vitalnutrientscontainedinprocessresiduesmustbereturnedtothesoil.Perennialcropsexpectedtobeusedforbiofuelsimprovesoilcarboncontentandmakehighlyefficientuseofmineralnutrients(seesidebar,TeArgumentforPerennialBio

massCrops,p.59).Additionalinformationaboutthecompositionandpopulationdynamicsofsoilmicrobialcommunitiesisneeded,however,todeterminehowmicrobescontributetosustainingsoilproductivity(seesection,EnsuringSustainabilityandEnvironmentalQuality,p.68).Mixedcultivarsofgeneticallydiverseperennialenergycropsmaybeneededtoincreaseproductivityandpreservesoilquality.Becauseconventionalannualfoodandfibercropsaregrownasmonocultures,relativelylittleresearchhasbeencarriedoutonissuesassociatedwithgrowingmixedstands.

TodayFuelEthanolProductionfromCornGrain(StarchEthanol)

In2004,3.41Bgalofstarchethanolfuelwereproducedfrom1.26billionbushelsofcorn11%ofallcorngrainharvestedintheUnitedStates.Tisrecordlevelofproductionwasmadepossibleby81ethanolplantslocatedin20states.Completionof16additionalplantsandotherexpansionsincreasedethanol-productioncapacityto4.4Bgalbytheendof2005;additionalplannedcapacityisonrecordforanother1Bgalfrom2006to2007(RFA2005).Althoughdemandforfuelethanolmorethandoubledbetween2000and2004,ethanolsatisfiedlessthan2%ofU.S.transportation-energydemandin2004.



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IntheUnitedStates,ethanolisproducedincornwetordrymills.Cornwet millsfractionatethecorngrainforproductslikegermandoilbeforeconvertingthecleanstarchtosugarsforfermentationorforsuchvaluablefoodproductsashigh-fructosecornsyrupandmaltodextrins. Tecornfiberby-productusuallyissoldasanimalfeed.Incorn dry mills,thegrainisground,brokenintosugarmonomers(saccharified),andfermented.Sincethegrainisnotfractionated,theonlyby-productistheremainingsolids,calleddistillersdriedgrainswithsolubles,ahighlynutritiousproteinsourceusedinlivestockfeed.Abushelofcornyieldsabout2.5galethanolfromwet-millprocessingandabout2.8galfromdrygrind(BothastandSchlicher2005).Some75%ofcornethanolproductionisfromdry-millfacilitiesand25%fromwetmills.

TomorrowBiorefineryConcepttoProduceFuelEthanolfromCellulosicBiomass

Cellulosicethanolhasthepotentialtomeetmost,ifnotall,transportation-fuelneeds.However,duetothecomplexstructureofplantcellwalls,cellulosicbiomassismoredifficultthanstarchtobreakdownintosugars.Treekeybiomasspolymersfoundinplantcellwallsarecellulose,hemicellulose,andlignin(seeLignocellulosicBiomassCharacteristicschapter,p.39).

Tesepolymersareassembledintoacomplexnanoscalecomposite,notunlikereinforcedconcretebutwiththecapabilitytoflexandgrowmuchlikealiquidcrystal.Tecompositeprovidesplantcellwallswithstrengthandresistancetodegradationandcarriesoutmanyplantfunctions.Teirrobustness,however,makesthesematerialsachallengetouseassubstratesforbiofuelproduction.

raditionalcellulosicbiorefinerieshavenumerouscomplex,costly,andenergy-intensivestepsthatmaybeincompatibleorreduceoverallprocessefficiency.Tecurrentstrategyforbiochemicalconversionofbiomasstoethanolhasitsrootsintheearlydaysofwoodchemistry.Developedinthe1930sfor

wartimeuseinGermany, itisusedinRussiatoday.Tisprocessinvolvesthreebasicsteps,eachelementofwhichcanbeimpactedbycellulosicbiomassresearch(seeFig. 4.raditionalCellulosicBiomassConversiontoEthanolBasedonConcentratedAcidPretreatmentFollowedbyHydrolysisandFermentation,p.14).Afteracquisitionofsuitablecellulosicbiomass,biorefiningbeginswithsizereductionandthermochemicalpretreatmentofrawcellulosicbiomasstomakecellulosepolymersmoreaccessibletoenzymaticbreakdownandtofreeuphemicellulosicsugars,followedbyproductionandapplicationofspecialenzymepreparations(cellulases)forhydrolysisofplantcell-wallpolysaccharidestoproducesimplesugars.Finalstepsintheprocessincludefermentation,mediatedbybacteriaoryeast,toconvertthesesugarstoethanolandothercoproductsthatmustberecoveredfromtheresultingaqueousmixture.Recentresearchanddevelopmenthasreduceddramaticallythecostofenzymesandhasimprovedfermentationstrainstoenablesimultaneoussaccharificationandfermentation(SSF),inwhichhydrolysisofcelluloseandfermentationofglucosearecombinedinonestep.



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INTRODUCTION

Figure5.ABiorefineryConceptIncorporatingAdvancedPretreatmentandConsolidatedProcessingofCellulosetoEthanol,p.15,depictskeytargetsforsimplifyingandimprovingthebiorefineryconcept.Feedstockresearchseeksfirsttoincreasebiomassyieldsandenhancebiomasscharacteristicstoenablemoreefficientprocessing.Advancedbiocatalystswillaugmentorreplacethermochemicalmethodstoreducetheseverityandincreasetheyieldofpretreatment.Morerobustprocessesandreductionofinhibitorswouldalloweliminationofthedetoxificationandseparationsteps.Developingmodifiedenzymesandfermentationorganismsulti

matelywillallowincorporationofhydrolysisenzymeproduction,hydrolysis,andfermentationintoasingleorganismorafunctionallyversatilebutstablemixedculturewithmultipleenzymaticcapabilities.ermedconsolidatedbioprocessing(CBP),thiscouldenablefourcomponentscomprisingsteps2and3(greenboxes)inFig.4tobecombinedintoone,whichinFig.5iscalleddirectconversionofcelluloseandhemicellulosicsugars.Furtherrefinementwouldintroducepretreatmentenzymes(ligninasesandhemicellulases)intotheCBPmicrobialsystemsaswell,

Fig. 4. raditional Cellulosic Biomass Conversion to

Ethanol Based on Concentrated Acid Pretreatment Followed

by Hydrolysis and Fermentation.Treestepsintheprocessare

(1) sizereductionandthermochemicalpretreatmentofrawcellulosicbiomasstomakecellulosepolymersmoreaccessibletoenzy

maticbreakdownandfreeuphemicellulosicsugars(blueboxesonleft);

(2) productionandapplicationofspecialenzymepreparations(cellulases)

thathydrolyzeplantcell-wallpolysaccharides,producingamixtureofsimple

sugars(greenboxes);and (3) fermentation,mediatedbybacteriaoryeast,to

convertthesesugarstoethanolandothercoproducts(yellowdiamonds).Recent

researchand developmenthasreduced dramatically thecostof enzymes andhas improvedfermentationstrains

toenablesimultaneoussaccharificationandfermentation(SSF,greenboxessurroundedbyorange),inwhichhydro

lysisofcelluloseandfermentationofglucosearecombinedinonestep.Cellulosicbiomassresearchistargetingthese

stepstosimplifyandincreasetheyieldofbiomassproductionandprocessing(seeFig.5.p.15).[Source:Adaptedfrom

M.HimmelandJ.Sheehan,NationalRenewableEnergyLaboratory]



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Ethical,Legal,andSocialIssues(ELSI)Usingbiomasstoproducebiofuelsholdsmuchpromiseforprovidingarenewable,domesticallyproducedliquid

energysourcethatcanbeaviablealternativetopetroleum-basedfuels.BiofuelR&D,therefore,aimstoachievemorethanjustscientificandtechnologicaladvancesperse.Itisconductedtoaccomplishimportantsocietalneeds,withthebroadergoalsofbolsteringnationalenergysecurity,economicgrowth,andtheenvironment.Analyzingandassessingthesocietalimplicationsof,andresponsesto,thisresearchlikewiseshouldcontinuetobeframedwithinthecontextofsocialsystemsandnotsimplyintermsoftechnologicaladvancesandtheirefficacy(seesidebar,Ethical,Legal,andSocialIssuesforWidespreadDevelopmentofCellulosicBiofuels,thispage).

EEREOBPPlatformforIntegratedBiorefineries

TeDepartmentofEnergysstrategicplanidentifiesitsenergygoal:oprotectournationalandeconomicsecuritybypromotingadiversesupplyanddeliveryofreliable,affordable,andenvironmentallysoundenergy.Oneofseveralstrategiesidentifiedtoachievethisgoalistoresearchrenewableenergytechnologieswind,hydropower,biomass,solar,andgeothermalandworkwiththeprivatesectorindevelopingthesedomesticresources.

TedepartmentsOfficeofEnergyEfficiencyandRenewableEnergy(EERE)OfficeoftheBiomassProgram(OBP)elaboratesonthatgoal:Improveenergysecuritybydevelopingtechnologiesthatfosteradiversesupplyofreliable,affordable,andenvironmentallysoundenergybyprovidingforreliabledeliveryofenergy,guardingagainstenergyemergencies,exploringadvancedtechnologiesthatmakeafundamentalimprovementinourmixofenergyoptions,andimprovingenergyefficiency.

Majoroutcomessoughtincludethefollowing.

By2012,completetechnologydevelopmentnecessarytoenablestartupdemonstrationofabiorefineryproducingfuels,chemicals,andpower,possiblyatanexistingornewcorndrymillmodifiedtoprocesscornstoverthroughasidestream.

By2012(basedonAEI),completetechnologyintegrationtodemonstrateaminimumsugarsellingpriceof$.064/lb,resultinginaminimumethanolsellingpriceof$1.07/gal.Ethanolwouldbeproducedfromagriculturalresiduesordedicatedperennialenergycrops.

Ethical,Legal,andSocialIssuesforWidespreadDevelopmentofCellulosicBiofuels

Societalquestions,concerns,andimplications

clearlymayvaryaccordingtotheevolutionarystageofbiofueldevelopment.Acceptanceandsupportfromdiversecommunitieswillbeneeded.Further,societalandtechnologicalinteractionsatearlierphasesofresearch,development,demonstration,deployment,anddecommissioning(RDDD&D)willaffectinteractionsatlaterphases.Withinthecontextofsocialsystems,threeoverarchingquestionsemerge.

Whatarethepossiblelong-termimplicationsofbiofueldevelopmentanddeploymentforsocialinstitutionsandsystemsifthestrategyworksasanticipatedandifitdoesnot?

Howareindividuals,organizations,andinstitutionslikelytorespondovertimetothisdevelopmentandthechangesintegraltoitsdeployment?

Whatactionsorinterventions(e.g.,regulations)associatedwithbiofueldevelopmentanditsuseanddeploymentwillprobablyorshouldbetakenatlocal,regional,andnationallevelstopromotesociallydeterminedbenefitsandtoavoid,minimize,ormitigateanyadverseimpacts?

Broadtopicsraisedattheworkshopincludedthefollowing:

Sustainabilityofthetotalintegratedcycle.

Competinginterestsforlanduse.

Creationanduseofgeneticallymodifiedplants.Whocreatesandusesthem,whodecidesbasedonwhatcriteria,andhowmightorshouldtheyberegulated?

Creationanduseofgeneticallymodifiedmicro

bialorganismsinacontrolledindustrialsetting. Individualsandgroupsthathavetheauthority

topromoteorinhibitR&D,demonstration,anduse.

Groupsmostlikelytobeaffected(positivelyornegatively)bybiofuelsatallevolutionarystagesofRDDD&Donthelocal,national,andgloballevels.



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INTRODUCTION

By2030,helpenabletheproductionof60billiongallonsofethanolperyearintheUnitedStates.Areportelaboratingonthisgoalwillbereleasedsoon.

TeBiomassProgramalsoisalignedwithrecommendationsintheMay2001NEPtoexpandtheuseofbiomassforwide-rangingenergyapplications.NEPoutlinesalong-termstrategyfordevelopingandusingleading-edgetechnologywithinthecontextofanintegratednationalenergy,environmental,andeconomicpolicy.

Fig. 7. DOE Energy Efficiency and Renewable Energy Strategic Goals as Tey Relate to Development of Biofuels.

[Source:Multi Year Program Plan 20072012,OBP,EERE,U.S.DOE(2005)]



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Teprogramsoverarchingstrategicgoalistodevelopbiorefinery-relatedtechnologiestothepointthattheyarecost- andperformance-competitiveandareusedbythenationstransportation,energy,chemical,andpower

industriestomeettheirmarketobjectives.Tenationwillbenefitbyexpandingclean,sustainableenergysupplieswhilealsoimprovingitsenergyinfrastructureandreducingGHGsanddependenceonforeignoil.TisgoalisinalignmentwithDOEandEEREstrategicgoalsasshowninFig.7.DOEEnergyEfficiencyandRenewableEnergyStrategicGoalsasTeyRelatetoDevelopmentofBiofuels,p.18.

PlanningdocumentsofEEREsOBPdescribeadvancestheprogramseeksforfourcriticalobjectives:(1)Alterfeedstocksforgreateryieldandforcon

vertinglargerportionsofrawbiomassfeedstockstofuelethanolandotherchemicals;(2)decreasecostsandimproveenzymeactivitiesthatconvertcomplexbiomasspolymersintofermentablesugars;(3)developmicrobesthat

canefficientlyconvertall5- and6-carbonsugarsreleasedfromthebreakdownofcomplexbiomasspolymers;and(4)consolidateallsaccharificationandfermentationcapabilitiesintoasinglemicrobeormixed,stableculture.

AcommercialindustrybasedoncellulosicbiomassbioconversiontoethanoldoesnotyetexistintheUnitedStates,butseveralprecommercialfacilitiesareindevelopment.TeCanadiancompany,IogenCorporation,aleadingproducerofcellulaseenzymes,operatesthelargestdemonstrationbiomass-to-ethanolfacility,withacapacityof1Mgal/year;productionofcellulosicethanolfromwheatstrawbeganatIogeninApril2004.OBPhasissuedasolicitationfordemonstrationofcellulosicbiorefineries(U.S.Congress2005,Section932)aspartofthepresidentialBiofuelsInitiative.

DOEOfficeofScienceProgramsTeDOEOfficeofScience(SC)playskeyrolesinU.S.research,includingthecontributionofessentialscientificfoundationstoDOEsnationalenergy,environment,andeconomicsecuritymissions(seeFig.8.DOEOfficeofScienceProgramsandGoalsasTeyRelatetoDevelopmentofBiofuels,p.20).Otherrolesaretobuildandoperatemajorresearchfacilitieswithopenaccessbythescientificcommunityandtosupportcorecapabilities,theories,experiments,andsimulationsattheextremelimitsofscience.AnSCgoalfortheOfficeofBiologicalandEnvironmentalResearch(OBER)istoharnessthepowerofourlivingworldandprovidethebiologicalandenvironmentaldiscoveriesnecessarytocleanandprotect

ourenvironmentandoffernewenergyalternatives.SCsgoalforitsOfficeofAdvancedScientificComputingResearch(OASCR)istodelivercomputingforthefrontiersofscience(U.S.DOE2004).

oaddressthesepriorities,OBERandOASCRaresponsoringtheGenomics:GenomestoLife(GL)program.Establishedin2002,GLusesgenomedataastheunderpinningsforinvestigationsofbiologicalsystemswithcapabilitiesrelevanttoDOEenergyandenvironmentalmissions.TeGLscientificprogramwasdevelopedwithinputfromhundredsofscientistsfromuniversities,privateindustry,otherfederal



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INTRODUCTION

Fig. 8. DOE Office of Science Programs and Goals as Tey Relate to Development of Biofuels.[DerivedfromOfficeofScienceStrategicPlanandGenomics:GLRoadmap]

agencies,andDOEnationallaboratories.Providingsolutionstomajornationalproblems,biologyandindustrialbiotechnologywillserveasanengineforeconomiccompetitivenessinthe21stCentury.DOEmissionsinenergysecurityaregrandchallengesforanewgenerationofbiologicalresearch.SCwillworkwithEEREtobringtogetherbiology,computing,physicalsciences,bioprocessengineering,andtechnologydevelopmentforthefocusedandlarge-scaleresearcheffortneededfromscientificinvestigationstocommercializationinthemarketplace.ResearchconductedbythebiofuelR&DcommunityusingSCprogramsandresearchfacilities

willplayacriticalroleindevelopingfuturebiorefineriesandensuringthesuccessofEEREOBPsplans.

Tenationsinvestmentingenomicsoverthepast20yearsnowenablesrapiddeterminationandsubsequentinterpretationofthecompleteDNAsequenceofanyorganism.Becauseitrevealstheblueprintforlife,genomicsisthelaunchingpointforanintegratedandmechanisticsystemsunderstandingofbiologicalfunction.Itisanewlinkbetweenbiologicalresearchandbiotechnology.



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Fig. 9. Understanding Biological Capabilities at All Scales Needed to Support Systems Biology Investigations of Cellu-

losic Biomass. Capabilitiesareneededtobringtogetherthebiological,physical,computational,andengineeringsciences

tocreateanewinfrastructureforbiologyandtheindustrialbiotechnologyinthe21stCentury.Tisfiguredepictsthefocus

ofGLonbuildinganintegratedbodyofknowledgeaboutbehavior,from

ing.DOE

genomicinteractionsthroughecosystemchanges.Simultaneouslystudying

multiplesystemsrelatedtovariousaspectsofthebiofuelproblemispower-

fullysynergisticbecauseenduringbiologicalthemesaresharedandgeneralprinciplesgoverningresponse,structure,andfunctionapply

throughout.Accumulatingdataastheyareproduced,theGL

KnowledgebaseandGLcomputationalenvironmentwill

interactivelylinkthecapabilitiesandresearchefforts,allowing

thisinformationtobeintegratedintoapredictiveunderstand-

stechnologyprogramscanwork

withindustrytoapplysuchcapabilities

andknowledgetoanewgenerationofproc-

esses,products,andindustries.

GLsgoalissimpleinconceptbutchallenginginpracticetorevealhowthestaticinformationingenomesequencesdrivestheintricateanddynamicprocessesoflife.Troughpredictivemodelsoftheselifeprocessesandsupportingresearchinfrastructure,GLseekstoharnessthecapabilitiesoflivingsystems.GLwillstudycriticalpropertiesandprocessesonfoursystemslevelsmolecular,cellular,organismal,andcommunityeachrequiringadvancesinfundamentalcapabilitiesandconcepts.Tesesameconceptsandcapabilitiescanbeemployedbybioprocessengineerstobringnewtechnologiesrapidlytothemarketplace.

AchievingGLgoalsrequiresmajoradvancesintheabilitytomeasurethephenomenologyoflivingsystemsandtoincorporatetheiroperatingprinciplesintocomputationalmodelsandsimulationsthataccuratelyrepresentbiologicalsystems.omakeGLscienceandbiologicalresearchmorebroadlytractable,timely,andaffordable,GLwilldevelopcomprehensivesuitesofcapabilitiesdeliveringeconomiesofscaleandenhancedperformance(seeFig.9.UnderstandingBiologicalCapabilitiesatAllScalesNeededtoSupportSystemsBiologyInvestigationsofCellulosicBiomass,thispage).In

verticallyintegratedbioenergyresearchcenters,thesecapabilitieswillincludetheadvancedtechnologiesandstate-of-the-artcomputingneededtobetter

http:///reader/full/systems.Tohttp:///reader/full/systems.To


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INTRODUCTIONFig. 10. Creating a

Common Research

Agenda.TeEERE

OfficeoftheBio

massProgramsMulti

Year Program Plan

20072012 containsaroadmapforbiofuel

developmentthat

identifiestechnological

barrierstoachieving

goalsdefinedinFig.7,

p.18.Tesechal

lengesincludetheneed

fornewfeedstocks,

theirdeconstruc

tiontofermentable

sugars,andfermentationofallsugars

toethanol.Within

theDOEOfficeof

Science,OBERand

OASCRsroadmapfor

theGenomics:GL

programoutlinesscientificgoals,technologies,computingneeds,andaresourcestrategytoachievetheGLgoalof

apredictiveunderstandingofbiologicalsystems.Tisdocumentisaroadmapthatlinksthetwoplans.

understandgenomicpotential,cellularresponses,regulation,andbehaviorsofbiologicalsystems.ComputingandinformationtechnologiesarecentraltotheGLprogramssuccessbecausetheywillallowscientiststosurmountthebarrierofcomplexitynowpreventingthemfromdeducingbiologicalfunctiondirectlyfromgenomesequence.GLwillcreateanintegratedcomputationalenvironmentthatwilllinkexperimentaldataofunprecedentedquantityanddimensionalitywiththeory,modeling,andsimulationtouncoverfundamentalbiologicalprinciplesandtodevelopandtestsystemstheoryforbiology.

BiomasstoBiofuelsWorkshop:CreatingaCommonResearchAgendatoOvercomeTechnologyBarriers

AproductoftheBiomasstoBiofuelsWorkshop,thisroadmapanalyzesbarrierstoachievingOBPgoals(asdescribedherein)anddeterminesfundamentalresearchandcapabilities(asdescribedintheGLRoad-map)thatcouldbothaccelerateprogressinremovingbarriersandallowamorerobustsetofendpoints(seeFig.10.CreatingaCommonResearch

Agenda,thispage).Relatinghigh-leveltopicalareasandtheirgoalstokeyscientificmilestonesidentifiedbyworkshopparticipantscouldhelpachieveprogresstowardOBPgoalsincollaborationwithSC(seeable2.OvercomingBarrierstoCellulosicEthanol:OBPBiologicalandechnologicalResearchMilestones,p.23).



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Table2.OvercomingBarrierstoCellulosicEthanol:OBPBiologicalandTechnologicalResearchMilestones

Office of the Biomass

Program (OBP) Barrier TopicTechnology Goals Science Research Milestones

Feedstocks Better compositions and structures for sugars Cell-wallarchitectureandmakeuprelativetoprocessability

Developsustainable production Genomesequenceforenergycrops

technologiestosupplybiomasstobiorefineries

Domestication:Yield,tolerance

Betteragronomics

Sustainability

Domesticationtraits:Yield,tolerance

Cell-wallgenes,principles,factors

Newmodelsystemstoapplymodernbiologytools

Soilmicrobialcommunitydynamicsfordeterminingsustainability

Feedstock Pretreatment Enzymes Cell-wallstructurewithrespecttodegradation

Deconstruction to

SugarsReducedseverity

Reducedwaste

Modificationofthechemicalbackboneofhemicellulosematerialstoreducethenumberofnonfermentableandderivatizedenzymes

Developbiochemicalconversion Highersugaryields Cell-wallcomponentresponsetopretreatments

technologiesto Reducedinhibitors Principlesforimprovedcellulases,ligninases,

producelow-costsugarsfrom Reductioninnonfermentablesugars hemicellulases

lignocellulosicbiomass Enzyme Hydrolysis to Sugars

Higherspecificactivity

Higherthermaltolerance

Reducedproductinhibition

Broadersubstraterange

Cellulasesandcellulosomes

Understandingofcellulosomeregulationandactivity

Actionofenzymesoninsolublesubstrates(fundamentallimits)

Fungalenzyme-productionfactors

Nonspecificadsorptionofenzymes

Originofinhibitors

Sugar Fermentation to Cofermentation of Sugars Fullmicrobialsystemregulationandcontrol

Ethanol C-5andC-6sugarmicrobes Rapidtoolsformanipulationofnovelmicrobes

Developtechnologies

toproducefuels,chemicals,and

Robustprocesstolerance

Resistancetoinhibitors

Utilizationofallsugars

Sugartransporters

powerfrombiobasedsugarsandchemical

Marketableby-products Responseofmicroorganismstostress

buildingblocks Newmicrobialplatforms

Microbialcommunitydynamicsandcontrol

Consolidated Processing Enzyme Production, Hydrolysis, and Fundamentalsofmicrobialcelluloseutilization

Reduceprocesssteps Cofermentation Combined in One Reactor Understandingandcontrolofregulatoryprocessesandcomplexitybyintegratingmultipleprocessesinsingle

Productionofhydrolyticenzymes

Fermentationofneededproducts(ethanol)

Engineeringofmultigenictraits

Processtolerancereactors Processtolerance

Stableintegratedtraits

Allprocessescombinedinasinglemicrobeorstableculture

Improvedgene-transfersystemsformicrobialengineering

Understandingoftransgenichydrolysisandfermentationenzymesandpathways

Teworkshopwasorganizedunderthefollowingtopicalareas:FeedstocksforBiofuels(p.57);DeconstructingFeedstockstoSugars(p.85);SugarFermentationtoEthanol(p.119);andCrosscutting21stCenturyScience,

echnology,andInfrastructureforaNewGenerationofBiofuelResearch(p.155).AcriticaltopicdiscussedinseveralworkshopgroupswasLignocellulosicBiomassCharacteristics(p.39).Tesefivetopicsandplanswould



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INTRODUCTION

tiethetwoofficesroadmapstogetherandalsoserveasakeydriverforimplementingthecombinedroadmapsinpursuitofahigh-levelnationalgoal:Createaviablecellulosic-biofuelindustryasanalternativetooilfortransportati

Breaking the Biological Barriers to Celluloic Ethanol: A Joint Research Agenda

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