Breakng the Bologcal Barrers to Cellulosc Ethanol- A Jont Research Agenda
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DOE/SC-0095
Breaking the Biological Barriersto Cellulosic Ethanol:A Joint Research Agenda
A Research Roadmap Resulting from the
Biomass to Biofuels WorkshopDecember 79, 2005Rockville, Maryland
Workshop Sponsoredby the
U.S. Department of Energy
Office of Energy Efficiency Office of Scienceand Renewable Energy Office of Biological and Environmental ResearchOffice of the Biomass Program Genomics:GTL Program
Publication Date: June 2006
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ii BiofuelsJointRoadmap,June2006 OfficeofScienceandOfficeofEnergyEfficiencyandRenewableEnergy U.S.DepartmentofEnergy
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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.
iv BiofuelsJointRoadmap,June2006 OfficeofScienceandOfficeofEnergyEfficiencyandRenewableEnergy U.S.DepartmentofEnergy
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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
Cited References.....................................................................................................................................................................................56
Feedstocksfor Biofuels.......................................................................................................................................................................57
Creation of a New Generation of Lignocellulosic Energy Crops...........................................................................................................60
MaximizingBiomassProductivity.......................................................................................................................................................61
TechnicalMilestones...........................................................................................................................................................................67
Ensuring Sustainability and Environmental Quality............................................................................................................................68
TechnicalMilestones...........................................................................................................................................................................70
Model Systems for Energy Crops............................................................................................................................................................71
TechnicalMilestones...........................................................................................................................................................................73
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
Cited References.....................................................................................................................................................................................80
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
TechnicalMilestones...........................................................................................................................................................................89
TheRoleofGTLandOBPFacilitiesandCapabilities.............................................................................................................................90
CrosscuttingTools,Technologies,andScience......................................................................................................................................91
Developing Better Enzymatic Systems for Biological Pretreatment: Ligninases and Hemicellulases.............................................91
ResearchGoals....................................................................................................................................................................................92
TechnicalMilestones...........................................................................................................................................................................94
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
vi BiofuelsJointRoadmap,June2006 OfficeofScienceandOfficeofEnergyEfficiencyandRenewableEnergy U.S.DepartmentofEnergy
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TechnicalMilestones.........................................................................................................................................................................106
TheRoleofGTLandOBPFacilitiesandCapabilities...........................................................................................................................107
Characterizing Cell Walls Using High-Throughput Methods..............................................................................................................108
TechnicalMilestones.........................................................................................................................................................................110
TheRoleofGTLandOBPFacilitiesandCapabilities...........................................................................................................................111
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
TechnicalMilestones.........................................................................................................................................................................130
TheRoleofGTLCapabilities...............................................................................................................................................................131
Advanced Microorganisms for Process Simplification.......................................................................................................................132
ScienceChallengesandStrategiesforProcessSimplification............................................................................................................135
TechnicalMilestones.........................................................................................................................................................................137
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
BiofuelsJointRoadmap,June2006 OfficeofScienceandOfficeofEnergyEfficiencyandRenewableEnergy U.S.DepartmentofEnergy
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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
TheRoleofGTLandOBPFacilitiesandCapabilities...........................................................................................................................183
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
viii BiofuelsJointRoadmap,June2006 OfficeofScienceandOfficeofEnergyEfficiencyandRenewableEnergy U.S.DepartmentofEnergy
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Introduction
Inhis2006StateoftheUnionaddress(Bush2006),thepresidentoutlinedthenewAdvancedEnergyInitiative(AEI)tohelpovercome
Americasdependenceonforeignsourcesofenergy(AEI2006)andtheAmericanCompetitivenessInitiativetoincreaseR&Dinvestmentsandstrengtheneducation(ACI2006).Heseekstoreduceournationaldependenceonimportedoilbyacceleratingthedevelopmentofdomestic,renewablealternativestogasolineanddieselfuels.
With America on the verge of breakthroughs in advanced energy tech-nologies, the best way to break the addiction to foreign oil is throughnew technologies. WhiteHousePressReleaseontheStateoftheUnion
AddressandAEI(January31, 2006)
Breakthroughtechnologiestorealizethepotentialofcellulosicbiofuelscanbeexpeditedbyapplicationofanewgenerationofbiologicalresearchcreatedbythegenomerevolution.Overcomingbarrierstodevelopmentofthesefuelsonanindustrialscalewillrequirehigh-performanceenergyfeedstocksandmicrobialprocesses,bothtobreakdownfeedstockstosugarsandtofermentsugarstoethanol.Afocusedsetofinvestmentslinkingrevolutionarybiofueltechnologieswithadvancesfromthebiological,physical,
computational,andengineeringscienceswillquicklyremovebarrierstoanefficient,economic,andsustainablebiofuelindustry.
JointWorkshopChallengesBiofuelScienceandTechnologyCommunities
woDepartmentofEnergy(DOE)officesareteamingtoadvancebiofueldevelopmentanduse:TeOfficeofBiologicalandEnvironmentalResearch(OBER)withintheOfficeofScience(SC)andtheOfficeoftheBiomassProgram(OBP)withintheOfficeofEnergyEfficiencyandRenewableEnergy(EERE)(seedescriptionsofthetwoDOEprograms,pp.17and
19).Teseofficesarechallengingtheircommunitiestoidentifycriticalscienceneedstosupportasubstantialandsustainableexpansionofbiomass-derivedfuels,specificallycellulosicethanol.InthejointlysponsoredBiomasstoBiofuelsWorkshopheldDecember79,2005,inRockville,Maryland,morethan50scientistsrepresentingawiderangeofexpertiseconvenedtodefinebarriersandchallengestothisnewbiofuelindustry.Te
workshopconcentratedonimprovementofbiomasscropsandtheirprocessingtotransportationfuels.Althoughthefocuswasethanol,thescienceappliestoadditionalfuelsthatincludebiodieselandtootherbioproductsorcoproductshavingcriticalrolesinanydeploymentscheme. References: p. 24
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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
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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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Fig 5. A Biorefinery Concept Incorporating Advanced Pretreatment
and Consolidated Processing of Cellulose to Ethanol.Testrategies
discussedinthisroadmaparebasedonfirstdevelopingtechnologiesto
allowmoreenergy-efficientandchemicallybenignenzymaticpretreat
ment.Saccharificationandfermentationwouldbeconsolidatedintoasimplestepandultimatelyintoasingleorgan
ismorstablemixedculture(consolidatedbioprocessing),thusremovingmultiplewholestepsinconvertingbiomass
toethanol.AlsoseeFig.6.p.16.[Source:AdaptedfromM.HimmelandJ.Sheehan,NationalRenewableEnergy
Laboratory]
reducingtoonesteptheentirebiocatalyticprocessingsystem(pretreatment,hydrolysis,andfermentation).Teseprocesssimplificationsandimprovementswilllessenthecomplexity,cost,andenergyintensityofthecellulosicbiorefinery.
Inadditiontopolysaccharidesthatcanbeconvertedtoethanol,thelignininplantcellwallsisacomplexpolymerofphenylpropanoidsubunitsthatmustbeseparatedfromcarbohydratesduringbiomassconversion.Energy-richlignincanbeburnedforheat,convertedtoelectricitycon
sumablebyotherstepsintheethanol-productionpathway,orgasifiedandconvertedtoFischer-ropsch(F)fuels(seeFig.6.MatureBiomassRefiningEnergyFlows:ExampleScenario,p.16,andableA.SummaryofEnergyFlowsinMatureBiorefineryConcept,p.16).Formoreinformation,seeDeconstructingFeedstockstoSugars,p.85,andSugarFermentationtoEthanol,p.119.Foranoverviewofhowgenomicscanbeappliedtodevelopingnewenergyresources,seemegasidebar,FromBiomasstoCellulosicEthanol,p.26.
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INTRODUCTION
Fig. 6. Mature Biomass Refining Energy F lows: Example Scenario.Amatureintegratedcellulosicbiomassbiorefin
eryencompassesbiologicalandthermochemicalprocesses,demonstratingthe
efficienciespossiblewithafullyintegrateddesign.Tisscenarioincorporates
theconsolidatedbioprocessing(CBP)concept,inwhichallbiologicalprocesses
areincorporatedintoasinglemicrobeormicrobialcommunity.Energyderivedfromfeedstocksischemicallyandphysicallypartitionedtoethanolandother
products.Dottedarrowsfromaboveindicateenergyinputsneededtorun
machinery.Tethermochemicalportionreleasesenergythatcanbeused,for
example,tosustainnecessarytemperatures,bothheatingandcooling,andto
powerpumpsandotherancillaryequipment.ableAisasummaryofenergy
flowsinthisbiorefineryconcept.[Source:AdaptedfromL.Lyndetal.,Envi
sioningMatureBiomassRefineries,presentedatFirstInternationalBiorefin
erySymposium,Washington,D.C.(July20,2005).]
TableA.SummaryofEnergy
FlowsinMatureBiorefineryConcept
Products
54%ethanol
5%power(electricity)
10%diesel
6%gasoline
Production Inputs
21%capturedforprocessenergyorlost
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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
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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-biofuelindustryasanalternativetooilfortransportation.Tesetopicsandtheirrelationshipsarediscussedinsubsequentchaptersoutliningtechnicalstrategyanddetailedresearchplansdevelopedintheworkshop.
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Bothast,R.J.,andM.A.Schlicher.2005.BiotechnologicalProcessesforConversionofCornintoEthanol,Appl. Microbiol. Biotechnol. 67,1925.
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