BIOFUELSFORA MORE SUSTAINABLE FUTURE
LifeCycleSustainability AssessmentandMulti-Criteria
DecisionMaking
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Contributors
KathleenB.Aviso
ChemicalEngineeringDepartment,DeLaSalleUniversity,Manila,Philippines
EricAlbertoOcampoBatlle
FederalUniversityofItajuba ´ —UNIFEI,Itajuba ´ ,Brazil
MonicaCarvalho
FederalUniversityofParaı´ba—UFPB,Joa ˜ oPessoa,Brazil
JoseLuizCasela
IndustrialandSystemsEngineeringGraduateProgram(PPGEPS),PolytechnicSchool, PontificalCatholicUniversityofParana ´ (PUCPR),Curitiba,Brazil
MaurizioCellura
DepartmentofEngineering,UniversityofPalermo,Palermo,Italy
HungPhuocDuong
InternationalCooperationDepartment,MinistryofNaturalResourcesandEnvironment, HaNoi,VietNam
FrancescoGuarino
DepartmentofEngineering,UniversityofPalermo,Palermo,Italy
OsirisCanciglieriJunior
IndustrialandSystemsEngineeringGraduateProgram(PPGEPS),PolytechnicSchool, PontificalCatholicUniversityofParana ´ (PUCPR),Curitiba,Brazil
JuarezCorr^ eaFurtadoJu ´ nior
StateUniversityofCampinas—UNICAMP,Campinas,Brazil
DinhSyKhang
HoChiMinhCityUniversityofNaturalResourcesandEnvironment,HoChiMinhCity, Vietnam
KaiLan
DepartmentofForestBiomaterials,NorthCarolinaStateUniversity,Raleigh,NC,United States
RuojueLin
DepartmentofIndustrialandSystemsEngineering,TheHongKongPolytechnicUniversity, HongKongSAR,China
YueLiu
DepartmentofIndustrialandSystemsEngineering,TheHongKongPolytechnicUniversity, HongKongSAR,China
SoniaLongo
DepartmentofEngineering,UniversityofPalermo,Palermo,Italy
ElectoEduardoSilvaLora
FederalUniversityofItajuba ´ —UNIFEI,Itajuba ´ ,Brazil
YasuakiMaeda
ResearchOrganizationforUniversity-CommunityCollaborations,OsakaPrefecture University,Sakai,Japan
YiMan
DepartmentofIndustrialandSystemsEngineering,TheHongKongPolytechnicUniversity, HongKongSAR;SchoolofLightIndustryandEngineering,SouthChinaUniversityof Technology,Guangzhou,China
RosanaAdamiMattioda
IndustrialandSystemsEngineeringGraduateProgram(PPGEPS),PolytechnicSchool, PontificalCatholicUniversityofParana ´ (PUCPR),Curitiba,Brazil
MarinaMistretta
DepartmentofHeritage,ArchitectureandUrbanPlanning,UniversityofReggioCalabria, ReggioCalabria,Italy
PiergiuseppeMorone
BioeconomyinTransitionResearchGroup(BiT-RG),UnitelmaSapienzaUniversityof Rome,Rome,Italy
KeitoNakagawa
PlantEngineeringDivision,MitsubishiHeavyIndustriesEnvironmentalandChemical EngineeringCo.,Ltd.,Yokohama,Japan
TuAnhNguyen
GraduateSchoolofHumanitiesandSustainableSystemSciences,OsakaPrefecture University,Sakai,Japan
KojiOtsuka
GraduateSchoolofHumanitiesandSustainableSystemSciences,OsakaPrefecture University,Sakai,Japan
JoseCarlosEscobarPalacio
FederalUniversityofItajuba ´ —UNIFEI,Itajuba ´ ,Brazil
SunkyuPark
DepartmentofForestBiomaterials,NorthCarolinaStateUniversity,Raleigh,NC, UnitedStates
MichaelAngeloB.Promentilla
ChemicalEngineeringDepartment,DeLaSalleUniversity,Manila,Philippines
LuisF.Razon
ChemicalEngineeringDepartment,DeLaSalleUniversity,Manila,Philippines
JingzhengRen
DepartmentofIndustrialandSystemsEngineering,TheHongKongPolytechnicUniversity, HongKongSAR,China
SerenellaSala
EuropeanCommission,JointResearchCentre(JRC),Ispra,Italy
LaurenceStamford
SchoolofChemicalEngineeringandAnalyticalScience,TheUniversityofManchester, Manchester,UnitedKingdom
AndrzejStrzałkowski
BioeconomyinTransitionResearchGroup(BiT-RG),UnitelmaSapienzaUniversityof Rome,Rome,Italy;UniversityofWarsaw,Warsaw,Poland
RaymondR.Tan
ChemicalEngineeringDepartment,DeLaSalleUniversity,Manila,Philippines
AlmonaTani
BioeconomyinTransitionResearchGroup(BiT-RG),UnitelmaSapienzaUniversityof Rome;FoodandAgricultureOrganization—FAO,Rome,Italy
DavidRibeiroTavares
IndustrialandSystemsEngineeringGraduateProgram(PPGEPS),PolytechnicSchool, PontificalCatholicUniversityofParana ´ (PUCPR),Curitiba,Brazil
OsvaldoJoseVenturini
FederalUniversityofItajuba ´ —UNIFEI,Itajuba ´ ,Brazil
YuanYao
DepartmentofForestBiomaterials,NorthCarolinaStateUniversity,Raleigh,NC,United States
KristaDanielleS.Yu
SchoolofEconomics,DeLaSalleUniversity,Manila,Philippines
JadwigaR.Ziolkowska DepartmentofGeographyandEnvironmentalSustainability,TheUniversityofOklahoma, Norman,OK,UnitedStates
JadwigaR.Ziolkowska DepartmentofGeographyandEnvironmentalSustainability,TheUniversityofOklahoma,Norman,OK,
1Introduction
Biofuelsaredefinedasfuelsproducedfromlivingplantmatteror by-productsofagriculturalproduction;theyareprimarilygroupedintobiodieselandethanol.Biofuelscanbedividedandseparatedintoseveralgroups basedontheirtechnologies,processes,andfeedstocks.
Biofuelstechnology canbedefinedasapplicationoffeedstocksina sequenceofprocessesleadingtotheproductionofdifferentbiofuelstypes. Biofuelsprocesses areeithernaturalorchemicalstagesofanindustrialorpilot projectdevelopmentleadingtothefinalproductionofbiofuels. Biofuelsfeedstocks areanyliving,dead,ordecomposedplantmaterialssuitableforprocessingandconversiontobiofuelsbymeansofdifferentprocesses.
Fromtheperspectiveoftheindustrialdevelopmentandmarketpresence, biofuelsfeedstocks,processes,andtechnologiescanbeclassifiedas “developed”(withwell-establishedmarkets),“developing”(withnewly createdorprogressingmarketshares),orinthe“demonstration”stage
(describingpilotprojectsorpotentialfuturedevelopments)(compare: Lane, 2017).Duetoahighfeedstockvariabilityaccessibletobeutilizedforbiofuelsgenerationtheexistingbiofuelstechnologiesandprocesseshave expandedovertimethuscreatingawidenetofproductionopportunities andinnovationpotentialinthisfield.
Generally,biofuelstechnologiescanbedividedinto“conventional”and “advanced”biofuels(Fig.1.1).Conventionalbiofuels(alsocalled“firstgenerationbiofuels”)designateethanolandbiodieselgeneratedfromeatable crops.Advancedbiofuels(encompassingthe“second,thirdandfourthgenerationbiofuels”)aredefinedasliquidfuelsfromnonfood/nonfeedsustainablygrownfeedstocksandagricultural(municipal)wastes.Theneedfor advancedbiofuelsoriginatedfromaconcernaboutthecompetitionfornaturalresources(e.g.,water,energy,land)betweenfuelandfoodproduction (Rathmannetal.,2010; HarveyandPilgrim,2011, Ajanovic,2011). Accordingly,advancedbiofuelscannotcreateanycompetitionwithfood cropproduction,whiletheyneedtomeethighersustainabilityrequirements,thatis,contributetogreenhousegas(GHG)emissionreduction byalargerpercentagethanconventionalbiofuels.
Thedesignationofbiofuels“generations”isdirectlylinkedandsubject tothespecifictechnologyandfeedstockusedforbiofuelsproduction.Italso relatestothetemporaldevelopmenttrendsoveryearsandthecomplexityof
Fig.1.1 Biofuelstechnologieswithcorrespondingdevelopmentstages. (Authors’ presentationmodifiedfromZiolkowska,J.R.,2014.Prospectivetechnologies,feedstocks andmarketinnovationsforethanolandbiodieselproductionintheUS.Biotechnol. Rep.4,94–98;Ziolkowska,J.R.,2018.Introductiontobiofuelsandpotentialsof nanotechnology.In:Srivastava,N.,Srivastava,M.,Pandey,H.,Mishra,P.K., Ramteke,P.W.(Eds.),GreenNanotechnologyforBiofuelProduction.Biofueland BiorefineryTechnologies.Springer,Basel,pp.1–15.)
thebiofuelsmarketwithagrowingnumberofpotentialfeedstockstobe usedforbiofuelsproduction.
Firstgenerationbiofuels areproducedfromfoodcrops:(a)biodiesel extractedfromoilplants/plantmaterials(inthechemicalprocessoftransesterificationandesterification),and(b)ethanolextractedfromsugarcontainingplants/plantmaterialsandconvertedtofuelintheprocessof fermentation. Secondgenerationbiofuels areproducedfromnonfoodcrops (e.g.,cropwaste,greenwaste,wood,andenergycropsplantedspecifically forbiofuelsproduction). Thirdgenerationbiofuels arebasedonimprovements inbiomassproduction,withalgaebeingthemainfeedstockrepresentingthis groupasoftoday. Fourthgenerationbiofuels aimatprovidingmoresustainable productionoptionsbycombiningbiofuelsproductionwithcapturingand storingCO2 withtheprocessofoxy-fuelcombustionorbyapplication ofgeneticengineeringornanotechnology.
Duetothewiderangeoffeedstockapplicationandprocessdevelopment theevaluationofdifferentbiofuelsintermsoftheirsustainabilitywillclearly dependonthecombinationofthosefactors.Thusinthefaceofthemultitudeofdiscussionsinthisfield,acloserlookateachofthebiofueltypesis neededforaholisticandscience-basedevaluation.
Althoughthischapterdoesnotaimatinvestigatingsustainabilityofthe respectivebiofuelstechnologies,processes,andfeedstocksperse,itwillprovideanoverviewforabetterunderstandingofthoseissuestobeaddressedin thefollowingchaptersinthisbook.
2Biofuelstechnologiesandfeedstocks
Globally,thetotalbiofuelsproductionhasincreasedovertime,withanestimatedethanolproductionat160billionliters(42.3billiongallons)in2019 andbiodieselproductionat41billionliters(11billiongallons)(OECD, 2010)(Figs.1.2and1.3).Thefeedstockcompositionintheglobalbiofuels productionhasvariedandchangedconsiderablyovertimeaswell.Accordingto OECD(2010) projections,ontheethanolmarket,coarsegrains (includingcorn)havereachedthepeakin2016,whileethanolproduction fromsugarcanewillincreasethroughout2019.Anincreasingtrendwasalso projectedforbiomass-basedethanolwith11billionliters(2.9billiongallons) onthemarketin2019.Onthebiodieselmarket,vegetableoilsconstitutethe mainfeedstockthatisexpectedtoincreaseupto30.7billionliters(8.1billiongallons)by2019(OECD,2010).Alsojatrophaandothernonagriculturalfeedstocks(animalfats)makeasmallershareinthebiodiesel 3
Others feedstocks
Roots
Biomass based (second generation)
Fig.1.2 Globalethanolproductionbyfeedstock projections(2007–19). (Modified fromOECD-FAO,2010.AgriculturalOutlook2010.BiofuelProduction2010–19; Ziolkowska,J.R.,2018.Introductiontobiofuelsandpotentialsofnanotechnology.In: Srivastava,N.,Srivastava,M.,Pandey,H.,Mishra,P.K.,Ramteke,P.W.(Eds.),Green NanotechnologyforBiofuelProduction.BiofuelandBiorefineryTechnologies.Springer, Basel,pp.1–15.)
Biomass-based (second generation)
Jatropha
Nonagric. (animal fats)
Vegetable oil
Fig.1.3 Globalbiodieselproductionbyfeedstock projections(2007–19). (Modified fromOECD-FAO,2010.AgriculturalOutlook2010.BiofuelProduction2010–19; Ziolkowska,J.R.,2018.Introductiontobiofuelsandpotentialsofnanotechnology.In: Srivastava,N.,Srivastava,M.,Pandey,H.,Mishra,P.K.,Ramteke,P.W.(Eds.),Green NanotechnologyforBiofuelProduction.BiofuelandBiorefineryTechnologies.Springer, Basel,pp.1–15.)
production.However,theirusehasincreasedovertimeandcouldeven becomeofahigherimportanceinthefuture.Biodieselproductionfrom animalfats,however,hasremainedratherstableovertimeintermsofthe percentageshareinthetotalbiofuelsproduction(Fig.1.3).
2.1Conventional(firstgeneration)biofuels
Thefirstattemptsofbiofuelsengineoperation(peanutoilenginerunby RudolfDieselin1900andvegetableoilrunenginesin1930s)aswellthe firstindustrialbiofuelswerebasedonfoodcrops(Ziolkowska,2018).In thepastdecades,foodcropapplicationforbiofuelsproductionhasincreasinglybeencriticizedduetotwomajorissues:“fuelvs.food”trade-offand concernsabouttherealCO2 reductionpotentialofbiofuels(somebiofuels couldreleasemorecarbonintheirproductionprocessthansequesteritinthe feedstockgrowthprocess).
Becauseoftheseurgentissues,moststudiesinthisareafocusoncompetitionforresourcesresultingfromcropcultivationandtheirapplication eitherforfood/feedorbiofuelsproduction.Thistrade-offsituationforfood, feed,fuel,andproductionfactorscanimpactproducers,distributors,andthe relatedmarkets,andfinallyregionalandnationaleconomies(Tomeiand Helliwell,2016; Baffes,2013; Filipetal.,2017).Mostattentionintheliteraturehasbeengiventolandresources(Rathmannetal.,2010; Harvey andPilgrim,2011)andimpactsofbiofuelsproductiononfoodmarketprices (Ake,2017; Encisoetal.,2016; Tyner,2013; Ajanovic,2011).
Conventionalbiofuelsencompassethanol(producedfromcropswith highsugarcontents,e.g.,corn,cereals,sugarbeet/sugarcane)andbiodiesel (producedfromhigholeicplants,e.g.,soybean,rapeseed,palmoil,animal fats,wasteoils).
Inthepastdecades,conventionalbiofuelshavedevelopedintoflourishingfuelmarkets.In2015intheUnitedStatesalone,theconsumptionof ethanolinBTUenergyunits(1BTU ¼ 1055J)amountedto1.14quadrillionBTU,whilebiodieselconsumptiontotaled0.26quadrillionBTU.The totalcapacityofethanolconsumptionwasestimatedat15billiongallons(57 billionliters),while2billiongallons(7.6billionliters)forbiodiesel (USEIA,2016).
Productionofconventionalbiofuelshasvariedindifferentpartsofthe world,subjecttofeedstockavailability.Globalproductionofconventional biofuelsforthetransportsectorreached140billionliters(37billiongal)in 2017(IEA,2018).In2015,BrazilandtheUnitedStatesaccountedfor 70%
oftheglobalbiofuelsupplyofsugarcane-andcorn-basedethanol(REN21, 2016; Arau ´ joetal.,2017).Othersuppliers,thatis,EuropeanUnioncountriesandAsiahaveenteredthebiofuelsmarketinthelasttwodecades.BiofuelsproductionintheEuropeanUnionismainlybasedonbiodieselfrom waste,soybeans,rapeseed,andpalm(HuentelerandLee,2015),whileinthe AmericasandAsiaethanolproductionisprevailingwiththefollowingfeedstocks:sugarcane,corn,wheat,andcassava.InAsia,additionaleffortsand investmentsinrecentyearshavecontributedtoagrowingbiodieselmarket utilizingpalm,soybean,rapeseed,andJatrophafeedstocks.Theregionaland feedstockdiversificationhasbeenrecognizedbyseveralGermanassociations andagencies(GTZ,2006)aspotentiallyconducivetotheformationofan internationalbiofuelcommoditiesmarket.
2.2Advancedbiofuels
Thedevelopmentofadvancedbiofuelswaspropelledinresponsetoconcernsrelatedtothe“fuel-foodtradeoff”aswellasenvironmentalandeconomicquestionssurroundingconventionalbiofuels(UNReport,2007).By utilizingbiomass(notsuitableeitherforfoodorfeedpurposes)andinmany casesgrownonmarginallands,theproblemofresourcecompetitionin food/fuelproductioncouldpotentiallybemitigatedtosomedegree.At thesametime,emergingrecognitionsandnewknowledgeaboutenergy valueofbiofuels(comparedtofossilfuels)spurredquestionsabouteconomic efficiencyofbiofuelsingeneral(Czekałaetal.,2018).Forinstance,productionofcellulosicbiofuelishighlyenergyintensivemeaningthatenergycontainedinthistypeofbiofuelislowerthantheenergyrequiredforits production(GeandLi,2018).
EnvironmentalquestionsaboutadvancedbiofuelsrelatedirectlytoCO2 emissionreduction.ManystudiesprovidedevidencethatbiofuelscontributetoCO2 emissionreductionsinthefuelburningprocess(Mendiaraetal., 2018; KousoulidouandLonza,2016; Subramanianetal.,2018).However, itneedstobeemphasizedthattheexactemissionreductionlevelsstrongly dependontheappliedfeedstock,withalgaebeingacknowledgedamongthe leadingfeedstocks(ShubaandKifle,2018; Suetal.,2017; SavakisandHellingwerf,2015)withcarbonnegativeproperties(ZiolkowskaandSimon, 2014).However,concernshavebeenraisedaboutotherbiomassfeedstocks (e.g.,timber)pointingoutthatforestbioenergyisnotcarbonneutraldueto highCO2 emissionsreleasedinthewoodburningprocess(Moomaw, 2018).Accordingto USEIA(2016),theconsumptionofwood/forestry
biomass(includingwoodpellets,hogfuel,andwoodchips)utilizedforelectricityandheatproductioninBTUenergyunitsislargerthanbioenergy fromconventionalbiofuels.IntheUnitedStatesalone,woodbiomassconsumptionamountedto2.04quadrillionBTUin2015,whileittotaled 11milliontonsinwoodpelletcapacity.
2.2.1Cellulosicethanol(secondgenerationbiofuels)
Cellulosicethanolcanbeproducedfromanymaterialcontainingcellulose andlignocellulose.Themainfeedstocksourcesforcellulosicethanolproductioncanbedividedasfollows:
(a) Energycropsgrownspecificallyforthepurposeofconversioninto biofuels(e.g.,switchgrass,miscanthus,wheatstraw,poplar,willow, jatropha).
(b) Greenwasteusedasaby-productofotherproductionprocesses(e.g., cornstoverandotherfieldresidue,e.g.,stalksandstubble(stems), leaves,seedpods,aswellasforest/parkresidues).
Accordingto Chenetal.(2010),40%–70%ofhemicelluloseand72%–90% ofcelluloseincorncobscouldbeconvertedtoethanolusingdifferentbacteriaandfungi.Alsoapplicationofmoreunconventionalfeedstockscontainingcelluloseorlignin(e.g.,kapokfiber,pineapplewaste,wastepapers,and coffeeresiduewasteforbioethanolproduction)hasrecentlybeeninvestigated(Duttaetal.,2014; Choietal.,2012; Ruangviriyachaietal.,2010; Chenetal.,2010).
Thequestionofeconomicefficiencyofthesecondgenerationbiofuels remainsopenduetohighcostsrelatedtobreakingdowncellulose,makingit alessercompetitivefeedstockandbiofuelingeneralcomparedtofossilfuels. Althoughmanyindustrialandlaboratoryattemptshavebeenundertakenin thepastdecadetolowertheproductioncostsofcellulosicethanol,the experimentswerenotassuccessfulasinitiallyanticipated,withtheaverage priceforcellulosicethanolstillnotbeingcompetitiveenoughwithtraditionalgasoline.Asof2010,productioncostsofcellulosicethanolequaled to $2.65/galoffuel(Coyle,2010),whichwas $1morethancostsofcorn ethanol.ThemorerecentresearchstudiesandscenariosbytheNational RenewableEnergyLaboratory(NREL)haveproventhatcellulosicethanol couldbecostcompetitiveat $2.15/gal(NREL,2013).Duetothiseconomiclimitationdeterminingthemarketaccess,moststudiesinthisarea arefocusedonimprovingtechnologicalprocessesofcellulosedecompositionandbreakdown(LiuandBao,2017; Gaoetal.,2018; Shadbahr etal.,2018; Songetal.,2018).Manystudiesattemptedtoprovidesolutions
tohighcostsofsecondgenerationbiofuelsbyintroducingmicrobialorfungalsystemsfacilitatingmoreeffectiveandfastercellulosebreakdownandfermentationprocess(Bhatiaetal.,2017; Ziolkowska,2014).However, researchanddevelopmentinthisfieldisongoingandnowide-scalecommercialsolutionhasbeenintroduced,whichagain,willdependonthe respectivefeedstocksandtheircelluloseandlignincontents.
Anadvantageofadvancedbiofuelsisthatfeedstocksusedfortheirproductiongenerallygenerategreatergreenhousegasemissionssavings,and thusaremoresustainableanddesirablefromtheenvironmentalpointof view.Forthisreason,intheUnitedStates,withthe2007EnergyIndependenceandSecurityAct,theRenewableFuelStandards(RFS)wereintroducedasamandatetoexpandthequantityofrenewablefuelsblendedinto transportfuelfrom9billiongallons(34.07billionliters)in2008upto36billiongallons(136.27billionliters)in2022(Ziolkowska,2018;Ziolkowska etal.,2010).Withinthesetotals,startingin2015,only15billiongallons (56.78billionliters)canbeprovidedonthemarketfromconventionalethanol,whiletheremainingannualmandatedquantityneedstobesupplied fromadvancedfeedstocks.InApril2010,theRFS2wasenactedbythe EPAasanextensionoftheoriginalmandatespecifyingminimumquantities fromdifferentfeedstocksorbiofueltypesneededtobeblendedtowardthe totalmandate(FAPRI,2010; Ziolkowskaetal.,2010).Accordingly,thecellulosicethanolproductionwasmandatedtoincreaseeachconsecutiveyear withthegoalof16billiongallons(60.5billionliters)in2022(USEPA, 2010).Furthermore,cellulosicethanolwasassignedaLifeCycleAssessment requirementtobeeffectivewithreducingGHGemissionsbyatleast60% comparedtotheemissionlevelsgeneratedfromcombustionoftraditional gasoline(i.e.,fossilfuelsusedintransportation)(Table1.1).Duetothe 2007EnergyIndependenceandSecurityActandrenewablefuelstandards establishedasmandates,productionofcellulosicethanolandcompliance withitssupplyforblendinghasbeenmainlydiscussedintheUnitedStates. InEurope,wherebiofuelspolicyisbasedonvoluntarytargetsratherthan mandates,cellulosicethanolproductiontookoffatalatertimeandhas gainedlessattentioningeneral.
Itneedstobementionedthatinadditiontobioethanolproductionfrom thesecondgenerationfeedstocks,alsootheradvancedbiofuels(isopropanol, butanol,isobutanol,andfarnesol)havebeengainingonimportancedueto theirhighenergydensityaswellaslowerhygroscopicpropertiesandlower corrositytopipelinesduringtransportationthanotherfuels(Chenetal., 2013; Yuaetal.,2011).Inaddition,metabolicengineeringofbiosynthetic fuelscanleadtoevengreaterproductivityofthesealcohols.
Biodiesel1billiongal(3.79 billionI) 50%For2012andbeyonda
Cellulosic biofuel
16billiongal(60.57 billionI)
Advanced biofuel 21billiongal(79.49 billionI)
Renewable biofuel 36billiongal (136.27billionI)
a Couldbeincreasedfrom2013onward.
60%Subjecttoannual assessments
50%Anythingbutcornstarch, minimumof4billiongal additional
20%b
Minimumof15billiongal additional
b Onlyappliestofuelfromnewfacilities.”Grandfathered”facilitiesarethose(domesticandforeign)that commencedconstructionbefore31December2007andethanolfacilitiesthatcommencedconstruction priorto31December2009andusenaturalgasand/orbiomassforprocessheat.
DatafromUSEnvironmentalProtectionAgency(EPA),2010.NationalRenewableFuelStandard Program—Overview.OfficeofTransportationandAirQuality,USEPA,Washington,DC,April14; Ziolkowska,J.,Meyers,W.H.,Meyer,S.,Binfield,J.,2010.Targetsandmandates:lessonslearnedfrom EUandUSbiofuelpolicymechanisms.AgBioForum13(4),398–412.
2.2.2Algaebiofuels(thirdgenerationbiofuels)
Thethirdgenerationofbiofuelsaimsatimprovingtheproductionofbiomasstomakeitamoreviable(andsustainable)feedstock.Sincethebeginningsofthistechnology,thethirdgenerationbiofuelshavereliedonalgaeas themainfeedstock(growneithernaturallyorartificially).Manystudiesconfirmedthatthealgaefeedstockcanbecompetitivewithotherbiomass sources( JonesandMayfield,2012; ZiolkowskaandSimon,2014; Laurens etal.,2017; Adeniyietal.,2018),thusmakingit,inmanycases,moreprospectiveforcompanyinvestmentsthancellulosicethanol.Theadvantagesof algaeasafeedstockrelateto:
(a) Negative(carbonneutral)environmentalfootprintasbygrowingalgae 2gofCO2 areconsumedforeverygofgeneratedbiomass(Pienkosand Darzins,2009).Atthesametime,onetonofCO2 canbeconvertedinto 60–70galofalgae-basedethanol(Hon-Nami,2006;Hirayama etal.,1998).
(b) Possiblynocompetitionforfreshwaterasalgaecangrowinwaste/ salinewaterenvironment.
(c) Nocompetitionforfertileland(i.e.,nodirectfood-fueltrade-off)as algaeisgrowninclosedphotobioreactorsoropenponds(waterenvironments)whichcanbelocatedonanyplotoflandnotsuitablefor
otherpurposes,whichthuseliminatespotentialopportunitycosts (ZiolkowskaandSimon,2014).
(d) Highoilcontentsinalgaebiomassmakeitsuitabletoproduce10–100 timesmoreoilperacrethantraditionaloilcrops(suchasoilpalm)
(e) Fastgrowingrateasalgaecangrow20–30timesfasterthanfoodcrops (ZiolkowskaandSimon,2014).
(f) Highfueldiversityasalgaebiomasscanbeconvertedintoamultitudeof fueltypes,suchasdiesel,petrol,andjetfuel(seealso Jonesand Mayfield,2012).
(g) Highnutritionaldiversityofthefeedstockasitcanbeprocessedboth throughsugarandoilprocessingprocedurestoextractsugars/oilsfor biofuelsproduction.
(h) Highcompatibilitywithtraditionalgasolineengines(thuseliminating theneedofautomobileengineadjustments)duetothesamebiochemicalcharacteristicsandcomposition(energydensity,numberofcarbon atomspermolecule)aspresentingasoline(Solazyme,2012).
Despitethemanyadvantagesofalgaebiomassandalgae-basedfuels,itseconomicfeasibilityhasbeenquestionedandchallengedmanytimes(Doshi etal.,2016; VassilevandVassileva,2016).Also,economicandpolicyissues havebeenpointedoutaspossibledeterminantsoffuturedevelopments (Doshietal.,2016).In2008,thepriceforalgae-basedfuelsamountedto approximately $8/gal(USDOE,2008),whilethereisnouniformmarket estimateasthefinalpriceisdeterminedbyeachproducingcompanysubject totheappliedtechnologyandproductionfactors.Formanydecades,the industryhasstruggledwithbringingdowntheproductioncostandthus thefinalpriceofalgae-basedfuelsthroughreducingcostsofsystemsinfrastructureandintegration,algaebiomassproductionprocess,harvestingand dewateringtechniques,extractionandfractionation,andfinallybiofuels conversionprocess(USDOE,2010).Sustainableormarketcompetitive solutionshavenotbeenfoundtodatetomakealgae-basedfuelaviable anddesirablefuelduetothehighfuelunitcosts.
2.2.3Futuretechnology(fourthgenerationbiofuels)
Thefourthgenerationbiofuelsareinthedevelopmentandexperimental stages,thustheycombineadiversityofdifferent(potential)applicationsboth onthetechnology,processing,andfeedstocklevel.
Themainfeedstockforthefourthgenerationbiofuelsproductionis geneticallyengineered,highlyyieldingbiomasswithlowligninandcellulosecontents(thuseliminatingtheissuespresentinthesecondgeneration
biofuelsproductionline)ormetabolicallyengineeredalgae(withhighoil contents,increasedcarbonentrapmentability,andimprovedcultivation, harvesting,andfermentationprocesses)(thusimprovingthethirdgeneration production)(Duttaetal.,2014).Whilealgaehavecommonlybeenrecognizedforitshighoilcontents,theexactparametersdependontherespective algaestrains. Botryococcusbraunii,Chaetoceroscalcitrans,Chlorella species, Isochrysisgalbana,Nannochloropsis,SchizochytriumlimacinumandScenedesmus specieshavebeenanalyzedintheliteraturesofarfortheirapplicabilityand suitabilityforbiofuelsproduction(Chisti,2007; Rodolfietal.,2008; Singh andGu,2010).Ithasbeenfoundthatthefastgrowingalgae(e.g.,Spirulina) havelowoilcontent,whilealgaestrainshighinlipidcontentsarecharacterizedbyslowergrowthrates.Thusintroducingnewtechnologieslike metabolicengineeringforacceleratedgrowthofalgaebiomassorincreased lipidcontentscanresultinfastercommercializationandimprovedeconomic feasibilityoffourthgenerationbiofuels(SinghandGu,2010).Nanotechnologycouldalsobeappliedinalgaefuelproductiontoincreaseefficiencyof algaebiomassanddecreaseproductioncosts,thusmakingitacostcompetitiveadditiontothebiofuelmarket(Ziolkowska,2018).
Thefourthgenerationbiofuelsisdistinguishedfromotherbiofuelsproductiontechnologiesalsobythefactthatinmostcasestheyrepresentacombinationofdifferenttechnologies,forexample,sustainableenergy production(biofuels)andcapturingandstoringCO2 emissions.Biomass absorbingCO2 duringitsgrowthismanufacturedintobiofuelbymeans ofthesameorsimilarprocessesassecondgenerationbiofuels.Thedifference betweenthefourthgenerationbiofuelscomparedtothesecondandthird generationproductionisthattheformercapturesCO2 emissionsatallstages ofthebiofuelsproductionprocessbymeansofoxy-fuelcombustion (Ohetal.,2018; Sheretal.,2018).Oxy-fuelcombustionisaprocessutilizingoxygen(ratherthanair)forcombustionyieldingfluegasCO2 andwater (Markewitzetal.,2012).Whiletheprocessismoreeffectiveingenerating CO2 streamofahigherconcentration(themassandvolumearereducedby about75%),makingitmoresuitableforcarbonsequestration,theeconomic problemoccursmainlyattheinitialstageofseparatingoxygenfromtheair andusingitforcombustion.Theprocessrequireshighenergyinputs;nearly 15%ofproductionofacoal-firedpowerstationcanbeconsumedforthis process(UniversityofEdinburgh,n.d.),whichcanultimatelydriveupproductioncostsandmakethefinalprocesseconomicallyinfeasible.Even thoughcurrentlystillnotcompetitive,oxy-fuelcombustionhasbeenstudiedasapotentialalternativeincombinationwithbiofuelsproduction.For
thisreason,thistechnologyisinthedevelopingstageasoftoday.However, ifsuccessfullyvalidatedinthefuture,itcouldbeusedtogeosequesterCO2 bystoringitinoldoilandgasfieldsorsalineaquifers.Inthisway,through carboncapturingandstorage,thefourthgenerationbiofuelsproduction couldbecalledcarbonnegativeratherthancarbonneutral.Thusenvironmentaladvantagesarisebothfromcarbonstorageandfromreplacingfossil fuelswithbiofuels(UniversityofEdinburgh,n.d.).
Theremainingfuelfromoxy-fuelcombustioniscleanedandliquefied andyieldsultracleanbiohydrogen,biomethaneorsyntheticbiofuelsthat canbeusedinthetransportsectoraswellasforelectricitygeneration.
Anotherpotentialtechnologicalcombinationforbiofuelsproductionhas beenproposedbytheJoulecompanywiththeirrenewablesolarfuelgeneration(Fig.1.4).
Thecompanydevelopedaprocessforhydrocarbon-basedfuelgenerationthroughtheapplicationofnonfreshwater,nutrients,cyanobacteria, carbondioxide,andsunlight.Theprocessisbasedonheliocultureusing photosyntheticorganisms;however,itisdistinctfromthetraditional algae-basedfuelinthatthelatterneedtoberefinedintofuel,whilehelioculturedirectlyproducesfuel(eitherethanolorhydrocarbons)notrequiring
Fig.1.4 Joulehelioculturerenewablesolarfuel. (FromSt.John,J.,2010.Joule PatentsSecretSauceforDiesel-ExcretingOrganisms.2010.GigaOm,September14. https://gigaom.com/2010/09/14/joule-patents-secret-sauce-for-diesel-excreting-organisms (24November2018).)
anyrefinement.Theprocessdoesnotproducebiomasseither,thusmaking thetechnologyeasiertoapplyinpractice.AlthoughthecompanywasdiscontinueditsoperationinAugust2017duetodifficultieswithraisingadditionalfundsforfuturedevelopments,thesuggestedinnovationbasedon helioculturepresentsanattractivetechnologicalattempt.Thecompany claimedtobeabletoproducemorethan20,000galoffuelperacreperyear (19,000m3/km2).TheeconomicestimatesbyJouleUnlimitedclaimedits producttobecostcompetitivewithcrudeoilat $50abarrel($310/m3) (St.John,2010).
Moreover,nanotechnologyhasalsobeenconsideredasatechnological solutiontoalleviatechallengesrelatedtoalgalbiomassgrowthandcultivation(Sekoaietal.,2019; GavrilescuandChisti,2005),mainlyhighcostsof algaeharvestingandproductionaswellasenergy-intensivelipidextraction (PattarkineandPattarkine,2012).Anewformof“nanofarming”technologyiscurrentlyinthepilotstageandcouldfindwidecommercialapplication.Itfacilitatesoilextractionfromalgaeevenmoreefficientlyasitrelieson aprocessof“milkingalgae,”thususingbiomasscontinually(upto70days) ratherthandestroyingitasisthecommoncasewithconventionalmaterial scienceprocesses(Vinayaketal.,2015; Chaudryetal.,2016; Ziolkowska,2018).
3Biofuelsprocesses
Fromthetechnologicalperspective,fourmainprocessescanbedistinguishedforbiofuelsproduction:
(a) Mechanicalprocesses involvingtraditionalprocessingofwoodmaterials throughmechanicaltreatment,forexample,chippingorgrinding, andpotentiallythefollowingdensificationofthematerialbypelletizing thebiomass.
(b) Thermochemicalprocesses convertingbiomassintoenergythroughcombustion,followedbypyrolysis.Thisprocessismoreefficientthan mechanicalprocessesduetogreaterenergydensityaswellaschemical andphysicalfuelpropertiesbeingmoresimilartofossilfuels.Another possibleprocessisgasificationgeneratingsyngasfortheproductionof differentliquidbiofuels,throughtheFischer-Tropsch(FT)process.
(c) Chemicalprocesses areusedmainlyfortheproductionoftransportation fuels,suchasbiodieselandcellulosicethanol.
(d) Biochemicalprocesses appliedtoproducefuelethanol,forexample,sugar/ starchfermentationleadingtobiogas(methane)generationinanaerobic conditions.
Intheproductionprocessoffirstgenerationbiofuels,mainlysugarfermentationfollowedbythedistillationprocessisappliedtoproducedryethanol. Biodieselisproducedthroughtransesterificationofoilswithachemicalcatalyst(acid/alkali)orenzyme(Duttaetal.,2009; vanGerpenetal.,2002), followedbyatwo-stepdistillationtoremoveby-products(e.g.,glycerol).
Inregardtothesecondgenerationbiofuelsproduction(e.g.,cellulosic ethanol,butanol),thefollowingprocessesareapplied:pretreatmenttoseparatecelluloseandhemicellulosefromlignin,enzymatichydrolysis(i.e.,saccharification)toextractsimplesugars,fermentation,andfinallydistillation. Alsobiogasscanbeproducedthroughthesamesequenceofthebiochemical processesuptodistillation.Accordingly,gasificationorpyrolysis(thermochemicalprocesses)isappliedtoconvertbiomassathighertemperatures andpressuresthanthoseappliedinbiochemicalprocesses.Theprocessof biomassgasificationanddirectliquefactioniscommonlycalled“biomassto-liquid.”Gasificationismorecostintensivethanotherprocesses;however,itproducescleanerfuelthatcanbedirectlyusedinengines(Larson, 2007).Throughthegasificationprocess,avarietyofbiofuelscanbeproduced,suchasFischer-Tropschliquids(FTL),dimethylether(DME), andotheralcohols(FitzPatricketal.,2010; Duttaetal.,2014).
Thethirdandfourthgenerationbiofuelscanbeextractedwiththesame processes,whilethedifferencerelatesonlytothefeedstockusedattheinput stage(traditionallycultivatedalgaeforthethirdgenerationfuels,andgeneticallymodifiedalgaebiomassforthefourthgenerationfuels).Thusdifferent finalindustrialfuelscanbeextractedindifferentprocessesofthethirdand fourthgenerationbiofuelsproduction,asfollows:
(a) Biodieselthroughoilextraction,transesterification,anddistillation.
(b) Ethanol,biomethane,andbiobuthanolthroughbiochemicalprocesses, whilebiomethaneandbiobuthanolareprocessedinadditionthrough anaerobicdigestion.
(c) Syngas,syntheticdiesel(aviationfuel),andbioenergythroughthethermochemicalprocessofgasification(Duttaetal.,2014).
4Summaryandconclusions
Biofuelsproductionhasfacedmanysustainabilitychallengesoverthe decadesoftechnological,feedstock,andprocessdevelopments.Highcosts
offeedstockprocessingandenvironmentalconcernshavebeenamongthe majorissuesdiscussedinscientificdebatesandpolicyconsiderations.While conventionalbiofuelswereintroducedwithanefforttoincreaseenergy independencyfromfossilfuels(andforeignfuelimports),advancedbiofuels emergedasinnovationspilloversandexpandedataprogressivepace. Accordinglyavarietyofnewfeedstockshasbeenexploredandexperimentedwithtoalleviateeconomiclimitationstothosenewtechnologies.The mainpurposeoftheseinvestmentswastobringdowntheproductioncosts andthefinalpriceofadvancedbiofuels,withtheaimofmakingthemcompetitivewithfossilfuelsastransportationfuelandbioenergy.Althougha considerablesuccesshasbeenachievedintheseareas,challengesstillexist. Newtechnologicalinventions,suchasnanotechnologyandgeneticengineeringofbiofuelfeedstockscouldproveasaviablesolution.However, environmentalandsocialissuesofthesetechnologies(includingunexplored consequencesoftheirapplicationandpotentialimpactsonwaterresources, soil,andthefollowinginfluenceonhumans)havenotbeenfullyexplored yet.Socialresistancetothesetechnologies(ascurrentlyalsoanalyzedinthe foodsector)mightbedecisiveinthemid-andlong-termalsoforbiofuels production.
Governmentalandprivatefundingforresearchanddevelopmentofnew biofuelstechnologiescanbringaboutprospectivesolutionstothosequestionsandmakenewgenerationbiofuelsmoreeconomicallyfeasible,environmentfriendly,andsociallyacceptable.
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19 Biofuelstechnologies:Anoverviewoffeedstocks,processes,andtechnologies
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Vinuselvi,P.,Park,J.M.,Lee,J.M.,Oh,K.,Ghim,J.M.,Lee,S.K.,2011.Engineering microorganismsforbiofuelproduction.Biofuels2(2),153–166.
