Long-Term Prospects for the Environmental Profile of Advanced Sugar Cane Ethanol

Long-Term Prospects for the Environmental Profile of AdvancedSugar Cane EthanolCinthia R U da SilvadaggerDaggersect Henrique Coutinho Junqueira FrancoDagger Tassia Lopes JunqueiraDagger

Lauran van Oerssect Ester van der Voetsect and Joaquim E A SeabradaggerDagger

daggerFaculdade de Engenharia Mecanica Unicamp Rua Mendeleyev 200 Cidade Universitaria ldquoZeferino Vazrdquo Campinas SP Brazil13083-860DaggerBrazilian Bioethanol Science and Technology Laboratory (CTBE) minus CNPEM minus Rua Giuseppe Maximo Scolfaro 10000 Polo II deAlta Tecnologia PO Box 6170 Campinas SP Brazil 13083-970sectInstitute of Environmental Sciences (CML) Leiden University PO Box 9518 2300 RA Leiden The Netherlands

S Supporting Information

ABSTRACT This work assessed the environmental impactsof the production and use of 1 MJ of hydrous ethanol (E100)in Brazil in prospective scenarios (2020minus2030) consideringthe deployment of technologies currently under developmentand better agricultural practices The life cycle assessmenttechnique was employed using the CML method for the lifecycle impact assessment and the Monte Carlo method for theuncertainty analysis Abiotic depletion global warming humantoxicity ecotoxicity photochemical oxidation acidificationand eutrophication were the environmental impacts categoriesanalyzed Results indicate that the proposed improvements(especially no-til farmingminusscenarios s2 and s4) would lead to environmental benefits in prospective scenarios compared to thecurrent ethanol production (scenario s0) Combined first and second generation ethanol production (scenarios s3 and s4) wouldrequire less agricultural land but would not perform better than the projected first generation ethanol although the uncertaintiesare relatively high The best use of 1 ha of sugar cane was also assessed considering the displacement of the conventionalproducts by ethanol and electricity No-til practices combined with the production of first generation ethanol and electricity(scenario s2) would lead to the largest mitigation effects for global warming and abiotic depletion For the remaining categoriesemissions would not be mitigated with the utilization of the sugar cane products However this conclusion is sensitive to thedisplaced electricity sources

INTRODUCTION

Bioethanol production has increased worldwide pushed by theneed to displace fossil fuels and reduce the emissions ofGreenhouse Gases (GHG) In Europe and US relevant ruleswere adopted to foster the sustainable use of biofuels12

although there are concerns about the possible negative impactsof these mandates on the global ethanol market3 Despite themethodological differences4 both regulations indicate that firstgeneration sugar cane ethanol has a substantial potential tomitigate GHG emissions Additionally if managed sustainablybiofuels can help to solve pressing environmental social andeconomic problems In this sense cellulosic biofuels andsustainable agriculture are quoted among the long-term ldquowin-winrdquo opportunities for biofuels5

In face of the vast availability of sugar cane residues6

investments on research and development of ethanol fromlignocellulosic materials compose the Brazilian efforts toimprove the environmental performance of sugar cane ethanolMore specifically the creation of the Brazilian BioethanolScience and Technology Laboratory (CTBE) reflects the

government support for the development of agricultural andconversion technologies aimed at the sustainable expansion ofethanol production in the country78

Some studies have already been published providinginformation about the projected environmental and economicperformance of ethanol production from sugar cane residues inBrazil considering different technological configurations andassumptions9minus14 In spite of the relative agreement on theeconomics results concerning environmental aspects (GHGemissions) can be controversial depending on the functionalunit adopted and other methodological choices910 Atechnoeconomic evaluation favored the biochemical conversionwhen compared to the thermochemical conversion of bagasseto ethanol11 while another study indicated the importance ofthe integration of second generation (biochemical route) into

Received May 27 2014Revised September 12 2014Accepted September 17 2014Published October 2 2014

Article

pubsacsorgest

copy 2014 American Chemical Society 12394 dxdoiorg101021es502552f | Environ Sci Technol 2014 48 12394minus12402

an optimized first generation plant to increase processfeasibility since part of the infrastructure could be shared andbagasse is already available in the plant12 The secondgeneration technology can also benefit from thermal andwater integration with positive implications for the paybacktime when integrated with sugar production13

Besides the development of second generation ethanolimprovements in the sugar cane cultivation are expected as wellMinimum tillage practices for instance have already beenintroduced in some sugar cane areas and no-til farming isexpected to be in place in the medium-long-term In thiscontext CTBE is developing a controlled traffic structure(ETC) to reduce soil compaction and hence reduce thenumber of required operations for soil preparation and facilitatethe introduction of the no-til farming8 Even withoutconsidering the use of ETC Bordonal et al15 already indicatea better performance of the first generation ethanol whenminimum tillage practices are usedThese developments are expected to favor the sustainability

of sugar cane ethanol but their environmental benefits are notclear yet Analyses are thus required to evaluate theenvironmental gains of the adoption of advanced cultivationpractices and conversion technologies (such as ETC and sugarcane residues-to-ethanol) in face of the alternative uses of sugarcane biomass and the incremental developments expected insugar cane production in the futureAssuming that such technologies could improve ethanolrsquos

environmental profile this work assessed the environmentalimpacts of the production and use of 1 MJ of hydrous ethanolin Brazil in prospective scenarios Comparisons were carriedout considering as reference the current life cycle performanceof Brazilian sugar cane ethanol and fossil gasoline In additionto ethanolrsquos life cycle profile the net environmental benefits ofeach scenario were also evaluated considering the displacementof the equivalent fossil alternatives of sugar cane bioenergy iegasoline as a transportation fuel and natural-gas-poweredthermoelectricityThe analysis employed the Life Cycle Assessment (LCA)

technique considering eight environmental impacts categoriesabiotic resource depletion global warming photochemicaloxidation human toxicity freshwater aquatic ecotoxicityterrestrial ecotoxicity acidification and eutrophication Land-use requirements for ethanol production were estimated andbriefly discussed Given the uncertainties associated with theprojected conditions an uncertainty analysis was conductedbased on the Monte Carlo method This analysis is expected tosupport decisions about the best utilization of biomassresources for the maximization of environmental gains

MATERIALS AND METHODSLife Cycle Assessment The study used the Life Cycle

Assessment (LCA) technique to evaluate the ethanol environ-mental profile for each scenario considering an attributionalwell-to-wheels approach The CML version 39 a problemoriented approach was the method employed in the Life CycleImpact Assessment (LCIA)1617 covering eight environmentalimpact categories abiotic resource depletion (fossil fuels)global warming photochemical oxidation human toxicityfreshwater aquatic ecotoxicity terrestrial ecotoxicity acid-ification and eutrophication These categories embrace themain emissions in the ethanol life cycle The CMLCAsoftware18 was used to create and link the life cycle processesand to assist in the interpretation phase including the

development of the contribution and uncertainty analysesThe functional unit for the comparative LCAs was 1 MJ ofhydrous ethanol and the allocation method was based onpartitioning using energy flowsIn addition to the ethanolrsquos life cycle profile the best use of 1

ha of sugar cane was also assessed In this case the studycompared the net environmental benefits of each scenariotaking into consideration the displacement of the conventionalproducts gasoline and thermoelectricity produced in a naturalgas power plantThe gasoline life cycle inventory was assembled using

representative parameters of the Brazilian conditions19

disregarding changes in the supply chain within the time-horizon of this analysis With respect to the electricitygeneration in natural gas-fired power plants the UCTE lifecycle inventory from the Ecoinvent database was used1020 Asensitivity analysis was performed to show the impact of twoextreme cases considering that the surplus electricity woulddisplace the average electricity mix in Brazil or electricity fromcoal-fired power plants using EcoInvent database for UCTE20

The life cycle inventory of the average electricity was based onan adapted process of the Ecoinvent database20 considering the2011 mix (817 hydroelectricity 65 biomass 05 wind14 coal 25 fossil oil 46 natural gas 27 nuclear21) Forthe coal-based electricity it was assumed the UCTE life cycleinventory from Ecoinvent20

Emissions and removals of biogenic carbon along the processchain were assumed to be synchronized so they were not takeninto account The land use change (LUC) impacts were not thefocus of this work but the land-use requirements for ethanolproduction in each scenario were estimated and brieflydiscussed In terms of the impacts it is worth mentioningthat the recent sugar cane expansion in Brazil has mostlyoccurred over pasture land and the overall effect may actuallybe of increasing the C stocks in soil although largeuncertainties exist because of the still lack of information oncarbon stocks22minus25

For the foreground systems representative data of Brazilianconditions were collected while Ecoinvent database was usedwhen data was not available for the background processes Asthe analysis considered projected conditions based on theestimations of different specialists ranges of values were verifiedand uncertainties exist A contribution analysis was performedas part of the interpretation phase to subsidize the uncertaintyanalysis The uncertainty assessment followed the Monte Carlomethod using 2000 trials The parameters for the Monte Carloanalysis are in the Supporting Information

Scenarios Definition and Description Four prospectivescenarios were considered in the analysis covering two optionsfor bagasse utilization and two different sugar cane productionsystems as presented in Table 1 One scenario (scenario s0)

Table 1 Description of the Prospective Scenarios

sugar canecultivationminimumtillage

sugar canecultivationno-tillage

production of first generation ethanol from canejuice and electricity surplus from sugar caneresidues (bagasse and straw)

scenario s1 scenario s2

combined production of first and secondgeneration ethanol with reduced level ofelectricity exports (surplus)


Environmental Science amp Technology Article

dxdoiorg101021es502552f | Environ Sci Technol 2014 48 12394minus1240212395

representing the current good practices for sugar cane andethanol production was also analyzed in order to estimate theenvironmental improvements enabled by the advancedtechnologies considered in this work This scenario assumesthe current sugar cane cultivation practices without preharvest-ing burning and production of first generation ethanol fromcane juice and electricity surplus from sugar cane residues(bagasse and straw)Further details about the production pathways are given

below while Figure 1 and Figure 2 show the product systemsconsidered

Sugar Cane Cultivation An important change expected insugar cane cultivation in the near future is the completeelimination of the preharvesting burning practice26 In theunburned system sugar cane harvesting is fully mechanizedand a relevant amount of biomass (sugar cane straw also calledsugar cane trash) becomes available for industrial applicationsHowever it can also be left on the field aiming at theenhancement of the soil condition including soil protectionand maintenance of soil moisture The amount of straw to beleft on the field and to be recovered for industrial applicationsshould be defined according to the soil properties of each farmobserving the expected agricultural and industrial benefits frombiomass utilization In this study it was assumed for theprospective scenarios that 50 of the straw (ie 70 kgdrytcane) would be left on the field and the remaining 50 wouldbe collected for industrial use Given that part of the residueswould remain on the field reduced tillage practices could beadoptedIn the scenario s0 it was assumed that all the unburned straw

is left on the field under the conventional sugar canecultivation practices27 In scenarios s1 and s3 minimum tillageis adopted which eliminates some operations (currently inpractice) for soil preparation due to the protection promotedby the straw blanket Sugar cane harvesting in these scenarios isperformed by conventional harvesters Scenarios s2 and s4 on

the other hand assume the implementation of the low impactmechanization to enable the no-til farming In this systemsugar cane harvesting is performed by the Controlled TrafficStructure (ETC) which is able to prevent soil compaction thuseliminating the need for soil preparation operations82829 Thisis possible because the wheels of the equipment run alongpermanent georeferenced tracks (spaced 9 m apart) Thissystem reduces the traffic of agricultural implements in the canefields from 60 (current mechanization) to less than 10 ofthe planted area8 Due to the conservationist managementpractices the projected gains in sugar cane productivity areexpected to be higher in scenarios s2 and s4 compared to thosein scenarios s1 and s3 because ETC would be able to maintainthe productivity of the ratoon cane In the same way sugar caneproductivity is expected to be higher in scenarios s1 and s3compared to s0 In terms of sugar cane quality (sugar content)no differences are expected between the scenarios but a higherTotal Recoverable Sugar content is expected in the future (160kgt) which will allow a higher ethanol yieldAnother improvement assumed for the prospective scenarios

was the stillage concentration (14 of the initial volume) whichwould favor the logistics of stillage distribution allowing itsapplication as fertilizer in the whole sugar cane field It wasassumed that the concentrated stillage has the same nutrientsthan the conventional stillage but in a smaller water volume(ie higher concentration) Stillage from second generationethanol however is assumed to be rather poor in nutrients sobasically all nutrients available are related to the stillageproduced from sugar cane juice processing (first generationethanol) The environmental legislation about stillage applica-tion on the field was observed in the calculation30 Because ofthe improved production practices and better use of theresidues from ethanol production it is expected that sugar canecultivation in the future will require less mineral phosphorusand no potassiumAs the product systems represent a future situation (2020minus

2030) parameters for the foreground systems were definedbased on the opinions of experts on sugar cane production andtransportation in Brazil These projected parameters fedspreadsheet models (Canasoft spreadsheet model developedby Technological Assessment Program at CTBE) dedicated tothe estimation of the total inputs and outputs from sugar caneproduction and transportation from the field to the mill foreach scenario

Sugar Cane Transportation The transportation of sugarcane from the field to the mill is performed by trucks withdifferent payload capacities In this work it was assumed that100 of the sugar cane will be transported by turnpike doublesThe uncertainty analysis takes into account the use of the othertypes of trucks

Ethanol Production In the last decades ethanol distilleriesin Brazil have experienced a considerable improvement in termsof the overall sugar conversion efficiency31 For the futurehowever little room has been left for further advances Stillsignificant progress is expected regarding the energy balance ofthe mill and the utilization of the sugar cane residues Todayethanol production in Brazil is self-sufficient in energy as thecogeneration plant provides all the steam and electricityrequired by the process using bagasse as fuel In additionmany mills are already able to export electricity to the gridminuseg532 of mills are connected to the grid in Sao Paulo State32

All green field (and several brown field) units are equipped withhigh pressure cogeneration systems (eg 68 bar) enabling

Figure 1 Product system for scenarios s0 s1 and s2



electricity exports greater than 60 kWht of cane using onlybagasse as fuel while the implementation and progress of canestraw recovery may practically double power exports32minus34

In this study these developments were taken into account inall prospective scenarios Basically it was considered theadoption of the following equipmentconfigurations (i)electrical engines instead of steam turbines as mechanicaldrivers (ii) juice extraction with diffusers (iii) high pressuretemperature cogeneration systems (iv) stillage concentrationStillage concentration was carried out considering theintegration to distillation columns35 using a series ofevaporators (multiple effect evaporation minus MEE) operatingbelow atmospheric pressure which allows a temperaturedifference between MEE and distillation columns In thiswork a 5-stage evaporation system was considered as

commonly used in sugar cane mills The low-grade heat fromthe rectification column condenser which condensates thehydrous ethanol was used as energy source for raising steamThus it was possible to concentrate stillage without increasingthe energy demandAdditionally it was considered the reduction of the process

steam consumption related to the first generation ethanolproduction and the use of straw as supplementary fuel tobagasse For scenarios s1 and s2 these improvements lead tolower energy consumption higher power generation andconsequently higher electricity surplus For scenarios s3 and s4they allow the utilization of more bagasse for biochemicalconversion while keeping some potential to export electricityIn scenarios s3 and s4 the production of first and second

generation ethanol takes place in an integrated plant As

Figure 2 Product system for scenarios s3 and s4

Table 2 Basic Data Related to Sugarcane Production and Processing and Ethanol Distribution

scenarios

item unit s0a s1 s2 s3 s4

cane productivity t cane haminus1 831 110 132 110 132straw (dry basis)b cane stalks 140 140 140 140 140sugar cane preharvesting burning area 00 00 00 00 00mechanized harvesting area 1000 1000 1000 1000 1000diesel consumption L haminus1 1614 1310 747 1310 747straw sent to the mill 00 500 500 500 500sugar cane transportation by turnpike doublesc 1000 1000 1000 1000 1000sugar cane TRS kg tminus1 cane 1400 1600 1600 1600 1600ethanol yieldd kg tminus1 cane 681 758 758 961 961electricity surpluse kWh kgminus1 EtOH 12 26 26 11 11mill capacity Mt yearminus1 20 30 30 40 40ethanol distributionminustruckf 1000 800 800 800 800ethanol distributionminuspipeline 00 200 200 200 200

aBased on ref 27 bReference 42 cDistance from the field to the mill 251 km (scenario s0) 266 km (future scenarios) dLower heating value 248MJ EtOH-1 e36 MJ kWhminus1 fAverage distance of 340 km41



illustrated in Figure 2 after the pretreatment (with steamexplosion) and the enzymatic hydrolysis the unreacted solidsare sent to the cogeneration plant while the hydrolyzed liquoris mixed with the sugar cane juice With such configurationconcentration fermentation and distillation operations areshared between first and second generation ethanol processes12

It was assumed that both pentoses and hexoses in thehydrolyzed liquor would be fermented into ethanolData related to sugar cane processing were obtained from

simulations using Aspen Plus software1233 taking into accountthe technological improvements described above Data relatedto enzyme production (for enzymatic hydrolysis) wereestimated from the literature3637 Data for sugar cane bagasseboiler emissions was retrieved from the GREET model38 sincemodern boilers assumed in this work are expected to emit lesspollutants than the current ones39 The use of capital goods(buildings and equipment) was estimated from an ethanoldistillery that processes 2 Mt of sugar cane per year40 For allcases the lifetime of the ethanol plant was assumed to be 30yearsEthanol Distribution This study assumed that ethanol

would be produced and used in Brazil For all scenarios it wasconsidered that ethanol would be distributed via pipeline andtrucks41

Ethanol Use It was considered the use of hydrous ethanol asneat fuel in spark ignition engines27

Table 2 summarizes the basic data for ethanol LCAmodeling Parameters collected from the interviews withspecialists and those used for hydrous ethanol productionsimulation are available in the Supporting Information alongwith all the remaining data used for the LCA modeling

RESULTS AND DISCUSSION

Sugar Cane Ethanol LCA The comparison between theprospective scenarios and the current scenario (s0) indicatesthat the technological improvements considered here wouldcontribute to decrease the environmental impacts in allcategories analyzed except photochemical oxidation inscenarios s3 and s4 Results for each scenario includinggasoline are shown in Figure 3 while the complete Life CycleInventories are available in the Supporting InformationThe main reasons for the environmental improvement of the

prospective scenarios in comparison to the current scenario

(s0) are (i) sugar cane cultivation practices with higher sugarcane productivity and lower diesel demand for agriculturaloperations as presented in Table 2 (ii) lower use of mineralfertilizers once prospective scenarios use stillage concentrationallowing its application in the whole sugar cane area (iii) loweruse of pesticides per tonne of cane since the application perarea are expected to be maintained along with more biologicalcontrol (iv) higher ethanol yield because of the expectedincrease in sugar canersquos sugar content in the prospectivescenarios (v) higher electricity surplus because of the strawcollection for power generationCompared to gasoline ethanol in all scenarios features

smaller impacts in the global impact categories abiotic depletionand global warming Gasoline on the other hand performsbetter with respect to the remaining regional impact categories(although this cannot be extrapolated to categories other thanthose studied here) In this sense it is interesting to note theconcentrated production of large volumes of gasoline in oilrefineries compared to the scattered production of ethanol insugar cane mills which could represent an environmentalconcern depending on the local conditions However suchanalysis is beyond the scope of this study and the conclusionalso depends upon the subjective political weighting of thedifferent environmental problemsAmong the prospective scenarios s2 and s4 feature the

smallest environmental impacts This is due to the ETC useassociated with the no-tillage practices which would enablehigher sugar cane productivities Such results suggest therelevance of advanced farming technologies for enhancingethanolrsquos environmental profile The reduced use of diesel inagricultural operations is another reason for the comparativeadvantage of scenarios s2 and s4 ETC is expected to consumeless diesel than the conventional harvester in good part becauseof the permanent tracks Besides sugar cane harvesting withETC would prevent some soil preparation operations beforeplanting Because of these aspects in scenarios s2 and s4 sugarcane farming is responsible for less than one-fourth of the totalethanolrsquos life cycle diesel consumption while in scenarios s1and s3 the diesel requirements for farming sugar canetransportation and ethanol distribution are approximately thesameRegarding the technology for ethanol production scenario s2

(first generation) is the most favorable and scenario s3 (secondgeneration) is the less favorable Since less electricity surplus is

Figure 3 Comparative environmental impact indicators of the different scenarios (1 MJ as functional unit)



cogenerated higher environmental load is allocated to ethanolAlso inputs associated with the second generation ethanolproduction contribute to the best results of first generationethanol The exceptions are acidification and eutrophicationwhich are smaller in scenarios s3 and s4 than respectively inscenarios s1 and s2 This is due to NOx emission associatedwith biomass combustion in the cogeneration plant so theseimpacts are higher in those scenarios featuring greater fuelconsumption (thus greater electricity surpluses)The land-use requirement would be smaller in scenario s4

due to the higher sugar cane productivity and ethanol yieldDespite the worst performance among the prospectivescenarios scenario s1 would still be better than scenario s0since higher sugar cane productivity is expected with theminimum tillage practices as well as higher electricity surplus

because of the recovered straw It is also possible to see that thesecond generation technology could contribute to decreaseland use more than better practices for sugar cane productionThe contribution analysis (illustrated in the Supporting

Information) indicates that carbon dioxide emissions associatedwith diesel consumption for sugar cane transportation andethanol distribution are the most relevant to global warmingwith significant contributions from N2O emissions related tonitrogen fertilizers For acidification and eutrophicationammonia emissions from nitrogen fertilizers are the mostrelevantCarbofuran and diuron used as nematicide and inseticide

are the main contributors to human toxicity and ecotoxicity(freshwater and soil toxicity) As indicated before the lesser useof pesticides per ton of sugar cane in comparison to the

Figure 4 Uncertainty analysis Error bars represent two standard deviations (2σ)



conventional production justifies the lower impacts related tothose categories So the replacement of those chemicalscomposes an important strategy for future mitigation ofethanolrsquos environmental impactsNOx emissions associated with bagasse combustion represent

a significant portion of the impact on acidification andeutrophication in scenarios s1 and s2 Those emissions aresmaller in scenarios where second generation ethanol isproduced (s3 and s4) It must be noted however that boileremissions were estimated based on emission factors obtainedfrom the literature and may not represent the reality of theBrazilian sugar cane sector in the future (though they are lowerthan to the current limits established by the Brazilianlegislation which may be altered within the time horizonconsidered in this work)Scenarios s3 and s4 have a higher impact on photochemical

oxidation due to ethanol emissions to air related to the sugarconsumed for enzyme production As sugar is coproduced withethanol in sugar cane mills part of the ethanol emissions hasbeen allocated to sugar (allocation by energy content) This is aconservative approach once there are no ethanol emissionsassociated with sugar production consequently photochemicaloxidation results for scenarios s3 and s4 are actuallyoverestimatedAs shown in Figure 4 the results are relatively uncertain for

most of the impact categories analyzed which makes thecomparative performance analysis less clear For somecategories the average and the reference case are considerablydifferent The uncertainty regarding global warming andeutrophication is related to N2O emissions due to ureaapplication on the field As pointed out before the N2Oemissions have significant impact on global warming and forthe reference cases the emission factor is smaller than theaverage from the assumed probability density function CO2emissions due to diesel use for sugar cane transportation alsoimpact significantly global warming and for the reference casesthe distance considered was smaller than for the average Forhuman toxicity and ecotoxicity on the other hand thereference cases are higher than the averages because of theapplication of carbofuran and higher use of diuronResults for photochemical oxidation are much less uncertain

because ethanol emissions from during ethanol distillation werenot included among the random variables It is important tohighlight that the uncertainty analysis was mostly based on

uncertain variables related to sugar cane production andtransportation in addition to ethanol yield

The Best Use of 1 ha of Sugar Cane The normalizedresults of the net environmental benefits considering thedisplacement of conventional products by renewable productsfrom one hectare of sugar cane (ethanol and electricity) arepresented in Figure 5 (further details are available in theSupporting Information) Negative values in the figure indicatethat the environmental impacts would be mitigated with theutilization of sugar cane productsAll scenarios have potential to mitigate global warming and

abiotic depletion (fossil fuel) but scenario s2 has the highestpotential followed by scenario s4 For the other impactcategories however benefits would not be verified Scenario s1would have lesser impacts on photochemical oxidationacidification and eutrophication on the other hand scenarios1 has smaller potential to mitigate abiotic depletion (fossilfuel) and global warming than scenarios s2 and s4These results are sensitive not only to the environmental

profile of the sugar cane products but also to the displacedproducts The sensitivity analysis (given in the SupportingInformation) indicates that the electricity source displaced bythe electricity surplus from the mill has a major influence on thenet benefit of the scenarios For instance scenario s4 wouldlead to greater benefits concerning abiotic depletion (fossilfuel) and global warming instead of s2 in case national averageelectricity mix was displaced This is due to the smallerenvironmental impacts associated with the average electricityfrom the grid (mostly hydro) compared to electricitygeneration in natural gas-fired power plantsRegarding the other impact categories the comparative

performance among the scenarios is not altered according tothe electricity source However the displacement of electricitygeneration in coal-fired power plants or average mix electricitycould contribute to decrease impacts on human toxicityecotoxicity and photochemical oxidation Impacts on acid-ification and eutrophication are higher when average electricityfrom the grid is displaced For all categories considered impactswould be smaller if electricity generation in coal-fired powerplants were displacedCombining all these elements it is possible to say that the

technological progress expected for the sugar cane industry willlikely improve ethanolrsquos environmental profile and the netenvironmental benefits promoted by the sugar cane products

Figure 5 Normalized net environmental impacts related to products from 1 ha of sugar cane



Ethanol would especially benefit from the proposed advances insugar cane farming even more than the higher yields enabledby the second generation technology The industry shouldtherefore pursue those developments also because they willprobably lead to economic gains in the future However noneof these technologies are commercially mature yet andsignificant demonstration efforts are still needed before wehave a clear indication about their technical and economicperformance at large scales in Brazil

ASSOCIATED CONTENTS Supporting InformationDetailed data used for each prospective scenario and foruncertainty analysis as well as additional results This material isavailable free of charge via the Internet at httppubsacsorg

AUTHOR INFORMATIONCorresponding AuthorPhone 55 19 3521 3284 Fax +55 19 3289 3722 E-mailcinthinha_ryahoocombr

NotesThe authors declare no competing financial interest

ACKNOWLEDGMENTSThis work benefited from the financial support of ConselhoNacional de Desenvolvimento Cientifico e Tecnolo gico(CNPqminusprocess no 1425652009-1) and Coordenacao deAperfeicoamento de Pessoal de Nivel Superior (CAPES minusprocess BEX 602311-8) Cinthia da Silva thankfully acknowl-edges the financial support The authors gratefully acknowledgethe attention of the specialists interviewed

REFERENCES(1) United States Environmental Protection Agency (EPA)Renewable Fuel Standard Program (RFS2) Regulatory ImpactAnalysis EPA-420-R-10-006 February 2010(2) EU RED minus European Renewable Energy Directive Directive200928EC of the European Parliament and of the Council of 23April 2009 on the promotion of the use of energy from renewablesources and amending and subsequently repealing Directives 200177EC and 200330EC Official Journal of the European Union562009(3) Souza R R Schaeffer R Meira I Can new legislation inimporting countries represent new barriers to the development of aninternational ethanol market Energy Policy 2011 39 (6) 3154minus3162(4) Khatiwada D Seabra J Silveira S Walter A Accountinggreenhouse gas emissions in the life cycle of Brazilian sugarcanebioethanol Methodological references in European and Americanregulations Energy Policy 2012 47 384minus397(5) Dale B E Anderson J E Brown R C Csonka S Dale VH Herwick G Jackson R D Jordan N Kaffka S Kline K LLynd L R Malmstrom C Ong R G Richard T L Taylor CWang M Q Take a closer look Biofuels can support environmentaleconomic and social goals Environ Sci Technol 2014 48 7200minus7203(6) Foster-Carneiro T Berni M D Dorileo I L Rostagno M ABiorefinery study of availability of agriculture residues and wastes forintegrated biorefineries in Brazil Resour Conserv Recycl 2013 77 78minus88(7) Nyko D Garcia J L F Milanez A Y Dunham F B A corridatecnolo gica pelos biocombustiveis de segunda gerac a o umaperspectiva comparada Biocombustiveis BNDES Setorial 2011 32httpwwwbndesgovbrSiteBNDESexportsitesdefaultbndes_ptGaleriasArquivosconhecimentobnsetset32101pdf (accessedSept 20 2014)

(8) CTBE minus Brazilian Bioethanol Science and Technology LaboratoryWebsite wwwctbeorgbr (accessed Sept 20 2014)(9) Luo L van der Voet E Huppes G Life cycle assessment andlife cycle costing of bioethanol from sugarcane in Brazil RenewableSustainable Energy Rev 2009 13 1613minus1619(10) Seabra J E A Macedo I C Comparative analysis for powergeneration and ethanol production from sugarcane residual biomass inBrazil Energy Policy 2011 39 421minus428(11) Seabra J E A Tao L Chum H L Macedo I C A techno-economic evaluation of the effects of centralized cellulosic ethanol andco-products refinery options with sugarcane mill clustering BiomassBioenergy 2010 34 (8) 1065minus1078(12) Dias M O S Junqueira T L Cavalett O Cunha M PJesus C D F Rossell C E V Filho R M Bonomi A Integratedversus stand-alone second generation ethanol production fromsugarcane bagasse and trash Bioresour Technol 2012 103 (1) 152minus161(13) Albarelli J Q Ensinas A V Silva M A Productdiversification to enhance economic viability of second generationethanol production in Brazil The case of the sugar and ethanol jointproduction Chem Eng Res Des 2014 92 1470minus1481(14) Raele R Boaventura J M G Fischmann A A Sarturi GScenarios for the second generation ethanol in Brazil TechnolForecasting Social Change 2014 87 205minus223(15) Bordonal R O Figueiredo E B Scala N J R Greenhousegas balance due to the conversion of sugarcane areas from burned togreen harvest considering other conservationist managementpractices Global Change Biol Bioenergy 2012 4 846minus858(16) Handbook on Life cycle assessment minus An operational guide to theISO standards Guinee J Ed Kluwer Academic Publishers 2002 Vol7 ISBN 1-4020-0228-9(17) CML-IA spreadsheet version 39 httpwwwcmlleidenedusoftwaredata-cmliahtml (accessed Sept 20 2014)(18) CMLCA Software (2012) httpwwwcmlcaeucmlca52betazip (accessed Sept 20 2014)(19) Chagas M F Cavalett O Silva C R U Seabra J E ABonomi A Adaptacao de Inventario de Ciclo de Vida da cadeiaprodutiva do etanol de cana-de-acucar no Brasil III Congresso Brasileiroem Gestao do Ciclo de Vida de Produtos e Servicos 2012(20) Swiss Centre for Life Cycle Inventories Ecoinvent databaseVersion 20 httpwwwecoinventch (accessed Sept 20 2014)(21) Balanco Energetico Nacional 2012 minus Ano base 2011 BrazilEmpresa de Pesquisa Energetica Rio de Janeiro EPE 2012 httpsbenepegovbrdownloadsRelatorio_Final_BEN_2012pdf (accessedSept 20 2014)(22) Macedo I C Seabra J E A Mitigacao of GHG emissionsusing sugarcane bioethanol In Sugarcane Ethanol Contributions toclimate change mitigation and the environment Zuurbier P Van deVooren J Eds Wageningen Academic Publishers The Netherlands2008 pp 95minus111(23) Nassar A M Rudorff B F T Antoniazzi L B Aguiar D ABacchi M R P Adami M Prospects of the sugarcane expansion inBrazil impacts on direct and indirect land use changes In SugarcaneEthanol Contributions to climate change mitigation and the environmentZuurbier P Van de Vooren J Eds Wageningen AcademicPublishers The Netherlands 2008 pp 66minus93(24) Walter A Dolzan P Quilodran O De Oliveira J G DaSilva C Piacente F Sergerstedt A Sustainability assessment of bio-ethanol production in Brazil considering land use change GHGemissions and socio-economic aspects Energy Policy 2010 39 (10)5703minus5716(25) Adami M Rudorff B F T Freitas R M Aguiar D ASugawara L M Mello M P Remote sensing time series to evaluatedirect land use change of recent expanded sugarcane crop in BrazilSustainability 2012 4 574minus585(26) Dispoe sobre a eliminacao gradativa da queima da palha da cana-de-acucar e da providencias correlatas Lei Estadual no 112412002HTTPwwwsigamambientespgovbrsigam2Repositorio24



DocumentosLei20Estadual_11241_2002pdf (accessed Sept 202014)(27) Cavalett O Chagas M F Seabra J E A Bonomi AComparative LCA of ethanol versus gasoline in Brazil using differentLCIA methods Int J Life Cycle Assess 2013 18 647minus658(28) Hamza M A Anderson W K Soil compaction in croppingsystems A review of the nature Causes and possible solutions SoilTillage Res 2005 82 (2) 121minus145(29) Bioetanol combustivel uma oportunidade para o Brasil Centro deGestao e Estudos Estrategicos Brasilia DF 2009 httpwwwcgeeorgbrpublicacoesbioetanol2_2009php (accessed Sept 20 2014)(30) Sao Paulo State CETESB (Companhia de Tecnologia deSaneamento Ambiental) (P4231 Dez2006)(31) Leal M R L V Walter A S Seabra J E A Sugarcane as anenergy source Biomass Convers Biorefin 2013 3 (1) 17minus26(32) Filho A B A Geracao Termoeletrica com a Queima do Bagacode Cana-de-Acucar no Brasil minus Analise do Desempenho da Safra2009minus2010 CONAB (Companhia Nacional de Abastecimento) 2011httpwwwconabgovbrOlalaCMSuploadsarquivos11_05_05_15_45_40_geracao_termo_baixa_respdf (accessed Sept 20 2014)(33) Dias M O S Modesto M Ensinas A V Nebra A S MacielFilho R Rossell C E V Improving bioethanol production fromsugarcane evaluation of distillation thermal integration andcogeneration systems Energy 2011 36 (6) 3691minus3703(34) Walter A Galdos M V Scarpare F V Leal M R L VSeabra J E A Cunha M P Picoli M C Oliveira C O F Braziliansugarcane ethanol Developments so far and challanges for the futureWIREs Energy Environ 2014 3 70minus92(35) de Almeida J L Sampaio P H Evaporator of vinasseconcentration for distilleries in general US Patent 20100055239 A1 4Mar 2010(36) Humbird D Davis R Tao L Kinchin C Hsu D Aden ASchoen P Lukas J Olthof B Worley M Sexton D Dudgeon DProcess Design and Economics for Biochemical Conversion ofLignocellulosic Biomass to Ethanol minus dilute-acid pretreatment andenzimatic hydrolysis of corn stover Technical Report NRELTP-5100-47764 National Renewable Energy Laboratory US Department ofEnergy Office of Energy Efficiency and Renewable Energy 2011httpwwwnrelgovbiomasspdfs47764pdf (accessed Sept 202014)(37) Hsu D D Inman D Heath G A Wolfrum E J Mann MK Aden A Life cycle environmental impacts of selected US ethanolproduction and use pathways in 2022 Environ Sci Technol 2010 44(13) 5289minus5297(38) GREET (The Greenhouse Gases Regulated Emissions and EnergyUse in Transportation Model) Versao 18c Argonne NationalLatoratory US Department of Energy 2007 httpsgreetesanlgov (accessed Sept 20 2014)(39) Primo K R Salomon K R Teixeira F N Lora E S Estudode dispersao atmosferica dos oxidos de nitrogenio (NOx) emitidosdurante a queima de bagaco em uma usina de acucar Biomassa Energia2005 2 79minus90(40) Boddey R M Soares L H B Alves B J R Urquiaga S Bio-ethanol Production in Brazil In Biofuels Solar and Wind as RenewableEnergy Systems Pimentel D Ed Springer Science+Business MediaBV 2008 Chapter 3 pp 321minus356(41) Seabra J E A Avaliacao tecnico-economica de opcoes para oaproveitamento integral da biomassa de cana no Brasil PhD ThesisUniversidade Estadual de Campinas Campinas 2008(42) Hassuani S J Leal M R L V Macedo I C Biomass Powergeneration sugarcane bagasse and trash PNUD Brasil and Centro deTecnologia Canavieira Piracicaba 2005 httpwwwsucre-ethiqueorgIMGpdfCTC_energy_-_biomass_1_pdf (accessed Sept 202014)



an optimized first generation plant to increase processfeasibility since part of the infrastructure could be shared andbagasse is already available in the plant12 The secondgeneration technology can also benefit from thermal andwater integration with positive implications for the paybacktime when integrated with sugar production13

Besides the development of second generation ethanolimprovements in the sugar cane cultivation are expected as wellMinimum tillage practices for instance have already beenintroduced in some sugar cane areas and no-til farming isexpected to be in place in the medium-long-term In thiscontext CTBE is developing a controlled traffic structure(ETC) to reduce soil compaction and hence reduce thenumber of required operations for soil preparation and facilitatethe introduction of the no-til farming8 Even withoutconsidering the use of ETC Bordonal et al15 already indicatea better performance of the first generation ethanol whenminimum tillage practices are usedThese developments are expected to favor the sustainability

of sugar cane ethanol but their environmental benefits are notclear yet Analyses are thus required to evaluate theenvironmental gains of the adoption of advanced cultivationpractices and conversion technologies (such as ETC and sugarcane residues-to-ethanol) in face of the alternative uses of sugarcane biomass and the incremental developments expected insugar cane production in the futureAssuming that such technologies could improve ethanolrsquos

environmental profile this work assessed the environmentalimpacts of the production and use of 1 MJ of hydrous ethanolin Brazil in prospective scenarios Comparisons were carriedout considering as reference the current life cycle performanceof Brazilian sugar cane ethanol and fossil gasoline In additionto ethanolrsquos life cycle profile the net environmental benefits ofeach scenario were also evaluated considering the displacementof the equivalent fossil alternatives of sugar cane bioenergy iegasoline as a transportation fuel and natural-gas-poweredthermoelectricityThe analysis employed the Life Cycle Assessment (LCA)

technique considering eight environmental impacts categoriesabiotic resource depletion global warming photochemicaloxidation human toxicity freshwater aquatic ecotoxicityterrestrial ecotoxicity acidification and eutrophication Land-use requirements for ethanol production were estimated andbriefly discussed Given the uncertainties associated with theprojected conditions an uncertainty analysis was conductedbased on the Monte Carlo method This analysis is expected tosupport decisions about the best utilization of biomassresources for the maximization of environmental gains

MATERIALS AND METHODSLife Cycle Assessment The study used the Life Cycle

Assessment (LCA) technique to evaluate the ethanol environ-mental profile for each scenario considering an attributionalwell-to-wheels approach The CML version 39 a problemoriented approach was the method employed in the Life CycleImpact Assessment (LCIA)1617 covering eight environmentalimpact categories abiotic resource depletion (fossil fuels)global warming photochemical oxidation human toxicityfreshwater aquatic ecotoxicity terrestrial ecotoxicity acid-ification and eutrophication These categories embrace themain emissions in the ethanol life cycle The CMLCAsoftware18 was used to create and link the life cycle processesand to assist in the interpretation phase including the

development of the contribution and uncertainty analysesThe functional unit for the comparative LCAs was 1 MJ ofhydrous ethanol and the allocation method was based onpartitioning using energy flowsIn addition to the ethanolrsquos life cycle profile the best use of 1

ha of sugar cane was also assessed In this case the studycompared the net environmental benefits of each scenariotaking into consideration the displacement of the conventionalproducts gasoline and thermoelectricity produced in a naturalgas power plantThe gasoline life cycle inventory was assembled using

representative parameters of the Brazilian conditions19

disregarding changes in the supply chain within the time-horizon of this analysis With respect to the electricitygeneration in natural gas-fired power plants the UCTE lifecycle inventory from the Ecoinvent database was used1020 Asensitivity analysis was performed to show the impact of twoextreme cases considering that the surplus electricity woulddisplace the average electricity mix in Brazil or electricity fromcoal-fired power plants using EcoInvent database for UCTE20

The life cycle inventory of the average electricity was based onan adapted process of the Ecoinvent database20 considering the2011 mix (817 hydroelectricity 65 biomass 05 wind14 coal 25 fossil oil 46 natural gas 27 nuclear21) Forthe coal-based electricity it was assumed the UCTE life cycleinventory from Ecoinvent20

Emissions and removals of biogenic carbon along the processchain were assumed to be synchronized so they were not takeninto account The land use change (LUC) impacts were not thefocus of this work but the land-use requirements for ethanolproduction in each scenario were estimated and brieflydiscussed In terms of the impacts it is worth mentioningthat the recent sugar cane expansion in Brazil has mostlyoccurred over pasture land and the overall effect may actuallybe of increasing the C stocks in soil although largeuncertainties exist because of the still lack of information oncarbon stocks22minus25

For the foreground systems representative data of Brazilianconditions were collected while Ecoinvent database was usedwhen data was not available for the background processes Asthe analysis considered projected conditions based on theestimations of different specialists ranges of values were verifiedand uncertainties exist A contribution analysis was performedas part of the interpretation phase to subsidize the uncertaintyanalysis The uncertainty assessment followed the Monte Carlomethod using 2000 trials The parameters for the Monte Carloanalysis are in the Supporting Information

Scenarios Definition and Description Four prospectivescenarios were considered in the analysis covering two optionsfor bagasse utilization and two different sugar cane productionsystems as presented in Table 1 One scenario (scenario s0)

Table 1 Description of the Prospective Scenarios

sugar canecultivationminimumtillage

sugar canecultivationno-tillage

production of first generation ethanol from canejuice and electricity surplus from sugar caneresidues (bagasse and straw)


combined production of first and secondgeneration ethanol with reduced level ofelectricity exports (surplus)
























scenarios












































































scenarios
























































Long-Term Prospects for the Environmental Profile of Advanced Sugar Cane Ethanol

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