Hinman, Norman D.

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Biomass: An Ideal Feedstock for Ethanol Production

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California Western Law Review Volume 28 Number 1 Article 9 1991 Biomass: An Ideal Feedstock for Ethanol Production Norman D. Hinman Follow this and additional works at: https://scholarlycommons.law.cwsl.edu/cwlr Recommended Citation Hinman, Norman D. (1991) "Biomass: An Ideal Feedstock for Ethanol Production," California Western Law Review: Vol. 28 : No. 1 , Article 9. Available at: https://scholarlycommons.law.cwsl.edu/cwlr/vol28/iss1/9 This Article is brought to you for free and open access by CWSL Scholarly Commons. It has been accepted for inclusion in California Western Law Review by an authorized editor of CWSL Scholarly Commons. For more information, please contact alm@cwsl.edu. BIoMAss: AN IDEAL FEEDSTOCK FORETHANOL PRODUCTION*NORMAN D. HINMAN**INTRODUCTIONThe recent Iraqi invasion of Kuwait reminded us once again that relianceon imported oil can cause strategic and economic vulnerability. The UnitedStates consumes about 17-18 million barrels of oil per day, approximatelyhalf of which is imported. Today's transportation fuels are almost totallyderived from petroleum and account for about two-thirds of the petroleumconsumed. Thus, transportation fuels are particularly vulnerable todisruptions in imported oil. In addition, imported petroleum accounted forabout 40% of the balance-of-payments deficit for the United States in 1989.1American oil consumption also exacerbates the growing environmentaldecay. Much of urban air pollution in the form of smog (ozone) and carbonmonoxide (CO) is a result of the combustion of transportation fuels invehicles.' The carbon dioxide (CO) emitted to the atmosphere fromburning transportation fuels contributes to global warming.3Ethanol produced from cellulosic biomass is an attractive alternativetransportation fuel that promises to improve energy security, decrease thebalance-of-payments deficit, reduce urban pollution, and mitigate theaccumulation of carbon dioxide.4 Work under way at the NationalRenewable Energy Laboratory (NREL) focuses on reducing the cost ofproducing ethanol so that it can compete with gasoline without the assistanceof tax incentives.This Article examines the use of ethanol as a fuel, the use of cellulosicbiomass as a raw material for the manufacture of ethanol, and the process for* This research is supported by the Ethanol from Biomass Program of the United StatesDepartment of Energy, Biofuels Systems Division.** Manager, Biofuels Program, National Renewable Energy Laboratory (formerly the SolarEnergy Research Institute).1. Wald, Greater Reliance on Foreign Oil Feared as U.S. Output Tumbles, N.Y. TIMES,Jan. 18, 1990, at Al, col. 1.2. See generally OFFICE OF PUBLIC AFFAIRS, U.S. ENVIRONMENTALPROTECTION AGENCY,EPA LISTS PLACES FAIIING TO MEET OZONE OR CARBON MONOXIDE STANDARDS (1989).3. See generally J. EDMONDS, W. ASHTON, H. CHENG, & M. STEINBERG, A PREIIMINARYANALYSIS OF U.S. CO2 EMISSIONS REDUCTION POTENTIAL FROM ENERGY CONSERVATION ANDSUBSTITUTION OF NATURAL GAS FOR COAL IN THE PERIOD TO 2010 (Office of Energy Research,U.S. Department of Energy, 1989) (DOE/NBB-0085).4. Wyman & Hinman, Ethanol-Fundamentals of Production From Renewable Feedstocksand Use as a Transportation Fuel, 24-25 APPL. BIOCHEM. BIOTECHNOL. 735 (1990); see alsogenerally N. HINMAN, D. SCHELL, C. RILEY, P. BERGERON & P. WALTER, ETHANOL ANNUALREPORT FISCALYEAR 1990 (National Renewable Energy Laboratory, 1990) (SERI/TP-231-3996)[hereinafter 1990 ETHANOL REPORT].1Hinman: Biomass: An Ideal Feedstock for Ethanol ProductionPublished by CWSL Scholarly Commons, 1991CALIFORNIA WESTERN LAW REVIEWand effects of converting biomass to ethanol.I. THE USE AND BENEFITS OF ETHANOL AS A FUELEthanol can be used as a fuel in three different forms: (1) as anhydrousethanol-gasoline blends currently use41 in the United States; (2) as acomponent of ethyl-tert-butyl ether (ETBE);5 and (3) as anhydrous (100%ethanol) or hydrous (95% ethanol and 5% water) ethanol. Differences existin automobile performance and emission levels among these fuels.The leaning effect of 10 % ethanol/90 % gasoline blends on engines adjustedfor gasoline can reduce carbon monoxide.6 Although the effect depends onthe emission control technology, an Environmental Protection Agency studyindicates that carbon monoxide emissions are reduced 10%-30% forautomobiles that are not even equipped with the latest adaptive learningtechnology.7As with gasohol, the addition of ETBE to gasoline causes an engine to runlean, reducing CO emissions, even without the latest adaptive learningclosed-loop technology.8  The recently completed 1988-89 ColoradoOxygenated Fuel Program dramatically reduced ambient carbon monoxideconcentrations in Denver by mandating the use of oxygenated additives ingasoline. During the program 90%-95% of the fuel sold contained 11%methyl-tert-butyl ether (MTBE). It is probable that ETBE would result insimilar reductions in ambient CO concentrations. Because ETBE significant-ly lowers the Reid Vapor Pressure of gasoline, the use of ETBE-gasolineblends should lower volatile organic compounds (VOCs) along with ozonethat results from the interaction of hydrocarbons and nitrogen oxides (NOr).The volatility of a fuel is one of the primary factors affecting VOCemissions. Compared to the concentrations from using 100% gasoline, usinganhydrous or hydrous ethanol with low vapor pressures should lowerconcentrations of organic compounds in the air. In addition, the photochemi-cal reactivity of ethanol is much less than that of hydrocarbons. Unlike therelatively high emissions of several types of hydrocarbons that are veryreactive in producing ozone, anhydrous and hydrous ethanol combustion5. Reisch, Ethyl-Tert-Butyl Ether Shows Promise as Octane Enhancer, 66 CHEMICAL &ENGINEERING NEWS, Oct. 24, 1988, at 11.6. Ideally, the air-fuel mixing device on an automobile engine provides the right mix of airand fuel to allow for complete combustion of the fuel. If not enough air is provided, the engineis said to be running "rich" and the fuel is not fully combusted. The result is undesirableproduction of carbon monoxide. The addition of oxygenated compounds, such as ethanol, togasoline provide additional oxygen and has the same effect as adding more air. This is knownan the "leaning effect." The result is fuller combustion of the fuel and less carbon dioxideproduction.7. NATIONAL ADVISORY PANEL ON COST-EFFECTIVENESS OF FUEL ETHANOL PRODUCTION,U.S. DEPARTMENT OF AGRICULTURE, FUEL ETHANOL COST-EFFECTIVENESS STUDY, FINALREPORT (1987).8. M. JACKSON, V. WIESE & J. WENTWORTH, TECHNICAL PROGRESS BOOK TP-6 (Societyof Automotive Engineers 1964) (preprint 486A).[Vol. 282California Western Law Review, Vol. 28 [1991], No. 1, Art. 9https://scholarlycommons.law.cwsl.edu/cwlr/vol28/iss1/91991] BIOMASS: AN IDEAL FEEDSTOCK FOR ETHANOL PRODUCTION 115produce very low levels of smog-producing compounds.9 Pure ethanolburning engines may also be effective in reducing NO. emissions becauseethanol burns at a lower temperature than gasoline and NO. formationdecreases as temperature decreases."0 Thus, ethanol's lower fuel evapora-tive emissions, lower photochemical reactivity, reduced tailpipe hydrocarbonemissions of reactive hydrocarbons, and lower NO, levels should result in areduction of ozone levels when using anhydrous and hydrous ethanol fuels.I1. CELLULosIC BIOMASS AS A RAW MATERIALFOR ETHANOL PRODUCTIONCellulosic biomass is the most abundant form of terrestrial plant matter.It is composed primarily of cellulose, hemicellulose, and lignin, as well assmall amounts of extractives and minerals. Cellulose consists of chains ofthe six carbon sugar glucose. Hemicellulose consists of chains of five carbonsugars, and lignin is a polyaromatic material. As shown in Figure 1,"cellulose biomass is generally composed of 40%-50% cellulose, 20%-40%hemicellulose, and 15%-22% lignin.Sources of cellulosic biomass suitable for ethanol production include under-utilized forests and forest residues, agricultural residues, municipal solidwaste (MSW), waste and low-value material from industrial processes, andenergy crops. Energy crops (short-rotation woody crops and herbaceouscrops) are being developed by a U.S. Department of Energy sponsoredprogram through Oak Ridge National Laboratory. For the United States, itis estimated that energy crops could provide about 1126 million dry tons ofcellulosic biomass per year. This quantity of feedstock could generate 124billion gallons of ethanol per year. Underutilized wood, agriculturalresidues, and MSW could also generate significant quantities of ethanol.III. PRODUCTION OF ETHANOL FROM CELLULOSIC BIOMASSA. Production ProcessThe process for producing ethanol from cellulosic biomass is outlined inFigure 2.12 After being milled to a small particle size, the feedstock ispretreated with dilute sulfuric acid to break the hemicellulose chains intotheir component sugars (mainly xylose in hardwoods). Several options havebeen considered for conversion of the xylose into ethanol including the useof certain strains of yeast, fungi, and bacteria. As yet, none of these is9. See generally D. SPERLING, NEW TRANSPORTATION FUELS: A STRATEGIC APPROACH TOTECHNOLOGICAL CHANGE (1988).10. See generally ENCYCLOPEDIA OF CHEMICALTECHNOLOGY (1984 Supp.).11. See generally 1990 ETHANOL REPORT, supra note 4.12. See generally id.3Hinman: Biomass: An Ideal Feedstock for Ethanol ProductionPublished by CWSL Scholarly Commons, 1991CALIFORNIA WESTERN LAW REVIEWoptimal. Another approach involves the use of a genetically engineeredbacteria to produce large quantities of xylose isomerase enzyme that convertsxylose into an isomer called xylulose that many yeast can ferment to highyields. 13 In a most promising approach, a genetically engineered bacteriahas been developed that appears to be able to ferment xylose directly toethanol at yields exceeding 90% .14Enzymes called cellulase are used to break down (hydrolyze) cellulose toform glucose sugar that can be fermented by yeast into ethanol. The mostpromising enzyme-based process is the simultaneous saccharification andfermentation process (SSF). 15 The SSF process combines the hydrolysisand fermentation steps in one vessel. The presence of yeast along with theenzymes minimizes the accumulation of sugar that inhibits cellulases andresults in high ethanol yields and higher rates of reaction.After conversion of the hemicellulose and cellulose to ethanol, theremaining material is mostly lignin. Because lignin has a high energycontent it can be used as boiler fuel to supply all the heat and electricitynecessary for the ethanol production process and the excess electricity can b,sold. Research is also under way to examine use of lignin for the productionof fuel additives and chemicals.B. Progress and Potential for ImprovementProgress with the enzyme-catalyzed process has been substantial over thelast ten years. As shown in Figure 3,16 ethanol selling prices have droppedfrom $3.60/gal. in 1980, to $1.35/gal. in 1989, to $1.27/gal. today.17 Thisreduction in selling price is due to improvements in enzymes, use of betterfermentative microbes, improved rates and yields of the SSF process, andadvances in xylose fermentations through genetic engineering. Technicaltargets, shown in Figure 4,"8 have been identified to bring the selling pricedown to about $0.67/gal. by the year 2000. At this price ethanol iscompetitive with fossil transportation fuels when oil is $26 per barrel.C. Near-Term OpportunitiesProduction costs for ethanol from biomass using current technology are13. Lastick, Mohagheghi, Tucker& Grohmann, Simultaneous Fermentation andlsomerizatio.nof Xylose to Ethanol at High Xylose Concentration, 24-25 APPL. BIOCHEM. BIO=TEHNOL. 431(1990).14. Ingram & Conway, Expression of Different Levels of Ethanologenic Enzymes fromZymononas mobilis in Recombinant Strains of Escherichia coil, 54 APPL. ENVIRON. MICROBIOL.397 (1988).15. J. Wright, Ethanol from Biomass by Enzymatic Hydrolysis, 84 CHEM. ENGINEERINGPROGRESS, Aug. 1988, at 62-74.16. See generally 1990 ETHANOL REPORT, supra note 4.17. See generally id.18. See generally id.[Vol. 281164California Western Law Review, Vol. 28 [1991], No. 1, Art. 9https://scholarlycommons.law.cwsl.edu/cwlr/vol28/iss1/91991] BioMAss: AN IDEAL FEEDSTOCK FOR ETHANOL PRODUCTION 117shown in Table 1. For this case, the feedstock, which was assumed to cost$42/dry ton, accounts for $0.46/gal. of the total production cost of $1.27/gal.If a cheaper feedstock is available, the production costs will be lower andcould reach a level that is competitive in today's ethanol market. Forexample, if the feedstock was free, ethanol made with today's technologywould cost $0.81/gal. This compares favorably to the current market priceof about $1.20/gal. Examples of potentially inexpensive cellulosic biomassthat could provide near-term opportunity include wastepaper, agriculturalresidues such as corn cobs, low-value fiber in grain processing operations,and cellulosic wastes from industrial operations.IV. EFFECT OF GLOBAL WARMINGIn the process shown in Figure 5, all fuels and chemicals used forproduction of the biomass feedstock are presumed to be made from biomass,hence the CO2 released during feedstock production is derived from biomass.Likewise, during the conversion of the biomass feedstock to ethanol, all CO2released is derived from the biomass feedstock. Finally, because the ethanolis derived from biomass, all the C0 2 released during combustion of this fuelin automobiles and trucks is derived from biomass. Thus although CO2 isreleased during the production of the biomass feedstock, during theconversion process, and during the utilization of the fuel, all of the CO2released is derived from biomass. Through the process of photosynthesis,this CO2 is recaptured to provide a new crop of biomass feedstock. Thus,the CO2 produced does not accumulate in the atmosphere and does notcontribute to global warming.In contrast, use of conventional fossil fuels does result in accumulation ofcarbon dioxide. This is because oil, coal, and natural gas are obtained belowground and converted to fuels and combusted above ground producing CO2.However, because there is no mechanism analogous to photosynthesis torecapture this CO2 to create a new crop of fossil fuel resource, CO2accumulates in the atmosphere and contributes to global warming.CONCLUSIONThe dependence of the United States on imported oil as a source oftransportation fuels is a significant factor in the strategic, economic, andenvironmental considerations of this nation. Ethanol produced fromcellulosic biomass could serve as an alternative transportation fuel whichwould reduce our dependence on imported oil. It is estimated that energycrops could provide over 124 billion gallons of ethanol per year which ismore than the total United States gasoline consumption of 112 billion gallonsper year. In addition, ethanol from cellulosic biomass will be useful indealing with urban air pollution and global warming. Moreover, energycrops will provide a way to use our ever increasing idle crop land for thegood of our country and will provide a new source of revenue to our farmers.5Hinman: Biomass: An Ideal Feedstock for Ethanol ProductionPublished by CWSL Scholarly Commons, 1991CALIFORNIA WESTERN LAW REVIEWTABLE 1PRODUCTION CoSTs-ToTAL COST BASISCost of EthanolCosts of ProductionFeedstockChemicalsLaborMaintenanceOverheadTaxes and InsuranceGross Cost of ProductionByproduct CreditsElectricitySolids DisposalNet Costs of ProductionAnnual Capital Charge @ 20.00 TICEthanol CostCents perMM$/Yr Gallon26.9 45.98.3 14.11.6 2.73.9 6.64.2 7.21.9 3.346.7 79.84.1(0.4)43.028.271.27.1(0.7)73.448.3121.7[Vol. 286California Western Law Review, Vol. 28 [1991], No. 1, Art. 9https://scholarlycommons.law.cwsl.edu/cwlr/vol28/iss1/91991] BIOMASS: AN IDEAL FEEDSTOCK FOR ETHANOL PRODUCTION 119a)00E0*aCDC-000E00.0-R*-2oU)0 o0)L 0: F-R I"00 a= 0o )C. 00=0U Z7Hinman: Biomass: An Ideal Feedstock for Ethanol ProductionPublished by CWSL Scholarly Commons, 1991120 CALIFORNIA WEsTERN LAW REVIEW [Vol. 28Cf) rjn(n 0D-CDCD. 00~2 CDCD CLCD 0 CDOC0-*0CDCD 0 po0CD 00o0 0 0 SD mCDO8California Western Law Review, Vol. 28 [1991], No. 1, Art. 9https://scholarlycommons.law.cwsl.edu/cwlr/vol28/iss1/91991] BIoMAss: AN IDEAL FEEDSTOCK FOR ETHANOL PRODUCTION 121C)o0o- QC.- 0CCE0LOEL.I~~C 0 .-CDocCv)CCo' o o~o ' 0 0...... 6 e* .,--o0 0D 0>C)Q:> co9Hinman: Biomass: An Ideal Feedstock for Ethanol ProductionPublished by CWSL Scholarly Commons, 1991122 CALIFORNIA WESTERN LAW REVIEW [Vol. 280' C) : -0Oo 0 0- 0 CD.- o (f)000 a- CD D00C)• 0q o "o o CD Eo- CD Co.0 < 0-" I"0 o N 0 o o -< < o < < < < 0 @M 0 CD (D , (D D CD -D N- (D (D =0ro oo gg ~- 2 o " --0 Cf(D.~. .0 C C x D 0 0200 0 o o o- a o ="m 0 0 0 0 30 3 < ' < 00 0o0) 0 031 ~0  0n 00 10  0o C @ - = a 0 0o0 - t0 0 (Dm ~ 0 l am rc2r 0 ~ 0 -. % -(D o 0 -~ 1CDhG) 0 0 0 0-0 0 LC E nCD CDO co I(10California Western Law Review, Vol. 28 [1991], No. 1, Art. 9https://scholarlycommons.law.cwsl.edu/cwlr/vol28/iss1/9

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Biomass: An Ideal Feedstock for Ethanol Production

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