Transcription

October 2000 NREL/TP-580-28893Determining the Cost ofProducing Ethanol from CornStarch and LignocellulosicFeedstocksA Joint Study Sponsored by:U.S. Department of Agriculture andU.S. Department of EnergyAndrew McAloon, Frank Taylor, and Winnie YeeU.S. Department of AgricultureEastern Regional Research CenterAgricultural Research ServiceKelly Ibsen and Robert WooleyNational Renewable Energy LaboratoryBiotechnology Center for Fuels and ChemicalsNational Renewable Energy Laboratory1617 Cole BoulevardGolden, Colorado 80401-3393NREL is a U.S. Department of Energy LaboratoryOperated by Midwest Research Institute Battelle BechtelContract No. DE-AC36-99-GO10337

October 2000 NREL/TP-580-28893Determining the Cost ofProducing Ethanol from CornStarch and LignocellulosicFeedstocksA Joint Study Sponsored by:U.S. Department of Agriculture andU.S. Department of EnergyAndrew McAloon, Frank Taylor, and Winnie YeeU.S. Department of AgricultureEastern Regional Research CenterAgricultural Research ServiceKelly Ibsen and Robert WooleyNational Renewable Energy LaboratoryBiotechnology Center for Fuels and ChemicalsPrepared under Task No. BFP1.7110National Renewable Energy Laboratory1617 Cole BoulevardGolden, Colorado 80401-3393NREL is a U.S. Department of Energy LaboratoryOperated by Midwest Research Institute Battelle BechtelContract No. DE-AC36-99-GO10337

NOTICEThis report was prepared as an account of work sponsored by an agency of the United Statesgovernment. Neither the United States government nor any agency thereof, nor any of their employees,makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy,completeness, or usefulness of any information, apparatus, product, or process disclosed, or representsthat its use would not infringe privately owned rights. Reference herein to any specific commercialproduct, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarilyconstitute or imply its endorsement, recommendation, or favoring by the United States government or anyagency thereof. The views and opinions of authors expressed herein do not necessarily state or reflectthose of the United States government or any agency thereof.Available electronically at http://www.doe.gov/bridgeAvailable for a processing fee to U.S. Department of Energyand its contractors, in paper, from:U.S. Department of EnergyOffice of Scientific and Technical InformationP.O. Box 62Oak Ridge, TN 37831-0062phone: 865.576.8401fax: 865.576.5728email: [email protected] for sale to the public, in paper, from:U.S. Department of CommerceNational Technical Information Service5285 Port Royal RoadSpringfield, VA 22161phone: 800.553.6847fax: 703.605.6900email: [email protected] ordering: http://www.ntis.gov/ordering.htmPrinted on paper containing at least 50% wastepaper, including 20% postconsumer waste

SummaryThe mature corn-to-ethanol industry has many similarities to the emerging lignocelluloseto-ethanol industry. It is certainly possible that some of the early practitioners of this newtechnology will be the current corn ethanol producers. In order to begin to exploresynergies between the two industries, a joint project between two agencies responsiblefor aiding these technologies in the Federal government was established. This jointproject of the U.S. Department of Agriculture’s Agricultural Research Service (USDAARS) and the U.S. Department of Energy (DOE) with the National Renewable EnergyLaboratory (NREL) looked at the two processes on a similar process design andengineering basis, and will eventually explore ways to combine them. This reportdescribes the comparison of the processes, each producing 25 million annual gallons offuel ethanol. This paper attempts to compare the two processes as mature technologies,which requires assuming that the technology improvements needed to make thelignocellulosic process commercializable are achieved, and enough plants have been builtto make the design well-understood. Assumptions about yield are based on the assumedsuccessful demonstration of the integration of technologies we feel exist for thelignocellulose process. In order to compare the lignocellulose-to-ethanol process costswith the commercial corn-to-ethanol costs, it was assumed that the lignocellulose plantwas an Nth generation plant, assuming no first-of-a-kind costs. This places thelignocellulose plant costs on a similar level with the current, established corn ethanolindustry, whose costs are well known. The resulting costs of producing 25 million annualgallons of fuel ethanol from each process were determined. The figure below shows theproduction cost breakdown for each process. The largest cost contributor in the cornstarch process is the feedstock; for the lignocellulosic process it is the depreciation ofcapital cost, which is represented by depreciation cost on an annual basis.Fuel Ethanol Cost ( /gal)Comparative Production Costs for Starch and Lignocellulose Processes (1999 )FeedstockVariable Operating CostsLabor, Supplies, and OverheadDepreciation of CapitalCo-productsTotal 1.70 1.50 1.30 1.10 0.90 0.70 0.50 0.30 0.10- 0.10- 0.30*Dry Milling ProcessSTARCH*CELLULOSE

.1VI.2VI.3VIIVII.1VII.2VIIIIXTable of ContentsIntroduction . 1Comparing the Corn Industry and a Lignocellulose-Based Industry. 3History of the Corn Ethanol Industry. 3Status of Lignocellulose-to-Ethanol Process. 4Process Descriptions . 6Corn Starch Feedstock-to-Ethanol Process Description . 6Lignocellulose Feedstock-to-Ethanol Process Description. 8Primary Process Differences . 9Normalization of Design and Economic Models . 10History of the Models. 11Methodology for Achieving the Same Basis. 12Changes Required in the Process Models . 15Starch Model . 15Lignocellulose Model. 15Production Costs of Fuel Ethanol. 17Production Costs for the Starch Process . 18Production Costs for the Lignocellulose Process. 20Comparison of Costs . 23Future Impact of Co-Products . 25The Future of Starch Process Co-Products . 26The Future of Lignocellulose Process Co-Products. 26Prospects and Challenges for a Combined Process. 27References . 29This report is also available electronically at http://www.ott.doe.gov/biofuels/database.htmli

List of Tables1.2.3.4.5.6.7.8.Corn and Stover Compositions . 3DDG and Lignocellulosic Residue Composition and Production. 10General Parameters . 12Production Costs for the Starch Process . 18Capital Costs by Process Area (1999 ). 19Production Costs for the Lignocellulose Process (1999 ) . 20Capital Costs by Process Area (1999 ). 22Utility Costs. 22ii

List of Figures1.2.3.4.5.6.7.8.Corn Starch-to-ethanol Process Flow. 6Lignocellulose-to-ethanol Process Flow . 8Comparison of Starch and Lignocellulose Process Stainless Steel Tank Cost13Comparison of Starch and Lignocellulose Process Heat Exchanger Cost . 14Production Costs in Dollars per Gallon of Fuel Ethanol (1999 ) . 17Effect of Changing Feedstock Cost on Fuel Ethanol Production Cost . 23Starch Costs by Process Area (1999 ) . 24Lignocellulose Costs by Area (1999 ). 25iii

List of IkWkWhNRELOEPNUORNLUSDAAgricultural Research Servicecarbon dioxidechemical oxygen demandCooperative State Research, Education, and Extension ServicesDiscounted Cash Flow Rate of ReturnDistillers' Dried GrainsU.S. Department of EnergyEconomic Research ServicesFluidized Bed Combustorgenetically modified organismgenerally regarded as safeGraphical User Interfacekilowattkilowatt-hourNational Renewable Energy LaboratoryOffice of Energy Policy and New UsesOak Ridge National LaboratoryU.S. Department of Agricultureiv

IIntroductionThe U.S. Department of Energy (DOE) is promoting the development of ethanol fromlignocellulosic feedstocks as an alternative to conventional petroleum transportationfuels. Programs sponsored by DOE range from research to develop better cellulosehydrolysis enzymes and ethanol-fermenting organisms, to engineering studies of potentialprocesses, to co-funding initial ethanol from lignocellulosic biomass demonstration andproduction facilities. This research is conducted by various national laboratories,including the National Renewable Energy Laboratory (NREL) and Oak Ridge NationalLaboratory (ORNL), as well as by universities and private industry. Engineering andconstruction companies and operating companies are generally conducting theengineering work.The U.S. Department of Agriculture (USDA) has an active program devoted to the cornethanol industry. This program includes economic and policy studies by the Office ofEnergy Policy and New Uses (OEPNU) and the Economic Research Services (ERS),scientific research programs by the Agricultural Research Service (ARS) and theCooperative State Research, Education and Extension Services (CSREES). Areas ofscientific research address the establishment of new higher-value ethanol co-products, thedevelopment of microbes capable of converting various biomass materials into ethanol,improved processes for the enzymatic saccharification of corn fibers into sugars, andvarious methods of improving corn ethanol process efficiencies.The mature corn-to-ethanol industry has many similarities to the emerging lignocelluloseto-ethanol industry. It is certainly possible that some of the early practitioners of this newtechnology will be the current corn ethanol producers.1,2,3 In order to begin to exploresynergies between the two industries, a joint project between two agencies responsiblefor aiding these technologies in the Federal government was established. This jointproject of the USDA-ARS and DOE with NREL looked at the two processes on a similarprocess design and engineering basis, and will eventually explore ways to combine them.This report describes the comparison of the processes, each producing 25 million annualgallons of fuel ethanol. This paper attempts to compare the two processes as maturetechnologies, which requires assuming that the technology improvements needed to makethe lignocellulosic process commercializable are achieved, and enough plants have beenbuilt to make the design well-understood. Assumptions about yield are based on theassumed successful demonstration of the integration of technologies we feel exist for thelignocellulose process. In order to compare the lignocellulose-to-ethanol process costswith the commercial corn-to-ethanol costs, it was assumed that the lignocellulose plantwas an Nth generation plant, assuming no first-of-a-kind costs. This places thelignocellulose plant costs on a similar level with the current, established corn ethanolindustry, whose costs are well known.The feedstock used for each process is different but related. There were 9.76 billionbushels of corn, a commodity crop, produced in the 1998-1999 crop year. Of this, 526million bushels (14.7 million tons at 15% moisture) were used in the corn ethanol1

industry to produce fuel ethanol.4 Corn stover, the residue left in the fields afterharvesting corn, has been identified as a near- to mid-term agriculture residue feedstockfor the lignocellulose-to-ethanol process. Corn stover has a high carbohydrate content,can be collected in a sustainable fashion, and will provide economic benefits to the farmcommunity.Corn kernels have starch, which is an alpha-linked glucose polymer that can be easilybroken down to glucose monomers and fermented to ethanol. It has fiber, which encasesthe starch, and about 15% moisture. An approximate composition of corn is shown inTable 1. In this analysis of the dry mill corn-to–ethanol process, a slightly different andsimpler composition for corn (on a dry weight basis, 70% starch, and for nonfermentables, 18% suspended and 12% dissolved) was used. The market price of cornvaries, ranging from 1.94 to 3.24 per bushel during the last 3 years.5 For this analysis