Key Differences between Pimentel/Patzek Study and Other Studies By Michael Wang Center for Transportation Research Argonne National Laboratory July 19, 2005 The recent article by Pimentel/Patzek concludes that: 1. Corn ethanol requires 29% more fossil energy than ethanol contains 2. Herbaceous cellulosic ethanol requires 50% more fossil energy 3. Woody cellulosic ethanol requires 57% more fossil energy 4. Soybean-based biodiesel requires 27% more fossil energy than biodiesel contains 5. and sunflower-based biodiesel requires 118% more fossil energy In contrast, many other studies, including Argonneâ??s study, conclude that corn ethanol, cellulosic ethanol, and biodiesel require less fossil energy than each of the fuel contains. In particular, Argonneâ??s study concludes: 1. Corn ethanol requires 26% less fossil energy 2. Cellulosic ethanol requires 90% less fossil energy In addition, NREL study sponsored by DOE and USDA in 1998 concludes that soybean-based biodiesel requires 69% less fossil energy than biodiesel contains. A review of Pimentel/Patzek reveals that they made pessimistic assumptions, had double-counted certain energy costs without detailed elaboration. Below is a quick summary of the key differences between Pimentel/Patzek and others. A. Corn Ethanol: 1. Corn farming energy use: a) Pimentel/Patzek conclude that corn farming requires 94,504 Btu/bushel, with 18.2% from farmer labor and farming machinery (77,304 Btu/bushel excluding farmer labor and farming machinery) b) A 2002 detailed USDA analysis showed that corn farming requires 57,480 Btu/bushel (excluding farmer labor and farming machinery) c) Pimentel/Patzek overestimate corn farming energy use (excluding farmer labor and farming machinery) by 34% d) It also appears that Pimentel and Patzek overestimate energy use related to farmer labor and farming machinery 2. Ethanol production energy use: a) Pimentel/Patzek conclude that ethanol production at ethanol plants consumes 56,440 Btu/gal. (56,000 Btu/gal, excluding energy embedded in ethanol plant construction materials) b) A detailed survey of ethanol plant energy use in 2001 showed an energy use of 48,770 Btu/gal. for dry mill ethanol plants and 54,240 Btu/gal., with an average of 53,010 Btu/gal in 2001. c) Recent dry mill plants (all new ethanol plants coming online in recent years have been dry mill plants) may have energy use of 42,530 Btu/gal. d) Pimentel/Patzek overestimate ethanol plant energy use by up to 30% e) Pimentel/Patzek assume an ethanol yield of 2.5 gallons per bushel of corn. Ethanol plants now produce ethanol at 2.7 gallons/bushel and they are approaching the yield of 2.8 gallons/bushel. 3. Animal feed co-products from corn ethanol plants: a) Pimentel/Patzekâ??s 29% increase in fossil energy by corn ethanol gives not credit to animal feeds b) Pimentel/Patzek acknowledge that animal feeds could have an energy credit of 6,680 Btu per gallon of ethanol produced c) Argonneâ??s conservative estimation shows that animal feeds and other coproducts from ethanol plants have an energy credit of 12,030 Btu per gallon of ethanol produced B. Cellulosic Ethanol: The key difference between Pimentel/Patzek and other studies is how steam and electricity needed for cellulosic ethanol plant operations is generated. Cellulosic biomass contains more than 25% of lignin, which may not be fermented into ethanol. For cellulosic ethanol designs supported by DOE and others, the lignin portion of biomass feedstocks is to be burned to provide steam and electricity for cellulosic ethanol plant operations. In fact, cellulosic ethanol plants will generate an excess amount of electricity for exporting to the electric grid. To the contrary of the commonly accepted cellulosic ethanol plant designs, Pimentel/Patzek assume that fossil fuels are to be burned in cellulosic ethanol plants to generate needed steam and electricity. If Pimentel/Patzek assumed use of lignin to produce steam and electricity in cellulosic ethanol plants, they would have had positive energy balance values for cellulosic ethanol similar to those from Argonne and others. C. Biodiesel: DOE and USDA in 1998 funded a study evaluating soybean-based biodiesel. That study concluded biodiesel consumes 69% less fossil energy. Argonne has not evaluated biodiesel. D. Costs Results by Pimentel/Patzek Pimentel/Patzek present cost estimates for corn, soybeans, switchgrass, woody biomass, soybeans, sunflowers, ethanol, and biodiesel. Argonne has not conducted cost estimates. Argonneâ??s review of Pimentel/Patzek shows that their production cost estimates are higher than market prices, implying that farmers, ethanol producers, biodiesel producers are in money-losing business, even taking into account subsidies they receive. Argonne also found that Pimentel/Patzek cost estimates for cellulosic ethanol contain calculation errors by using a cost of $100 per tonne for cellulosic biomass feedstock, instead of their own estimate of $23 per tonne. E. General Issues: 1. Though self evaluation of ethanolâ??s energy balance is easy to understand, it does not reveal the true energy benefit of ethanol in replacing gasoline; a meaningful way for energy policy debates is to compare ethanol and gasoline to assess the relative merit of ethanol. It is important to put a given energy product into a broad perspective with other energy products for serving same functions in society. 2. Decisions on pursuing certain energy products by society have not been based on their energy balance values. For example, even though electricity generation has a huge negative energy balance value (2.3 unit of fossil energy input for a unit of electric energy output in the US), we do not question the practice of electricity generation. The quality of energy products should be taken into account in making energy choices. 3. In conclusion, energy balance calculations for individual energy productions in their isolations could be arbitrary; results are less meaningful or could be misleading. **************************VIRGINIA BIOFUELS FORUM************************** Your email address is subscribed to the Virginia Biofuels Forum mailing list. The list is maintained by Blue Ridge Clean Fuels Inc. (BRCFI). To UNSUBSCRIBE go to //www.freelists.org/list/biofuels-forum and select that option from the menu. 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