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Christianson & Associates, August 2008
A recent report by John Christianson, CPA of the independent accounting firm Christianson & Associates, PLLP, catalogues the energy improvements being made at ethanol biorefineries across country. According to the report, the average amount of energy as measured by British Thermal Units (BTUs) required to produce ethanol and a livestock feed co-product across all ethanol production technologies was reduced by 13.5 percent between 2004 and 2007. In 2007, the average ethanol plant used 27,298 BTU’s to produce a gallon of ethanol with the most efficient ethanol refineries now using only 21,000 BTU’s to produce a gallon of ethanol.
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Argonne National Laboratory, December 2005
The Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model was developed by Dr. Michael Wang, Argonne National Laboratory’s Center for Transportation Research, with support from the U.S. Department of Energy’s (DOE’s) Office of Energy Efficiency and Renewable Energy (EERE). The peer-reviewed model has laid to rest some long-held misunderstandings about ethanol and its important role in reducing petroleum use and greenhouse gas emissions. In terms of key energy and environmental benefits, Argonne’s GREET shows that cornstarch ethanol clearly outpaces petroleum-based fuels, and that tomorrow’s cellulose-based ethanol would do even better.
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Argonne National Laboratory, March 2008
The average dry mill facility requires 31,070 British thermal units (Btu), including
electricity, to produce a gallon of fuel ethanol. Electricity usage for dry mills averaged 0.70 kilowatt hours per gallon. A majority of dry mill facilities (86%) generate heat to produce the steam necessary to run the facility using natural gas, on a Btu basis. For wet mills, 47409 Btu are required to produce a gallon of ethanol. Although wet mills require large amount of electricity, most of them are equipped with co-generation capabilities to meet internal electricity needs and thus reduce net grid electricity demand.
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U.S. Department of Agriculture (USDA)
Corn ethanol has a positive energy balance, even before subtracting the energy allocated to co-products. The net energy balance of corn ethanol adjusted for byproduct credits is 27,729 and 33,196 Btu per gallon for wet- and dry-milling, respectively, and 30,528 Btu per gallon for the industry. This study results suggest that corn ethanol is energy efficient, as indicated by an energy output/input ratio of 1.67.
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U.S. Department of Agriculture (USDA), slide
Different sources of energy vary on their respective energy balances. This slide compares ethanol to several of the alternatives.
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Science Magazine, January 2006
It has long been recognized that calculations of net energy are highly sensitive to assumptions about both system boundaries and key parameter values. In addition, net energy calculations ignore vast differences between different types of fossil energy. Moreover, net energy ratios are extremely sensitive to specification and assumptions and can produce uninterpretable values in some important cases. However, comparing across published studies to evaluate how these assumptions affect outcomes is difficult owing to the use of different units and system boundaries across studies. Finding intuitive and meaningful replacements for net energy as a performance metric would be an advance in our ability to evaluate and set energy policy in this important arena.
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Argonne National Laboratory, August 2005
Energy balance value for fuel ethanol alone is not meaningful in evaluating its benefits. Any type of fuel ethanol helps substantially reduce fossil energy and petroleum use, relative to petroleum gasoline. Corn-based fuel ethanol achieves moderate reductions in GHG emissions.
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