He's at it again. David Pimentel, professor of ecology and agriculture at Cornell University, has released a new study criticizing the energy use in ethanol and biodiesel production.
Pimental, along with Tad W. Patzek, professor of civil and environmental engineering at Berkeley, say turning plants such as corn, soybeans and sunflowers into fuel uses much more energy than the resulting ethanol or biodiesel generates.
Samantha Slater, director of public policy for the National Corn Growers Association, says Pimental's study often ends up in media sources, but gets little traction in places of importance including Capitol Hill.
Pimental's study claims that in terms of energy output compared with energy input for ethanol production, the study found:
- corn requires 29% more fossil energy than the fuel produced;
- switch grass requires 45% more fossil energy than the fuel produced; and wood biomass requires 57% more fossil energy than the fuel produced.
The results of a USDA report by Hosein Shapouri of the Chief Economist's Office indicate that corn ethanol has a positive energy balance, even before subtracting the energy allocated to by 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. The study results suggest that corn ethanol is energy efficient, as indicated by an energy output/input ratio of 1.67.
The report explains that during the past two years, Pimentel, Patzek, and Andrew Ferguson criticized USDAâ€™s studies of the net energy balance of corn ethanol. It is argued that USDA underestimates energy used in the production of nitrogen fertilizer and the energy used to produce seed-corn, over estimating the energy allocated to produce corn ethanol byproducts. They also argued that USDA excludes energy used in corn irrigation and secondary energy inputs used in the production of corn, such as farm machinery and equipment and cement, steel, and stainless steel, used in the construction of ethanol plants.
Slater explains that USDA's report uses 2001 figures, and the ratio is probably higher today thanks to technological advancements in corn and ethanol production.