The debate over biodiesel and ethanol ragesLast week
Cornell University Professor David Pimentel and University of California-Berkeley Professor Tad Patzek released a study claiming to show that it takes 29% more fossil energy to turn corn into its equivalent amount of ethanol, and 118% more fossil fuel to convert sunflower plants to the equivalent amount of biodiesel and 27% more to covert soybean plants into biodiesel.
The issue of net energy production is of utmost importance. For example, some studies show that, with federal subsidies, some oil well continue to produce even after they have to expend more energy to get the oil than they get from it. Similarly, oil sands take much more energy to produce than conventional oil and therefore have a lower net enrergy production, while shale oil has yet to prove that it can produce an energy surplus.
But the biodiesel and ethanol issue has been fiercely debated. The National Biodiesel Board
this week issued it's response to the Pimentel and Patzek study, citing a comprehensive, peer reviewed study on biodiesel produced from soybeans. Its findings included the facts that for every one unit of fossil energy used in this entire production cycle, 3.2 unit of energy are gained when the fuel is burned, or a positive energy balance of 320%; the energy balance for biodiesel produced from soybeans is so high because the starting component, soybean oil, is already high in energy content. Oils and fats are nature’s preferred way to store high density energy; this study started with bare soil and took into account all the energy inputs associated with growing and harvesting soybeans: transporting and processing the soybeans into oil and meal, transportation and production of the soybean oil into biodiesel, and transportation of the biodiesel to the end user.
The Board criticized Pimentel and Patzek's assumtions on energy use. For example, the researchers’ assumption regarding the use of lime does not reflect current farming practices. Lime inputs account for over 36% of the total energy inputs for soybean production in Pimentel and Patzek study. While the use of lime on acidic soils may help improve yields, its use is dependent upon the requirements of the soil and is not a universal input for soybean production. Moreover, in most parts of the country, the use of lime is limited and, if used, is not applied on an annual basis.
The study includes labor as an energy input. Even though the calories consumed by farm workers can be converted to energy equivalents, most researchers do not treat the calories as fossil energy. Labor associated with soybean production has no significant effect on the total number of calories consumed in the United States and calories are not considered to be a scarce resource. Moreover, people must consume food to sustain life, regardless of their occupation.
The study does not acknowledge that producing biodiesel also results in the production of glycerin, a highly valued product used in pharmaceuticals, soaps, and other products. To be accurate, biodiesel’s energy balance should have been credited for the glycerin co-product.
The study uses a 1979 study to derive energy estimates for the energy required to manufacture construction materials and farm equipment. The U.S. manufacturing sector has increased energy efficiency dramatically over the past 25 years. There is no comparison between modern production facilities and farm equipment today and those constructed in 1979.
Pimentel erroneously reports that the USDA/DOE life cycle study concluded that the net energy balance of biodiesel was negative. The Pimentel study misrepresents the 1998 joint study by U.S. researchers from the Department of Energy and U.S. Department of Agriculture. The study actually concluded that biodiesel made from soybean oil resulted in an energy savings of more than 3 to 1.
Given the paucity of data included in the Pimentel and Patzek study, the edge in the argument would seem to be in favor of biodiesel and ethanol at this point.