A new Cornell University and University of California-Berkeley study from long-standing critics of biofuels slams both ethanol and biodiesel.
“There is just no energy benefit to using plant biomass for liquid fuel,” says David Pimentel, professor of ecology and agriculture at Cornell. “These strategies are not sustainable.”
Pimentel and Tad W. Patzek, professor of civil and environmental engineering at Berkeley, conducted a new analysis of the energy input-yield ratios of producing ethanol from corn, switch grass and wood biomass as well as of producing biodiesel from soybean and sunflower plants.
The two have collaborated before on similar research. The current report is published in Natural Resources Research (Vol. 14:1, 65-76).
In terms of energy output compared with energy input for ethanol production, their calculations determined that:
Corn requires 29% more fossil energy than the fuel produced;
Switch grass requires 45% more fossil energy than the fuel produced;
Wood biomass requires 57% more fossil energy than the fuel produced.
In terms of energy output compared with the energy input for biodiesel production, the study found that:
Soybean plants requires 27% more fossil energy than the fuel produced;
Sunflower plants requires 118% more fossil energy than the fuel produced.
In assessing inputs, the researchers considered such factors as the energy used in producing the crop (including production of pesticides and fertilizer, running farm machinery and irrigating, grinding and transporting the crop) and in fermenting/distilling the ethanol from the water mix.
Although additional costs are incurred, such as federal and state subsidies that are passed on to consumers and the costs associated with environmental pollution or degradation, these figures were not included in the analysis.
Pimentel has for a number of years been one of the most outspoken critics of ethanol. His conclusions and methodologies are vigorously contested by biofuel supporters, such as Hosein Shapouri at the USDA (earlier post). This current paper, and well as a different study published in BioScience (earlier post) will undoubtedly provoke a counter response.
Pimentel would prefer to see the country focus its efforts on producing electrical energy from photovoltaic cells, wind power and burning biomass and producing fuel from hydrogen conversion.