substitute

via ScienceDaily, from a new Cornell study. Everyone knows that the ethanol subsidy is just a farm subsidy, but it's sort of depressing to see data that makes biodiesel generally look like a net loss. If it takes more fossil fuel to produce the biodiesel than we get out of it, we're taking a step back.

Ethanol And Biodiesel From Crops Not Worth The Energy

ITHACA, N.Y. -- Turning plants such as corn, soybeans and sunflowers into fuel uses much more energy than the resulting ethanol or biodiesel generates, according to a new Cornell University and University of California-Berkeley study.

"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 detailed analysis of the energy input-yield ratios of producing ethanol from corn, switch grass and wood biomass as well as for producing biodiesel from soybean and sunflower plants. Their report is published in Natural Resources Research (Vol. 14:1, 65-76).

In terms of energy output compared with energy input for ethanol production, the study found that:

• corn requires 29 percent more fossil energy than the fuel produced;
  
• switch grass requires 45 percent more fossil energy than the fuel produced; and
  
• wood biomass requires 57 percent 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 percent more fossil energy than the fuel produced, and
  
• sunflower plants requires 118 percent more fossil energy than the fuel produced.

( more details )