A new study shows U.S. biodiesel production continues to be astonishingly energy-efficient in making biodiesel for diesel vehicles and home heating, demonstrating its long-term sustainability.

Newly published research from the University of Idaho and U.S. Department of Agriculture (USDA) shows that for every unit of fossil energy needed to produce biodiesel, the return is 5.54 units of renewable energy. This energy-in, energy-out ratio is called "energy balance" or "fossil energy ratio."

The U.S. Department of Energy and USDA completed the first comprehensive life-cycle assessment for biodiesel produced in the U.S. in 1998. That study found a 3.2-to-1 energy balance. The energy inventory for this analysis was updated in 2009 using 2002 data, finding the ratio had improved to 4.56-to-1.

In the new study, three things are primarily responsible for the leap in biodiesel's energy balance number: new data from USDA and the National Biodiesel Board shows that soybean crushing facilities and biodiesel production plants have become increasingly energy efficient; soybean farmers have adopted energy-saving farm practices, such has minimum-tillage; and increases in soybean yields.

"In addition to improved energy efficiency at processing facilities, soybean growers have accomplished greater yields with lower inputs of water and fertilizer per bushel, even as cropland has declined," said USDA Senior Agricultural Economist Jim Duffield, who co-authored all three life cycle analysis studies.

"Biodiesel deserves some credit for this progress — the demand it creates is helping to drive the new technologies that make American agriculture more efficient."

Biodiesel production in the U.S. predominantly utilizes soybean oil as a feedstock. Biodiesel’s powerful greenhouse gas reductions compared to petroleum diesel make it the only commercially-available advanced biofuel in the U.S.