For years, biodiesel has been touted as a cleaner-burning alternative to petroleum-derived diesel for on and off-road applications. Now, the industry can feel more confident than ever in biodiesel's ability for meeting today's energy needs without sacrificing the ability of future generations to do the same. A newly published report co-authored by researchers from the University of Idaho and the USDA, titled “Energy Life-Cycle Assessment of Soybean Biodiesel Revisited,” found that for every unit of fossil energy needed to produce biodiesel, it returns a stunning 5.54 units of renewable energy.

This energy-in, energy-out ratio is called energy balance or fossil energy ratio. Biodiesel derived from soybeans, for example, benefits from “free” energy from the sun. The study also compared biodiesel with other alternative fuels receiving mainstream attention such as liquefied propane and natural gas. A comparison with gasoline was also evaluated.

“This study shows the clear trend that biodiesel production continues to improve when it comes to efficient use of resources,” said Don Scott, director of sustainability for the National Biodiesel Board. “No other fuel available in the U.S. comes close to such a high energy balance.”

The objective of the study was to construct a new biodiesel energy life cycle with 2006 data that reflects current soybean production and biodiesel plants built after 2002, which make up the majority of plants producing biodiesel today. Additionally, a comparison of the three time periods from past studies conducted in 1990, 2002 and 2006 indicated how energy life cycles change over time.

Scott highlighted that the most recent data available for this study was from 2006.  "Using data from 2009 or 2010 would likely show an even greater gain in energy efficiency," he said.

The U.S. DOE and USDA completed the first comprehensive life-cycle analysis for biodiesel production back in 1998. That study, however, found a 3.2-to-1 energy balance. The energy inventory for this study was updated in 2009 using 2002 data, which found that the ratio had improved to 4.56 to 1.

Specifically, the new University of Idaho study found three critical factors that led to the leap in biodiesel’s energy balance number. First, new data from the USDA and the NBB indicate that soybean crushing facilities and biodiesel plants have become increasingly more energy efficient over the years. Second, soybean farmers have adopted energy-saving farm practices such as minimum tillage. Thirdly, overall yields of soybeans have increased.

In comparison to the 2009 study, the new study found: the energy input in soybean agriculture was reduced by 52 percent; the energy input in soybean processing was reduced by 58 percent; the energy input in biodiesel production (transesterification) was reduced by 33 percent, per unit volume of biodiesel produced; overall, the energy input reduction was 42 percent for the same amount of biodiesel produced, and the addition of secondary inputs, such as farm machinery and building materials, did not have a significant effect on the fossil energy ratio.

"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 Jim Duffield, USDA senior agricultural economist 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."

Dev Shrestha, an associate professor in the Department of Biological and Agricultural Engineering at the University of Idaho, and co-author of the report, told Biodiesel Magazine in email correspondence that he expects higher energy balance of biodiesel to continue improving in coming years.

“USDA projects soybean yield to increase over time and the biodiesel industry is likely to continue to increase energy efficiencies, which will eventually contribute to higher[fossil energy ratio],” Shrestha said. “Also, possible replacement of fossil energy with renewable energy in the future, for instance, biofuel use in farm equipment, could also significantly improve biodiesel FER over time.”