Biodiesel energy-balance numbers published in new benchmark study

Posted October 20, 2009

Assessing the energy balance of soy biodiesel is a continuous effort. The University of Idaho and the USDA have been involved with the project for years-they've found that biodiesel's numbers keep improving. "New data becomes available as the industry evolves," says Jon Van Gerpen, biological and agricultural engineering department head at UI. "Ag-production practices and energy efficiencies are getting better and better all the time."

The collaborative report concludes that biodiesel returns 4.5 units of energy for every unit of fossil energy required for its production. The National Biodiesel Board used the circumstance of the report's publication to criticize the U.S. EPA's proposed rule to implement RFS2. "EPA used 2005 baseline numbers for petroleum and biodiesel to project carbon impact 22 years in the future," NBB stated. "That stacks the deck in favor of petroleum."

New seed varieties and management practices have reduced the need for pesticides, tilling and fuel, and today's biodiesel plants are more energy efficient. "The EPA should take this into account when considering biodiesel's greenhouse gas reductions," said Joe Jobe, CEO of the NBB.

Some of the necessary data needed to perform this work are only processed every five years, so researchers can only study it as it becomes available or is published. "Energy efficiency data isn't available year to year," Gerpen told Biodiesel Magazine regarding the energy balance figure correlating with actual improvements in the field over the same period. "When we did our study in 2006, biodiesel had an energy balance around 3.9-it might have been better then but we didn't have all of the data available to us."

Biodiesel is also the source of "valuable coproducts" like glycerin, which have been overlooked in the plan to implement RFS2. "This [energy balance study] is one more piece of information that helps to quantify the environmental benefits of biodiesel," Van Gerpen said.

Biodiesel conversion was the most intensive, accounting for about 60 percent of the total energy required in the life-cycle inventory. Soybean agriculture accounted for 18 percent of the total energy requirements, followed by soybean crushing, which required almost 15 percent of the total energy. The secondary inputs added were farm machinery, and building materials for a crushing plant and biodiesel refinery.