Released February 11, 2011
MOSCOW, ID – If you have been following the reports from the U.S. Environmental Protection Agency (EPA) over the past few years regarding the greenhouse gas (GHG) reductions achieved by using biofuels, you know that the numbers have changed dramatically.
The EPA’s first attempt, in May of 2009, at quantifying the GHG reductions of soy biodiesel raised enormous concerns in the biodiesel industry, because according to those initial numbers, soy biodiesel achieved only a 22% reduction in greenhouse gases compared to petro-diesel -- not enough to meet the 50% reduction needed for an Advanced Biofuel under the Renewable Fuel Standard 2 (RFS2).
After gathering comments and revising their model, the EPA’s final rule, released in February of 2010, states that soy biodiesel achieves on average a 57% reduction in greenhouse gases compared to petro-diesel.
Where did these numbers come from? Why did they change so much? The answer is that the EPA used a controversial form of life cycle analysis called “consequential life cycle analysis” to come up with these numbers. Results from a CLCA can change dramatically when assumptions change.
University of Idaho professor Dev Shrestha has written a new Tech Note explaining the differences between “attributional” and “consequential” life cycle analyses.
Read the complete Tech Note at the University of Idaho's Biodiesel Education Program web site.
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