As we talked about two weeks ago, two new studies have shown that biofuels may produce more greenhouse gas emissions than fossil fuels when factors like production and transportation are considered. The studies were released just as EPA told us it was raising the renewable fuel standard for 2008.

This week, Department of Energy scientists criticized the accuracy of one of the biofuels reports, and its author was quick to fire back. On Feb. 18, Greenwire reported (subscription required) that DOE scientists Michael Wang and Zia Haq challenged several aspects of German Marshall Fund researcher Tim Searchinger’s lifecycle analysis, including changes in land use and crop yields.

According to Greenwire, “Perhaps most significantly, Wang and Haq said [Searchinger’s] study looks at a scenario for ethanol use unlikely to occur, because it envisions 30 billion gallons of domestic corn ethanol being produced annually by 2015, when the energy bill passed late last year calls for 15 billion gallons from corn.”

Searchinger dismissed the scientists’ comments, telling Greenwire, "Everything they say is either logically irrelevant or false.” Ouch.