A peer-reviewed study performed at the Energy Department's Argonne National Laboratory in 2012 found that biofuels made with corn residue were 95 percent better than gasoline in greenhouse gas emissions. That study assumed some of the residue harvested would replace power produced from coal, reducing greenhouse gas emissions, but it's unclear whether future biorefineries would do that.
Liska agrees that using some of the residue to make electricity, or planting cover crops, would reduce carbon emissions. But he did not include those in his computer simulation.
Still, corn residue is likely to be a big source early on for cellulosic biofuels, which have struggled to reach commercial scale. Last year, for the fifth time, the EPA proposed reducing the amount required by law. It set a target of 17 million gallons for 2014. The law envisioned 1.75 billion gallons being produced this year.
"The study says it will be very hard to make a biofuel that has a better greenhouse gas impact than gasoline using corn residue," which puts it in the same boat as corn-based ethanol, said David Tilman, a professor at the University of Minnesota who has done research on biofuels' emissions from the farm to the tailpipe.
Tilman said it was the best study on the issue he has seen so far.
Follow Dina Cappiello's environment coverage on Twitter at http://www.twitter.com/dinacappiello
Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.