A new study finds that using biofuels made from corn harvest residue could actually increase carbon dioxide emissions in the short term, contrary to both popular belief and U.S. government environmental strategy. 

According to the report, published over the weekend in the scientific journal Nature Climate Change, using biofuels made from corn stover — stalks, leaves and cobs left over from corn harvests — can increase greenhouse gas emission by about seven percent more than gas in early years. That's because removing the residue from the field, also takes carbon out of the soil where it's needed.

Phys.org explains the scientists' methodology: 

The researchers, led by assistant professor Adam Liska, used a supercomputer model at UNL's Holland Computing Center to estimate the effect of residue removal on 128 million acres across 12 Corn Belt states. The team found that removing crop residue from cornfields generates an additional 50 to 70 grams of carbon dioxide per megajoule of biofuel energy produced (a joule is a measure of energy and is roughly equivalent to 1 BTU). Total annual production emissions, averaged over five years, would equal about 100 grams of carbon dioxide per megajoule — which is 7 percent greater than gasoline emissions and 62 grams above the 60 percent reduction in greenhouse gas emissions as required by the 2007 Energy Independence and Security Act.

This means, per the researchers, that these types of biofuels shouldn't be considered a renewable fuel as it is defined by a 2007 energy law, even though they are beneficial in the long run. Which means that the U.S. government, which funded the study and has poured billions into the cellulosic biofuels, or plant-derived biofuels, might have to change course — if they accept the legitimacy of the research.

According to the Associated Press reports, however, that's not happening: 

The biofuel industry and administration officials immediately criticized the research as flawed. They said it was too simplistic in its analysis of carbon loss from soil, which can vary over a single field, and vastly overestimated how much residue farmers actually would remove once the market gets underway. "The core analysis depicts an extreme scenario that no responsible farmer or business would ever employ because it would ruin both the land and the long-term supply of feedstock. It makes no agronomic or business sense," said Jan Koninckx, global business director for biorefineries at DuPont.

DuPont is set to open a $200 million biofuel facility this year, so the company's global business director might not be totally objective in assessing gains from biofuels. Last year, a DuPont-funded assessment found that their biofuels would be 100 percent better for the environment than gas. 

To be fair, the Environmental Protection Agency (EPA) had previously found that corn-based biofuels could stand up to the 2007 law's standards if farmers leave enough residue on the fields. According to EPA spokesperson Liz Purchia, the study "does not provide useful information relevant to the life cycle greenhouse gas emissions from corn stover ethanol." But the AP found last year that the EPA's research into corn-based ethanol was faulty. 

And Liska stands by his team's work. "I knew this research would be contentious," he said, adding that "If this research is accurate, and nearly all evidence suggests so, then it should be known sooner rather than later."