Ethanol made from the waste left after harvesting corn is worse for the environment than gasoline in the short term, according to a new study that contradicts the Environmental Protection Agency (EPA).
The study published Sunday in Nature Climate Change found that the biofuel from corn residue, also known as stover, releases 7 percent more greenhouse gases in the first few years it is harvested. In the long term, the stover ethanol has lower greenhouse gas emissions, the study said.
The researchers also concluded that the higher greenhouse gas emissions could disqualify stover ethanol from being considered a renewable fuel for the purposes of federal regulations. Such fuels must emit 60 percent of the greenhouse gases as traditional fuels in order to count toward fuel refiners’ renewable fuel requirements.
The EPA and the biofuels industry said the research was flawed, in part because it assumes that an entire corn field’s waste would be harvested for stover.
“This paper is based on a hypothetical assumption that 100 percent of corn stover in a field is harvested; an extremely unlikely scenario that is inconsistent with recommended agricultural practices,” said EPA spokeswoman Liz Purchia.
“As such, it does not provide useful information relevant to the lifecycle GHG emissions from corn stover ethanol.”
The agency's own analysis assumes that half of a field is harvest for stover, Purchia said. The EPA consulted with the U.S. Department of Agriculture to determine that a 50 percent assumption is close to standard agricultural practices.
“The results are based on sweeping generalizations, questionable assumptions and an opaque methodology,” Bob Dinneen, president of the Renewable Fuels Association, said in a statement. “The authors offer no robust explanation for why their findings contradict other recent, highly regarded research.”
Dinneen said the research “bears no resemblance to the real world.”