Using corn residues – stalks, husks and cobs – to make biofuels appears to create more carbon dioxide over their life cycle than the target set by federal standards, says research at the University of Nebraska. “The findings cast doubt on whether corn residue can be used to meet federal mandates to ramp up ethanol production and reduce greenhouse gas emissions,” says a summary at Science Daily. The emissions are 7 pct higher per megajoule than allowed for the fuel energy produced.
Corn is the most widely grown crop in the United States so stover has seemed a ready-made way to make biofuels without a food-vs-fuel argument. Stover is one of the feedstocks expected to bring ‘advanced’ biofuels to market. They would make biofuels out of cellulose, found in crop residue, grasses and trees. The EPA is considering a reduction in U.S. biofuel mandates because second-generation biofuels are only a fraction of their anticipated volumes.
To mitigate for soil carbon lost when stover is used to make biofuel, the University of Nebraska study suggested the planting of cover crops to fix carbon into the soil. It said cellulosic plants could use perennial grasses or wood residue, or they could generate and sell electricity to offset emissions from coal-fueled power plants.