The report said that "cellulosic" species -- such as switchgrass -- are a better option for curbing emissions than corn because they don't require annual replowing and planting. In contrast, a single planting of cellulosic species will continue growing and producing for years while trapping more carbon in the soil.
"Until cellulosic ethanol production is feasible, or corn-ethanol technology improves, corn-ethanol subsidies are a poor investment economically and environmentally," Jackson added.
However, the report noted that a cost-effective technology to convert cellulosics to ethanol may be years away. So the Duke team contrasted today's production practices for corn-based ethanol with what will be possible after the year 2023 for cellulosic-based ethanol.
By analyzing 142 different soil studies, the researchers found that conventional corn farming can remove 30 to 50 percent of the carbon stored in the soil. In contrast, cellulosic ethanol production entails mowing plants as they grow -- often on land that is already in conservation reserve. That, their analysis found, can ultimately increase soil carbon levels between 30 to 50 percent instead of reducing them.
"It's like hay baling," Pieiro said. "You plant it once and it stays there for 20 years. And it takes much less energy and carbon dioxide emissions to produce that than to produce corn."
As part of its analysis, the Duke team calculated how corn-for-ethanol and cellulosic-for-ethanol production -- both now and in the future -- would compare with agricultural set-asides. Those comparisons were expressed in ec
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| Contact: Monte Basgall monte.basgall@duke.edu 919-681-8057 Duke University Source:Eurekalert |