Duke Study Boosts Cellulosic
A comprehensive Duke University-led study reaffirms the decision by North Carolina scientific and policy leaders to focus a statewide effort on developing ethanol from cellulosic sources rather than corn.
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.
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.
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 economic terms with a standard financial accounting tool called "net present value."
For now, setting aside acreage and letting it return to native vegetation was rated the best way to reduce greenhouse gas emissions, outweighing the results of corn-ethanol production over the first 48 years. However, "once commercially available, cellulosic ethanol produced in set-aside grasslands should provide the most efficient tool for greenhouse gas reduction of any scenario we examined," the researchers added.
The worst strategy for reducing carbon dioxide emissions is to plant corn-for-ethanol on land that was previously designated as set aside -- a practice included in current federal efforts to ramp up biofuel production, the study found. That would remove a lot of soil carbon, which would escape into the atmosphere as CO2, the researchers found.