A new study concludes that, depending on prior land use, carbon (C) releases from the soil after planting corn for ethanol may in some cases completely offset C gains attributed to biofuel generation for at least 50 years. Based on an analysis of 142 soil studies, the study also found that soil carbon sequestered by setting aside former agricultural land was greater than the carbon credits generated by planting corn for ethanol on the same land for 40 years and had equal or greater economic net present value.
The study also found that once commercially available, cellulosic ethanol produced in set-aside grasslands should provide the most efficient tool for GHG reduction of any scenario examined. The researchers from DUke University, Texas A&M University and Universidad Nacional de San Luis om Argentina suggested that conversion of CRP lands or other set-aside programs to corn ethanol production should not be encouraged through greenhouse gas policies.
The paper appears in the March edition of the journal Ecological Applications.
One of our take-home messages is that conservation programs are currently a cheaper and more efficient greenhouse gas policy for taxpayers than corn-ethanol production...Until cellulosic ethanol production is feasible, or corn-ethanol technology improves, corn-ethanol subsidies are a poor investment economically and environmentally.—Robert Jackson, the Nicholas Professor of Global Environmental Change at Duke’s Nicholas School of the Environment
Nevertheless, farmers and producers are already receiving federal subsidies to grow more corn for ethanol under the Energy Independence and Security Act of 2007.
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.
The report noted that a cost-effective technology to convert cellulosics to ethanol may be years away. So the 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% 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% instead of reducing them.
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.
The research was funded by the National Science Foundation, the Center for Global Change at Duke University and by the Agencia Nacional de Promoción Científica y Tecnologíca of Argentina.
Gervasio Piñero et al. Set-asides can be better climate investment than corn ethanol. Ecological Applications, 19(2) pp. 277–282 doi: 10.1890/08-0645.1