Ethanol as the next generation of alternative fuels has stirred significant controversy. While some tout its lower-than-gasoline greenhouse-gas emissions and its usefulness in creating carbon sinks in its agricultural fields, many other ecologists call ethanol production the most inefficient of alternative fuel options. Even the most optimistic scenarios still show that using current technologies, it can take years – in some studies, up to 1,000 – to overcome ethanol’s accumulated carbon debt.
Writing in the March issue of Ecological Applications, a group of ecologists based at Duke University say that until technologies for producing ethanol from cellulosic materials improve drastically, leaving land in a conservation reserve program will produce fewer greenhouse gases on the whole than using the land for ethanol production.
Current federal programs to increase ethanol production are investing in transforming conservation lands to corn-for-ethanol agricultural production, a practice that the researchers found was the worst strategy for reducing carbon dioxide emissions.
“Until cellulosic ethanol production is feasible, or corn-ethanol technology improves, corn-ethanol subsidies are a poor investment economically and environmentally,” said author Rob Jackson of Duke’s Nicholas School of the Environment.
The researchers found that cellulosic ethanol practices, including farming switchgrass, are a more eco-friendly biofuel production method than using corn, since cellulosic species often require little or no tilling. Tilling corn can release 30 to 50 percent of the carbon stored in the soil; mowing switchgrass, by contrast, can increase soil carbon content by 30 to 50 percent.
Still, the researchers say that until cellulosic ethanol practices are commercially available, setting aside land for natural vegetation creates the best greenhouse gas benefits. But once these practices are available, they write, “cellulosic ethanol in set-aside grasslands should provide the most efficient tool for greenhouse gas reduction of any scenario” they examined.
Read the open-access paper here.
Gervasio Piñeiro, Esteban G. Jobbágy, Justin Baker, Brian C. Murray, Robert B. Jackson (2009). Set-asides can be better climate investment than corn ethanol Ecological Applications, 19 (2), 277-282 DOI: 10.1890/08-0645.1