Five-Year Study Shows Net Energy Gain from Switchgrass Ethanol

Switchgrass grown for biofuel production produced 540 percent more energy than what is needed to grow, harvest and convert it to cellulosic ethanol, according to a new study published by the Proceedings of the US National Academy of Science (PNAS). The result of the five-year study also revealed that greenhouse gas emissions from switchgrass-derived ethanol were 94 percent lower than estimated greenhouse gas from gasoline production. The study was conducted by the US Department of Agriculture-Agricultural Research Service (USDA-ARS) and the University of Nebraska-Lincoln.

Unlike earlier studies that made use of small research plots and estimated energy inputs, the new study managed large field trials (3-9 ha) on farms and marginal lands across the US. The researchers determine the net energy estimates by taking into account all production operations, agricultural inputs and field biomass yields for a five-year period. Using a conservation cellulosic conversion value, the researchers found that switchgrass grown in marginal fields produced an average of 300 gallons of ethanol per acre compared to mean yields of 350 gallon per acre for corn. The switchgrass varieties used in the study were developed for use in pastures. High yielding cultivars specifically for biofuel use are currently being developed by scientists.

The abstract of the PNAS article, including links to the open access article is available at http://www.pnas.org/cgi/content/abstract/0704767105v1