The results of a five year study by the USDA conducted on farms in Nebraska and North and South Dakota show that switchgrass (Panicum virgatum) can deliver more than five times the amount of energy used to farm it. For comparison, corn, which is currently the biofuel crop of choice in the U.S. delivers only 25% more energy than is used to farm it. However, in a March 2005 paper David Pimentel and Tad Patzek report that corn based ethonol is produced at a 29% energy deficit.
Switchgrass, which is native to North America, is a permanent crop, meaning that it does not need to be replanted every year like most commercial crops. And because the switchgrass fields are not tilled under every year, the crop is effective at permanently storing the CO2 it takes out of the atmosphere.
One might wonder why all commercially produced ethonol is still being made with corn. For starters, there are no commercial cellulosic biorefineries to process the switchgrass, although the Department of Energy is contributing funding for the construction of six such refineries. Also, corn farming is heavily subsidised in the U.S., with the Farm Bill distributing an average of $5.1 billion per year to corn farmers.