Farmers in Nebraska and the Dakotas have worked with the USDA to plant switchgrass and measure the native plant's ability to deliver Ethanol more efficiently than corn. The results are dramatic. Switchgrass delivers 540 percent of the energy used to produce it, compared with just roughly 25 percent returned by traditional corn-based ethanol.
Check out the Scientific American article that discusses the work of plant scientists and farmers that show that "switchgrass will store enough carbon in its relatively permanent root system to offset 94 percent of the greenhouse gases emitted both to cultivate it and from the derived ethanol burned by vehicles." (Good News Network)