"Biofuels such as ethanol are compounds derived from plants that can be used to fuel internal-combustion engines such as those in cars and small machinery. Creating these fuels from plants can reduce the environmental and political problems caused by a reliance on oil. Although much ethanol production, especially in the United States, comes from corn, switchgrass is a promising alternative. It is a North American native grass that can grow on marginal land without the extensive inputs that corn or sugar cane require, and it produces a much better energy yield. Making ethanol from switchgrass, though, is a challenging process."