Much attention has been given to biofuels derived from renewable plant sources, like corn. A new study from the USDA, though, suggests that there is great potential in growing plain old grass. Switchgrass, a perennial grass native to North America, may yield as much as 5 times the energy required to plant, cultivate, and process it into fuel (ethanol). This number looks pretty impressive compared to corn, which is estimated to yield only 25% more energy. Researchers pointed out, though, that a direct comparison of energy yield between the two energy sources is not quite apples to apples - as explained in this second article.