Switch grass is one of the most efficient biofuels yet developed. It is a perennial crop,meaning that it grows all year long. Normally,switch grass grows on the prairies and canreach 2.2 meters tall. Through a refining process,switch grass is turned into cellulosic ethanol which can be usedin car engines. Some studies show that biofueis using switch grass produce 540 percent more energy than needed to grow,process and refine it. This is a very high net energy yield, much better than corn ethanoi. Currently,the technology used to convert switch grass into ethanol is not as advanced as that for turning corn into ethanol. Fortunately,switch grass is the one biofuel that does not adversely affect food prices.Both of these biofuels are promising for the future