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 on the prairies and can reach 2.2 meters tall. Through a refining process, switch grass is turned into cellulosic ethanol which can be used in car engines. Some studies show that biofuels using switch grass produce 540 percent more energy than needed than corn ethanol. Currently, the technology used to convert switch grass into ethanol is not as advanced as that for turning corn into ethanol. Fortunaely, these biofuels are promising for the future.