A corn-like plant that can grow as high as an elephant's eye on some of Earth's driest farmland shows promise as a "smart" biofuel that won't cut into world food supplies, an agriculture expert said on Monday. Sweet sorghum, used in the United States mostly as animal feed, offers a 10-foot (3 metre) stalk that can be turned into ethanol without damaging the food grain that grows at its top, Mark Winslow said in an interview.