Improving Ethanol Yield From Corn

Ethanol to fuel cars early in the 21st century may come from fiber-laden crop residues—instead of feed grains—if a vision of agricultural researchers at Peoria, Illinois, pans out. But before that vision is fully realized, science and technology will most likely enable ethanol producers to squeeze a bit more ethanol from corn—the main source at present. Through fermentation of starches and sugars found inside the grain, modern ethanol plants now produce 2.5 gallons of ethyl alcohol—ethanol—from each bushel of corn, says Rodney J. Bothast. He’s an ARS microbiologist at the National Center for Agricultural Utilization Research (NCAUR) in Peoria, Illinois. Bothast and his colleagues have their sights set on making fiber in the grain's outer layer yield nearly 0.3 additional gallon per bushel. In 1994, about 1.3 billion gallons of fuel ethanol were produced in the United States from corn, with more than 60 percent obtained through wet milling. The wet-milling process involves soaking, or steeping, the corn in water, grinding it, and separating high-protein germ, oil, and fiber from the starchy endosperm that is fermented to produce ethanol. The current practice is to mix the fiber fraction with fermentation solubles before drying it and forming animal feeds. Agricultural engineer Michael R. Ladisch and colleagues at Purdue University in West Lafayette, Indiana, teamed up with the NCAUR scientists to assess ways to increase ethanol production from corn. "We estimate that if the fiber were