Fuels: Corn Ethanol Goal Revives Dead Zone Concerns

A 242 VOLUME 116 | NUMBER 6 | June 2008 • Environmental Health Perspectives The Energy Independence and Security Act of 2007 calls for the production of 36 billion gallons of renewable fuels by 2022, including 15 billion gallons of corn-based ethanol, a tripling of current production that would require a similar increase in corn production. Yet scientists are coming to understand that biofuels, which originally sounded like a sensible response to the twin problems of climate change and dependence on foreign oil, create environmental problems of their own. One such problem is an increase in nitrogen runoff as farmers rush to plant more corn to meet growing demand for ethanol. According to the National Corn Growers Association, rising corn prices prompted farmers to plant 92.9 million acres of the grain in 2007, a 19% increase over the prior year. Fred Below, a professor of crop physiology at the University of Illinois at Urbana–Champaign, explains that corn requires more nitrogen fertilizer compared with other crops because of its higher production of grain per unit area than other crops. “Also,” he adds, “unlike crops like soybeans that form symbiotic relationships with soil bacteria to obtain a portion of their nitrogen from the atmosphere, corn is completely dependent on available nitrogen in soil.” Naturally occurring nitrogen usually must be supplemented with fertilizer to meet corn’s needs. The nitrogen applied as fertilizer to corn does not stay in the Corn Belt. Instead, it travels via local streams and rivers to the Mississippi River and eventually enters the Gulf of Mexico. Once there, the excess nitrogen fuels explosive algal blooms. When the algae die, they are decomposed by bacteria that consume much of the oxygen in the water. The result is a so-called Dead Zone about the size of New Jersey that is so depleted of oxygen that fish, shellfish, and other aquatic life cannot survive there. The boom in biofuel production “is a disaster for the