Corn ethanol may sound like a good alternative energy source, but a high taxpayer burden and heavy environmental costs make this clean-burning fuel as destructive as it is sustainable.

First implemented in 1978, U.S. corn ethanol subsidies now cost taxpayers more than $3 billion annually. At current rates, corn ethanol will cost $5 billion per year by 2010. The government also supports genetically engineered (GE) corn, which arguably has the potential to damage biodiversity, posing health risks to humans and animals. Without strict management it's difficult to prevent GE corn from cross-pollinating with non-GE corn, so inedible substances, such as deep-sea organisms — spliced into ethanol corn — could crossbreed with edible crops, spreading new allergens into the food supply. Nonetheless, as a result of pressure from GE giant Monsanto, a 2008 USDA agreement reduces federal crop insurance premiums for farmers who plant Monsanto-brand GE corn. Corporate lobbying such as this has helped ensure that 80 percent of domestically grown corn is now genetically modified.

On the environmental front, nitrogen used to fertilize corn crops produces toxic runoff that harms oceans. (Heard of the Gulf of Mexico's Dead Zone?) Meanwhile, the diesel machinery, natural gas, and coal used during harvest and distillation pollute the air. Even with this dirty pedigree, corn ethanol received 76 percent of all renewable-energy tax credits ($3 billion) in 2007, largely because of the pro-ethanol 2007 Energy Act. Other sources of alternative energy, such as wind and solar, received only $690 million — more than four times less.

BY THE NUMBERS

4: Gallons of water used to convert corn into 1 gallon of ethanol

450: Pounds of corn required to fill a 25-gallon SUV gas tank with ethanol

25: Percentage of U.S.-grown corn used for ethanol production

45 cents: Per-gallon subsidy refiners get for blending their gasoline with ethanol

WHAT YOU CAN DO

VOTE WITH YOUR DOLLARS: When shopping, avoid sneaky GE ingredients like corn syrup and maltodextrin by buying organic food, which by definition is GE-free. Instead of grain-finished beef, select meat and dairy from grass-fed animals.

WRITE CONGRESS: Contact the House Committee on Agriculture to share your views on GE organisms and ethanol subsidies. For contact info, go to agriculture.house.gov/inside/members.html.

GET EDUCATED: Learn the latest on corn ethanol issues from the Environmental Working Group (ewg.org). Visit the Cool Foods Campaign (coolfoodscampaign.org) for carbon footprint-reducing shopping tips.

LEARN MORE: Read up on issues surrounding genetically modified organisms (GMOs).