Corn-fed animals are fuelling America

Biofuel demand is not the only market pressure being felt by US corn farmers. Much of the fast food that powers Americans - a $100 billion annual market - is indirectly made from corn as well, according to researchers in Hawaii.

Hope Jahren and Rebecca Kraft of the University of Hawaii purchased 486 servings of hamburgers, fries and chicken sandwiches from McDonald's, Burger King and Wendy's in Los Angeles, San Francisco, Denver, Detroit, Boston and Baltimore.