Former Discovery colleague Richard Rahn answers the question in an article that should be read out loud at the next presidential debate in Iowa. If America used all the land now under production for food to produce corn for ethanol instead--if we imported all our food, in other words--we still would not meet more than two thirds of America's oil requirements. As is, with highly politicized federal subsidies, we are using up huge tracts of land previously cultivated for food or livestock, plus wilderness, to plant corn for ethanol; the ethanol acreage is equivalent in size to the state of Indiana. For what? For the amount of energy we could get out of a few thousand acres of oil drilling in Alaska.
In what way is this a justifiable trade-off for the environment, let alone the economy?
Here is Dr. Rahn's article from The Washington Times.