As a crop, corn is very water- and nitrogen-intensive, meaning it requires massive amounts of water and fertilizers to grow. Year after year, corn crops on the same land exhaust the soil of nutrients and is ultimately unsustainable.
The United States produces 11 billion bushels of corn every year, and that crop makes some pretty extensive rounds around and outside the country.
It feeds U.S. livestock and is used in vast amounts of processed foods in the form of corn syrup, corn starch and other additives. The United States also uses our cheap, taxpayer-subsidized grain crops for trade with other countries, including Middle Eastern nations. The government then takes what's left and ships it to Africa in the form of food aid for poverty-stricken nations.
If the price of corn continues to rise and the United States continues to allot more of it to the ever-increasing amount of ethanol plants, domestic and international food prices will rise and the amount of food we're able to send to our neighbors in Africa may diminish.
Also, since it absorbs too much water, shipping ethanol through pipelines is impossible. What this means is it must be trucked from the refinery to the gas station, according to the Lansing State Journal.
Modern agriculture uses copious volumes of diesel to run the plows and other machines, so a large-scale switch to corn-based biodiesels will still promote extensive fossil fuel use