OK, here are some basic facts:
- In 2004, U.S. farmers produced a record 11.8 billion bushel corn harvest, and some 1.4 billion bushels (about 13 percent) were used in ethanol production. [Link]
- In June 2004, the U.S. Department of Agriculture… determined that the net energy balance of ethanol production is 1.67 to 1. For every 100 BTUs of energy used to make ethanol, 167 BTUs of ethanol is produced. (Same link as above.)
- In 2004, 81 ethanol plants in 20 states produced 3.41 billion gallons of ethanol. [Link]
- In 2003, U.S. gasoline consumption totaled 139 billion gallons. [Link]
All in all, the U.S. production of ethanol is roughly 2.5% of the U.S. gasoline consumption. Bringing the percentage up to 10% (modern engines allow that much) would require a 39% increase in corn production.