As reported in “The Energy Balance of Corn Ethanol: an Update,”the energy returned on energy invested (EROEI) for ethanol made from corn in the U.S. is 1.34 (it yields 34% more energy than it takes to produce it).
Input energy includes natural gas based fertilizers, farm equipment, transformation from corn or other materials, and transportation. However, other researchers report that the production of ethanol consumes more energy than it yields.
Oil has historically had a much higher EROEI, especially on land in areas with pressure support, but also under the sea, which only offshore drilling rigs can reach. Apart from this, the amount of ethanol needed to run the United States, for example, is greater than its own farmland could produce, even if fields now used for food were converted for production of non-food-grade corn.
It has been estimated that “if every bushel of U.S. corn, wheat, rice and soybean were used to produce ethanol, it would only cover about 4% of U.S. energy needs on a net basis.”It is for these reasons that ethanol alone is generally not seen as a solution to replacing conventional oil.