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Pimentel is a known and proven liar using out of date data to deceive people about the mass energy balance of ethanol.

Nor does ethanol take much out of the food chain. Half of all corn is used as animal feed, the food value of the DDG’s is still there after processing. The main problem is that they put the stillage back in with the DDG’s, which gives it too high of a fat content to be fed in large quantities.

Short but good article from the Dept of Energy on ethanol mass/energy balance:

http://www1.eere.energy.gov/biomass/net_energy_balance.html

Net Energy Balance for Bioethanol Production and Use
Bioethanol production for transportation fuel is not without environmental concerns. Current U.S. fuel ethanol production is based almost entirely on starch from corn grain. To achieve its tremendous production levels, modern U.S. corn farming makes relatively intense use of energy and chemicals. Early ethanol plants were also energy intensive, raising concerns as to whether the transportation fuel being produced was worth the energy going into making it. American agriculture, however, has made great efficiency gains in recent years, as has the fuel ethanol industry.

The most official study of the issue, which also reviews other studies, concludes that the “net energy balance” of making fuel ethanol from corn grain is 1.34; that is, for every unit of energy that goes into growing corn and turning it into ethanol, we get back about one-third more energy as automotive fuel. That may not sound impressive, but bear in mind that while the gasoline that ethanol displaces is largely imported and a high-level pollution source, the mix of energy inputs for producing bioethanol includes much domestic and relatively cleaner energy. On the basis of liquid fuels alone, the net balance is 6.34 (USDA Office of Energy Policy and New Uses, The Energy Balance of Corn Ethanol: An Update).

A public interest environmental organization study (Institute for Local Self Reliance), 1995 shows how much net energy balance can improve. Calculating the current balance at 1.38, it goes on to calculate a ratio of 2.09, if you base it on corn grown in the most efficient farming state and ethanol produced in the most efficient existing facilities. That is, if the industry averages move to the current industry bests, as you would expect them to tend toward, there would be more than twice as much energy in the fuel ethanol as went into making it.

For cellulosic bioethanol—the focus of the Biomass Program—that study projects an energy balance of 2.62. That is based on growing and harvesting energy crops such as fast-growing trees, so bioethanol from corn stover or other residue that requires no production effort would have an even more favorable energy balance. A Biomass Program life-cycle analysis of producing ethanol from stover, now underway, is expected to show a very impressive net energy ratio of more than 5. It should be noted, though, that much of the energy gain comes from generating electricity by burning the co-product lignin, rather than from the ethanol itself.

One of the most persistent critics of fuel ethanol [David Pimentel, Cornell University, (see for example Journal of Agricultural and Environmental Ethics, vol. 4, no. 1, pp. 1-13. 1991.)] asserts that it takes about 70% more energy to grow corn and make ethanol from it than goes into the ethanol. Among other things, however, his analysis is based on old data and does not give any credit for the energy value of the animal feed co-product of making ethanol (both dry-mill- and wet-mill-ethanol plants produce high-protein animal feeds as a major co-product, a key economic element of the production processes). The use of old data is significant because the modern ethanol industry is only about 20 years old and plants today are far more efficient than the first ones built. Productivity of corn production has also increased dramatically.

Ethanol critics also question the wisdom of growing fuel instead of food, but corn (field corn, not to be confused with sweet corn) is used mostly for livestock feed and for products such as beverage sweeteners, rather than direct human consumption. As the largest U.S. agricultural crop, it is generally in surplus, requiring price supports, so to whatever extent ethanol supports corn prices, taxpayer costs are reduced. Cellulosic bioethanol production would have even less impact on food supplies. It would use either residues such as stover that are produced as a byproduct of producing other crops or dedicated energy crops grown on land not economically suitable for food crops.

With lower fertilizer requirements for soybeans than corn and simpler processing, biodiesel production and use has a net energy balance of 3.2.