There was a good article about ethanol production on the commercial scale in the October 2007 issue of National Geographic magazine. In the case of American production, it operates at an energy deficit currently because of the energy consumed during fermentation and distillation. Brazil, on the other hand, operates much better. Good article, worth reading.
FWIW, the maximum purity of ethanol achievable through distillation is 95%, as it distills as what is called an "azeotrope" with water as a 5% constant. This assumes perfect distillation, which is uncommon. More commonly, the alcohol is distilled at a lower purity and dehydrated by chemical means, typically using something called a "molecular seive" in an apparatus that is similar to a water softener. At least that's what they did when ethanol was simply a chemical and not considered fuel.
Here is a not-so-rosy article that i found after reading the Nat'l Geo:
ecoholistic...ethanol