On the making of ethanol, from National Geographic:
The corn is ground, mixed with water, and heated; added enzymes convert the starch into sugars. In a fermentation tank, yeast gradually turns the sugars into alcohol, which is separated from the water by distillation. The leftover, known as distillers’ grains, is fed to the cows, and some of the wastewater, high in nitrogen, is applied to fields as a fertilizer.
The process also gives off large amounts of carbon dioxide, and that’s where ethanol’s green label starts to brown. Most ethanol plants burn natural gas or, increasingly, coal to create the steam that drives the distillation, adding fossil- fuel emissions to the carbon dioxide emitted by the yeast. Growing the corn also requires nitrogen fertilizer, made with natural gas, and heavy use of diesel farm machinery. Some studies of the energy balance of corn ethanol–the amount of fossil energy needed to make ethanol versus the energy it produces–suggest that ethanol is a loser’s game, requiring more carbon-emitting fossil fuel than it displaces. Others give it a slight advantage. But however the accounting is done, corn ethanol is no greenhouse panacea.
“Biofuels are a total waste and misleading us from getting at what we really need to do: conservation,” says Cornell University’s David Pimentel, who is one of ethanol’s harshest critics. “This is a threat, not a service. Many people are seeing this as a boondoggle.”
Exactly. Conserve more, waste less, pollute less. And if we’re going to look to a “fuel” to be the environmental savior, let’s find one that is actually good for the environment.