How is ethanol produced?

The production of ethanol is a complicated process, but the basic concept involves transforming plant matter, usually sugars, into ethanol and then distilling it to obtain pure ethanol. The transformation of plant matter into ethanol is usually done by organisms suchas yeasts.

The energy involved to just to produce ethanol can be seen already here. First the crops must be grown, which in modern times demands irrigation, fertilizers, and pesticides. The final step of distillation purification also requires a large amount of energy to heat the ethanol and water. Yet if this entire process uses less energy than put out, then we have a renewable fuel.