"He who refuses to do arithmetic is doomed to talk nonsense."
—Dr. John McCarthy
I recently did a few quick calculations to estimate the amount of land that would have to be devoted to growing corn if we wanted to replace gasoline with corn ethanol. This involved pulling numbers from a variety of government web sites and reports. In areas of disagreement, I used numbers favorable towards ethanol, such as an energy balance of 1.5 and a harvest of 200 bushels of corn per acre.
The US consumes about 550 billion liters of gasoline each year. Ethanol has 34% less energy per unit volume than gasoline, so we need to grow enough corn to make 840 billion liters of ethanol. A bushel of corn produces about 10.5 liters of ethanol, and growing 200 bushels of corn on an acre of land is considered quite good. Hence, we need to dedicate 400 million acres of cropland to ethanol production. We're beginning to run into a problem here because the US only has 434 million acres of cropland. Americans love their cars but probably wouldn’t be willing to give up their high-fructose corn syrup.
But here's the killer: we have not yet accounted for the energy input required to farm, distill, etc. the ethanol! The highest estimate I've seen is an energy balance of 1.5: each unit of energy fed into the process results in 1.5 units of output energy. Hence, using ethanol to provide the energy input (e.g., run the tractors) means that we need to plant 667 million acres of farmland with corn. Those extra 267 million acres provide the energy to grow, harvest, and distill the remaining 400 million acres.
But won’t technological progress improve the situation? Of course! But why bet on a loosing proposition when there are significantly more promising alternative fuels out there? Every dollar spent on corn ethanol research is a dollar not spent on one of them or reducing demand.
All of this disregards the sheer absurdity of burning the last of the country's topsoil in some soccer mom's SUV.
Corn ethanol only makes great sense when you look at it as a vote-buying program.