Ethanol is being promoted as one of the solutions for controlling global warming. US Congress has followed this reasoning and has provided a subsidy for ethanol production in the amount of $0.51 per gallon. This subsidy created a minor boom in corn growing states in the USA. In 2006, the annual ethanol production reached 4.85 billion gallons. The Federal Government had to pay out 2.48 billion dollars and the consumer was faced with a major increase of corn prices, which resulted in a considerable jump in food prices. Corn farmers were happy, a large number of corn fermentation plants were built, and ethanol is now dispensed in special fuel stations.

What did society get in return? After all, the need for a subsidy was promoted by the argument that we need to reduce global warming and petroleum imports. In the past, ethanol has been produced predominantly in Brazil, has replaced a large percentage of Brazil's petroleum imports, and is sold and used widely in that country.

Ethanol is an acceptable motor fuel. Its major shortcoming is its energy density, which is only two thirds that of gasoline. Instead of driving 375 miles on a tank full of gasoline, one can drive only 250 miles on the same tank filled with ethanol. Minor engine modifications are required, which are now standard on most cars in Brazil and on many cars in the US. There is one major difference between the ethanol produced in Brazil and the ethanol produced in the United States. In Brazil, the ethanol is produced from sugarcane, in the US from corn.

Ethanol is produced in both cases from biomass. Biomass is grown on arable lands. Plants remove carbon dioxide from the atmosphere and convert it into energy-rich wood or other plants by using only water and sunshine for the conversion. When biomass or fuels derived from biomass are combusted, they can only release as much carbon dioxide as they previously removed from the atmosphere. Therefore, burning motor fuels produced from biomass does not contribute to the accumulation of heat absorbing gases in our atmosphere! Combustion of biomass fuels is carbon-neutral!

The question now becomes; how much does it cost the US public to reduce carbon dioxide emissions by producing ethanol from corn? To arrive at an answer one has to make mass and energy balances. The rules for making such balances are well established in thermodynamics and in chemical engineering.

Present production processes for making ethanol from corn can only use roughly ten percent of the corn plant, which consists of 10 % corn kernels and of 90 % stover, the rest of the plant. The ripened corn is harvested in the usual fashion, is ground, fermented, and distilled. The product is 200-proof moonshine, which can be used directly in cars. At colder temperatures, it is advantageous to add a small percentage of gasoline. It is presently possible to produce 2.8 gallon of ethanol from one bushel (56 pounds) of corn (the energy conversion efficiency of corn to ethanol is 57.5 %).

Before one can harvest corn, one must prepare the soil, fertilize the ground, seed the corn, and harvest it. Each of these steps consumes energy. Additional energy is consumed when the corn is converted into ethanol. Energy consumption of all these production steps has been measured. Under the very best conditions, one-half of the produced energy must be used to grow, harvest, and process the corn. At present, this energy portion is supplied in the form of fertilizing chemicals, diesel fuel for tractors, and natural gas for corn converting. This means that we produce 1.4 gallon net usable energy in the form of ethanol but pay $1.43 in subsidies for 2.8 gallons produced.

Ethanol production is great when intended as a sophisticated form of agricultural subsidy. Effects of ethanol consumption on overall carbon dioxide emissions are minute. The premium the public has to pay for this (well-intended?) political maneuver is huge. The lessons learned are simple and sobering. Political solutions to technical issues are usually ineffective, expensive, counterproductive, and produce a multitude of unintended consequences. Let us hope that our US Congress did not really attempt to legislate a major jump in food prices.

There is one major, redeeming feature. Farmers, who are growing corn for ethanol production, will be more open to grow plants with higher energy yields, eventually. We must breed and grow plants with much higher energy yields and we must develop more efficient conversion processes for the production of motor fuels from biomass. Otherwise, we will run out of arable lands quickly.