Corn Ethanol as Fuel | Drawing the Line

A friend of mine used to call the alcohol you drink "stupid juice." Is the alcohol you burn in your engine "smart juice"?

Ethanol is a pretty good fuel. For the same volume, it's got about 62 percent of the energy of gasoline. Said another way, it takes 1.6 gallons of ethanol to do the same work as a gallon of gas. Of course, we don't use pure ethanol; we mix it with gasoline in various ratios. E10 is 90% gas and 10% ethanol. In parts of the country they are going to a new standard, E15, and there is some controversy there.

The problem is for a hundred years we've designed our bikes and cars to run on gasoline. It's only relatively recently that we've included ethanol, and there's a lot of infrastructure to change. New vehicles don't (or shouldn't) have problems, but on older vehicles ethanol can soften or degrade some non-metallic parts like O-rings, gaskets, hoses, plastic fittings and even gas tanks. The more ethanol in the gasoline, the more we'll see these problems.

Ethanol is usually produced by fermenting the sugars in plant materials and then using fractional distillation to separate the ethanol released in the fermenting process from the other materials. This introduces another variable, as the ethanol that results from fractional distillation is actually 95% ethanol and 5% water. It's possible to refine ethanol to very near 100% purity, but that's too expensive for fuel use.

That water presents additional problems. Ethanol can't be stored and moved through the same equipment as petroleum products because water causes corrosion and oxidation (rust). Similarly, the internal parts on some carburetors, fuel-injection systems and fuel pumps can become corroded.

So ethanol is a useful fuel that can replace some of the petroleum fuels we're used to. Its problems have more to do with our gasoline-oriented infrastructure than with ethanol itself. But there's a deeper problem with the ethanol we use in the U.S.

Almost all of our ethanol is produced from corn. We know how to grow corn, and we grow an amazing amount of it-enough to feed ourselves and our livestock, and to make a lot of our fuel. But is it the best crop for making ethanol? To determine that, there's a useful scale called EROEI: Energy Returned On Energy Invested.

In the case of corn, we know that it takes energy (in the form of liquid fuels, electricity or natural gas) to plow and harvest, to pump water for irrigation, to make the mash that will be fermented, to distill the ethanol from the result, to ship the ethanol, to blend it with gasoline and, finally, to get it to the gas stations. And there are other energy inputs: Many fertilizers and insecticides are produced from petroleum. It takes energy to build and maintain the plants and equipment, storage and transportation facilities for the ethanol industry.

We know how much corn ethanol we produce, and we add up all the energy used in producing it. Put in the form of a fraction it looks like this: Energy Returned/Energy Invested. What's the result? In study after study going back to the 1980s, the EROEI for corn ethanol is very close to 1/1. That means that it takes approximately one unit of energy (from various sources) to make one unit of (corn ethanol) energy.

In Brazil, most ethanol is made from sugar cane, which is easy to grow and yields a lot of sugar-much more than corn does. EROEI for Brazilian sugar cane ethanol is about 8/1, meaning it yields 8 times the energy that goes into making it.

If corn ethanol yields only as much energy as goes into it, how can the industry survive, or justify itself financially? It survives because it's subsidized. There are government subsidies to grow the corn and to make the ethanol. We (the taxpayers) also pay the oil companies a 45-cent-per-gallon subsidy to add it to gasoline. That subsidy may expire soon, but don't bet on it.

The corn ethanol industry can make a lot of money from subsidies. What it can't do is make net energy-make more energy than it uses. Maybe corn ethanol as fuel is indeed "stupid juice." It certainly doesn't seem smart to produce a fuel that doesn't provide net energy.