Illustration: Mateusz Zdanko

The Berkeley researchers sought to evaluate a range of ethanol options. At one extreme, they placed a futuristic technology called cellulosic ethanol, still in development, which would derive the alcohol from crops like switchgrass. The cellulosic plants will have much better energy balances than corn ethanol, experts say.

At the other extreme, the researchers postulated a carbon-intense plant—specifically, Red Trail Energy’s. For the purposes of the study they assumed that the corn for the plant would come from Nebraska, where the energy needed to grow crops is about the highest in the United States, though they were careful to note that they could not say for sure where most of Red Trail’s corn will actually come from.

In the Berkeley model, the Red Trail plant emits 91 grams of carbon—strictly speaking, carbon dioxide equivalent—to produce the amount of ethanol necessary to generate a megajoule of energy. For comparison, the industry average for ethanol plants is 77 grams of carbon per megajoule, according to Ethanol Today, an industry publication. Cellulosic ethanol’s emissions are estimated at 11 gC/MJ.

In terms of net energy gain, the postulated carbon-intense plant yields 1.3 MJ per liter of ethanol produced, roughly a quarter of the 4.6-MJ/L energy yield obtained on average from ethanol plants using today’s usual technologies. The plant’s poor energy performance results from Nebraska’s energy-intensive farming. There is enormous room for improvement: cellulosic ethanol’s net energy is estimated at 23 MJ/L.

Bear in mind when considering these figures that calculations of energy, oil, and greenhouse gas balances are complicated not only by energy inputs and gas emissions in agriculture but also by those associated with the output mix. Besides producing ethanol, dry mill plants typically produce distillers’ grain, which is dried and fed to livestock. The larger wet mills produce a more varied and valuable range of products, including vegetable oil and other foodstuffs meant for people.

Ironically, the wet mills, which tend to be coal-fired, are classified as food-making facilities and therefore face relatively relaxed air regulation. They are subject to permitting procedures for major polluting facilities only if their emissions of any one specific pollutant exceed 100 metric tons per year. Owners of dry mills are now trying to get the U.S. Environmental Protection Agency to make them subject to the same liberal air regulation as wet mills.

Some of the more respected estimates of ethanol-versus-­gasoline balances have been done by Michael Wang, director of systems assessment in the Transportation Technology R&D Center, at Argonne National Laboratory, in Illinois. Wang has concluded that for a blend of 15 percent gasoline and 85 percent ethanol, with the ethanol produced from currently operating plants, wet ­milling—a reasonably close proxy for coal-made ethanol—yields a 13.7 percent greenhouse gas saving compared with straight gasoline. Dry milling—for our purposes, ethanol made with natural gas—yields an 18.8 percent improvement. The savings in net energy and imported oil are about the same, wet or dry: about 35 percent for energy and roughly 72 percent for oil.

Although the differences between the average coal and natural gas ethanol plants are not dramatic, consider how much better the job of making ethanol can be done. The NRDC’s Greene says four corn ethanol plants now under construction will have near-zero emissions. One of them, in Mead, Neb., is next to a cattle farm, so that methane from animal waste can be used to power the plant—
a win-win situation. Two new plants in Minnesota are expected to rely on gasified biomass, and a demonstration facility in Illinois is being powered by thermal solar collectors.

The Nebraska plant is being built by E³ BioFuels, of Shawnee, Kan., with backing from the prominent venture capitalist Vinod Khosla. The facility is almost completely closed-loop—that is, virtually all its by-products will be captured and recycled, so that it will be nearly self-sustaining. It is designed to generate about 5275 joules in ethanol for every joule consumed in the production process, while a typical ethanol plant yields only 1375 to 1900 joules, Khosla claimed in a recent magazine article. Corn protein not good for making ethanol will be fed back to the cattle, and waste left over when methane is obtained from manure will be used to produce ammonia fertilizer for the cornfields.

That kind of plant may be eligible for especially high subsidies, but even the ordinary subsidies for corn ethanol are generous. To begin with, U.S. ethanol producers are protected from imports of cheaper Brazilian ethanol by a 54-cent-per-gallon tariff. Producers also benefit from a federal subsidy of 51 cents per gallon, additional state subsidies, and federal crop subsidies that can bring the total to 85 cents per gallon or more. Most important of all, language in the 2005 energy law mandates that billions of gallons of ethanol be blended into vehicle fuel each year, guaranteeing demand. Without that mandate, comments Jerry Taylor, a senior fellow at the Cato Institute, based in Washington, D.C., demand for ethanol would not be what it is, considering its price last summer on the Chicago Board Options Futures Exchange was twice that of gasoline.

A recent report done by Earth Track’s Koplow, “Biofuels—At What Cost?” found that total U.S. corn ethanol subsidies are “large, between $5.5 [billion] and $7.3 billion per year,” and soon will be even bigger, between $8 billion and $11 ­billion. Because the unit cost of displacing imported oil or avoiding carbon emissions is so highly subsidized, Koplow concluded, “there may be many quicker and cheaper ways to achieve these same goals.” Worldwatch, an environmentally minded organization in Washington, D.C., came to essentially the same conclusion earlier last year.

Because ethanol made from corn yields such modest environmental returns at such a high price, groups like Worldwatch and the NRDC prefer to focus on next-­generation ethanol technologies. Never­theless, a few good corn ethanol plants are showing some ways to a better future. One is the Nebraska plant backed by Khosla. Another is the Goodland Energy Center in Kansas, where plans call for a coal-fired boiler to supply steam and electricity to a biodiesel production plant and an ethanol plant while also putting electricity into the grid.

That’s a big improvement on the way ethanol traditionally has been produced. But the best of all possible worlds would be a plant that runs on biofuels, perhaps its own waste products, and generates at least enough electricity to power itself—even though such plants are more expensive to design and build than your standard coal or natural gas mill.

Contemplating the closed-cycle approach, the NRDC’s Greene comments, “There’s so much potential to do this right. Why step back with coal?”