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Tilman and Hill's work was the cover feature in the December 8, 2006 issues of Science.

Listen to the hype about corn-based ethanol and it’s easy to get the wrong impression.

“The world’s demand for energy will never stop,” intones the narrator of a television ad by Illinois-based Archer Daniels Midland Company, the largest fuel ethanol producer in the United States, “which is why a farmer is growing corn . . . and why ADM is turning these crops into biofuels.” Read ADM’s fuel brochure, and you’d learn that “ethanol not only extends gasoline supplies—it also provides an environmentally friendly alternative to fossil fuels.”

Or check out the South Dakota–based American Coalition for Ethanol, an ethanol industry lobbying group, which contends that ethanol production “moves our nation toward energy independence.”

Or click on the Minnesota Department of Commerce Web site: “Minnesota’s ethanol mandate helps reduce our reliance on imported petroleum. Nearly all gasoline sold in Minnesota is blended with 10 percent ethanol, which allows us to offset our demand for gasoline by 10 percent.”

Or listen to Minnesota Governor Tim Pawlenty (B.S. ’83, J.D. ’86), who has promoted legislation doubling the amount of ethanol in gasoline to 20 percent by 2012. The self-proclaimed “most pro-ethanol governor in the country” argues that Minnesota can become the “Saudi Arabia of renewable fuels.” The state government has subsidized the construction of 16 ethanol plants, with another on the way. These plants convert 148 million bushels of corn, 12 percent of the state’s crop, into 550 million gallons of ethanol annually.

Listening to these endorsements, you’d think turning corn into motor fuel is a good thing, a formula for protecting the environment and weaning the nation from foreign oil. But you’d be wrong.

“The effect on foreign energy independence is minimal,” contends Jason Hill (Ph.D. ’04), an applied economics researcher at the University of Minnesota. “It can have only a minimal effect on our energy consumption.” Hill is the lead author of a University study published in summer 2006 on the environmental, economic, and energy costs of corn ethanol and soy-based biodiesel.

“Why should we take two very limiting factors for human quality of life—food and energy—and convert one into the other?” asks Regents professor David Tilman, a world-renowned University ecologist and lead author of a new study about prairie grasses as a biofuel source.

According to the University studies, the environmental benefits of corn-derived ethanol are limited and are offset by serious environmental drawbacks. And ethanol, as currently produced, won’t make us energy independent—unless we expand the Corn Belt to every state in the union.

Here are five reasons why ethanol fails to live up to the hype:

[ 1 ] Ethanol production requires almost as much energy as it yields.

A moonshiner, or anyone who has spotted steam billowing from a Minnesota ethanol plant, can tell you it takes a lot of energy to distill fermented corn into nearly pure alcohol. What’s more, a tremendous amount of energy resources are used simply to grow corn; the biggest agricultural input is nitrogen fertilizer, made from natural gas.

In the U study published last summer, in the journal Proceedings of the National Academy of Sciences, researchers tried to account for all the energy inputs of the process, from growing corn (even the energy use of farm households) to energy burned in transportation and the construction of processing plants. They found that corn-derived ethanol yields only 25 percent more energy than is required to make it. (Studies by researchers at Cornell and Berkeley even contend that ethanol actually produces less energy than goes into its production, though U of M researchers dispute those findings.)

Burning fossil fuels to make ethanol can be justified, to some extent. Not all fuels are created equal, explains Douglas Tiffany (B.S. ’74, M.S. ’77), study co-author and research fellow in the University’s Department of Applied Economics. “Some of them are much more valuable to us.” Ethanol is a much more convenient and versatile fuel than coal, for example. You can’t run a car on wood or coal, but you can on gas and ethanol.

“We pay a price to have it in a convenient form,” Tiffany says. And that price is burning fossil fuels. If energy savings is your goal, you’re off to a bad start if you burn nearly as much in fossil fuels as you gain in biofuels.

[ 2 ]  It isn’t easy being “green” when growing corn.

Corn hungers for high-nitrogen fertilizers. It thirsts for water, including from ancient aquifers. And it’s addicted to chemicals. None of these conditions are good for the environment.

Corn requires heavy doses of fertilizer—an average of 135 pounds of nitrogen spread on every acre—as well as phosphorus and phosphate. Corn accounts for nearly half of the crop nutrient use in the nation; nothing else comes close. Corn also requires heavy applications of herbicides and insecticides; corn makes up approximately a quarter of the acres of crops planted in the United States but accounts for nearly two-thirds of total herbicide use.

Trouble is, these chemicals don’t stay put. Excess nitrogen leaches into the groundwater, posing potentially fatal hazards to infants. Pesticides pollute nearby lakes and streams, killing fish such as smallmouth bass. Runoff of soil and phosphorus causes algae blooms in nearby lakes. Nitrogen and phosphorus from the Midwest Farm Belt flow down the Mississippi River, feeding algae growth and decomposition that create “hypoxia”—an oxygen-depleted “dead zone” roughly the size of New Jersey in the Gulf of Mexico.

[ 3 ]  Corn crowds out wildlife.

During the last half-century, agricultural fields have become bigger, obliterating the wetlands and biodiverse landscape that once characterized rural areas. As all but the rockiest, steepest, or wettest land was cultivated, 99 percent of our native prairie disappeared and all but a fraction of our original wetlands were drained. Many prairie species, especially birds, became rare or endangered. In Illinois, for example, seven species of grassland birds, including upland sandpipers, meadowlarks, and several species of sparrows, declined more than 90 percent between the late 1950s and the mid-1980s. Game species, such as ducks and pheasants, have also suffered.

In recent decades, the federal government has rented land from farmers across the United States, especially highly erodible land, through the Conservation Reserve Program (CRP). These set-aside acres are planted with native grasses and trees and slowly restored. Since the program began, CRP lands have showed impressive increases in grassland birds such as bobolink and dickcissel. In one study in Iowa, the number of pheasants increased 13-fold on CRP lands.

But as a burgeoning ethanol program boosts demand for corn, crop prices are predicted to rise. As they do, Tiffany says, farmers will be tempted to pull their acres out of CRP and put them back into production. In fact, the National Grain and Feed Association recently asked a U.S. House Agriculture Committee to alter CRP to free up more farmland to raise crops for a burgeoning biofuels industry.

Loss of CRP lands means a net loss for wildlife.

[ 4 ]  Corn ethanol doesn’t cut enough greenhouse gases.

Ethanol indeed reduces air pollution—in small doses. Ethanol has become a much-needed replacement for the gasoline additive MBTE (a possible carcinogen and pervasive groundwater pollutant) to help gasoline burn cleaner. Blending a small amount of ethanol with gasoline reduces carbon monoxide, volatile organic compounds, and particulates.

But when you look at the entire life-cycle of ethanol—from growing to harvest to processing to combustion—burning E85 (85 percent ethanol) as fuel actually produces more carbon monoxide, volatile organics, particulates, and oxides of sulfur and nitrogen than an energy-equivalent amount of gasoline, according to the University’s study.

And ethanol doesn’t do much to address the big issue: global warming. “We found corn ethanol as currently produced saves about 12 percent greenhouse gases from gasoline,” Hill says. And that’s if the corn is grown on existing fields. “If you take land out of CRP you may have a net greenhouse gas release.” That would actually exacerbate global warming.

[ 5 ] We can’t grow enough corn.

Twelve percent of the U.S. corn crop is converted to ethanol, which replaces less than 2 percent of U.S. gasoline usage. Diverting all our corn to ethanol production (which would mean no more corn flakes, marbled beef, fructose-sweetened soda, or any other corn product), would reduce gasoline consumption by only 12 percent.

But, according to Hill’s study, even that dismal statistic is overly sanguine. Because so much fossil fuel is burned just to make ethanol, turning our entire corn crop to ethanol production would reduce our fossil fuel use by just 2.4 percent.

So why do governments subsidize corn-based ethanol production? “If the energy source is environmentally benign, especially compared to alternatives, then a subsidy can be justified,” explains Stephen Polasky, University professor of applied economics and co-author of the study. “What we found for corn ethanol is there really isn’t much basis to justify a subsidy on environmental grounds.”

But what about ethanol’s contribution to local economies? “I don’t think ethanol is a job engine,” says C. Ford Runge, professor of applied economics and law at the University. “It’s not going to have an appreciable impact on rural employment opportunities.”

Once a plant is built, its operation requires only a few people. And while corn farmers benefit from a better market, livestock producers worry that competition for corn from ethanol plants will drive up prices and make their products less competitive. “There’s enormous anxiety in the surrounding countryside that the ethanol plant is going to suck all the corn out of the local economy,” Runge says.

Meanwhile, the subsidies to support corn growing and ethanol production are funneled from a broad base of taxpayers and consumers to a small number of beneficiaries—mainly investors in ethanol plants. These include not only local farmer cooperatives, but also giant agriculture processors like Archer Daniels Midland.

If corn isn’t the answer, what is?

Ethanol isn’t the only biofuel in town. Minnesota—as does much of the rest of the nation—also produces biodiesel from soybeans. According to Hill’s study, soy diesel trumps ethanol by almost any measure:

• Biodiesel yields 93 percent more energy than is required to produce it.

• Compared with corn, soy uses 1 percent of the nitrogen, 8 percent of the phosphorus, and 13 percent of the pesticides—and less toxic chemicals too.

• Soy produces less air pollution. Whereas E85 over its life-cycle actually pollutes more than gasoline, biodiesel containing 20 percent soy burns cleaner than the diesel it replaces. Particulate matter is reduced by 31 percent, carbon monoxide by 21 percent, and total hydrocarbons by 47 percent. It produces 41 percent fewer greenhouse gases than diesel.

“Biodiesel provides sufficient environmental advantages to merit subsidy,” states the report.

A second

Cedar Creek Natural History Area study plots.

way to improve the efficiency of biofuels is to find alternative sources of heat to distill it. For example, says Tiffany, corn stalks and husks contain enough energy to distill ethanol. According to the National Renewable Energy Laboratory, part of the U.S. Department of Energy, 85 percent of the stalks and other plant material rots on the ground, releasing carbon dioxide. The rest is incorporated into the soil. By collecting and burning a portion, “we could certainly get some excellent energy balances,” Tiffany says.

The third—and possibly the real hope—for making a viable biofuel lies in making ethanol and the energy to process it, not from cultivated crops, but from the cellulose in native perennials.

The prairie proposition

“We have a vision of restoring a lot of prairie throughout the Midwest, and having something that will be mowed every year for hay and then either pelletized and burned, or converted into ethanol,” says Tilman, who has conducted prairie grass research at the U’s Cedar Creek Natural History Area for 12 years.

According to a study by Tilman, Hill, and University research associate Clarence Lehman (B.A. ’67, M.S. ’92, Ph.D. ’00), published in December 2006 in the journal Science, producing “cellulosic” ethanol from diverse plots of perennial grasses promises several advantages over corn-grain ethanol: greater yields, more ethanol, less pollution, and fewer greenhouse gases. And all that without diverting a food source.

According to Tilman’s study:

• Perennial biomass such as native grasses would need little in the way of chemicals, energy, or even work—just mow it once a year. It wouldn’t even need to be planted. “What we’ve seen is that we can get a lot of biomass produced in plots with no input of fertilizer, no irrigation, no input of pesticides, almost no energy input at all,” says Tilman. With low energy inputs, cellulosic ethanol might produce four times more energy than the fossil fuel it consumes.

• With little need for fertilizer or pesticides, native grass production produces little polluted runoff. Since the soil is never bare or plowed, little erosion occurs. According to University of Minnesota soil scientist Gyles Randall (B.S. ’63, M.S. ’72), nitrogen losses from land planted with perennial grasses are only 2 to 3 percent of the losses from corn and soybean fields. Loss of phosphorus and sediment are similarly low.

• Diverse grasslands, such as native prairie, produce 51 percent more energy per acre than corn, even though corn grain produces more ethanol per weight. After 10 years, diverse plots produced 238 percent more energy than monocultures, such as switchgrass. Multispecies plots are more resilient too. And Tilman’s past research has shown that diverse grasslands outproduce monocultures during drought.

• Prairie grasses’ massive root systems sequester carbon, actually reducing greenhouse gases in the atmosphere. Raising prairie grasses for biofuels would not only produce less greenhouse gas than burning fossil fuels, it would actually remove and store 1.2 to 1.8 tons of carbon dioxide per acre per year over the course of a century.

• The researchers estimate that growing mixed prairie grasses on all of the world’s degraded land would produce enough bioenergy to replace 13 percent of global petroleum consumption and 19 percent of global electricity consumption.

Ultimately, says Hill, biomass could produce many fuels to power vehicles. Grasses or woody plants could be burned for electricity, such as to charge electric cars, or converted to synthetic fuels. “There are many technologies out there that can produce transportation fuels,” he says. “Ethanol is just one of them.”

Several cellulosic ethanol research plants already operate in the United States. Canada’s Iogen runs a demonstration-scale plant in Ottawa to make cellulosic ethanol from wheat, oat, and barely straw. Ontario-based SunOpta is working with Abener Energia of Seville, Spain, to build a commercial demonstration plant in Spain that is scheduled to begin converting wheat stalks to ethanol in 2007. SunOpta has also supplied the technology for a similar sized plant in Jennings, Louisiana, to produce ethanol from the crushed fiber of sugar cane stalks. Xethanol, a U.S. company, is building a plant in Georgia to brew cellulosic ethanol from various industrial wastes, including waste wood products.

The National Energy Policy Act of 2005 provides several incentives to encourage cellulosic ethanol production, including grants, loan guarantees, research, and “credits” that give preference to production of cellulosic ethanol in meeting renewable energy targets, Tiffany explains. “Maybe that’s enough for now, until the technology moves along,” he says.

At the University of Minnesota, much of that research is being conducted under the Initiative for Renewable Energy and the Environment and has been instrumental in funding research, such as the biofuels study, on alternative energy sources. “We have to explore many different avenues for doing this,” Hill says. “That would benefit our state, our nation, and not just the pockets of large energy companies.”

Ultimately, it could benefit our environment. By generating fuel from prairies, says Hill, “you could both take off the biomass and have minimal disturbance to wildlife. . . . It could be that we could actually increase the wild habitat in our states. We would have something that would serve the aesthetic value, the sportsman, and the biofuels.”

Greg Breining, St. Paul, writes about nature and the environment for several publications, including the New York Times, National Geographic Traveler, and Wildlife Conservation.