These improvements are crucial. From the start, the ethanol industry has been dogged by concerns about its net energy balance—whether ethanol requires more fossil fuel to make than it replaces. This is measured by adding up all the energy inputs at every stage of production, from growing corn seeds to cultivating and harvesting the grain, transporting it to the factory, and shipping the ethanol to a terminal. If ethanol runs a negative energy balance, as asserted by some critics (including those nattering West Wing characters), then the enterprise is doomed: What is the point of wasting fossil fuels that could be consumed directly somewhere else?
Studies by researchers at the Department of Agriculture over the last decade give reason for optimism. They consistently show a positive and improving energy balance. By 2001 every BTU consumed in ethanol production generated 67 percent more energy, when coproducts like distillers' grains are taken into account. Other researchers have reported a similar trajectory; taken together, their findings show an unmistakable upward trend.
Yet nagging doubts remain, stoked by two persistent skeptics: David Pimentel, a professor of ecology and agricultural sciences at Cornell University, and Tad Patzek, a professor of geoengineering from the University of California at Berkeley who started the UC Oil Consortium, an industry-sponsored research group. In their latest studies they conclude that ethanol's balance is negative. The researchers, who found that ethanol requires 29 percent more fossil energy than it provides, question the morality of using grain to fuel cars in the face of world hunger. "Expanding ethanol production," they write, "could entail diverting valuable cropland from producing corn needed to feed people to producing corn for ethanol factories."
Most researchers agree, more or less, on the energy required in the conversion process, but unlike Patzek and Pimentel, they include an energy credit for the coproducts. Most of the discrepancy, though, comes from different measurements about the growing of corn. Patzek and Pimentel count many more inputs than the others, including labor energy expended by field hands and energy embedded in farm equipment and in the ethanol factory itself. Such external sources are not normally calculated when the fuel is gasoline.
A more relevant issue is whether ethanol's energy balance is better or worse than gasoline's. After all, as energy economist Philip Verleger points out: "We don't keep our balances in BTUs; we keep them in dollars and cents. So if I can find an energy source that's cheap and easy to use, then it may make sense to use a lot more of that to produce a gallon of gasoline."
By definition, petroleum's fossil energy balance is negative. Making a gallon requires 23 percent more energy than it contains. Even using Patzek's unreconstructed estimates, ethanol outperforms the incumbent. Corn Plus's fluidized bed reactor further tips the argument in ethanol's favor. Using Patzek's methodology for every aspect of ethanol production save the conversion process itself, a gallon of Corn Plus ethanol consumes less energy than it contains—even before factoring in credit for coproducts.
Meanwhile, ethanol's efficiency is continuing to improve. New machinery developed by Biorefining Inc. in Minnesota precisely breaks kernels into their constituent elements, which may convert more of the starch into ethanol at a lower cost, while also freeing up more of the valuable coproducts like corn oil. The biotech companies Genencor and Novozymes have developed enzymes that convert starches into sugars and ferment the sugars into ethanol in a single step, streamlining the process. Seed companies are trying to engineer corn that is tailored to ethanol conversion.
At some point, though, corn ethanol will hit a wall. Even if the United States decided to ferment its entire corn crop, that would displace less than 20 percent of our gasoline consumption. A more realistic, if still optimistic, scenario sketched by the National Corn Growers Association anticipates that corn ethanol production will quadruple to 16 billion gallons by 2015, not quite 7 percent of the likely demand. That's where President Bush picks up the story.
It turns out that Rick Lunz left a lot of energy out in his field that night. Corn stover—the husks, stalks, and cobs chewed up and spit out by the combine—is, in a sense, about two-thirds sugar. The problem is that the sugar is accessible only after it is chemically converted from the tough molecules that make up the walls of plant cells: fibrous cellulose, hemicellulose, and lignin.
Lignocellulosic biomass, as it is called, represents a vast, untapped natural resource. If we could find an effective way to convert it, corn residue could provide another 20 billion gallons of ethanol by around 2040, according to a recent report from the Oak Ridge National Laboratory in Tennessee. Better yet, every plant contains cellulose, so there is no need to restrict the fermentation process to corn stover.
Switchgrass, a tall prairie grass native to North America, is a much more promising raw material. It can reach nine feet high, and it grows easily from the Gulf of Mexico to the Canadian plains, from the Rockies to the Atlantic Coast. It can grow in poor soil as well as in dry climates, says agronomist David Bransby of Auburn University, so it requires little fertilizer and water and can grow in places that are not now useful cropland. An acre of switchgrass can produce more than twice as much ethanol as an acre of corn. By 2030 the Department of Energy envisions American farmers harvesting fields of switchgrass purely for their energy content.
People have coveted that energy for a long time. "When I first looked into the ethanol industry, there was this promise that the cellulose technology was just a few years away," Lunz recalled. "Well, it's been 25 years now." Biomass research that began at the Solar Energy Research Institute in Golden, Colorado, during the Carter years nearly came to a halt in the early 1980s and did not revive until George H. W. Bush became president. President Clinton expanded the facility, now called NREL, short for the National Renewable Energy Laboratory. Researchers there say they are tantalizingly close to fulfilling that early promise.
They have managed to solve a problem that has long bedeviled ethanol researchers: how best to split cellulose into simple sugars that can be fermented into alcohol. One method bathes the cellulose in sulfuric acid at high temperatures and high pressure, an expensive technique developed by Germany during World War II. Instead NREL researchers sought an enzyme that would do the job more cleanly and cheaply. Coincidentally, research into such a cellulose splitter, or cellulase, also dates to World War II, when the U.S. Army investigated the "jungle rot" that dissolved uniforms in the South Pacific. The most profitable application of cellulase so far has been to set it loose on the fibers in blue jeans just long enough to make them look "stonewashed."
In 2000, NREL made available a suite of patents for its protein research to Novozymes and Genencor, asking them to bring cellulase to the market while splitting the investment. Since 2004, each firm has announced that it has managed to cut the cost of a cellulase suitable for industrial production, although exactly how much is in dispute. The biotech companies claim a 30-fold reduction since 2000, from about $5.60 per gallon of ethanol to at most 18 cents; NREL puts the cost at 32 cents.
Thomas Foust, the biotechnology manager at NREL, says the cost of making ethanol from cellulose has dropped to $2.26 a gallon or less. The goal, however, is $1.07—what NREL and the Energy Department figured was the cost to make a gallon of ethanol from corn kernels at the time NREL made the enzyme pact.
Reaching that target will be a difficult, messy task. After handing me goggles and a hard hat, Foust and engineer Dan Schell usher me into the lab's pilot ethanol plant. It is clean and quiet, a collection of valves, tubes, and tanks unblemished by the grime of production because it is used mostly to test processes. We stand in front of a squat vessel. This is the pretreatment reactor, where hemicellulose is dissolved into a liquid of simple sugars, exposing the cellulose to enzymatic attack. Here, though, the lab still uses a variant of the old acid-bath technique, which is both expensive—this reactor is made of zirconium—and fussy. If the acid concentration isn't strong enough, some of the small polymers aren't broken up and don't get fermented. Too strong, and some degrade beyond use, inhibiting the fermentation of other sugars. Ultimately, NREL hopes to replace the acid bath with a more reliable cocktail of cellulase and hemicellulase enzymes.
That hasn't happened yet because hemicellulose is a tough nut to crack. It is an amalgamation of xylose, glucose, and small amounts of three other sugars, and so far NREL has been unable to engineer a bacterium that can digest all of these at once. "Twenty years ago, it seemed it was going to be real simple—just get your genetic tweezers out and away you go," Foust says. "It's proved infinitely more difficult than that." As a result, today's technology can coax only about 65 gallons of ethanol out of every ton of corn stover, instead of the 90 NREL is counting on.
A number of researchers think the solution is to abandon the whole idea of fermentation in favor of making ethanol through a technique called gasification. If a feedstock—grain, grass, husks, whatever—is burned in an environment where oxygen is limited, the reaction creates hydrogen, carbon monoxide, and methane. These can be burned in a turbine, but in the presence of the right catalyst, they will instead combine into ethanol.
BioConversion Technology, a start-up in Denver, claims to have developed such a catalyst and says that it can make more ethanol from a ton of feedstock for less money than NREL can by fermentation. "NREL has been extremely biased," says David Bransby of Auburn. "I think they're betting on the wrong horse." Foust does not deny gasification's potential—he considers the two technologies complementary. NREL, he says, has spent 40 percent of its biomass research budget on gasification. Still, BioConversion Technology has received no funding from the Department of Energy.