Wouldn’t it be great if we could grow our own fuel? That thought probably occurred to many Americans this year, particularly those in the seemingly endless fields of the heartland. Despite recent declines, gasoline prices stubbornly stuck around $3.00 per gallon for much of 2006. Now, engineers, investors and even President Bush are saying the solution to the country’s energy woes could be harvested from America’s fruited plain in the form of biofuel.

After decades of being dismissed as too expensive and impractical, biofuel—ethanol, diesel and other combustible liquids made from plants—is coming back into fashion. And it doesn’t look like biofuel will be slipping into obscurity anytime soon, thanks to historically high prices at the pump, the war in Iraq, instability in the Middle East and growing demand for fuel from developing nations such as China.

At the moment, biofuel accounts for roughly 3 percent of U.S. transportation fuel, little more than a proverbial drop in the barrel. But by 2025, the U.S. Department of Energy (DOE) would like biofuel to account for 30 percent of what we put in our tanks. While there are several different types of plant-derived fuel, ethanol—the alcoholic component of beer, wine and spirits—constitutes 99 percent of all the biofuel in the United States. To reach DOE’s ambitious goal, engineers say we will have to rethink everything about ethanol, from crop growth to fuel distribution. It’s a challenge, they say, that will require the expertise of bioengineers, agricultural engineers, chemical engineers and systems engineers alike.

Brazil is the best example of a biofuel success story. Fifteen years ago the country started making ethanol from sugar cane. Now the Brazilians use 50 percent less gasoline and pay less for transportation fuel when they fill up with ethanol and ethanol-gas blends. But Brazil’s success with ethanol fuel isn’t something that can simply be copied. The country’s agricultural conditions, inexpensive land and cheap labor make Brazil an ideal location for producing large amounts of ethanol from sugar cane inexpensively, explains Robert C. Brown, a professor of thermal science and engineering at Iowa State University.

A Better Option?

The U.S. climate is better suited to growing corn than sugar cane, so ethanol producers in this country use corn as their primary feedstock. From an energy standpoint, however, corn isn’t the most energy-efficient source of ethanol. Given the choice of growing an acre of corn, soybeans or switchgrass, which would yield the most transportation fuel? That’s the homework question that gets engineering students in Brown’s Fundmentals of Biorenewable Resources course scratching their heads and poking at their calculators.

“It’s really a trick question,” Brown confesses. Since they’re in Iowa, most of the students choose corn, he says. But after some back-of-an-envelope calculations, the students discover that an acre of switchgrass could yield almost twice the biofuel as an acre of corn. Brown’s simple homework exercise points to larger issues for ethanol. The Energy Information Administration estimates that Americans currently consume 400 million gallons of gasoline every day. If ethanol producers are ever going to meet that kind of demand, they are probably going to have to turn to switchgrass and other cellulosic sources of ethanol, such as crop waste and wood chips, says Daniel Kammen, director of the Renewable and Appropriate Energy Laboratory at the University of California, Berkeley.

There are several problems in pinning our transportation fuel goals solely to corn-based ethanol. To begin with, the payoff in energy efficiency for switching from petroleum products to corn-based ethanol isn’t all that big. To make one gallon of ethanol using current farming and production methods, it takes around 0.7 gallons of nonrenewable fuel, according to a recent study from Kammen’s group.

Another problem is that we use corn for other things. Using corn-based ethanol to fuel our cars means increased demand and higher prices for corn and corn-based products. The ramp-up in ethanol production has already driven up corn prices by more than 20 percent this year, pushing up the cost of livestock feed and soft drink sweeteners as well. Rising corn prices, along with a 51-cent tax credit on each gallon of corn-based ethanol fuel sold, have some wondering just how economical an alternative the fuel really is.

Corn-based ethanol could probably displace up to 10 percent of total gas in this country, Kammen says. While that’s not bad, it’s not the coup everyone is hoping for. “Ultimately, if we really want to make a big dent in petroleum use we need to look at broadening our feedstock base to use cellulosic materials,” says Charles E. Wyman, professor of chemical and environmental engineering at University of California, Riverside, who works on renewable energy technologies.

It’s not just academics who see a future for ethanol made from cellulosic material. Iogen, a Canadian biotech company, has already built a demonstration-scale cellulosic ethanol plant in Ottawa. President Bush, during his 2006 State of the Union address, stressed the need to develop cellulosic technology. “Our goal is to make this new kind of ethanol practical and competitive within six years,” he said.

“I think cellulosic ethanol is a powerful option that has been underappreciated,” Wyman says. “Now, because of high gas prices, people are realizing that there aren’t many other options.” Cellulosic materials, also known as biomass, cost very little, he explains. And unlike corn, we’ve got sources of cellulosic ethanol in abundance. Hardy switchgrass, for example, thrives in the Great Plains and Southeast, resisting floods, droughts, pests and disease. “That material is virtually unused,” Wyman notes. Corn stover, the leftover husks and stalks from corn normally left to rot in the field, is another good source of cellulosic ethanol, he adds.

The energy return on cellulosic ethanol blows corn-based fuel away. Every gallon of nonrenewable fuel invested could produce more than 8 gallons of cellulosic ethanol, according to Kammen’s study. He estimates that with engineering improvements in fuel efficiency and cellulosic ethanol production, the fuel could replace 35 to 40 percent of the gasoline consumed in the nation. “The potential is truly huge,” he says.

Huge Promise,
Huge Problems

As promising as cellulosic ethanol looks on paper, there’s a lot that needs to be done before Americans can fill their tanks with the stuff. The United States currently has no commercial industry devoted to making cellulosic ethanol, and the largest precommerical plant—Iogen’s Ottawa demonstration facility—only makes 700,000 gallons of cellulosic ethanol annually. That’s about 0.25 percent of Americans’ daily gasoline consumption.

Cellulosic ethanol also needs to be cost competitive. In June, Michael Pacheco, director of the National Bioenergy Center, told the Senate Committee on Energy and Natural Resources that with current technology, the cost of producing cellulosic ethanol is twice that of corn-based ethanol. To bring the cost of cellulosic ethanol close to gasoline, he said, “will require revolutionary approaches for producing, collecting and converting biomass.”

Engineers are already hard at work tackling those challenges. They range from molecular problems—how to break down cellulosic plants cheaply and efficiently—to infrastructure issues—how to get ethanol produced in the agricultural heartland to the coasts, where demand is greatest.

Since ethanol production literally starts in the field, agricultural engineers are on the front lines of making cellulosic ethanol viable. An acre of perennial grass or woody crop currently produces about 335 gallons of ethanol, according to the DOE. If agricultural engineers can boost biomass yields, the DOE estimates an acre of crops could produce up to 1,000 gallons of ethanol.

After the president named switchgrass as a source for ethanol in his State of the Union address, the crop has gotten a lot of attention. But according to Larry P. Walker, biological and environmental engineering professor at Cornell University, engineers need to look at which sources work best for a particular region. In some areas, it makes sense to grow switchgrass, but in other areas, different grasses or even trees may be the best source of ethanol.

“Whatever we do needs to be sustainable,” Walker adds. Consequently, engineers also have to figure out how to get the most out of cellulosic crops without depleting nutrients in the soil or fostering erosion.

Even with cellulosic crops harvested and in hand, engineers still face one of their biggest challenges: converting that recalcitrant material into fuel. Ethanol is made by fermenting sugars. In corn and sugar cane, that sugar is easily accessible to the microbes that can turn it into ethanol, which is why those crops are popular choices for ethanol feedstocks. In cellulosic materials, the sugar is stored as cellulose, a long chain of sugar molecules, and hemicellulose, a random mix of five- and six-carbon sugars.

Both the cellulose and the hemicellulose have to be converted into their constituent sugars before they can be fermented into ethanol. “These materials are not easy to break down,” Wyman explains, which is one of the reasons cellulosic ethanol production is far behind that of corn or sugar cane ethanol, despite its enormous potential.

Once the cellulose and hemicellulose have been stripped out of a plant, material called lignin remains. Lignin can’t be converted into ethanol but it is the secret to cellulosic ethanol’s big energy payoff. “We can burn the lignin to generate heat, so we don’t have to bring in any fossil fuels” to produce ethanol, Wyman says. “In fact, you generate more heat and electricity than you need.”

Bioengineers are taking a few different approaches to overcome the high costs inherent in breaking down hardy cellulosic materials. Researchers in industry and academia are trying to genetically engineer more robust, less expensive enzymes for processing cellulosic biomass. UC Berkeley’s Kammen points out that cellulosic feedstocks are usually a mixture of different plants. “You need different enzymes to digest all that stuff,” he says.

Lee R. Lynd, Dartmouth University engineering professor and chief scientific officer at cellulosic ethanol start-up company Mascoma, for example, has been working to genetically engineer a multifunctional microbe that can break down cellulose and hemicellulose into sugars and then ferment those sugars into ethanol. This type of “consolidated bioprocessing” could radically cut the cost of producing cellulosic ethanol, Lynd says.

Another approach is to genetically modify the cellulosic crops themselves so that they are easier to process. A team at Purdue University is trying to make genetically engineered hybrid poplars that have either modified lignin or less lignin altogether. The cellulose in these low-lignin trees, should be easier to break and will likely yield more ethanol per acre.

“There are two areas where engineering is meeting challenges,” Walker points out. “There’s the basic R&D process of converting cellulosic material into ethanol, but there is also a systems engineering approach that considers infrastructure, resources and transportation.” Engineers need to examine cellulosic ethanol from a broad perspective, he explains. Where does it make the most sense to build production facilities—in the rural areas where the crops are or in the urban areas where there’s high fuel demand? Ethanol can’t travel through the pipelines we use for gas, so what’s the most efficient way to transport it?

Renewable energy experts have been saying cellulosic ethanol has been just around the corner for at least a decade. Now, however, they think the time has come to build facilities that pump the fuel out on a commercial scale.

“Unless you have the will to put the necessary infrastructure in place, all the biomass in the world doesn’t mean anything,” Iowa State’s Brown explains. The big question, he says, is whether companies will invest the hundreds of millions of dollars that are needed to build commercial-scale plants in the next five to seven years. Brown believes that window of time is critical. After that, he believes we’ll start to see shortfalls in transportation fuels that drive the prices of already costly gasoline even higher.

Some are making the investment. Abengo Bioenergy is currently building the world’s first commercial-scale cellulosic ethanol plant in Babilafuente, Spain. And a handful of U.S.-based companies have announced they will either build new plants or retrofit old ones to produce ethanol from biomass. In February, the Bush administration announced it would contribute $160 million dollars to construct up to three biorefineries. The DOE has already received more than 75 applications for the funds.

The administration’s recent interest in cellulosic ethanol pleases biofuel experts, but they say they’re still not convinced that renewable energy is a priority in Washington. Getting enough funding, they say, is still one of their biggest challenges. “I don’t think that the government is investing in this in a way that’s serious,” Lynd says. To illustrate this point, he continues, one need only to compare the amount of funding for cancer research ($4.75 billion) to that for renewable energy ($342 million) in Bush’s federal budget for fiscal 2007. “The disparity is large,” Lynd asserts, “and yet those problems are arguably of similar importance.”

Not Enough Funding

Of the $342 million budgeted for renewable energy, about $149 million is set aside for biofuel-related programs. While that’s a $60 million increase over 2006, it’s still far less than the $330 million devoted to coal research and $347 million for nuclear power R&D, both of which are mature technologies. “We are underfunding energy research across the board,” Kammen says. “When you want to ramp up a promising technology like cellulosic ethanol, you have to ramp up funding,” even if the private sector ultimately takes over the technology’s development.
Aside from holding cellulosic ethanol technology back, Lynd thinks another problem has arisen from a decade of underfunding renewable energy—a manpower shortage. “We’re not training the people we need,” he says. Now, with investors and venture capitalists clamoring for commercial-scale cellulosic ethanol facilities, Lynd worries that there aren’t enough engineers with the expertise to build top-quality biomass refineries.

Lynd has a few ideas for filling the pipeline with engineers with renewable energy know-how. “Engineering educators need to develop their curriculum to include examples from the so-called bioeconomy in traditional courses that will reach more students, not just specialized courses that attract students who are already interested,” he explains.

Getting students involved in relevant research experiences, Lynd says, is another good way to foster interest in renewable energy. Kammen agrees. “You really don’t learn about which problems are more important just by sitting in the lab,” he says. To focus on the energy issues facing the world today, students at the Renewable and Appropriate Energy Laboratory combine research with outreach. Past projects include developing sustainable biomass energy in Zimbabwe’s eastern highlands and in Cuba.

“We need to get away from the perspective of applied research competing with basic research,” says Kammen, who was trained as a physicist. “You can do basic science and engineering as well as applied research and field research. Exceptional advances in engineering really come from that mix.”

Kammen agrees that there aren’t enough engineers working in renewable energy, but in his experience it’s not because students aren’t interested in the field; it’s because there aren’t enough educational programs for them. He says that the graduate program at UC Berkeley’s Energy and Resources Group, an interdisciplinary program in which Kammen is a professor, receives 200 applications each year for just 15 to 20 spots. There are enough qualified applicants in that pool, he says, to host a class three times that size.

“The students that come to these programs want to change the world,” Brown says. As director of the Office of Biorenewables at Iowa State, he helped established the nation’s first graduate program to offer advanced degrees in biorenewable resources. Students in the program concentrate on biorenewables while also completing degree requirements in a more traditional engineering field like chemical engineering or agricultural and biosystems engineering. Having graduated about a dozen students since its inception in 2002, Brown thinks the program is still small. In an effort to expand, he is currently helping to set up a consortium with the University of Idaho and the University of Kentucky.

The recent interest in biorenewable energy signals how important biology is going to be for the next generation of engineers, Brown notes. “In the past, we have tended to let those biological problems be solved by scientists, which is fine until you try to take those solutions and make them into a practical process,” he says. “We need to engage more engineers in looking at the biological issues of the bioeconomy. There is tremendous potential in this area and we need to start thinking creatively.”

Bethany Halford is a freelance writer based in Baltimore.

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