HAVING SPENT HIS CAREER STUDYING A TYPE OF LEAF-CUTTING ANT native to the rainforests of Costa Rica, Cameron Currie never imagined he’d have much to offer on the subject of America’s insatiable thirst for gasoline. A native of the Canadian prairie with an abiding curiosity about evolutionary biology, Currie came to CALS in 2004 as an assistant professor of bacteriology with his ants in tow. These days he is caretaker to some 50 nests of the insects in his laboratory, where he studies their symbiotic relationships with fungi and bacteria. Fascinating and enlightening work, yes––but hardly connected to the problems of gas-guzzling SUVs and spiraling oil prices.
Except that maybe it is. Currie’s ants, belonging to the genus Atta, do something remarkable, a capacity shared only by humans and a few other insects. They grow their own food, tending vast gardens of leaves that provide nutrients for the main source of the ants’ diet, a strain of fungi related to common mushrooms. And while humans began farming around 10,000 years ago, these ants have been at it for some 50 million years. Is it possible––especially as we enter the dawn of a new era of agriculture, in which we hope to cultivate crops that we can easily convert into energy sources––that the ants in Currie’s lab could teach us a trick or two?
That possibility intrigues Tim Donohue, scientific director of UW-Madison’s newly minted Great Lakes Bioenergy Research Center. Launched by the largest federal research grant ever received by CALS, a five-year, $125 million award from the U.S. Department of Energy, the center has lassoed a diverse group of researchers to come up with new ways of drawing energy from non-food sources, such as plant stalks, wood chips, crop residues and agricultural waste. The idea of turning the planet’s organic leftovers, collectively called biomass, into energy has great appeal as an alternative to fossil fuels, but the methods for making fuel from plant biomass aren’t yet anything close to a commercial reality, a bottleneck Donohue and the center hope to overcome.
And that’s where ants come in. As opposed to corn kernels, which are made up of simple sugars like glucose, plant stalks and leaves are comprised mainly of cellulose, a tough polymer that gives plants structure. One of the most common organic materials on the planet, cellulose is a polysaccharide, a long chain of linked sugar molecules that must be broken apart before the sugars can be processed. The reason we can’t eat tree branches, for instance, is because our bodies lack the digestive enzymes to attack the chemical bonds in cellulose and get at its sugars. The same problem exists in the ethanol process; we don’t have efficient means for degrading cellulose into soluble materials that can be fermented into alcohol-based fuels.
But Currie’s ants may. Their nests harbor an array of microbes, most of which are unknown to science, and Currie believes many of those microbes play essential roles as leaves are broken down and cycled through the ants’ gardens. Given that this collaboration has been perfected over millions of years of evolution, it’s not unreasonable to expect that we might find something useful––a microbe particularly adept at degrading cellulose, for example––in those nests if we looked.
The thing is, no one has thought to look, not until Donohue struck up a conversation with Currie about his new bioenergy center.
“It’s not an obvious connection,” says Currie. “But there is enormous potential to learn how these ants are using microbes to break down plant material, and those discoveries could be highly relevant to bioenergy.”
ANTS may never solve the world’s energy problems, but it says something that they’re getting a chance. Certainly, it speaks to the growing urgency surrounding the search for alternatives to fossil fuels, which provide more than 85 percent of the human-generated energy on the planet. With supplies of crude oil dwindling and worldwide energy demands projected to rise by more than 50 percent in the next two decades, it’s hard to make the math add up to anything less than a crisis.
“As a planet, we’re facing big problems,” says Donohue. “In the last 100 years or so, we have gone through a very significant fraction of fuels that it has taken this planet millions of years to accumulate, and when those are gone, we’re going to have to have entirely new technologies. This is an experiment we only get to do once.”
Bioenergy potentially settles some of those big problems. Drawing energy from crops, grasses and trees––renewable resources that can be grown season after season––helps answer the supply issue, while also easing the political pressure of dependence on foreign oil. The environment could benefit, as well. Because oil and coal form as organic material decays underground, dredging them up and burning them releases several billion tons of carbon dioxide into the atmosphere each year, a factor chiefly blamed for global warming. Fuels such as biodiesel and ethanol can help stem the flow of greenhouse gases because the plants used to make them absorb carbon dioxide from the atmosphere as they grow, offsetting the amount released when they are burned.
Still, one problem with current biofuels is that nearly all of them are made from food, such as ethanol from corn kernels or biodiesel from soybeans. Economists fear a major expansion of the existing ethanol industry would threaten food supplies and raise prices. Deriving fuel from materials such as corn stover, plant residues and animal waste, on the other hand, would pose no threat to food markets, while also creating new economic opportunities for agricultural states such as Wisconsin. Brett Hulsey, an environmental analyst who wrote Governor Jim Doyle’s policy paper on bioenergy, estimates that Wisconsin creates some 15 million tons of excess biomass each year, which if converted to ethanol would supplant half of the state’s annual petroleum use. “It’s like sitting on an oil reserve,” says Hulsey. “You’ve got fuel literally laying on the ground that could be used.”
But this is hardly a new dream. People have envisioned replacing petroleum-based chemicals in fuels and plastics with the carbohydrates in plants for most of the last century. Henry Ford designed his first Model T in 1908 to run on ethanol, believing it would be the fuel of the future. The great horticulturist George Washington Carver foresaw whole industries built on agricultural residues. “I believe the Great Creator has put ores and oil on this earth to give us a breathing spell,” Carver once wrote. “As we exhaust them, we must be prepared to fall back on our farms, which are God’s true storehouse and can never be exhausted. For we can learn to synthesize materials for every human need from the things that grow.”
While science long ago mastered the fermentation of simple sugars to make beer, wine and grain-based ethanol, however, it has yet to dent the steelier challenge of making fuel from the cellulose-laden leftovers. The best existing methods rely on harsh chemical treatments and complicated microbial reactions, all of which are too inefficient, too expensive or too caustic to make ethanol from biomass a commercial reality.
Solving this dilemma has been likened to a Manhattan Project-scale quest, involving thousands of scientists and the backing of powerful interests. Responding in part to rising public frustration with high gasoline prices, governments and private industry have staked multiple millions of dollars on research into biomass-to-biofuel technologies. Petroleum giant BP has committed $500 million over the next decade to this effort, funding a research consortium led by the University of California-Berkeley. Exxon, Chevron and Conoco Phillips have made smaller-scale arrangements with other university labs.
“I see bioenergy as a research field in 10 or 15 years being as large as biomedicine,” Donohue says. “This industry is going to be as big as Silicon Valley, as big as Route 128 in Massachusetts.”
AS principal investigator of the Great Lakes Bioenergy Research Center, Donohue will attempt to secure a piece of that future for the Midwest. Announced in June, the center is one of three such facilities funded by the Department of Energy to speed progress on biomass energy sources. (The others are based at the DOE’s Oak Ridge and Lawrence Berkeley laboratories.) Its administrative home will be Madison, but it will draw on expertise from Michigan State University, as well as a handful of other university labs and institutions. Fifty-seven scientists are listed as primary investigators, an unprecedented alliance of plant geneticists, chemists, microbiologists, computational scientists, engineers and agronomists.
Gregarious and broad-shouldered, with an unmistakable note of New York City in his speech, Donohue has spent 20 years studying bacteria that turn sunlight into renewable fuels and other organic compounds. Under his leadership, the center will have a strong bent toward microbiology. Among his main goals is to probe the genetic pathways that microbes use to break down cellulose and other plant materials, which would allow scientists to optimize the processes that are currently used in industrial fermentation systems and to engineer new, more effective ones.
But the center will attack the scientific knots of bioenergy conversion from multiple angles, from breeding new plants better suited for the energy pipeline to rethinking existing processes for making ethanol to pioneering entirely new energy solutions, such as the direct production of hydrogen or electricity from sunlight. For example, the center will fund research by James Dumesic, a professor in the UW-Madison College of Engineering and one of the nation’s leading experts on the chemical conversion of sugar into liquid hydrogen, which as a transportation fuel may have 40 percent more energy content than ethanol. Dumesic is co-founder of Virent Energy Systems, a Madison-based company that already is making hydrogen fuel from the simple sugars in fruits and starches, and his lab is working on the conversion of other sugars found in plant biomass.
Another intriguing idea comes from the lab of Sandra Austin-Phillips, a senior scientist in the UW-Madison Biotechnology Center. For the past 10 years, Austin-Phillips has been changing the genetic makeup of plants such as alfalfa and tobacco to cause them to make certain chemicals as they grow, essentially turning them into manufacturing centers for compounds that can be used in pharmaceuticals or animal feeds. Her lab is now trying to get plants to churn out microbial cellulases, the proteins that trigger the chemical breakdown of cellulose, the critical first step to any biomass-to-biofuel process.
“For biomass conversion technology to have a major impact, we’re going to need millions of tons of these enzymes, and there’s no way that we can produce these quantities in fermentation systems with our current capacity,” says Austin-Phillips. “Our idea is to produce them in the plants.”
Since cellulases break down plant cell walls, Austin-Phillips says she was met with open skepticism when she sought funding for her work. “People told me the plants would fall over,” she says. But the cellulases she’s working with are active only at relatively high temperatures, meaning they have virtually no effect on the plants that make them. Once the plants are harvested, the cellulases can be separated for use in biorefineries, which could help reduce the cost of currently expensive enzymatic treatments.
True, some of these projects have a considerable hike to reach field applications. But that’s the nature of fundamental research, says Donohue. “This is not CSI Miami, where you can bring me a plant and tomorrow and I’m going to tell you how to use it,” he says. “This is going to take a long time.” Many of the center’s projects will be speculative and may never prove fruitful at all. But they are shots worth taking.
Such is the case with Cameron Currie’s work with leaf-cutting ants. Currie’s team has begun studying the compost-like heap of organic material left after the ants finish their meals, which they believe teems with a microbial stew that helps chew up the remaining cellulose and cycle it back to soil. Given that a tiny fraction of microbial life has been characterized in the lab, they must first do genetic analyses to figure out what all is living in those sites. These studies have already identified a microbe that is active at high temperatures, a sign of energy efficiency that could be valuable in industrial applications.
“There’s this massive process of converting plant material through the whole system,” says Currie. “But our understanding of what goes on in terms of the breakdown of plant materials is really fairly limited. There are microbes playing roles in there that we don’t know about, and those have potential interest for bioenergy.”
But ant nests are hardly the only natural system that attacks the tough defenses of plant cellulose. Termites and ruminant animals such as cows do essentially the same thing, and very few of those systems have been explored with bioenergy in mind. This kind of inquisitiveness may be exactly what the bioenergy field needs to move forward, says Robert Landick, a professor of biochemistry who is coordinating the center’s research on bioconversion.
“The spirit of this center will be to fund numerous small projects that are high-risk, but also high-reward,” he says. “If you really want to crack a problem, the rational way to do it is to get 10 different ideas from 10 different people. You know at the outset that eight of those 10 are going to be a bust, but the key is that you don’t know which eight. What you can be reasonably sure of is that if you enable highly motivated, bright scientists to go after these problems from a bunch of different angles, that’s your best shot at really producing a breakthrough. All of our biotechnologies have come from that kind of basic research, with breakthroughs that come from all kinds of unanticipated, weird places, but in the end get assembled into a very powerful technology.”
SCIENCE is ultimately one variable in the matrix that will determine if bioenergy lives up to its promise. As important are the policy decisions that will affect how the industry grows and matures. And right now, at least, bioenergy is moving with such speed that policy can barely keep up.
Consider the U.S. corn ethanol industry, which in 2000 produced about 1.8 billion gallons of ethanol from corn kernels. Since gas prices spiked and venture capital began pouring into the construction of biorefining plants, production has rocketed, tripling by 2006 and likely to eclipse 10 billion gallons in the next year or two. Wisconsin, which produced not a single drop of ethanol in 2000, now has seven operating ethanol plants, with eight more on the way. This year, more than 20 percent of the corn grown in the state is expected to be converted into ethanol. Nationally, it may soon be the case that one in every three ears of corn goes to fuel.
“The industry is moving faster than our ability to develop the infrastructure to support it,” says Randy Fortenbery, a professor of agricultural economics who directs CALS’ Renk Agribusiness Institute. “It’s moving faster than our understanding of the economic and sociological issues, and it’s moving faster than the public policy is keeping pace.” The key question, says Fortenbery, is whether the social good created by renewable energy sources justifies the social investment necessary to make those sources competitive in the marketplace.
At least in the case of ethanol from corn kernels, many are not convinced that the answer is positive. With ethanol fueling increased demand for grain, corn prices soared to $4 per bushel this past winter and remain some 30 percent higher than 2005 levels. While farmers have welcomed the boost to long-depressed commodity prices, the spike has also illustrated the potential of ethanol to shake up food prices. In Mexico, for example, the price of corn tortillas, a prime source of protein in the Mexican diet, quintupled last year, causing the government to cap prices.
High corn prices have also led farmers to plant 12 million more acres of corn this year than last, marking the largest crop shift since World War II. This historic movement toward corn has sparked concerns that farmers are abandoning crop rotations or tilling lands that are poorly suited for intensive row crops. Environmentalists are warning that high corn prices might lead farmers to withdraw lands from the federal Conservation Reserve Program, which pays farmers not to plant on highly erodable lands. According to John Panuska PhD’06, a UW extension specialist who has studied Wisconsin’s CRP lands, returning those lands to corn will increase nitrogen runoff and exacerbate water-quality problems in the state’s lakes and rivers.
Citing such troubling side-effects as the clearing of rainforests in Asia to harvest palm oil for biodiesel, the United Nations has adopted a similarly cautionary tone on the promise of bioenergy. In May, the U.N. made one its first public reports on the subject, which concluded none too cheerily: “Unless new policies are enacted to protect threatened lands, secure socially acceptable land use, and steer bioenergy development in a sustainable direction overall, the environmental and social damage could in some cases outweigh the benefits.”
Scientists say these problems underscore the need for new technologies that enable fuel production from a wider array of feedstocks. They point to the potential of crops such as switchgrass, a perennial prairie grass native to the Midwest that can be burned to generate electrical power or fermented into fuels. Low in input and high in energy yield, switchgrass holds great promise as a feedstock in a sustainable bioenergy pipeline, especially since it can be grown on marginal lands such as those in the conservation reserve.
But many questions remain before we will know if it’s a viable option. “I can go out and make bails of switchgrass, and I can take those to the biorefinery right now,” says Kevin Shinners BS’81 MS’82 PhD’85, a professor of biological systems engineering. “But it’s going to cost me more to bring it to their gate than they’re going to be able to pay me. If we can’t figure out more effective ways to grow and harvest and store these materials, there will be no biorefinery.”
Typically in such cases, the research community needs money and time to sort out the big picture. With the influx of recent funding, no one these days is complaining about money. But what about time? The Department of Energy’s plans call for the United States to be making 250 million gallons of cellulosic ethanol by 2013, perhaps not an overwhelming quantity compared to the 139 billion gallons of gasoline Americans consume each year, but a steep climb from where we are today, which is more or less zero. Can science move fast enough––and carefully enough––to meet those expectations?
“It is a short amount of time, and we have a long way to go,” says Donohue. “But, you know, we’ve done this before. In the sixties, we had a president who said, ‘Let’s go to the moon.’ He issued a bold challenge, and with the support and technology that was there, we achieved that goal. This is our chance to say, ‘Let’s go to the moon.'” And lest we forget, such hopeful journeys involve not only giant leaps, but small steps.This article was posted in Cover Story, Energy, Fall 2007, Features, Main feature and tagged Bacteriology, Bioenergy, fungus, Insects, Microbiology.