DuPont-Danisco and other advocates are touting biofuels derived from switchgrass, but the environmental benefits are highly questionable
This is part of IEEE Spectrum’s special report: Winners & Losers VII
Of all the possible biofuel crops that can be grown in the United States, perhaps the most attractive is Panicum virgatum, otherwise known as switchgrass. A hardy perennial native to North America, it needs little fertilizer and water, and pests don’t seem to like it much. So it holds out the shimmering promise of one day producing vast quantities of fuel in “carbon neutral” fashion, absorbing as much carbon dioxide in growth as it releases when burned.
Compared with sugarcane or corn, though, switchgrass is tricky to use, because it provides cellulose—the natural polymer that gives plants their rigidity—rather than simple sugars. So you need to do some elaborate processing, first to break down the cellulose and then to ferment the resulting sugary brew so that it turns into ethanol, which can be served neat or blended with gasoline. As yet, nobody has succeeded in producing switchgrass ethanol on a commercial scale, and the economics of doing so remain fuzzy.
One company that believes it’s on the verge of success is DuPont Danisco Cellulosic Ethanol (DDCE), based in Itasca, Ill. Founded in May 2008 by DuPont and Danisco, DDCE has just completed a pilot ethanol plant in Vonore, Tenn., which is slated to open officially in a few months. The facility, built in partnership with the University of Tennessee, will be able to produce almost a million liters (250 000 gallons) of ethanol per year from either switchgrass or corncobs. DDCE then plans to build a much larger plant in Tennessee with a capacity of nearly 60 million L a year. Meanwhile, it’s taking advantage of more than US $70 million in state support to enlist farmers to start growing the grass now. The company is thus positioning itself on the cutting edge of a new “grassoline”-based economy.
“We’re doing scale-up and commercialization,” says Vonnie Estes, vice president of commercial development and marketing for DDCE. “Once we get it up and going, it’ll be competitive with gasoline—I have no doubt.”
Perhaps she should have doubts. Here’s one: Will it be possible to transform the half billion or so cars and trucks in the United States so that they can use more homegrown ethanol and less gasoline? Even Estes sees that hurdle. “That’s one of the big issues—creating the market,” she says.
But even if a market does emerge and DDCE’s production process proves highly profitable, this technology can’t be considered a winner. Why? Because it will fail to satisfy the main premise for adopting it in the first place: to benefit the environment. A simple thought experiment sheds light on the dark side of grassoline.
Suppose you replaced all the gasoline the United States now uses with switchgrass-derived ethanol. How much land would that take? The United States consumes 522 billion L of gasoline a year. Because of the difference in energy density, you need about 1.5 L of ethanol to replace a liter of gasoline. So the yearly requirement for ethanol would be about 780 billion L. A hectare of switchgrass can supply about 4700 L of ethanol a year, so the United States would need to devote roughly 170 million hectares (420 million acres) to it.
That’s an enormous quantity of land—almost as much as the country now devotes to farming. And even if you covered all that land with switchgrass, it wouldn’t produce enough fuel to supply the country’s diesel trucks and buses, its jet aircraft, or the homes and businesses that use petroleum for heating fuel.
Carpeting the continent with enough switchgrass to displace all that petroleum use is theoretically possible—but it would be an environmental catastrophe on many counts. For one, it would devastate what’s left of the already besieged wilderness. And according to estimates that Timothy Searchinger of Princeton University and his colleagues published in the journal Science in 2008, it would also exacerbate the world’s greenhouse-gas problem, not help solve it. That’s because even if switchgrass agriculture were limited to established cropland, we’d end up having to convert forests and other land to agriculture just to feed ourselves. That in turn would release huge amounts of carbon dioxide into the atmosphere. Many of the wonks now working out carbon-emissions policy have missed this simple fact, an oversight that Searchinger and his colleagues pointed out in another piece in Science this past October.
Biofuel can’t be considered carbon neutral, Searchinger says. “Even the strongest advocates in the biofuel industry would agree that it’s not,” he says. But biofuel advocates downplay that and other environmental risks.
Estes argues that switchgrass would be planted mainly on fallow farmland. “Where we’re looking at growing these crops, there isn’t anything growing there anyway,” she says. Her collaborator Kelly Tiller, director of external operations for the University of Tennessee’s office of bioenergy programs, notes that planting switchgrass “has good wildlife benefits” and that it stores carbon in the soil. And she points out that there are some places where switchgrass could be grown with no environmental costs at all: within highway medians, for example, or along power-line rights-of-way. And, she asks, what are the alternatives? “There is no perfect solution. This is a sustainable bridge while we develop new technologies,” she says.
“If we required that all the energy for today’s corn-based ethanol plants—including trucking, lighting, power generation, and distillation—come from the plants’ own ethanol production, there’d be little ethanol left over.”
— T.J. Rodgers
“To be more than a niche solution, switchgrass would have to be raised on a huge scale, increasing food prices and thus creating massive humanitarian problems.”
— Kenneth R. Foster
The benefits to wildlife and the carbon storage Tiller is talking about are, however, only valid if your baseline is traditional farming. But as Searchinger and his colleagues pointed out in their 2008 Science article, truly excess cropland eventually reverts to forest. And when that happens, you’d get all the wildlife-friendly, carbon-storing benefits that ensue. If you plant switchgrass there instead, those benefits are lost. “You have to look at what you give up,” says Searchinger. As for growing switchgrass along highways or under power lines, that’s all good, but it would put just a small dent in the problem.
What’s more, if switchgrass proves highly profitable, what’s to prevent farmers from raising it everywhere? Strict U.S. regulations may save forests from being replaced by fields of switchgrass, but elsewhere in the world trees would inevitably be chopped down, either to make way for biofuel feedstock or to grow the crops that switchgrass displaces elsewhere. For this reason alone, DDCE’s project is destined to be a loser, even if it one day proves a commercial success.
This article originally appeared in print as “Biofoolish.”
For all of 2010’s Winners & Losers, visit the special report.