plants, such as those being developed as feedstocks for cellulosic ethanol, would be environmentally preferable, he says. ing electricity generation.) PreviAround the world, pockets of In the U.S. and most European ous studies have provided rough land lie fallow that could help and Asian countries, biomass estimates of the potential for meet the world’s ever-growing grown on these lands would progrowing bioenergy crops on abanenergy demands. Some of this vide less than 10% of the total endoned agricultural land, but the former agricultural land was once ergy demand, according to the new study gives the first entirely pasture grazed by cattle, and study, and Campbell calculates it data-driven global picture of this some was cropland that was could supply only 9% of U.S. transpotential energy source. abandoned for greener fields portation energy. However, or because of changing some countries with relaneeds. Now, research pubtively productive land and lished in ES&T (DOI low energy demand, such 10.1021/es800052w) maps as some African nations, abandoned agricultural could potentially grow a land worldwide and finds larger portion of their enough available to grow energy. crops for ethanol or other A focus on total energy energy uses to meet up to rather than transportation 8% of the world’s current fuel is appropriate, says energy demand. Most imecologist Joseph Fargione, portantly, planting these central U.S. science direccrops would not take away tor at the Nature Conserland now used to grow vancy, a nonprofit food and would not conDiverse plant species that could provide biomass for energy organization. Converting tribute to deforestation. grow on former farm- and pastureland at the Cedar Creek all biomass grown on “In the past, people experimental reserve in Minnesota. abandoned land would have criticized biofuels for contribute 10–25% of curthe potential problems rent global transportation The researchers estimate that with food prices and climate fuel demand, Fargione says, based the global area of abandoned agchange,” says a study coauthor, on his own calculations using the ricultural land is 385–472 million ecologist J. Elliott Campbell of the new study’s findings. “But there hectares, which could yield less Department of Global Ecology at are lots of ways to get energy out than 8% of current global energy the Carnegie Institution for Sciof plants, and liquid transportademand. “Strong proponents of ence. For example, the UN Food tion fuel may not be the most efbiofuels might be disappointed and Agriculture Organization estificient one,” he says. “If you take with that,” Campbell says, “but mates that competition for land a ton of biomass and convert it to for a multifaceted approach to between food and biofuels is at electricity, you can drive your car energy and climate, one might least partly responsible for recent farther on that electricity than if consider that a small but meanfood price increases and that bioyou make ethanol.” ingful contribution to our energy fuels can worsen climate change “This was an excellent study to future.” if grown on land converted from do,” given today’s search for new The researchers calculated land carbon-storing forests. But scienenergy and food sources, says Rik area by using historical databases tists have also suggested that bioLeemans of Wageningen Univerand estimated potential bioenergy fuels might be grown on sity (The Netherlands), a plant crop yields based on natural plant abandoned agricultural lands to ecologist who studies land-use growth on those lands today. Past avoid these problems. change. He notes, however, that studies have found that agriculCampbell and colleagues set some of the abandoned land tural yields are about 65% of out to learn how much abanmapped in the study has probably those from natural plant growth doned agricultural land is availalready gone back into food proon the same land, Campbell able worldwide and how much duction because of recent price notes, though improved methods energy could be produced if the spikes. Campbell agrees and says can increase agricultural producland were devoted to bioenergy the group hopes to map those tivity. One important caveat, he crops. (This is the collective term areas and their plant yields. adds, is that conventional biofuel for crops that are used to make —ERIKA ENGELHAUPT crops such as corn may exacerbiofuels or other kinds of energy, bate nutrient runoff and soil erosuch as biomass pellets used for sion. Planting diverse perennial ES801609K home heating or for cofiring durDAVE TILMAN/CEDAR CREEK ECOSYSTEM SCIENCE RESERVE
Growing energy on unused agricultural land
5380 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / August 1, 2008
10.1021/es801609k
2008 American Chemical Society
Published on Web 06/24/2008
