As the debate over what do about human-caused global warming increases and "green fever" sweeps the nation, many environmentalists and politicians have viewed biofuel as a logical replacement for fossil fuels.
But two new studies released Thursday call into question the global movement toward biofuel. According to these researchers, production of biofuel actually contributes to global warming, doing more harm than good.
The studies, one conducted by Minnesota-based Nature Conservancy and one by Princeton University, examined the same issue: What environmental impact does growing vegetation used for biofuel have on global warming?
U.S. demand for ethanol crops like corn, soy and switchgrass has resulted in the conversion across the globe of natural habitats – like grasslands and rainforests – into fuel-ready farmland, according to the studies. That development has released mass amounts of carbon into the air, researchers said.
"You ask the world's farmers to produce energy and that's going to take additional land and that land has to come from somewhere. Unfortunately, much of it is coming from our natural ecosystem. What's the consequence of that?" Joe Fargione, the regional science director for the Nature Conservancy and the lead author of one study, told ABCNews.com. "If you imagine a grassland and a cornfield, there's much more carbon in the grassland soil. When you convert a grassland into a cornfield, that carbon has to go somewhere. It goes into the air as carbon dioxide and contributes to global warming."
"Any biofuel that causes the clearing of natural ecosystems will increase global warming," he continued.
In the Princeton study, which was led by Timothy Searchinger, a German Marshall Fund fellow and a researcher at Princeton University, numbers told a striking story.
Past data that has outlined the benefits of biofuels didn't include the issues surrounding the impact of land use and the carbon released into the air as a result, both studies said.
Using models that calculated carbon emissions in various countries, the Princeton researchers found that the production of corn-based ethanol nearly doubles greenhouse emissions over 30 years and increases greenhouse gasses for 167 years. Similarly, biofuels made from switchgrass, if grown on land originally intended for corn, increase carbon emissions by 50 percent.
"By excluding emissions from land-use change, most previous accountings were one-sided," the researchers wrote. "Because they counted the carbon benefits of using land for biofuels but not the carbon costs – the carbon storage and sequestration sacrificed by diverting land from its existing uses."
"Twenty percent of CO2 emissions come from land use change and deforestation," Searchinger said. "We're simply transferring the problem ... from the fossil fuel side to the land-use side" when we produce biofuel.
Researchers in the Nature Conservancy study, which has been going on since March 2007, found nearly identical results. In this study, researchers compared the amount of carbon in the air in natural ecosystems and crop land around the world.
"There is three times as much carbon in the plants and soil as there in the air," Fargione said. "This is a globally significant concern that is dramatically contributing to global warming."
What researchers found was a vast creation of carbon in the conversion of peatlands for Indonesian palm oil plantations and soy production in the Amazon. The research led Fargione to conclude that biofuel, if farmed from converted land, is not a practical replacement for fossil fuels.
Fargione also argues that the findings call into question the energy bill recently passed by Congress, which calls for increased biofuel production — 15 billion gallons by 2015.
"If you create a carbon tax or a low carbon fuel standard that penalizes fuel based on the amount of carbon it emits and then you miscalculate how much carbon biofuels are actually emitting, then biofuels are actually worse than the fossil fuels they replace," he said.
But according to the Renewable Fuels Association, a trade organization representing the U.S. ethanol industry, the studies failed to put biofuel production in context with fossil fuel production.
"Without biofuels and some increase in fuel economy, more and more petroleum will be required to meet the increasingly ravenous demand for liquid fuels around the world," Bob Dinneen, the association's president, said in a statement. "As the 'easy' sources of oil decline, development of exotic resources, like tar sands in Canada, are being pursued. Tar sands, by comparison, release some 300 percent more greenhouse gas emissions than traditional petroleum recovery."
For those committed to biofuel, there is hope, both sets of researchers said, in biofuel made from abandoned, depleted farmland and biomass waste, like unused parts of a corn plant.
"The holes from your Cheerios could be used for energy," Fargione said.
Still, Fargione maintains that biofuels aren't the only answer in the fight against global warming.
"It's worth doing, but it's not a silver bullet," he said.