T. Searchinger et al., “Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change,” Science, 319:1238–40, 2008. (Cited in 204 papers)
Fossil fuel energy systems are one-sided: emitting carbon, but not sequestering it. Crops, on the other hand, help sequester carbon as they grow, a fact that led most prior research to conclude that replacing gasoline with biofuels would help reduce greenhouse gas emissions. But as demand for biofuels increases, farmers would need to convert maturing forest and grassland to cropland, a lower-quality carbon sequester. Using worldwide agricultural models and land-conversion rates, Timothy Searchinger from Princeton University and colleagues found that using corn-based ethanol would actually double greenhouse gas emissions over 30 years. “People saw land use change as an unrelated component to emissions estimates,” says Searchinger. “But not including it was a basic error” in analyzing the benefits of biofuels.
“The biofuels industry was livid,” says Jason Hill, a bioenergy researcher at the University of Minnesota. “And a tremendous amount of debate broke out within the industry, policymakers, and the general public over what our energy future should look like.”
At the time the paper was published, former President George W. Bush had just signed the Energy Independence and Security Act into law. A large portion of the bill required biofuels to achieve lower net emissions than petroleum.
As a result of this paper, most biofuel assessments today incorporate land use change into their emission calculations.
|Land subject to conversion with corn-based ethanol use:|
|Worldwide: 10.8 million hectares|
|United States: 2.2 million hectares|
|Brazil: 2.8 million hectares|
|China: 2.3 million hectares|