Reuters reports:
Corn-based ethanol, which for years has been mixed in huge quantities into gasoline sold at U.S. pumps, is likely a much bigger contributor to global warming than straight gasoline, according to a study published Monday. The study, published in the Proceedings of the National Academy of Sciences, contradicts previous research commissioned by the U.S. Department of Agriculture (USDA) showing ethanol and other biofuels to be relatively green.... The research, which was funded in part by the National Wildlife Federation and U.S. Department of Energy, found that ethanol is likely at least 24% more carbon-intensive than gasoline due to emissions resulting from land use changes to grow corn, along with processing and combustion.... The RFS requires oil refiners to mix 15 billion gallons of corn-based ethanol into the nation's gasoline each year. The policy was supposed to help farmers and reduce U.S. dependence on energy imports.
"Today, most gasoline sold in the U.S. contains 10 percent ethanol, and about a third of the corn crop in the country is used to produce the fuel..." reports
Ars Technica:
The extra land put under the plow released a significant amount of carbon, enough to flip the assessment of corn ethanol from a carbon-negative fuel to a carbon-emitting one. The biggest decline came when new cropland released carbon that had been stored in soils and vegetation, including roots of living plants. Farmers were also less likely to enter a field into the Conservation Reserve Program, which pays farmers to plant perennial vegetation on unused farmland. A potent greenhouse gas that warms the atmosphere 300 times more than the same amount of carbon dioxide over 100 years was released after the fertilization of the crop. The authors didn't calculate how much pollution the manufacturing process released or the extent to which degraded water quality in downstream waterways released more greenhouse gases.
