(Reuters) — 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 recent study.
The study, published in the Proceedings of the National Academy of Sciences, contradicts previous research commissioned by the U.S. Department of Agriculture showing ethanol and other types of biofuel to be relatively green.
President Joe Biden’s administration is reviewing policies on biofuel as part of a broader effort to decarbonize the U.S. economy by 2050 to fight climate change.
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“Corn ethanol is not a climate-friendly fuel,” said Tyler Lark, an assistant scientist at the University of Wisconsin-Madison’s Center for Sustainability and the Global Environment and lead author of the study.
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 percent more carbon-intensive than gasoline because of emissions resulting from land use changes to grow corn, along with processing and combustion.
Geoff Cooper, president of the Renewable Fuels Association, called the study “completely fictional and erroneous,” arguing the authors used “worst-case assumptions and cherry-picked data.”
Under the U.S. Renewable Fuel Standard, a law enacted in 2005, the nation’s oil refiners are required to mix 15 billion gallons of corn-based ethanol into the nation’s gasoline annually. The policy was intended to reduce emissions, support farmer, and cut U.S. dependence on energy imports.
As a result of the mandate, corn cultivation grew 8.7 percent and expanded into 6.9 million additional acres of land between 2008 and 2016, the study found. That led to widespread changes in land use, including the tilling of cropland that would otherwise have been retired or enrolled in conservation programs and the planting of existing cropland with more corn, the study found.
Tilling fields releases carbon stored in soil, while other farming activities, such as applying nitrogen fertilizers, also produce emissions.
A 2019 study from the USDA, which has been broadly cited by the biofuel industry, found that ethanol’s carbon intensity was 39 percent lower than gasoline, in part because of carbon sequestration associated with planting new cropland.
However, that research underestimated the emissions impact of land conversion, Lark said.
The U.S. Environmental Protection Agency, which administers the nation’s biofuel policy, is considering changes to the program. Under the Renewable Fuel Standard, Congress set blending requirements through 2022, but not beyond, giving the EPA authority to impose reforms. It plans to propose 2023 requirements in May.
