Corn-based ethanol, which has been blended in large quantities into gasoline sold at the United States pumps for years, is likely to contribute far more to global warming than straight gasoline, says a new study.
The research, published on February 14, in the Proceedings of the National Academy of Sciences, contradicts previous studies commissioned by the US Department of Agriculture (USDA) that show ethanol and other biofuels are relatively green.
Corn ethanol is currently the leading source of ethanol fuel in the US and is required to be blended with gasoline in the Renewable Fuel Standard.
The administration of President Joe Biden is reviewing policies on biofuels as part of a broader effort to decarbonise the US economy by 2050 to combat climate change.
“But, corn ethanol is not a climate-friendly fuel,” says Dr Tyler Lark, an assistant scientist at the Center for Sustainability and the Global Environment at the University of Wisconsin-Madison, and lead author of the study.
In the United States, a law passed in 2005 sets a quota of approximately 57 billion litres of bioethanol incorporated each year into conventional gasoline in the country. All this is to reduce the country’s energy dependence and with a lot of subsidies. As a result, corn cultivation increased by 9% and spread over nearly 3 million hectares in the country between 2008 and 2016. According to the government, this is a great success: a 2019 study by the USDA showed at the time that ethanol pollutes 39% less than conventional gasoline in its production.
According to this study, intensive agriculture now covers land that would have been placed in ecological fallow without the arrival of bioethanol. Worse, the very intensive methods (because profitable thanks to subsidies and quotas) of the culture of the corn are harmful to the environment, in particular, because of the use of nitrates.
The study, therefore, draws the conclusion that American E85 bioethanol is not a clean fuel. It pollutes more than gasoline if we take the production chain as a whole. Its two other missions, reducing energy dependence and giving a boost to farmers, are, therefore, done at the cost of ecology, even though super ethanol is often presented as “green”. In France, however, the production methods are different since the local ethanol is also made from beets, among other things.