For years, corn-based ethanol has been mixed with the gasoline sold at gas stations across the U.S., but a recently published study has found that its carbon intensity is “likely at least 24% higher” than gas, Roadshow by CNET reported.

The study, “Environmental Outcomes of the US Renewable Fuel Standard,” was published by the journal Proceedings of the National Academy of Sciences. It examined U.S. use of water and land resources from 2008 to 2016, during the country’s Renewable Fuel Standard (RFS) program. The program was a national governmental policy that required a certain amount of fuel from renewable sources to reduce or replace heating oil, transportation fuel or jet fuel that was petroleum-based.

The study refutes earlier research commissioned by the U.S. Department of Agriculture (USDA) that showed that biofuels like ethanol were relatively clean, Reuters reported.

“Corn ethanol is not a climate-friendly fuel,” said assistant scientist at the University of Wisconsin-Madison Center for Sustainability and the Global Environment Dr. Tyler Lark, who was the study’s lead author, as reported by Reuters.

The study was partially funded by the National Wildlife Federation and U.S. Department of Energy. It found that the combination of changes in land use made in order to grow corn, in addition to its combustion and processing, made corn-based fuel more polluting than gas.

Geoff Cooper, president and CEO of ethanol trade lobby the Renewable Fuels Association, referred to the study as “completely fictional and erroneous,” saying that “worst-case assumptions [and] cherry-picked data” were used by the study’s authors, as Reuters reported.

Read the full article about corn-based ethanol by Cristen Hemingway Jaynes at EcoWatch.