Under the U.S. Renewable Fuel Standard (RFS), corn-based ethanol has been mixed into gasoline sold at pumps in the U.S. since 2005, when a policy was enacted aimed at reducing emissions. Corn-based ethanol had been thought to be a relatively greener energy source compared to other biofuels, but now, a new study published in the Proceedings of the National Academy of Sciences reports it may be actually worse for the climate than straight gasoline. Tyler Lark, an assistant scientist at the University of Wisconsin-Madison's Center for Sustainability, joined Cheddar News' Closing Bell and discussed the pushback against the study. "Essentially when you need to produce more corn to meet the demand for use as ethanol as fuel, farmers respond and they switch more crops like soybeans and wheat into corn," Lark said. "They also bring more land into production, so things that used to be pasture grassland, and both those activities are associated with increased greenhouse gas emissions."