The environmental impact would be the equivalent of removing “46,489 passenger vehicles off the road in Iowa every year,” says Fuels America, a coalition that supports the Renewable Fuel Standard. The federal mandate requires ethanol and biodiesel to be blended in the American fuel supply.

The report looks at the environmental impact of Iowa motorists switching the 1.5 billion gallons of gasoline they purchase annually to E15, gasoline with a 15 percent ethanol blend. Most gasoline purchased in Iowa is a 10 percent ethanol blend. Stefen Mueller, a research economist at the University of Illinois at Chicago, provided the analysis.

The American Petroleum Institute, an oil advocacy group, points to an Environmental Working Group report that claims ethanol is less environmental friendly than gasoline.

The group claims cutting the amount of ethanol required under the RFS standard would reduce carbon pollution in the nation, up to 3 million tons in 2014 with a 1.39 billion gallon reduction in corn ethanol use. The U.S. Environmental Protection initially recommended that sized corn ethanol reduction in 2013 but has not acted on it. A decision is expected this spring.

But the Argonne National Laboratory has strongly disagreed with Environmental Working Group’s report. Argonne’s research shows ethanol made from corn, sugarcane, switchgrass and miscanthus all have fewer greenhouse emissions than gasoline.

The oil group also pointed to concerns raised by AAA and others about engine problems in cars that haven’t been approved for E15. AAA says it includes “most 2001-2013 models.” But the U.S. Environmental Protection Agency says cars, light-duty trucks and SUVs 2001 and newer can safely use E15.

Some congressional lawmakers are pushing to change or repeal the Renewable Fuel Standard that requires increasingly more ethanol to be included in the country’s gasoline supply. Growth, says renewable fuels supporters, is hindered by the inability of consumers to get access to E15 and higher blends of ethanol.

It’s available in 26 stations across Iowa, but not in the Des Moines metro area.

Fuels America also says E15 also costs about 5 cents per gallon less than regular gasoline. “The analysis shows that if consumers in Iowa had access to and chose to fill up with E15 gasoline, emissions of carbon dioxide pollution across the state would be reduced,” according to Fuels America.

Transportation creates 32 percent of the carbon pollution that contributes to greenhouse gas and climate change, the U.S. Environmental Protection Agency says. The agency says human activities have contributed substantially to climate change by adding carbon dioxide and other heat-trapping gases to the atmosphere.

The report also looked at the environmental impact of switching to E15 gasoline in six other states — Illinois, Kansas, North Carolina, Ohio, Michigan and Wisconsin. The total annual carbon savings would be 3.4 million tons, according to the analysis.