For decades, American farm policy has funneled tens of billions of taxpayer dollars toward renewable, crop-based fuels, with elected leaders and the biofuels industry lauding them as cleaner, greener alternatives to petroleum.

But a new review of industry data published Wednesday finds that the country’s biofuel refineries, mostly located in the Midwest, are spewing out toxic air pollutants, in some cases in greater amounts than their petroleum counterparts.

“The industry claims biofuels are a better alternative,” said Kira Dunham, a researcher with the Environmental Integrity Project (EIP) and co-author of the new report. “But what we found is that biofuels are a pretty significant source of hazardous air pollutants.”

Dunham and her colleagues at EIP reviewed emissions data reported to the Environmental Protection Agency (EPA) and to states from the country’s 275 ethanol, biodiesel and renewable diesel plants. They found that these facilities release carcinogenic formaldehyde and other potentially dangerous substances, including acetaldehyde, hexane and acrolein, in larger volumes than petroleum refineries. 

In 2022, biofuel refineries released 12.9 million pounds of hazardous air pollutants, compared to 14.5 million pounds emitted by oil refineries, and they emitted significantly more hexane, acetaldehyde, acrolein and formaldehyde, according to the collected data. While petroleum refineries emit acrolein and acetaldehyde, hexane and formaldehyde are among the most frequently reported toxic chemicals by that industry.

EIP’s review found that the biofuel industry was the largest source of acrolein—which causes vomiting and shortness of breath, among other health impacts—of any industry. And one ethanol and grain processing plant in Illinois, operated by grain giant Archer Daniels Midland (ADM), was the country’s single largest source of hexane, which is known to cause nerve damage.

“People near Decatur [Illinois] are constantly exposed to air pollution that can harm their brains and cause dizziness and nausea,” said Robert Hirschfeld, a director at the Prairie Rivers Network, an environmental nonprofit, in a prepared statement. “ADM’s ethanol plant also emits more greenhouse gases than places like oil refineries in Illinois. On top of that, corn production for ethanol has resulted in so much pollution that Illinois residents are advised not to swim in, eat fish out of, or drink water from streams and rivers across the state. EPA needs to regulate the facility like it would regulate any other large-scale polluter.”

The new report comes as the biofuels industry is expected to expand, largely with billions in support from the Biden administration for the development of sustainable aviation fuel, or SAF. EIP found that of the 32 new or expanded biofuels facilities under construction or currently proposed, two-thirds are slated to manufacture aviation fuel from wood or plants. 

Aviation fuel could provide yet another boost to an industry that has boomed this century. The Renewable Fuel Standard, first passed by Congress in 2005 and updated in 2007, required that petroleum refiners blend billions of gallons of renewable fuels into the country’s transportation fuel every year. The U.S. has since become, by far, the world’s biggest producer of biofuels, mostly corn-based ethanol. Now about 40 percent of the nation’s corn—its largest and most lucrative crop—and half of its soybeans, its second largest, ultimately end up in gas tanks.  

Since 2000, the number of ethanol plants in the U.S. quadrupled and capacity rose eight-fold, EIP says. As of early 2024, the U.S. has 191 ethanol plants, 71 biodiesel plants and 13 plants devoted to renewable diesel. 

The idea behind biofuels, initially, was to wean the country off of foreign fuel. But the law also required that biofuels demonstrate environmental benefits—specifically that they reduce greenhouse gas emissions. 

Research has since found that ethanol has forced the conversion of grasslands and forests into cropland for corn, both in the U.S. and abroad, releasing massive amounts of carbon in the process. A study published in 2022 found that farmers expanded corn production on nearly 7 million acres each year after the new standard took effect. The result was that the carbon intensity of corn ethanol is “no less than gasoline and likely at least 24 percent higher,” according to the study. 

This expansion, the EIP report says, has come with the support of policy and funding but without adequate oversight. 

Ethanol plants are exempt from some air pollution permitting requirements, largely because of industry pressure. In 2007, the EPA removed corn ethanol plants from its list of facilities subject to more stringent Clean Air Act thresholds, allowing them to release twice as much air pollution before having to obtain permits that required stronger limits. 

EIP calculates that there are now 41 federal incentives, programs, laws and regulations in effect promoting renewable fuels—a figure that does not factor in subsidy programs for corn and soybeans, which have directed nearly $161 billion toward these crops in the last 30 years.

The EIP report also found that more than 40 percent of biofuels plants violated air pollution control permits at least once between July 2021 and May 2024, and 36 percent failed “stack tests” designed to determine if facilities are in compliance with the Clean Air Act. 

Though the report focuses on hazardous air pollutants, it also notes that biofuels plants reported emitting over 33 million metric tons of greenhouse gases in 2022, or as much as 27.5 oil refineries.

Geoff Cooper, president and CEO of the Renewable Fuels Association, the largest biofuels industry group, called the report fundamentally flawed and said that hexane is not used in the ethanol production process anywhere in the U.S.  

Cooper added that “ethanol facilities are tightly regulated on their emissions, and producers are in compliance with all federal and state emissions limits. When violations have been noted, which is very rare, producers have immediately taken corrective action and quickly moved into compliance.”

EIP spokesman Tom Pelton said the group stands by the report’s accuracy, noting that their research is based on data biofuels companies released to the EPA. That data shows 86 percent of ethanol plants released hexane in 2022, the last year for which data was available, with an average of more than 20,000 pounds per plant.

Pelton also reiterated the report’s findings that 98 out of 240 biofuels plants violated their air pollution control permits at least once between July 2021 and May 2024. “Those aren’t rare violations,” Pelton added. “Those are frequent violations.”