Governors' Biofuels Coalition

Ethanol refineries may emit more air pollution than commonly thought, according to a new study led by researchers from the National Oceanic and Atmospheric Administration.

The NOAA team, which also included scientists from NASA and academic institutions, measured the air downwind from an ethanol plant in Illinois and found emissions of total volatile organic compounds (VOC) to be five times higher than 2011 federal data.

Emissions of ethanol in the air — considered a type of VOC — were up to 30 times higher than previously thought downwind from the plant, the team said.

Lead researcher Joost de Gouw, an atmospheric scientist at NOAA’s Cooperative Institute for Research in Environmental Sciences, called the study one of the first comprehensive looks into the air emissions from ethanol operations.

“Over the past decade, because of the renewable fuel mandate, we have added 10 percent of ethanol to all the gasoline that is sold in the U.S. and so the question is: what does that do to the environment,” de Gouw said in a statement. “That is a very complicated question and it has many different aspects. One of the aspects is the air-quality implications and, to get at them, we have to know what are the emissions associated with producing ethanol and using ethanol. That is where this study fits in.”

The study has been accepted for publication in the Journal of Geophysical Research: Atmospheres. NOAA and U.S. EPA provided funding for the measurements taken by the team.

Using a small NOAA airplane outfitted with special instruments, the team measured air quality at 9, 12 and 30 kilometers downwind from the Archer Daniels Midland ethanol plant in Decatur, Ill., in June and July 2013. The plant is the third-largest ethanol operation in the country and is powered by coal.

They compared the emissions with estimates in the 2011 National Emissions Inventory, which EPA maintains.

According to the results, measured emissions of sulfur dioxide and nitrogen oxides compared well with the EPA data. But they found that the National Emissions Inventory underestimated emissions of volatile organic compounds — gases that are a main ingredient in ground-level ozone — generated by the refining process by factors of five to 30.

Among the VOCs that were highest were ethanol, formaldehyde and acetaldehyde. They also found that emissions from the Decatur plant transformed chemically into ozone, particles, aldehydes and other compounds.

While there are some uncertainties associated with the experiment, the authors said the results show that the inventory was “inconsistent” with the actual emissions of the plant. They compared the results with studies that have shown VOC emissions from other industrial processes have previously been underestimated.

“It should also be noted that severe underestimates in VOC emissions from industrial sources are not unprecedented,” they wrote, “and were observed downwind from petrochemical plants near Houston, TX, and in an oil and gas production region.”

The authors also used production figures obtained from the Renewable Fuels Association to compare the results to the ethanol emissions that come out of the tailpipe from burning ethanol. They found that producing 1 kilogram of ethanol at a refinery could emit 170 times more ethanol into the air than burning the same amount in a car.

Dylan Millet, an associate professor of atmospheric chemistry at the University of Minnesota, said in a statement that the study highlights the need for more research into the air pollution impact of ethanol refineries.

“If we are going to accurately assess the air-quality implications of our fuel choices,” said Millet, who was not part of the study, “then these are important emissions to know.”

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