Study links ethanol to higher ozone levels

Source: Amanda Peterka, E&E reporter • Posted: Monday, May 5, 2014

Ozone pollution levels fell when drivers in São Paulo, Brazil, switched from ethanol to gasoline, according to a study released this week that researchers say is the first to link consumer fuel purchases and air quality.

Northwestern University researchers found that ambient ozone in the São Paulo region fell 20 percent during 2010 and 2011 as the share of flex-fuel vehicles running on gasoline rose from 14 percent to 76 percent, according to the study that was conducted over four years and published Monday in the journal Nature Geoscience.

Ethanol use fell sharply in that period because of large fluctuations in the price of the alcohol-based fuel due to changes in sugar prices.

“Individuals often don’t realize it, but, in the aggregate, you can have a real impact on the environment,” Alberto Salvo, an associate professor of economics at the National University of Singapore and formerly with Northwestern’s Kellogg School of Management, said in a news release. “In São Paulo, there were more than a million cars switching from ethanol to gasoline in the same season, and we found that ozone levels went down. We didn’t expect this, but it is a precise result.”

Ethanol-based vehicles are widely believed to spew less pollution than petroleum-based vehicles because ethanol contains lower concentrations of mono-nitrogen oxides.

But this is not the first study to link ethanol to smog. A study in 2012 led by the University of Minnesota found that gasoline had a slight advantage compared to ethanol blends of 85 percent regarding ozone impacts. But that study and other previous research, though, has been based on computer modeling.

The authors of the new paper said they figured São Paulo, which has the world’s largest flex-fuel vehicle fleet, to be an ideal location to study real-world impacts.

Salvo and Northwestern chemist Franz Geiger based their results on fuel sales data, 14,000 consumer surveys, road traffic levels, pollutant concentrations and meteorology across 600 miles of roads in the São Paulo region. Previous studies have generated data using computer simulations.

While the study found ozone levels increased as ethanol use went down, it also found that nitric oxide and carbon monoxide concentrations increased as more gasoline was used in the vehicle fleet. Ozone and nitric oxide are both contributors to smog found in cities.

The authors cautioned that the results were only valid for São Paulo, but they said that the work provides the basis for research in other metropolitan areas.

“This work allows us to start thinking about the urban metabolism of Chicago, which is an emerging megacity surrounded by ‘corn country,'” Geiger said in a release. “Ethanol from corn is a particularly intriguing option for future, possibly more competitive, energy markets. It’s an area we need to watch.”

They also said that pollution mitigation strategies around the world will vary depending on local chemistry and other pollutants in the air, especially fine particulates.

The study was funded by the Institute for Sustainability and Energy at Northwestern, the National Science Foundation and the dean’s office at Northwestern’s Kellogg School of Management.

In a statement, Joel Velasco, board adviser at the Brazilian Sugarcane Industry Association (UNICA), defended ethanol, pointing to a 2010 study by the Air Pollution Laboratory at São Paulo University’s Faculty of Medicine that found replacing gasoline and diesel with ethanol would improve air quality in the city and reduce public health costs.

The Renewable Fuels Association, which represents U.S. ethanol producers, questioned the methodology used in the study because it relied on atmospheric concentrations of ozone and did not measure actual emissions from tailpipes. The group faulted the study for also failing to analyze the composition of the gasoline to which ethanol was added.

RFA President and CEO Bob Dinneen said that results weren’t applicable to the United States.

“Vehicles in the U.S. must comply with emissions control requirements that are different — and more stringent — than Brazil,” Dinneen said. “Further, urban ozone formation occurs from rather complex photochemistry that is influenced by a number of factors unique to local climates.”

Jonathan Lewis, a senior counsel for climate policy at Clean Air Task Force, said that the study was useful because of its reliance on real-world data, rather than complex modeling.

While he also said it was unclear yet what its implications were on other places, he cautioned against the United States using higher ethanol blends in gasoline until more research is done. U.S. EPA recently approved E15, gasoline containing 15 percent ethanol, for use in the United States. Blends of up to 85 percent are also used in flex-fuel vehicles.

“Until we better understand how and to what extent E15, E85, and other blends might contribute to the United States’ ozone problems, the research by Salvo and Geiger reinforces our perspective that EPA and Congress should postpone any move to higher ethanol blends,” Lewis said in an email.