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January 25, 2019
A recent review of nearly 100 different peer-reviewed vehicle emission studies, by the independent consulting group Future Fuel Strategies, found that there is no consensus in the literature regarding the health effects of ethanol-blended fuel. Despite the fact that ethanol is a cleaner-burning fuel than gasoline, the reviewers conclude that conflicting and negative results in the literature have brought confusion about the potential benefits of ethanol-blended fuels, and reluctance from policymakers and the public to embrace the fuel. According to Future Fuel consultant Tammy Klein, “It’s time to take another look at ethanol’s emissions because what we find may be surprising.”
Peer-reviewed studies on emissions have produced conflicting results regarding ethanol’s potential contribution to air pollution formation, particularly nitrogen oxide [NOx] and particulate matter [PM], largely due to variations in the test fuels used to conduct the studies. According to the World Health Organization (WHO), 7 million people die each year due to air pollution, and 90 percent of the world’s children breathe toxic air each day. The reviewers state in their key findings, “The perception that ethanol may raise particulate matter [PM] emissions is particularly damaging considering the designation as a human carcinogen by the WHO and governments’ increasingly aggressive actions to decrease these emissions, including in transport.”
The reviewers state that despite the urgent need to reduce transportation emissions as much as possible, most fuel studies should not be used to predict real-world emission effects, due to the enormous variability between studies. The inconsistencies also lead to a fundamental lack of agreement on the attribution of various air pollutants. The majority of these studies have been designed and carried out by the federal government as well as the Coordinating Research Council (CRC), a group that produces research on fuels and vehicles, and is comprised of the petroleum industry and vehicle manufacturers, and is relied upon by EPA to understand fuels and emissions.
The conflicting results were attributed to two factors: the rapid pace of changes in engine technology over the last few decades, and the use of specially-designed test fuels that don’t reflect real-world fuels. This review points to the need to create test-fuel specifications that reflect real-world fuels that are created at refiners and fuel terminals, not in laboratories. Additionally, the reviewers note that ethanol and gasoline do not interact in a linear fashion, meaning emissions testing of 10 percent ethanol fuel blends (E10) cannot be extrapolated to infer results for E15 or E20.
Thanks to ethanol, the refining industry has reduced use of toxic aromatic compounds in gasoline from 28 percent to 21 percent (a 25 percent decrease). Ethanol is the cleanest, cheapest source of octane, and its use, even in small amounts, has replaced some of these compounds in the gasoline pool. As policymakers seek to reduce greenhouse emissions in the transportation sector, whether through state level Low Carbon Fuel Standards, the Renewable Fuel Standard, Zero Emitting Vehicle (ZEV) or other measures, it is paramount to understand the health effects of various fuel sources.
The ethanol industry, for one, would simply like a seat at the table as test fuels are designed. According to the Urban Air Institute (UAI), the group which commissioned the review, there are no guidelines for test fuels. UAI Director Trevor Hinz commented, “It seems like the EPA only works with the refiners and the petroleum industry when it comes to test fuels and modeling emissions from test fuels, and I think it would be a big step forward if we could just get a seat at the table when they’re putting these programs together and blending the fuels and running the tests.”
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