E85 may not be an improvement over gas

William Atkins
Wednesday, 09 May 2007 21:14

Science - Energy

Switching from gasoline to ethanol may not reduce air pollution and improve health conditions, at least according to a study just conducted by a U.S. atmospheric scientist at Stanford University (California).        

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Mark Z. Jacobson, with Stanford’s Department of Civil and Environmental Engineering, created a mathematical model that compares chemicals emitted from automobile exhaust and sent into the atmosphere, both from gasoline and from E85 (85% ethanol and 15% gasoline). These results were then used with population and health-effects data to determine risks from each type of fuel.

Although E85 is often advertised as a potential replacement for gasoline, Jacobson did not find a result that supported such action.

Assuming that the year 2020 would be the first year that E85 is used primarily as a fuel of choice in cars, Jacobson found that E85 would increase health risks with respect to ozone and carcinogens by about 4% across the United States (as compared with gasoline), primarily due to two ozone precursors: acetaldehyde and formaldehyde.

Acetaldehyde and formaldehyde are two of four major carcinogens (chemicals that cause cancer) found in both E85 exhaust and gasoline exhaust. The other two carcinogens found both in E85 and gasoline are 1.3-butadiene and benzene. E85 had less effect on these two carcinogens than did gasoline.

Therefore, gasoline was worse with respect to 1.3-butadiene and benzene and E85 was worse with respect to acetaldehyde and formaldehyde.

Thus, Jacobson’s model concluded that, overall, E85 was about the same as gasoline with respect to health risks and air pollution.

He states, “The bottom line is, you aren’t getting an improvement in air quality.” He also said that the results when cancer is considered “somewhat cancel each other out, so there’s not much difference between E85 and gasoline.” [New Scientist, “Not-So-Clear Alternative: In its air-quality effects, ethanol fuel is similar to gasoline”, May 5, 2007, page 278]

Jacobson’s study, on the one hand, should question the value of E85 in the future as a replacement for gasoline. On the other hand, it is only one study comparing E85 and gasoline. More scientific studies are needed to support or deny these results.

Additional information on the comparison of E85 and gasoline is found within the Jacobson article “Effects of Ethanol (E85) Versus Gasoline Vehicles on Cancer and Mortality in the United States” at http://www.stanford.edu/group/efmh/jacobson/E85PaperEST0207.pdf.