Higher ozone levels from renewable fuels
By Catherine M. CooneyEnvironmental Science and Technology, May 16, 2007
The Bush Administration touts its new Renewable Fuels Standard (RFS) to increase ethanol and other biofuels in gasoline as a step toward oil independence, clean air, and lower greenhouse-gas emissions. Yet the U.S. EPA’s own analysis reveals that an increase in corn-based ethanol will raise levels of ozone in certain Midwestern states, even as research points toward more premature deaths when ozone levels are high.
Farmers and other Midwesterners are likely to see decreased air quality.
Unveiled on April 10, RFS is a set of new EPA regulations designed to push up the amount of ethanol or other renewable fuels used in cars from today’s 4.7 billion gallons per year (gal/yr) to 7.5 billion gal/yr by 2012. Almost all U.S. ethanol is produced from corn, the U.S. Department of Agriculture says, and by 2030, refineries will generate 14.6 billion gal/yr (or 8% of gasoline), the U.S. Energy Information Agency reports.
RFS will cut petroleum use by as much as 3.9 billion gal/yr by 2012, EPA Administrator Stephen Johnson says. Annual greenhouse-gas emissions will drop by up to 13.1 million metric tons (t) by 2012; EPA says this is the equivalent of taking 2.3 million cars off the roads, or of cutting about 0.4–0.6% of the anticipated greenhouse-gas emissions from U.S. cars by 2012.
The program implements a provision approved by Congress in the Energy Policy Act and is part of a larger initiative by the Bush Administration to increase the use of biofuels.
Bill Becker, director of the National Association of Clean Air Agencies, criticizes the rule, noting that EPA’s own analysis shows that the production and use of ethanol will increase emissions of nitrogen oxides (NOx) by 6–7% and of volatile organic compounds (VOCs) by 4–5%. Companies in approximately 120 counties, most in Midwestern states, will be expanding ethanol plants or building new ones, EPA writes. People in Arkansas, Ohio, Indiana, Illinois, and the southern states of Louisiana and Alabama will see the biggest ozone increases, but the air-quality impact will be “minimal”, Johnson says, because many counties in these states already meet EPA standards for ozone. Other Clean Air Act provisions will do their job to keep a lid on emissions of VOCs and NOx, adds Jennifer Wood, EPA’s spokesperson.
But Americans are currently suffering from high ozone levels, according to the American Lung Association (ALA). In a new report, ALA notes that ozone levels across the country have decreased significantly since 2006, because of cooler summers and the installation of pollution-control equipment. Still, one-third of the population lives in areas with unhealthful levels of ozone. Created by a mixture of NOx and VOCs zapped by sunlight, smog exacerbates asthma and can lead to premature death from heart failure or lung disease. “The good news is that there’s less ozone everywhere. Yet the science shows that millions are still at risk from ozone that exceeds acceptable levels,” says Terri Weaver, ALA chair. Citing research commissioned by EPA, ALA shows that three groups of scientists, working independently to review all the research, found a “robust association” between daily ozone exposure and premature death (Am. J. Epidemiol. 2006, 163, 579–588).
Low-ethanol blends (E5.7 and E10) increase smog levels because the ethanol raises the vapor pressure of the fuel, so more VOCs evaporate into the air. Fuels like E5.7 and E10 also boost the fuel-oxygen content of the gas, creating an air-rich fuel that, when combusted in a regular engine, results in higher levels of NOx. Although environmental groups such as the Natural Resources Defense Council support high-ethanol blends (E85), recent ES&T indicates that these could lead to more health problems in places like Los Angeles that already have poor air quality.
The air quality in Midwestern states will not be helped by a separate EPA rule that increases the amount of pollution that ethanol production plants can emit. The rule, released on April 12, raises the “threshold” of ambient air pollution—such as NOx, carbon monoxide, and sulfur—for these facilities from 100 to 250 t/yr. This means that new or expanding plants responding to the surging ethanol demand won’t have to install pollution-control equipment if their emissions don't exceed the threshold. The producers won’t have to control emissions from leaks or evaporative processes either, the rule states. Several ethanol plants were cited in 2002 for uncontrolled emissions of VOCs, including the carcinogens formaldehyde and acetaldehyde.
Becker and other state regulators aren’t optimistic. President Bush asked Congress to cut $35 million from EPA’s clean-air budget that is set aside for state grants, Becker says. The increases in VOCs and NOx will only thwart states’ efforts to keep the air clean, he adds. —CATHERINE M. COONEY
Copyright © 2007 American Chemical Society