SOLAR TODAY - May 2010

EPA Publishes Improved Air Quality Standard

By ROBERT UKEILEY

robert Ukeiley (rukeiley @ igc.org) is a lawyer who represents environmental nonprofits in Clean air act litigation affecting energy issues.

On Feb. 9, the Environmental Protection Agency (EPA) published its new Clean Air Act National Ambient Air Quality Standard (NAAQS) for nitrogen oxides (NOx). This should represent a major step forward in leveling the economic playing field for renewable energy and energy efficiency versus fossil fuels.

Background first: The EPA sets NAAQS for various pollutants. NAAQS are the level of air pollution above which the EPA believes there are unacceptable adverse impacts to public health and welfare. The EPA determines, usually county by county, which areas have ambient pollution above the NAAQS, or contribute pollution to such areas, and designates these areas “nonattainment.” Nominally clean air areas are designated “attainment.” Each state then has to come up with a plan to clean up the air in the nonattainment areas and prevent significant deterioration in attainment areas. A critical component of NAAQS is the averaging time. Longer averaging times generally make for less protective NAAQS and make it easier for polluting sources to comply.

The old NOx NAAQS was based on an annual averag-
ing time. The new NOx NAAQS is based on a one-hour
averaging time. This is a very significant change for the
better. Inherently dirty fossil fuel power plants will have a
much harder time complying with one-hour averaging time
NAAQS. This is because almost all new, and many old, coal-
fired power plants use an “end of the pipe” pollution-control
device called a selective catalytic reduction (SCR) system
to reduce NOx emissions. However, like many other pollu-
tion-control devices on coal-fired power plants, SCRs can
be safely operated only when they reach a certain operating
temperature. Thus, during startups, shutdowns and malfunc-
tions, coal-fired power plants can have much higher NOx
emission rates. With the old annual averaging time NAAQS,
this wasn’t a problem. A power plant could have higher emis-
sions during the periods when its pollution- control device
could not work, have lower emissions during other times and
thus average out its emissions to be well below the standard.
The problem, of course, is that people continue to breathe
even when the SCRs aren’t working, and toxic emissions can
make people very sick even at short exposures. So the short
averaging time is much better.

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