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NOx Never Sleeps

Peter Spinney

Market and Technology Assessment

NeuCo, Inc.

10/4/2015 11:02:19 PM

Or was that rust? As most of you have probably seen or heard, the much anticipated revision to the EPA National Ambient Air Quality Standards (NAAQS) were announced by the US EPA October 1st, lowering the ozone limit from 75 to 70 ppm, a 6.7% reduction.

Iím not going to spend precious blog real estate talking about how this 6.7% is about half the amount of boiler NOx reduction typically achieved with properly designed and executed software-based combustion optimization. Because my intent is to discuss how todayís news figures into the overall scheme of US air emissions regulations for power generation, not to promote software.

Now back to the rust. Itís been quite a long time since there has been any real news on US NOx emissions regulations. When I tried to answer some questions about the relationship between NAAQS and the Cross-State Air Pollution Rule (CSAPR), I found that articulating clear responses was difficult. I had become rusty on the topic, and so decided to refresh my understanding.

Here is what I distilled. NAAQS is about Ozone, NO2 (together referred to as ďNOxĒ) and SO2 at the county level. Ozone is relevant for the five month season of that name; NO2 and SO2 for 12 months.

CSAPR (and its predecessor CAIR) is about interstate transport of these pollutants for the 27 states in which the creation of ozone, NO2 and SO2 impedes the ability for counties in other states downwind to comply with NAAQs.

So logically, I concluded, lower NAAQS will mean tighter restrictions on transport, in the form of lower state NOx budgets for the upwind states. But upon considering this a question arose. Did CSAPR as currently formulated build-in some anticipated minimum reduction for NAAQS, such as the 5 ppm ozone reduction published October 1st?

The answer to this question was not hard to find, right at the bottom of the EPA web page on Interstate Air Pollution Transport :

"Most recently, CSAPR addresses pollution transport for the 1997 ozone NAAQS, 1997 PM2.5 NAAQS, and 2006 PM2.5 NAAQS. As appropriate, EPA will work with our state partners to develop paths forward to address transport for newer NAAQS."

So it is likely that state NOx budgets, at least for Ozone Season, will have to be adjusted even lower than the current caps for CSAPR Phase 2, which is already going to impose modest but widespread addition NOx compliance efforts in the 27 affected states. Thus it is true: NOx -- at least US regulation of it -- never does sleep, or at least not for long.

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