Originally published as a Schiff Hardin Environmental Update newsletter

In the wake of the vacatur of the Clean Air Mercury Rule in 2008, the United States Environmental Protection Agency (“USEPA”) has proposed national standards for emissions of mercury and other hazardous air pollution from all coal- and oil-fired electric generating units (“EGUs”) with a capacity of at least 25 megawatts. The proposed EGU national emission standards for hazardous air pollutants (“NESHAP”) primarily sets technology-based emission limitation standards (known as maximum available control technology or MACT) for mercury and other toxic air pollutants. Existing sources subject to the rule will have up to four years to install the requisite pollution control technology and comply with the standards.

In addition, USEPA is simultaneously proposing revisions to the new source performance standards (“NSPS”) for particulate matter (“PM”), sulfur dioxide (“SO2“) and nitrogen oxides (“NOx”).1 The proposed revisions would apply only to EGUs under 40 C.F.R. part 60, subpart Da, constructed, reconstructed or modified after the effective date of the rule. The proposed NSPS rule also includes “less significant” amendments (e.g., changes to certain monitoring and performance testing requirements), technical clarifications and corrections to various portions of the existing utility and industrial steam generating unit NSPS.

USEPA claims that the proposed emission standards will prevent the emission of 91% of the mercury in coal burned in power plants and reduce emissions of acid gas and SO2 by 91% and 55%, respectively. With respect to the proposed NESHAP, the proposed rule sets forth numerical emission limits for mercury, other metals such as arsenic and chromium (with PM proposed as a surrogate), and acid gases (with hydrogen chloride proposed as a surrogate).2 Different emission limits are set for coal- and oil-fired EGUs, and alternative standards are proposed for certain subcategories of power plants (such as an SO2 standard3 as an alternate to hydrogen chloride emission limits for acid gases). In addition, USEPA is proposing that emissions from startup and shutdown, but not malfunction, are accounted for in assessing compliance with the proposed emission standards. Lastly, the proposed rule identifies a number of control technologies for achieving the proposed emission limits, including wet and dry scrubbers, dry sorbent injection systems, activated carbon injection systems, and baghouses, many of which have a co-benefit reduction of other pollutants likes SO2 and PM.

The proposed rule was issued on March 16, 2011, but has not been published in the Federal Register. Copies of the proposed rule and related guidance are available here. Once it is published, USEPA will accept comments on the proposed rule for 60 days. Please contact us with questions, including assistance with drafting public comments on the proposed rule.


1 The proposed amended NSPS emission standards for EGUs are as follows: total PM – 0.055 lb/MWh for new/reconstructed EGUs and 0.034 lb/MMBtu for modified units; SO2 – 1.0 lb/MWh for new/reconstructed EGUs and no revision to the SO2 emission standard for modified units; and NOx plus carbon monoxide combined emission standard – 1.2 lb/MWh for new/reconstructed EGUs and 1.8 lb/MWh for modified EGUs.

2 By way of example, proposed emission limits for existing coal-fired EGUs designed to burn coal with a heat content greater than or equal to 8,300 BTU/lb are as follows: total PM emission limitation of 0.030 lb/MMBtu (0.30 lb/MWh); hydrogen chloride emission limitation of 0.0020 lb/MMBtu (0.020 lb/MWh); and mercury emission limitation of 1.0 lb/TBtu (0.0008 lb/GWh).

3 The proposed alternate emission limit for SO2 for coal-fired EGUs designed to burn coal with a heat content greater than or equal to 8,300 BTU/lb is 0.20 lb/MMbtu.