On July 8, 2020, the U.S. Environmental Protection Agency (EPA) published proposed amendments to the 2013 National Emission Standards for Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers and Process Heaters. The proposed amendments, the result of three remands issued by the U.S. Court of Appeals for the D.C. Circuit, revise certain maximum achievable control technology (MACT) limits and provide more explanation about other aspects of the rule.
The revised MACT limits affect 34 subcategories of boilers, 28 of which are more stringent than prior limits. In setting these limits, EPA relied on “co-benefits” of reducing pollutants that are not the target of the limit, including annual average emissions reductions of 251 tons of fine particulate matter and 393 tons of sulfur dioxide.
EPA also explains two issues related to the carbon monoxide (CO) standards. First, the proposal explains the rationale for using CO as a surrogate for hazardous air pollutants (HAPs). One comment on the 2013 rule related to the availability of alternative control technologies that reduce organic HAP without affecting CO emissions. According to EPA, “none of the best performing units employ any add-on alternative control device for controlling organic HAP.” Second, EPA pointed to scientific studies to support the 130 ppm CO concentration threshold as an appropriate measure of whether HAPs are sufficiently controlled.
There will be a 60-day comment period once the proposed rule is published in the Federal Register.