July 23, 2024

Mercury and Air Toxics Standards NESHAP Final Rule

MATS, the mercury and air toxics standards, is a more common name for the coal- and oil-fired electric utility steam generating units (EGUs) NESHAP. Part 63, Subpart UUUUU contains emission standards for pollutants such as mercury (Hg), non-Hg HAPs, and hydrogen chloride (HCl), provides for alternative pollutant monitoring such as for filterable particulate matter (fPM), and requires a multitude of work practice standards. EPA estimates that since the standard’s promulgation in 2012, emissions from affected sources have decreased by 90% for Hg, 96% for acid gas HAPs, and 81% for non-Hg metals. On May 7, 2024, EPA finalized amendments to MATS, mostly as proposed and as discussed in a previous article. [89 FR 38508] Finalized provisions include:

The non-Hg metal surrogate of fPM standard for existing coal-fired EGUs has been lowered from 0.03 lb/MMBtu to 0.01 lb/MMBtu. Sources choosing to comply with the individual metal HAP limits or the total non-Hg metal HAP limit will also see decreased emission limits by a proportional two-thirds.
All coal-fired EGUs must demonstrate compliance with the fPM emission standard via a PM continuous emission monitoring system.
Lignite-fired EGUs must meet the same 1.2 lb Hg/TBtu emission standard as bituminous- and subbituminous-fired EGUs or an alternative output-based standard of 0.013 lb/GWh. [Note: lignite coal has less heating value per ton than bituminous or subbituminous coal.]
Two definitions of “startup” exist in Subpart UUUUU. The definition of “startup” that ends four hours after the EGU generates electricity that is sold or used for any other purpose (including onsite use), or four hours after the EGU makes useful thermal energy for industrial, commercial, heating, or cooling purposes, whichever is earlier, has been removed. The more-stringent definition of “startup” that ends when any steam from the boiler is used to generate electricity for sale over the grid or for other purposes, such as on-site use, has been retained.

This rule is effective July 8, 2024, and compliance deadlines for existing sources range from 180 days to three years after the effective date. EPA estimates that once compliance has been achieved, emissions reductions will include 1,000 pounds of Hg, 770 tons of fPM, 280 tons of nitrogen oxides, 65,000 tons of carbon dioxide, and 7 tons of non-Hg metal HAPs. In addition to environmental protection, the agency anticipates an annual savings of $33 million in health benefits, $14 million in climate benefits, and $96 million in compliance costs. More information is available via EPA’s fact sheet and Docket ID No. EPA-HQ-OAR-2018-0794.

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This document addresses issues of a general nature related to the federal environmental regulations. Persons evaluating specific circumstances dealing with the environmental regulations should review state and local laws and regulations, which may be more stringent than federal requirements. In addition, the assistance of a qualified professional should be enlisted to address any site-specific circumstances.