4 The record articles

Recent Updates to the MATS Rule

Posted: June 25th, 2020

Authors: David R. 

There were two recent Federal Register notices related to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Coal- and Oil-Fired Electric Utility Steam Generating Units (EGUs), commonly referred to as the “Mercury and Air Toxics Standards” (MATS).  Each action, along with some background, is provided below.

Eastern Bituminous Coal Refuse-fired Electrical Generating Units – New Hazardous Air Pollutant Emissions Limitations

The MATS rule was proposed on May 3, 2011 and finalized on February 16, 2012, under 40 CFR Part 63, Subpart UUUUU (Subpart UUUUU). The U.S. Environmental Protection Agency (U.S. EPA) originally promulgated a single acid gas Hazardous Air Pollutant (HAP) emissions standard for all coal-fired EGUs using hydrochloric acid (HCl) as a surrogate for all acid gas HAP, as well as an alternative emissions standard for sulfur dioxide (SO2) as a surrogate for the acid gas HAP that may be used if a coal-fired EGU is operating some form of flue gas desulfurization (FGD) system and an SO2 continuous emissions monitoring system (CEMS). Since the original publication of MATS and following a series of petitions and requests for reconsideration, U.S. EPA acknowledged that there are differences in HAP emissions profiles based on the type of coal refuse fired.  Specifically, U.S. EPA recognized that there are differences between anthracite coal refuse and bituminous coal refuse, and additionally between western and eastern bituminous coal refuse (WBCR and EBCR, respectively). This distinction is the basis for the Final Rule “NESHAP: Coal- and Oil-Fired EGUs—Subcategory of Certain Existing EGUs Firing Eastern Bituminous Coal Refuse for Emissions of Acid Gas HAP” effective April 15, 2020 (85 FR 20838). With this action, U.S. EPA proposed the establishment of a new subcategory for EBCR-fired EGUs to reflect the different coal refuse emissions profiles.

After receiving public comments supporting the proposal and evaluating emissions data available when the 2012 MATS rule was established, in addition to new data provided in recent years, U.S. EPA is establishing a new subcategory for certain existing EBCR-fired EGUs for emissions of acid gas HAP.  With the Final Rule, U.S. EPA is establishing a specific maximum achievable control technology (MACT) floor and a new emission standard applicable to the subcategory.

Does this rule apply to my facility?

The Final Rule defines the new, very limited, subcategory as “any existing (i.e., construction was commenced on or before May 3, 2011) coal-fired EGU with a net summer capacity of no greater than 150 megawatts (MW) that is designed to burn and that is burning 75 percent or more (by heat input) EBCR on a 12-month rolling average basis.” The new acid gas emissions limitations for EBCR-fired EGUs are as follows:

HCl – 0.04 pounds per million British thermal units (lb/MMBtu) or 0.4 lb/MW-hr


SO2 – 0.6 lb/MMBtu or 9.0 lb/MW-hr

There are six EBCR-fired EGUs in the new subcategory that are operating near legacy piles of EBCR in two states:

  • Pennsylvania:
    • Colver Power Project (110 MW Summer Capacity; located in Colver)
    • Ebensburg Power (50 MW Summer Capacity; located in Ebensburg)
    • Scrubgrass Generating Company LP Unit 1 and Unit 2 (42 MW Summer Capacity each; located in Kennerdell)
  • West Virginia:
    • Grant Town Power Plant Unit 1A and Unit 1B (40 MW Summer Capacity each; located in Grant Town)

Sources must be in compliance with the applicable HCl and SO2 limitations upon the effective date of the Final Rule (i.e., no later than April 15, 2020).  No later than 180 days after the compliance date, sources must demonstrate compliance has been achieved by conducting the required tests and then must make the required notifications. If an HCl or SO2 CEMS is initially used to establish compliance, the initial performance test consists of 30 boiler operating days of CEMS data. The sustained compliance with the newly established emissions limits is required to be verified on a 30-boiler operating day rolling average.

Can EBCR-fired EGUs meet the new limits?

The limits in this new subcategory are quite a bit higher than the current limits included in the MATS rule for other existing coal-fired EGUs (2.0E-03 lb/MMBtu or 0.02 lb/MWh for HCl and 0.2 lb/MMBtu or 1.5 lb/MWh for SO2).  The new subcategory was created to specifically address the ability of EBCR-fired EGUs to comply with the MATS acid gas limits.  The revised emissions limits were established based on emissions rates that the currently operating EBCR-fired EGUs have achieved and are consistent with EPA’s 90 percent SO2 reduction target. Sulfur and chloride contents of eastern bituminous coal are higher than anthracite or coals from other regions of the U.S so combustion of EBCR leads to higher emissions of SO2 and HCl than combustion of other coal types.

Coal refuse fuels are fired in fluidized bed combustors that use limestone in the bed, which provides control of acid gases. However, there is a limit to the amount of solid material that can be in a combustor at one time, and U.S. EPA admitted that injecting large amounts of limestone could result in a decrease in the amount of coal refuse a unit is able to fire, with a corresponding decrease in steam and power production. In addition, increased use of sorbents in the bed or injected into the ductwork could alter the characteristics of the fly ash and prevent beneficial reuse. With the new emissions limitations, there is no longer a need for additional acid gas control technology or fuel switching in EBCR-fired EGUs.

Reconsideration of Supplemental Finding and Residual Risk and Technology Review

The Clean Air Act (CAA) required U.S. EPA to analyze HAP emissions and perform a risk assessment to inform a determination of whether it was “appropriate and necessary” to regulate HAP emissions from EGUs.  U.S. EPA originally determined in December 2000 that it was appropriate and necessary to regulate coal- and oil-fired EGUs under CAA Section 112.  However, U.S. EPA reversed course in 2005 and instead promulgated the Clean Air Mercury Rule (CAMR) under CAA Section 111.  The D.C. Circuit Court vacated the 2005 actions and the U.S. EPA then completed additional analyses, found again that it was appropriate and necessary to regulate HAP emissions from coal- and oil-fired EGUs, and promulgated the MATS rule in 2012.  Litigation resulted in a U.S. Supreme Court Decision in 2015 that U.S. EPA should have considered cost in its analyses.   As a result of that decision, U.S. EPA published a reconsideration of its finding in the Federal Register on May 22, 2020 (85 FR 31286).  The revised finding is that it is not “appropriate and necessary” to regulate EGUs under section 112 of the Clean Air Act (CAA) because the costs of the regulation outweigh the benefits of the emissions reductions when only the HAP emissions reductions are considered.  However, U.S. EPA did not revoke the MATS rule as part of the finding.

U.S. EPA also finalized the results of the Risk and Technology Review (RTR) of MATS that the Agency is required to conduct within eight years of finalizing each NESHAP.  U.S. EPA performed a risk assessment and determined that the residual risks from emissions of HAPs from the coal- and oil-fired EGUs source category are acceptable and that the current standards provide an ample margin of safety to protect public health and prevent an adverse environmental effect.  The technology review determined that there are no new developments in HAP emissions controls that would achieve further cost-effective emissions reductions.  Therefore, no changes to the standards are necessary as a result of the RTR.

Although the new EBCR subcategory affects only a small number of regional plants across the country, it will prove to be extremely beneficial, both economically and environmentally, to these sources.  That the RTR did not indicate U.S. EPA should make the MATS rule any more stringent was a good result for facilities complying with the rule, but the determination that it was not appropriate and necessary to establish the MATS rule in the first place has sparked legal action and we are waiting to see how that plays out.  The MATS rule resulted in significant emissions reductions in both criteria pollutants and HAPs, and a court could determine that the rule should be vacated since U.S. EPA has now determined it was not appropriate and necessary.  If you have any additional questions, please don’t hesitate to reach out to David Ross at dross@all4inc.com or 610-933-5246 ext. 103.


    Sign up to receive 4 THE RECORD articles here. You'll get timely articles on current environmental, health, and safety regulatory topics as well as updates on webinars and training events.
    First Name: *
    Last Name: *
    Location: *
    Email: *

    Skip to content