Final Rules – MATS Residual Risk & Technology Review and Greenhouse Gas (GHG) Performance Standards

In May of 2024, the EPA finalized stricter rules for Mercury Air Toxic Standards (MATS) and Greenhouse Gas (GHG) Performance Standards. Key changes include tighter limits on particulate matter and mercury emissions, mandatory use of PM Continuous Emissions Monitoring Systems (CEMS), and new compliance timelines. Learn more about how these final rules can affect your facility.
Final Rules - MATS Residual Risk & Technology Review and Greenhouse Gas (GHG) Performance Standards

MATS and Greenhouse Gas (GHG) Standards Background

On May 7th, the EPA finalized a proposed rule to address findings from the 2020 Residual Risk and Technology Review (RTR) for the Mercury Air Toxic Standards (MATS). This rule includes requirements for:


  1. PM CEMS
  2. Lowered fPM limit
  3. Lowered Hg limit for Lignite Coal Plants
  4. Removal of Startup Definition #2


This rule’s effective date is July 8, 2024 (60 days from publication), and the timeline for compliance is 3 years (with an option for a one-year extension) for PM Limit, PM CEMS, and Hg Limits and 180 days for Startup Definition #2 removal.


On May 9, 2024, EPA finalized the New Source Performance Standards for Greenhouse Gas Emissions for New, Modified, and Reconstructed Electric Generating Units and Emission Guidelines for Existing Electric Generating Units. Standards for coal-fired boilers include Carbon Capture and Sequestration (CCS) and co-firing with natural gas depending upon retirement dates; for natural gas and oil-fired boilers, routine methods of operations are included; and for new stationary turbines, phased limits dependent on capacity factors (CP) are also included.

What Do These Changes Mean?

EPA expects the new MACT standards (for MATS) to include 300+ coal-fired steam generating units, approximately 60 oil-fired steam generating units, and 5 IGCC (integrated gas combined cycle) units by 2028.


Below is a list of fundamental proposed changes for MATS:

  • New fPM limit – 0.01 ln/MMBtu
  • PM CEMS is required for all plants – Testing and CPMS are no longer options, and LEE status for PM is no longer relevant.
  • CMS as an alternative method for HAPs – EGU owners/operators can petition to use a HAP metal continuous monitoring system as an alternative test method.
  • New Hg Limit for Lignite Coal Plants – 4.0 lb/TBtu to 1.2 lb/TBtu
  • Removes the option for Startup Definition #2, which gives an additional 4 hours for startup. All plants will have to comply with Startup Definition #1.


EPA has set deadlines for final carbon pollution standard compliance:

  • Coal units as 1/1/2032 and 1/1/2039
  • Natural gas and oil-fired boilers as 1/1/2030
  • New stational combustion turbines as 1/1/2032


Note that existing combustion turbines are not included in the final standard and will be addressed with another rule expected in 2025.


Summary of key carbon pollution standards:

Existing Units

  • Coal operating after 1/1/2039 – CCS with 90% CO2 capture
  • Coal operating after 1/1/2032, but not after 1/1/2039 – co-firing 40% natural gas
  • Natural gas/Oil Boilers – CP > 45% – 1,400 lbs CO2/MWh-gross
  • Natural gas/Oil Boilers – 8% < CP < 45% – 1,600 lbs CO2/MWh-gross
  • Natural gas Boilers – CP < 8% – 130 lb CO2/MMBtu
  • Oil Boilers – CP < 8% – 170 lb CO2/MMBtu


New Units

  • Natural gas turbines – CP < 20% – 160 lb CO2/MMBtu
  • Natural gas turbines – 20% < CP < 40% – 1170 lb CO2/MWh-gross
  • Natural gas turbines – CP > 40% – 800 to 900 lb CO2/MWh-gross; then by 1/1/2032 100 lb CO2/MWh-gross and 90% CCS


Final Rules Additional Resources

For more information, please refer to the EPA MATS website and the summary table from the final GHG Standards. ESC Spectrum is closely following these proposed changes as they will impact many of our customers, and we will continue to update you as needed. If you have any questions, feel free to contact Susan Kennedy at


How can ESC Spectrum Help?

If you have any questions about how the Proposed MATS RTR may affect your air emissions compliance and monitoring processes, please contact the ESC Spectrum Regulatory Services team. We also provide full CEMS solutions, including CEMS Maintenance to ensure your equipment is functioning properly, as well as repair and upgrade services. Our team is standing by to assist facilities in effectively managing the operation of Selectric Catalyst Reduction Monitoring (SCRs). For an overall assessment of your CEMS equipment, schedule a sidewalk with one of our CEMS Technicians


Interested in learning more about regulations and staying in compliance? Read our Definitive Guide to Air Emissions Regulations.

Picture of Susan Kennedy, QEP - Regulatory & Reporting Manager

Susan Kennedy, QEP - Regulatory & Reporting Manager

Susan joins ESC Spectrum from the Power Industry sector where she spent 25+ years helping power plants and associated facilities comply with environmental laws and regulations. During her tenure at Progress Energy (now Duke Energy Florida) and Gulf Power Company, she supported various environmental programs covering all media. Her technical background includes permitting, compliance and reporting for wastewater, water use, groundwater, remediation, Title V, Title IV, CEMS, Green House Gas, Florida Annual Operating Reports, Air Testing, Reciprocal Internal Combustion Engine (RICE), Risk Management Plans and Toxic Release Inventory. She received both her Bachelor of Science (’92) and Master of Science (’96) degrees from Auburn University.

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