August 16, 2024

Revisions to the NSPS and Emission Guidelines for Electric Generating Unit Greenhouse Gas Emissions

On May 9, 2024, EPA finalized a series of CAA rules addressing greenhouse gas (GHG) emissions from fossil fuel-fired electric generating units (EGUs). [89 FR 39798] As the agency developed these final rules, it recognized the need to maintain reliable and affordable electricity. To support these goals, four aspects were critical to the rule-making effort:

Flexibility by extending compliance deadlines and simplifying subcategories regulated by the standards;
Allowing states to consider reliability while implementing the necessary changes in their state plans;
Providing an allowance of annual averaging and emissions trading; and
Creating two reliability mechanisms, one associated with grid emergencies and the other with compliance deadline extensions for units with cease operation dates.

With these considerations in focus, the agency’s GHG rule makes four main changes:

The 2019 Affordable Clean Energy (ACE) rule has been repealed. EPA concluded the ACE rule did not contain the best system of emissions reduction (BSER) for existing coal-fired EGUs, erroneously rejected carbon capture and sequestration (CCS) and natural gas co-firing as the BSER, and conflicted with CAA Section 111.
Emission guidelines for GHG emissions from existing EGUs have been finalized in a new Part 60, Subpart UUUUb. This standard contains different BSERs depending on the EGU subcategory, such as a 90% capture rate for CCS or co-firing with natural gas at 40% of the unit’s annual heat input. The emission guidelines of Subpart UUUUa have been removed and that subpart is reserved.
Revisions to the NSPS for GHG emissions from new and reconstructed fossil fuel-fired stationary combustion turbine EGUs have been finalized in Part 60, Subpart TTTT and a new Subpart TTTTa. The BSER for affected turbines varies depending on whether they are used for base, intermediate, or low loads.
New Part 60, Subpart TTTTa includes standards for modified coal-fired steam EGUs. These provisions were promulgated to mirror the emission guidelines for existing coal-fire steam generators in Subpart UUUUb.

The effective date for these rules is July 8, 2024. Due to the complexity of the rules and the considerations for maintaining reliable sources of electricity, compliance deadlines vary and, in some instances, extend to 2039. More information is available at Docket ID No.EPA-HQ-OAR-2023-0072.

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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.