Key Contacts
Practice Areas
Proposed New Source Performance Standards for Stationary Combustion Turbines
On December 13, 2024, the Environmental Protection Agency issued a proposal to strengthen the New Source Performance Standards (NSPS) for large stationary combustion turbines (CTs) with a designed base load rating equal to or greater than 10.7 gigajoules per hour/10 million Btu per hour based on the higher heating value of the fuel. If finalized, the proposal would be codified at 40 C.F.R. Part 60, Subpart KKKKa (“Proposed Subpart KKKKa”). Proposed Subpart KKKKa would apply to affected sources that are constructed, modified, or reconstructed after December 13, 2024. EPA is accepting comments on Proposed Subpart KKKKa through March 13, 2025.
The most significant provisions of Proposed Subpart KKKKa would require constructed or reconstructed CTs across most size and capacity subcategories to achieve meaningful reductions in emissions of oxides of nitrogen (NOx) by operating selective catalytic reduction (SCR) in combination with combustion controls. Within each size-based subcategory, there are individual NOx standards for both natural gas and non-natural gas fuels. The proposed SCR requirement flows from EPA’s determination that SCR now represents the best system of emission reduction (BSER) for NOx, whereas the current NSPS for stationary CTs codified at Subpart KKKK impose NOx limits based only on the use of wet and dry combustor controls. The distinct BSER determinations for Subpart KKKK and Proposed Subpart KKKKa parallel the different approaches to subcategorizing affected sources under the two regulations – i.e., one final and one proposed. More stringent NOx standards are also proposed for modified CTs. Proposed Subpart KKKKa would maintain the current Subpart KKKK-imposed emission standards for sulfur dioxide (SO2), however, as EPA determined that the use of low-sulfur fuels remains BSER for SO2.
Distinct from the proposed substantive standards, the preamble to Proposed Subpart KKKKa provides some helpful information regarding how to determine whether a stationary CT is “reconstructed” thereby triggering NSPS applicability. Historically, this question has caused some consternation among CT owners and operators because it is often unclear what CT-related equipment comprises the “facility” for purposes of performing the “reconstruction” calculation. Every NSPS applicability analysis requires a comparison of the fixed capital cost of the proposed new equipment components to the fixed capital cost of a comparable entirely new “facility.” But while the comparison is relatively straightforward for most affected source categories, it can be difficult for CTs for which the scope of the “facility” definition – on its face at least – is materially different between the two NSPS regulations for CTs that are currently on the books, NSPS Subpart GG and Subpart KKKK. The new preamble language clarifies that if a source owner/operator intends to replace only the components of the CT engine, then the total fixed capital cost of such components should be compared to the fixed capital cost of only an entirely new CT engine – not the combined fixed capital cost of an entirely new CT engine and the ancillary equipment listed in the broader “facility” definition in existing Subpart KKKK, including notably but not limited to, equipment comprising the heat recovery steam generator.
Of course, we won’t know for some time whether Proposed Subpart KKKKa will be finalized by a Trump-led EPA, but with increasing electricity generation and distribution challenges largely driven by demand spikes from AI and large data centers, the new administration might not want to further burden CT facilities. Either way, the Proposed Subpart KKKKa preamble offers some guidance on how to perform the reconstruction analysis for CTs under Subpart KKKK that was previously lacking. If Proposed Subpart KKKKa is ultimately finalized, the same guidance will be similarly helpful.
