Legal & Regulatory

EPA Denies Industry Petition to Delist Stationary Combustion Turbines as Hazardous Pollutants

The U.S. Environmental Protection Agency (EPA) has denied an industry petition seeking to delist stationary combustion turbines from the agency’s list of hazardous air pollutants (HAP) major source categories regulated under section 112 of the Clean Air Act (CAA).

The agency’s final action on April 11 responds to an August 2019 petition filed by several trade groups that urged the agency to remove the Stationary Combustion Turbines source category from its list of HAP major sources. Groups that filed the petition include the American Fuel & Petrochemical Manufacturers, the American Petroleum Institute, the American Public Power Association, the Gas Turbine Association, the Interstate Natural Gas Association of America, and the National Rural Electric Cooperative Association.

The EPA’s denial of the petition will mean no changes—for now—to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Stationary Combustion Turbines (40 CFR part 63, subpart YYYY). According to agency estimates, the source category includes about 1,015 stationary combustion turbines at 310 facilities, mostly at power plants, compressor stations, and chemical plants.

However, as POWER reported in March, the EPA could include a proposed revision to the rule as part of a more “comprehensive approach” to regulate “climate, toxic, and criteria air pollution” from “the entire fleet of natural gas-fired turbines.” The approach, announced on Feb. 29, stems from the agency’s recent move to drop requirements covering existing natural gas-fired power plants in its final Section 111 rule regulating power sector greenhouse gas (GHG) emissions, which is expected in the coming weeks.

A Significant Denial

The 2004-promulgated NESHAP for Stationary Combustion Turbines stems from the EPA’s 1992 action to establish a list of HAP source categories. Subpart YYYY applies to stationary combustion turbines at major sources of HAP and includes turbines that are generally operated using natural gas, distillate oil, landfill gas, jet fuel, or process gas.

As the EPA explains, “Emissions of HAP in the exhaust gases of turbines are the result of combustion of the gaseous and liquid fuels.” HAP present in these exhaust gases include formaldehyde, toluene, benzene, acetaldehyde, and metallic HAP ( for example, cadmium, chromium, manganese, lead, and nickel). “These pollutants are known to cause—or are suspected to cause—cancer or other serious adverse health and environmental effects. Formaldehyde and acetaldehyde are probable human carcinogens,” it notes.

Currently, the EPA’s Stationary Combustion source category includes eight subcategories: lean premix gas-fired turbines; lean premix oil-fired turbines; diffusion flame gas-fired turbines; diffusion flame oil-fired turbines, turbines that burn landfill or digester gas or gasified municipal solid waste; turbines of less than 1 MW rated peak power output; emergency turbines, and turbines operated on the North Slope of Alaska.

During the agency’s 2004 rulemaking, in response to industry petitions, the EPA proposed to delist the lean premix gas-fired turbines, diffusion flame gas-fired turbines, emergency turbines, and turbines located on the North Slope of Alaska categories. At the same time, it moved to stay the effectiveness of the NESHAP for new lean premix gas-fired and diffusion flame gas-fired turbines. But while the EPA ultimately acted to finalize the stay on NESHAP for new lean premix-gas fired and diffusion-flame turbines, it never finalized its proposal to delist the four subcategories given a 2007 D.C. Circuit court decision. In 2022, meanwhile, the EPA removed the 2004-promulgated stay for new lean premix and diffusion flame gas-fired turbines that were promulgated in 2004.

In August 2019, several trade groups asked the EPA to remove the Stationary Combustion Turbines source category from the list of major source categories regulated under Section 112. The groups pointed to a risk and technology (RTR) that the EPA proposed in April 2019 (and ultimately finalized in March 2020), whose results indicated that the maximum lifetime individual cancer risk is 3-in-1 million. Under Section 112, the EPA has the authority to delist source categories if the EPA finds that the cancer risk from HAP emissions from all stationary combustion turbines is less than the 1-in-1 million delisting threshold, they noted. 

While petitioners submitted revised versions to correct estimates, they essentially argued that delisting of the Stationary Combustion Turbines source category was warranted because their analyses showed that all the evaluated risks—including lifetime cancer risk, acute and chronic inhalation hazards, and multi-pathway risks for the most exposed individuals—were below acceptable thresholds. These analyses indicated compliance with statutory criteria for delisting, including showing risks significantly below the 1-in-1 million threshold for lifetime cancer risk, they argued.

However, on Monday, the EPA denied the petition because it deemed the petition incomplete. “We have found that the submitted information is inadequate to determine that no source in the category emits HAP in quantities that may cause a lifetime risk of cancer greater than 1-in-1 million to the individual in the population who is most exposed to emissions of such pollutants from the source,” it said. “We have reached this decision based on review of the risk analysis and other information submitted by petitioners and on consideration of turbine testing results received from a CAA information request.”

EPA Working on Future Proposals to Regulate Emissions From Gas Turbines

For now, denial of the petition “will ensure that stationary combustion turbines subject to the NESHAP will continue to be regulated, protecting human health and the environment,” the EPA confirmed on Monday.

However, as POWER reported in March, the EPA is considering a proposed revision to the NESHAP for Stationary Combustion Turbines to include new and existing sources (40 CFR part 63 subpart YYYY). It also plans to issue its 8-year Review of the Criteria Pollutant New Source Performance Standards for Stationary Combustion Turbines (40 CFR part 60 subpart KKKK), alongside a rule that will address Section 111(d), which will cover the GHG portion.

Ultimately, the three proposals will be part of a “suite of rulemakings” that will fully address GHG emissions, air toxics, and emissions of nitrogen oxides from power sector gas turbines. The “comprehensive approach” stems from a Feb. 29 announcement by EPA Administrator Michael Regan that seeks to keep the forthcoming final Section 111 rule tightly focused on existing coal and new gas-fired power plants.

The EPA’s May 2023 proposed emission guidelines, which included stringent requirements for existing gas turbines, were fiercely contested by industry. Among contentions voiced by industry were that the proposed rules would have required sources to eventually meet an emission standard based on either the use of carbon capture and sequestration (CCS) or co-firing with low-GHG hydrogen. Industry also especially railed against the EPA’s “unrealistic” timeframe, which proposed a compliance deadline of Jan. 1, 2035, for sources meeting a CCS-based standard and Jan. 1, 2032, for sources to meet a 30% hydrogen co-firing deadline (and 96% by 20238).

While the EPA has not confirmed a timeline for its new approach, on March 26, it opened a non-regulatory docket (EPA-HQ-OAR-2024-0135) to collect input from the public and stakeholders. The non-regulatory docket will be open for public comment for 60 days – through May 28, 2024. 

The EPA has so far justified the approach by suggesting GHG emissions from gas-fired combustion turbines will need to be addressed. “Fossil-fired steam-electric EGUs are currently the largest source of GHG emissions among fossil fuel-fired EGUs. In 2021, coal-fired EGUs emitted 909 MMT CO2e. But GHG emissions from these predominantly coal-fired EGUs have been decreasing and are projected to continue to do so,” it notes in a document attached to the docket

“In contrast, GHG emissions from natural gas-fired combustion turbines were 613 MMT CO2e in 2021 and are projected to continue to increase, at least into the 2030s. Most analysis suggests that sometime in the later 2020s, GHG emissions from natural gas-fired EGUs will surpass those from coal-fired EGUs,” it says. “For these reasons, EPA believes it is essential to move forward expeditiously to develop emission guidelines that encompass all existing natural gas-fired combustion turbines.”

The document urges industry and other stakeholders to share their views on seven “key framing” questions. The EPA, for example, is seeking feedback on various technologies as part of the Best System of Emission Reduction (BSER) for reducing GHG emissions from existing combustion turbines, including through CCS, hydrogen co-firing, battery integration, and efficiency improvements.

The questions also seek more input on the incorporation of market mechanisms, such as mass-based trading. Additionally, the EPA is exploring ways to subcategorize the diverse existing combustion turbine fleet, provide compliance flexibilities, and address concerns such as reliability, environmental impacts, and new infrastructure for hydrogen and carbon dioxide. It also seeks input on workforce changes, while concurrently updating related emissions guidelines and standards.

Finally, the agency asks about potential interactions between the three separate rulemakings. “Along with developing proposed emission guidelines for existing stationary combustion turbine [electric generating units], the EPA is also, on a similar timeline, developing proposals to review the criteria pollutant NSPS (40 CFR 60 KKKK) for stationary combustion turbines and to review and update the NESHAP (40 CRF 63 YYYY) for stationary combustion turbines. Are there interactions between these three rulemakings that the EPA should be aware of and take into consideration?” it asks.

Sonal Patel is a POWER senior editor (@sonalcpatel@POWERmagazine).

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