The EPA recently announced a proposed regulation to strengthen limits on emissions of nitrogen oxides (NOx) from most new, modified, and reconstructed fossil fuel-fired stationary combustion turbines. The regulation, if finalized, will “ensure that new turbines built at power plants or industrial facilities — especially large ones that could operate for decades — would be among the most efficient and lowest-emitting turbines ever built.”

 

The EPA suggests that this regulation will provide regulatory certainty for industry.

“This proposal ensures that new turbines at power plants or industrial facilities will minimize emissions of harmful, smog-forming nitrogen oxides,” said EPA Assistant Administrator for Air and Radiation Joseph Goffman in an Agency news release. “These stronger standards are necessary to better protect nearby communities’ health, and the power sector has already shown that the additional pollution controls can affordably and reliably do the job.”

Exposure to NOx has been linked to asthma and respiratory infections. It also reacts with other volatile organic compounds to form ground-level ozone (smog) and fine particulate matter.

The EPA based the proposed New Source Performance Standards (NSPS) on the application of combustion controls and selective catalytic reduction (SCR). The EPA classifies the associated costs as “reasonable and widely used add-on control technology that limits emissions of NOx.”

Under the proposed regulation, the EPA didn’t suggest raising the limits for sulfur dioxide.

The proposed stronger standards for NOx would apply to facilities that begin construction, reconstruction, or modification after the proposed standards’ publication in the Federal Register.

“[The] EPA estimates this proposed rule would reduce NOx emissions by 198 tons in 2027 and 2,659 tons in 2032,”according to the Agency news release. “The present value of net benefits to society is estimated at up to $340 million, with an equivalent value of up to $46.4 million per year.”

Specific items in the proposed regulation include:

• To determine that combustion controls with the addition of post-combustion SCR is the best system of emissions reduction (BSER) for most combustion turbines;
• To lower the NOx standards of performance for affected sources based on the application of the BSER; and
• To establish more protective NOx standards for affected new sources that plan to fire or co-fire hydrogen, ensuring these units have the same level of control for NOx emissions as sources firing natural gas or non-natural gas fuels.

The EPA is proposing size-based subcategories based on baseload heat input:

• Large combustion turbines—facilities with a baseload heat input rating of > 850 million British thermal units per hour (MMBtu/h) (> ~ 85 megawatts (MW))
• Medium combustion turbines—facilities with a baseload heat input rating of > 250 MMBtu/h and = 850 MMBtu/h (> ~ 25 MW and = ~ 85 MW)
• Small combustion turbines—facilities with a baseload heat input rating of = 250 MMBtu/h (= ~ 25 MW)

“The EPA is proposing to further subcategorize affected sources based on whether they operate at high, intermediate, or low loads and whether they burn natural gas or non-natural gas fuels,” the Agency news release continues. “When classifying low, intermediate, or base load units, EPA will consider the 12-calendar-month capacity factor of these combustion turbines.”

• High load: capacity factor greater than 40% (i.e., baseload)
• Intermediate load: capacity factor greater than 20% and less than or equal to 40%
• Low load: capacity factor of less than or equal to 20%

For stationary combustion turbines that aren’t energy-generating, the capacity factor would be determined based on the prior 12 calendar months of data on a rolling basis updated each month.

“[The] EPA also recognizes that at smaller sizes and at lower or more variable operating levels the cost-reasonableness on a per-ton basis and efficacy of SCR technology becomes less favorable,” the Agency’s release adds. “Thus, EPA proposes to establish standards for certain combustion turbines based on the use of combustion controls without SCR. This includes small combustion turbines that operate at low and intermediate loads; medium combustion turbines that operate at low loads; and large combustion turbines that operate at low loads.”

For more information, see the EPA’s Fact Sheet on the proposed regulation and the EPA Stationary Gas and Combustion Turbines: New Source Performance Standards (NSPS).

Comments on the proposed rule will be accepted for 90 days after publication in the Federal Register and may be submitted on the federal e-Rulemaking platform under Docket ID No. EPA-HQ-OAR-2024-0419.