The EPA recently announced a proposed regulation to tighten limits on nitrogen oxide (NOx) emissions from most new, modified and converted fossil fuel stationary combustion turbines. If passed, the regulation will “ensure that new turbines built at power plants or industrial facilities – especially large ones that could operate for decades – are among the most efficient and lowest-emission turbines ever built.”
EPA believes this regulation will provide regulatory certainty to the industry.
“This proposal ensures that new turbines at power plants or industrial facilities minimize emissions of harmful, smog-forming nitrogen oxides,” Joseph Goffman, EPA assistant administrator for air and radiation, said in an agency news release. “These stricter standards are necessary to better protect the health of surrounding communities, and the energy sector has already shown that the additional pollution controls can accomplish this task cost-effectively and reliably.”
Exposure to NOx is associated with asthma and respiratory infections. It also reacts with other volatile organic compounds to form ground-level ozone (smog) and particulate matter.
EPA based the proposed New Source Performance Standards (NSPS) on the use of combustion controls and selective catalytic reduction (SCR). The EPA classifies the associated costs as “reasonable and widely used supplemental control technology that limits NOx emissions.”
Under the proposed regulation, EPA did not propose to increase sulfur dioxide limits.
The proposed stricter standards for NOx would apply to installations that start construction, conversion or modification after the publication of the proposed standards in the EU Federal Register.
“[The] “EPA estimates that this proposed rule would reduce NOx emissions by 198 tons in 2027 and by 2,659 tons in 2032,” the agency’s press release said. “The current value of the net benefit to society is estimated to be up to $340 million, equivalent to up to $46.4 million per year.”
Specific points in the proposed regulation include:
- It should be noted that combustion control with the addition of post-combustion SCR is the best emissions control system (BSER) for most combustion turbines;
- Lowering NOx performance standards for affected sources based on the application of the BSER; And
- Establishing more stringent NOx protection standards for affected new sources that burn or co-burn hydrogen to ensure that these units have the same level of control over NOx emissions as sources that burn natural gas or non-natural gas fuels.
EPA proposes size-based subcategories based on baseload heat input:
- Large Combustion Turbines – Plants with a base load thermal output of > 850 million British thermal units per hour (MMBtu/h) (> ~ 85 megawatts (MW))
- Medium combustion turbines – systems with a base load thermal output of > 250 MMBtu/h and ≤ 850 MMBtu/h (> ~ 25 MW and ≤ ~ 85 MW)
- Small combustion turbines – systems with a base load thermal output of ≤ 250 MMBtu/h (≤ ~ 25 MW)
“EPA proposes to further classify affected sources into subcategories based on whether they operate at high, medium, or low loads and whether they burn natural gas or non-natural gas fuels,” the agency's press release continued. “When classifying low-, medium-, or base-load units, EPA considers the 12-calendar-month capacity factor of these combustion turbines.”
- High load: capacity factor greater than 40% (i.e. base load)
- Medium load: capacity factor greater than 20% and less than or equal to 40%
- Low load: capacity factor less than or equal to 20%
For stationary combustion turbines that do not produce energy, the capacity factor would be determined based on monthly updated data for the last 12 calendar months.
“[The] “EPA also recognizes that at smaller sizes and at lower or more variable operating levels, the cost-effectiveness per ton and effectiveness of SCR technology become less favorable,” the agency statement continued. “Therefore, EPA proposes to establish standards for certain combustion turbines based on the use of non-SCR combustion controls. These include small combustion turbines operating at low and medium loads; medium combustion turbines operating at light loads; and large combustion turbines operating at low loads.”
For more information, see EPA's fact sheet on the proposed regulation and 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 can be accessed on the federal government's e-Rulemaking platform under Docket ID No. EPA-HQ-OAR-2024-0419 must be submitted.