Updated: Sep 14
Lower emission limits could be coming soon to local coal-fired plants thanks to an Ozone Transport Commission (OTC) recommendation that the Environmental Protection Agency require daily limits on oxides of nitrogen on electricity generating units in Pennsylvania.
The recommendation applies to coal-fired plants equipped with selective or non-selective catalytic reduction units (known as SCR and NSCR, respectively). For those who are unfamiliar: SCR and NSCR units control NOx emissions.
The new recommended daily NOx limits would be at least as stringent as those in place at coal-fired EGUs in Delaware, Maryland, and New Jersey, and would theoretically force those here in the Keystone State to operate their NOx emissions control units at all times during the summer ozone season.
For those who may be unfamiliar: Ozone is not emitted directly by power plants. Rather, ozone can form when power plants’ NOx emissions are exposed to sunlight, especially during summer. Often, ozone in one location results from NOx that is emitted by distant, downwind sources in other states. In the northeastern United States, the summer ozone season runs from the beginning of May through the end of September.
Who serves on the Ozone Transport Commission and why was the recommendation made? The OTC consists of representatives of the various federal and state agencies that are responsible for regulating air pollution in the Ozone Transport Region (otherwise known as OTR) created by the 1990 amendments to the federal Clean Air Act.
The commission is empowered to recommend additional air pollution controls to the EPA that it deems necessary to bring all areas of the Ozone Transport Region into attainment of the National Ambient Air Quality Standards (NAAQS) for ozone.
By way of background: The Ozone Transport Region includes northern Virginia, the District of Columbia, and the states of Maryland, Delaware, Pennsylvania, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, Vermont, New Hampshire, and Maine.
The Ozone Transport Region was created in recognition of a simple fact: Pollution emitted in one state in the region can make attainment of the ozone NAAQS more difficult for its downwind neighbors.
Within the Ozone Transport Region, sources of air pollution that lead to the formation of ozone are generally subject to stricter regulation than they might otherwise be under the Clean Air Act.
“It’s unclear exactly what the Ozone Transport Commission’s recommendation would mean if accepted by the EPA,” GASP senior staff attorney John Baillie explained.
That’s because regulations limiting NOx emissions from coal-fired electricity generating units in Delaware, Maryland, and New Jersey differ from state-to-state – and in Maryland, even from plant to plant within the state):
Delaware – 0.125 lb/MMBtu
Maryland – 0.07 lb/MMBtu – 0.33 lb/MMBtu
New Jersey – 1.50 lb/megawatt hour (approximately 0.44 lb/MMBtu)
It bears mention that in addition to its hourly emission limits, Maryland also requires coal-fired electricity generating units to operate all installed pollution controls during the summer ozone season.
The limits on NOx emissions that are already incorporated into the Title V Operating Permits for the five coal-fired electricity generating units currently operating in southwestern Pennsylvania are, in some instances, significantly higher than those in place in Maryland and Delaware, but are – at their highest – only slightly higher than the requirement in place in New Jersey:
Cheswick Station (Allegheny County) – 0.12 lb/MMBtu (if SCR inlet temperature ≥ 600° F) – 0.35 lb/MMBtu (if SCR inlet temperature ≤ 600° F)
Keystone Conemaugh Station (Armstrong County) – 0.45 lb/MMBtu
Conemaugh Plant (Indiana County) – 0.45 lb/MMBtu
Homer City Station (Indiana County) – 0.50 lb/MMBtu
Seward Station (Indiana County) – 0.15 lb/MMBtu
“That means that if it’s granted, the commission’s recommendation could lead to substantially-reduced hourly limits on NOx emissions from the coal-fired electricity generating units in our region,” Baillie said. “Or perhaps not if the EPA only requires that Pennsylvania units meet New Jersey’s standard.”
For those who would like to learn more, mark your calendars: The EPA will hold a virtual public hearing on the Ozone Transport Commission’s recommendation on or before Sept. 4. More information about that hearing will be published here.