NOx · Nitrogen oxides
The combustion pollutant that sets the air-permitting envelope for on-site generation; the cheapest NOx is the NOx never combusted, the next cheapest is abated by design.
Current numbers
~5 ppm -> sub-2 ppmNOx from a high-utilization natural-gas turbine with combustion controls + SCR (NSPS bar); 2026 SCR platforms market sub-2 ppm