Q505. How does a natural gas compressor station that operates compressors for natural gas transmission and an emergency generator determine subpart applicability?

A505. Based on the question, we assume the facility is potentially included in only the stationary fuel combustion source category and the petroleum and natural gas systems source category. For the purpose of determining the applicability of 40 CFR part 98, the facility should calculate the emissions from fuel combustion in the engines or other compressor drivers (and any other stationary fuel combustion units) according to the procedures in subpart C, and calculate the emissions from all source types listed in 40 CFR 98.232(e) according to the methodologies specified in 40 CFR 98.233, as applicable. As stated in 40 CFR 98.30(b)(2), emergency generators are not part of the stationary fuel combustion source category, provided the definition of emergency generator in 40 CFR 98.6 is met. Thus, emissions from emergency generators do not need to be calculated or considered in determining applicability.

 Pursuant to 40 CFR 98.2, if a facility’s calculated total annual emissions are less than 25,000 metric tons of CO₂e and the facility does not contain any other source categories listed in either Table A-3 or Table A-4 of 40 CFR part 98, subpart A, then the facility does not have to report under 40 CFR part 98 as a direct emitter. If the facility’s emissions exceed the 25,000 metric tons of CO₂e threshold, then the facility should follow the reporting requirements in each applicable subpart of 40 CFR part 98. Once a facility begins reporting under 40 CFR part 98, the owner or operator must continue reporting for each year thereafter unless and until the facility meets the provisions of 40 CFR 98.2(i). 

Information and resources regarding the applicability and requirements of the aforementioned subpart are available at: https://www.epa.gov/ghgreporting/subpart-w-petroleum-and-natural-gas-systems.