Q478. Are the emissions factors provided in subpart W for equipment leaks for both leaking components and non-leaking components? How do you calculate emissions from leaking components if onshore production sources are not required to monitor components?

A478. There are two overarching methods for estimating emissions from equipment leaks for the onshore petroleum and natural gas production industry segment: the leak survey method described in in 40 CFR 98.233(q) and the population count method described in 40 CFR 98.233(r). If leak monitoring surveys are required nor voluntarily performed, equipment leak emissions are to be estimated using the population count method provided in 98.233(r). 

For RY 2024 and prior year reporting, Table W-1A provides population emission factors, which represent the average emissions from the entire population of components – both leaking and non-leaking – by the type of component; please see section 6(d) of the Technical Support Document (https://www.epa.gov/sites/production/files/2015-05/documents/subpart-w_tsd.pdf) for further details on the concept of population emission factors.

For RY 2025 and later year reporting, Tables W-1 provides population emission factors, which represent the average emissions from the entire population of components – both leaking and non-leaking – by the type of major equipment; please see section 10 of the Technical Support Document (https://www.regulations.gov/document/EPA-HQ-OAR-2023-0234-0453) for further details on the basis of the current population emission factors.

If leak surveys are conducted according to the provision in 40 CFR 98.233(q), emissions are estimated using the number of leaking components identified times the appropriate “leaker emissions factor.” For RY 2024 and prior year reporting, Table W-1E provides leaker emissions factors. For RY 2025 and later year reporting, Table W-2 provides leaker emission factors; please see section the Technical Support Document (https://www.regulations.gov/document/EPA-HQ-OAR-2023-0234-0453) for further details on the basis of the current leaker emission factors.