Q517. Do I have to calculate emissions from operational LNG storage tank venting at LNG storage facilities or LNG import or export terminals? Also, the list of equipment to be surveyed for leaks does not include pressure relief valves in LNG service. Am I required to survey and report emissions from pressure relief valves?

A517. Regarding the first question: 40 CFR 98.232(g) and 40 CFR 98.232(h) do not include venting from LNG storage tanks as an emission source; therefore, venting emissions from LNG storage tanks are not required for LNG storage facilities or for LNG import and export equipment. However, if the LNG storage tank is blown down to atmosphere, then sections 40 CFR 98.232(g)(9) and 40 CFR 98.232(h)(3) do require reporting.

To answer the second question about pressure relief valves, we first note that pressure relief valves will typically be in gas service. For RY 2017 and later, if the reporter is required or elects to conduct a leak survey of LNG storage components (or LNG terminal components) in gas service, then there is a specific leaker emission factor for pressure relief valves and emissions from leaking pressure relief valves must be reported. For RY 2017 to RY 2024 reporting, the leaker emission factor for pressure relief valves in gas service is in Tables W-5A and W-6A. For RY 2025 and later year reporting, the leaker emission factor for pressure relief valves is in Table W-6.

For pressure relief valves in LNG service per 40 CFR 98.232(g)(4), 40 CFR 98.233(h)(5) and 40 CFR 98.233(q)(2)(viii-ix), the appropriate default methane  emission factors for “…equipment leaks detected from valves, pump seals, connectors, and other” shall be used from the appropriate tables in the rule. For RY 2024 and earlier reporting, the leaker emission factor for other components in LNG service is in Tables W-5A and W-6A. For RY 2025 and later reporting, the leaker emission factor for other components in LNG service is in Table W-6. A pressure relief valve is a special type of valve and falls in the category of "other," so this emission source is included in the leak detection survey and required to be reported.