Q593. Emissions from flares are specifically excluded under 98.232(e) but methods for these emissions are provided in 98.233. Can you clarify which section of the rule is the correct guiding action?

Q593. Under 40 CFR 98.232, several industry segments have flare stack emissions identified as a specific source type from which GHG emissions are to be reported. However, there are other emission source types throughout Subpart W (e.g., transmission tanks and associated gas source types) for which flared emissions also must be reported. Please provide clarification and identify the section(s) of the rule which give the correct guiding action for reporting flare emissions.

A593. Under 40 CFR 98.232 of both the rule as amended on May 14, 2024, and the rule as it existed prior to the amendments, flare stacks is a distinct emission source type subject to reporting for the following industry segments:

• onshore petroleum and natural gas production;
• onshore natural gas processing;
• onshore natural gas transmission compression;
• underground natural gas storage;
• liquefied natural gas (LNG) storage;
• LNG import and export equipment; and
• onshore petroleum and natural gas gathering and boosting. 

For reporting years up to and including Reporting Year (RY) 2024, the procedures  for calculating total emissions from each flare at facilities in these industry segments are specified in 40 CFR 98.233(n). In addition, the procedures in 40 CFR 98.233 for calculating flared emissions from several other emission source types cross-reference the procedures in 40 CFR 98.233(n). The source types for which flared emissions must be reported include dehydrators (40 CFR 98.233(e)), completions and workovers (40 CFR 98.233(g) and (h)), atmospheric storage tanks (40 CFR 98.233(j)), transmission storage tanks (40 CFR 98.233(k)), well testing (40 CFR 98.233(l)), and associated gas (40 CFR 98.233(m)). Note that some of the industry segments listed above do not report emissions from any of these emission source types and thus report all flared emissions under the flare stacks emission source type.

According to 40 CFR 98.233(n)(9) in the rule that applies until December 31, 2024 (i.e., for RYs up to and including RY 2024), the total calculated mass emissions from a flare must be corrected (i.e., adjusted downward) based on the amount of flared emissions calculated and reported for other emission source types. For example, if the gas sent to a flare is from atmospheric tanks and compressors, then the emissions from combustion of the gas from the atmospheric tanks would be reported as atmospheric tanks emissions (in accordance with 98.236(j)(1)(xiv) and (2)(iii)), and emissions from combustion of the gas from compressors would be reported as flare stacks emissions (in accordance with 40 CFR 98.236(n)). If the total volume of gas sent to a flare is from one or more of the emission source types for which flared emissions must be reported separate from flare stacks emissions, then the mass emissions to report for the flare stacks source type in accordance with 40 CFR 98.236(n)(9) through (11) would be zero metric tons. However, for each flare, all of the flare activity data (i.e., the data elements in 40 CFR 98.236(n)(1) through (8) must still be reported regardless of the quantity of mass emissions reported in accordance with 40 CFR 98.236(n)(9) through (11).

Beginning with RY 2025, reporters must calculate total emissions from each flare using the procedures in amended 40 CFR 98.233(n). Typically, the procedures for calculating flow and composition of gas routed to flares are the same as the procedures specified for individual source types in the rule for prior reporting years. For RY 2025 and subsequent years, reporters must report total emissions from each flare as specified in 40 CFR 98.236(n), and they must disaggregate the total emissions to the source type(s) that routed gas to the flare. The source types are the same as those for which source-specific flared emissions must be report for years prior to RY 2025, except that acid gas removal units are included for RY 2025.  The disaggregation must be based on source-specific data when the total emissions from the flare are calculated using stream-specific data; otherwise, disaggregate the emissions using engineering calculations and best available data.