On February 5, 2018, the EPA finalized its review of the existing VOC emissions factor for flares at natural gas production sites.
EPA evaluated test data available for flares at natural gas production sites, data from testing conducted by manufacturers under 40 CFR part 60, subparts OOOO and OOOOa and 40 CFR part 63, subpart HH and HHH, and information submitted during the public comment period. The available flare data pertained to THC emissions and did not provide sufficient information for estimating VOC emissions from the tested flares. Therefore, EPA's review did not result in a revision to this VOC emissions factor.
While EPA did not revise the existing VOC emissions factor, They did use the available THC emissions data for enclosed ground flares to develop six new THC emissions factors for enclosed ground flares. The six emissions factors are finalized as an update to Section 13.5 of AP-42, Compilation of Air Pollutant Emission Factors. AP-42 is the primary compilation of EPA's emissions factor information. They also clarified the heating value basis for the emissions factors in AP-42 Tables 13.5-1 through 13.5-3 and clarified that the emissions factors in the tables represent the emissions at the exit of a flare, not the uncontrolled VOC or THC emissions routed to the flare.