Air Emissions Factors and Quantification

New Emissions Factors for Enclosed Ground Flares

Background

On February 5, 2018, EPA completed its review of the emissions factor for volatile organic compounds (VOC) for flares at natural gas production sites pursuant to section 130 of the Clean Air Act.

EPA evaluated test data available to the Agency for elevated and enclosed ground flares from natural gas production sites. The agency’s review of available flare data did not result in a revision to this VOC factor, which remains available for estimating VOC emissions from elevated flares at natural gas production sites.

EPA has developed two new THC emissions factors for enclosed ground flares at natural gas production sites. The EPA recommends the use of the new THC emissions factors to estimate VOC emissions for enclosed ground flares with the SCCs specified in Table 1, as this new emissions factor is based on field data from similar units. Additionally, EPA has developed four new THC emissions factors for enclosed ground flares at certain chemical manufacturing processes.

Additional information about the review of the factor is below.

Final Emissions Factors

The final emissions factors are presented in Table 1. A description of the relevant source classification codes (SCCs) that describe the processes covered by these emissions factors is presented in Table 2.

Table 1. Final Emissions Factors
Emissions Source	SCC	Pollutant	Emissions Factor	Representativeness
Enclosed Ground Flares at Natural Gas Production Sites	31000205 31000212 31000227	THC	332 lb THC/MMscf gas burned or 0.335 lb THC/MMBtu heat input	Poorly
Enclosed Ground Flares for Certain Chemical Manufacturing Processes (low percent load)	30119701 30119705 30119709 30119741 30190099	THC	8.37 lb THC/MMscf gas burned or 3.88e-3 lb THC/MMBtu heat input	Moderately
Enclosed Ground Flares for Certain Chemical Manufacturing Processes (normal to high percent load)	30119701 30119705 30119709 30119741 30190099	THC	2.56 lb THC/MMscf gas burned or 1.20e-3 lb THC/MMBtu heat input	Moderately

Table 2. SCC Descriptions
SCC	Level 1 Description	Level 2 Description	Level 3 Description	Level 4 Description
31000205	Industrial Processes	Oil and Gas Production	Natural Gas Production	Flares
31000212	Industrial Processes	Oil and Gas Production	Natural Gas Production	Condensate Storage Tank
31000227	Industrial Processes	Oil and Gas Production	Natural Gas Production	Glycol Dehydrator Reboiler Still Stack
30119701	Industrial Processes	Chemical Manufacturing	Butylene, Ethylene, Propylene, Olefin Production	Ethylene: General
30119705	Industrial Processes	Chemical Manufacturing	Butylene, Ethylene, Propylene, Olefin Production	Propylene: General
30119709	Industrial Processes	Chemical Manufacturing	Butylene, Ethylene, Propylene, Olefin Production	Propylene: Fugitive Emissions
30119741	Industrial Processes	Chemical Manufacturing	Butylene, Ethylene, Propylene, Olefin Production	Ethylene: Flue Gas Vent
30190099	Industrial Processes	Chemical Manufacturing	Butylene, Ethylene, Propylene, Olefin Production	Other Not Classified

Additional Documents

Review and Analysis of Emissions Test Reports for Purposes of Reviewing the Natural Gas Production Flares Volatile Organic Compounds Emissions Factor Under Clean Air Act Section 130 - February 2018 (PDF 43 pp, 622K).

We have finalized AP-42 Section 13.5 to incorporate the new factors. Section 13.5 can be accessed at the following link:

AP-42 Chapter 13: Miscellaneous Sources Section 13.5 Industrial Flares

Fact Sheet Summarizing the February 5, 2018 Action (PDF 2 pp, 365K)

Response to Comments

EPA received three comments on its June 2017 proposal. Below is a link to the comments received and the agency’s responses:

Comments as of August 21, 2017 (PDF 12 pp, 1,327K)

Response to Comments Document (PDF 84K)