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Why the Proposed New Emission Factor For Flares Could Have Huge Impacts on Industry

Posted: September 12th, 2014

Author: All4 Staff 

U.S. EPA is proposing a substantial increase in the emission factor for nitrogen oxides (NOX) emitted from industrial flares.  The change, if finalized as currently written, could have far-reaching impacts in industrial sectors that rely on the use of industrial flares, including petroleum refineries, chemical plants, natural gas processing plants, oil or gas production sites, and offshore oil and gas rigs.

In May 2013, environmental groups filed a lawsuit against U.S. EPA for failure to perform compulsory duties pursuant to the Clean Air Act (CAA) to review, and, if necessary, revise the emission factors for volatile organic compounds (VOC) for flares, liquid storage tanks, and wastewater collection, treatment, and storage systems.  Section 130 of the CAA states that this review should be completed at least once every three (3) years.  As a result of the litigation, in early 2014, U.S. EPA entered into a consent decree stipulating that they were to review and, if necessary, propose new emissions factors for VOC for the aforementioned sources.

In August 2014, based largely on data collected during the 2011 Refinery Information Collection Request (ICR), the data referenced in the litigation, and other test data available to U.S. EPA, it was determined that the data was not adequate to allow for revisions to existing emissions estimation methods for tanks and wastewater treatment systems.  However, U.S. EPA decided to propose a new VOC emission factor for flares, as well as other emission factors for refinery operations and pollutants that were not specifically covered by the 2014 consent decree. 

Of particular note, U.S. EPA has proposed to update Section 13.5 of AP-42 (Compilation of Air Pollutant Emission Factors), emissions factors for industrial flares, to incorporate the following new and revised emissions factors.

Facilities that are most likely to be impacted by this proposed revision are those who operate industrial flares and have relied upon the current NOX emission factor for emissions reporting and/or permit compliance.  Please note, U.S. EPA has not proposed to adjust the flare emission factors of Chapter 2, which are specific to flares operated at Municipal Solid Waste Landfills.  As seen in the table above, the proposed NOX emission factor is approximately 43 times the existing factor!  Additionally, the data used to develop the new and revised emission factors reflects both steam-assisted and air-assisted flares; therefore the new factor applies to all types of flares.

Many flare owners and operators rely on emission factors from Chapter 13 of AP-42 for the purposes of calculating flare emissions because it is difficult and costly to perform emissions tests of an individual flare that is already in operation on-site. As stated in “Parameters for Properly Designed and Operated Flares” written by U.S. EPA Office of Air Quality Planning and Standards (OAQPS) in April 2012, “measuring emissions from a flare can be difficult and dangerous because flares lack an enclosed combustion chamber, may be elevated, and come in many different designs and sizes. With combustion taking place at and above the tip of the flare, the combusted gases are released into the atmosphere in any direction given the meteorological conditions and flare vent gas velocity that exist at that moment.”

Extractive test methods have been used, however, to measure flare emissions.  These techniques require placement of a hood-like structure, sampling rake with multiple sample ports, or another method to capture the flare plume.  Though these methods are technically feasible, testing industrial flares using extractive techniques is impractical and relegated to research studies, usually on much smaller flares.

Another testing method that has only become available recently due to technological advances, involves the use of remote sensing instruments to identify combustion products without the difficulties of physically extracting a sample of a flare plume.  These remote sensing techniques include: Active Fourier Transform Infrared (AFTIR) and Passive Fourier Transform Infrared (PFTIR).  The main difference between AFTIR and PFTIR is that AFTIR requires the remote sensor be aligned to an artificial light source; whereas PFTIR simply detects infrared radiation emitted as heat (i.e., PFTIR uses thermal imaging).  U.S. EPA notes that “AFTIR and PFTIR remote sensing offers an attractive alternative to characterize emissions from flares; AFTIR and PFTIR are relatively expensive, new tools that currently have no approved methods for universal use on flares.”  Furthermore, AFTIR and PFTIR do not capture and/or account for all chemical species that may be found in flare vent gas, and, as of 2012, the U.S. EPA Office of Air Quality Planning and Standards (OAQPS) are only aware of one company currently using the PFTIR test technique on flares. (Parameters for Properly Designed and Operated Flares, 2012)

In conclusion, this proposed action is expected to have far reaching impacts on industry.  and there is sure to be additional information released in the coming weeks.  According to the consent decree, U.S. EPA must finalize the revision to the emission factors by December 19, 2014.  The proposed emission factors could impact reported emissions as soon as 2015. Anyone wishing to comment on the proposed action is instructed by U.S. EPA to submit written comments by October 19, 2014.  Comments should be e-mailed to refineryfactor@epa.gov.


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