Proposed EPA Greenhouse Gas Reporting Rules

On June 21, 2022, the U.S. Environmental Protection Agency (EPA) published proposed changes for the rules in 40 CFR 98 – Mandatory Greenhouse Gas Reporting. This rule requires facilities that emit 25,000 metric tons or more of greenhouse gases (GHG) to annually report their GHG emissions. EPA is proposing that the revisions become effective on January 1, 2023. Reporters would carry out the changes for the 2023 reporting year (submitted April 1, 2024).

See link for documents related to the proposed changes: 40 CFR 98 Proposed Rule Changes

This blog discusses proposed changes that affect the oil and gas (O&G) industry.

Rule Commenting

Comments on the proposal are due October 6, 2022. Submit online comments, identified by Docket Id. No. EPA–HQ–OAR–2019–0424 to the Federal eRulemaking Portal: (preferred method). Follow the online instructions for submitting comments.


General Affected Areas

The proposed rules clarify wording used and affect:

  • Revised confidentiality determinations
  • Revised/new calculation (emission factors, equations) and monitoring methods
  • New parameters requiring data collection and reporting
  • New emission sources for specific reporting sectors


Affected Subparts

Subparts affected by the proposal that are O&G industry related include:

  • A (General Provisions)
  • C (Stationary Fuel Combustion Sources)
  • W (Petroleum and Natural Gas Systems)
  • Y (Petroleum Refineries)
  • OO (Suppliers of Industrial Greenhouse Gases)
  • PP (Suppliers of Carbon Dioxide)


Global Warming Potentials (GWP)

The proposal does not change global warming potentials currently used in 40 CFR 98.

Methane Slip and Subparts C and W

The proposed changes to subpart W discuss methane (CH4) slip from natural gas compressor engine drivers. CH4 slip (also called combustion slip) is unburned CH4 entrained in the exhaust of natural gas compressor engines. Existing factors used in subpart W (and subpart C) reporting for compressor engines do not account for CH4 slip. Accounting for CH4 slip increases the amount of reported CH4 from the combustion of natural gas by compressor engines. Studies cited by the proposal indicate that the type of engine (not the sector it operates in) increases CH4 slip. Lean-burn (2-stroke and 4-stroke) engines are expected to have higher CH4 slip than rich-burn engines (4-stroke).

To address CH4 slip, EPA is proposing changes to the emission factors (Subpart C and W) required for natural gas compressor engine drivers located at facilities reporting under Subpart W. These are included in the new Table W-9.


Table W-9 to Subpart W of Part 98—Default Methane Emission Factors for Natural Gas Fired Compressor-Drivers

Compressor-Driver Engine Design Class Emission factor (kg CH4/mmBtu)
2-stroke lean-burn 0.658
4-stroke lean-burn 0.522
4-stroke rich-burn 0.045


The current emission factor in Subpart C for natural gas combustion is 0.001 kg CH4/mmBTU. This factor will be used for O&G natural gas fueled engines that are not compressor drivers.

Other Large Release Events – Subpart W

“Other large release events” is a new source type proposed all oil and gas industry segments (onshore and offshore) required to report under Subpart W reporting. This new source type covers events such as:

  • Gas storage wellhead leaks (the proposal references the Aliso Canyon gas storage release)
  • Well releases and blowouts
  • Large pressure relief venting
  • Other large, atypical release events

Reporting for this source type is required for release events that emits GHGs greater than 250 metric tons CO2e per event. This includes venting and flaring natural gas releases. Approximately 522,000 standard cubic feet of methane equals 250 metric tons CO2e.

Reporters would calculate GHG emissions using measurement data or engineering estimates of the volume and composition of gas released.

Glycol Dehydration Units

The proposal adds a glycol flash tank separator to the definition of included emissions for dehydration units. The proposal specifically states that emissions from still column vents and glycol flash tank separators must be calculated and reported.

This is a good reason to use Cimarron’s BTEX Eliminator is to control (combust) the methane emitted by glycol dehydration unit still column vents and glycol flash tank separators.

In the definition of a vapor recovery system, in regards to calculating glycol dehydration units emissions, routing emissions from a dehydrator regenerator still vent or flash tank separator vent to a regenerator fire-box/fire tubes does not meet the definition of vapor recovery system

Acid gas removal units

LNG import and export facilities will be required to report emissions from acid gas removal units under Subpart W. The current rule does not require reporting for acid gas removal units.

Storage Tank Emissions

The proposal specifically states that facilities using emission controls (e.g., flare and vapor recovery system) account for gas not routed to flares or not routed to the vapor recovery unit (VRU). Causes of this can be when the flare is not lit, when the VRU is not operating and emissions due to open or unseated thief hatches. Reporting requires accounting for unrecovered, uncontrolled emissions as vented directly to the atmosphere.

Natural gas pneumatic devices – Gas Processing

Onshore natural gas processing facilities will be required to report emissions from natural gas pneumatic devices under Subpart W. The current rule does not require reporting natural gas pneumatic devices for gas processing facilities.

Intermittent Bleed Natural Gas Pneumatic Devices Leak Surveys

The proposal anticipates the final regulations proposed for NSPS OOOOb and EG OOOOc (no rule language publicly available at this time). The NSPS OOOOb/EG OOOOc rules are expected to require a transition to zero emissions for all pneumatic devices. Also, NSPS OOOOb/EG OOOOc may require periodic leak surveys of intermittent bleed natural gas pneumatic devices. The basis for this requirement is that a properly functioning device would have short, small releases during device actuation. For intermittent bleed pneumatic devices, operators can identify malfunctioning (leaking gas) devices using routine monitoring with optical gas imaging (OGI) or other technologies.

Facilities required to conduct LDAR surveys under NSPS OOOOb (new sources) or EG OOOOc (existing sources) would use LDAR survey data to calculate GHG emissions. Intermittent bleed pneumatic devices found to be leaking would use the “malfunctioning intermittent bleed emission factor” to calculate emissions.

Continuous low bleed devices, continuous high bleed devices and intermittent bleed devices that are not monitored would use the appropriate whole gas population emission factors in Tables W-1A, W-2B, W-3B and W-4B.

Pneumatic Devices and Pumps Operating Hours

The proposed rule would require calculations to use the hours that pneumatic devices and pumps are “in service.” In service means that the device supplied with natural gas. In the current Subpart W rule, the term “operational” is used, which was typically understood to mean hours actually operating (e.g., pneumatic device actuating).

Equipment Leaks and Leak Detection and Repair (LDAR)

For equipment leaks (fugitive emission), the proposed rules clarify existing LDAR requirements and the use of voluntary LDAR monitoring. The rules reference the use of leak detection and repair (LDAR) monitoring data as required by the proposed NSPS OOOOb/EG OOOOc.

The proposal uses the term “Leaker Measurement Methodology” for calculating equipment leaks based on a LDAR program.

There were no significant changes proposed for use of the equipment leaks by population count methods.


Summary and Conclusions

The USEPA proposed changes to the GHG reporting rules in 40 CFR 98 in June 2022. The target data for the revisions to become effective is January 1, 2023. Reporters would implement the changes for the 2023 reporting year that would be submitted April 1, 2024.

A summary of some of the changes include the following.

  1. Many changes to terminology and clarifications of the current rule’s language used.
  2. Adds “other large release events” as a new source type proposed for all oil and gas industry segments (onshore and offshore) required to report under Subpart W reporting. This new source type covers events such as: gas storage wellhead leaks, well blowouts, other large pressure relief venting and large, atypical release events that emit more than 250 metric tons CO2e (approximately 522 MSCF/event).
  3. Changes emission factors for natural gas compressor engine drivers based on expectation of methane slip (uncombusted methane) in the exhaust. New, much higher emission factors would be required for these compressor engine drivers.
  4. For glycol dehydration units, the proposal adds a glycol flash tank separator as an emission source for dehydrators.
  5. Acid gas removal units would be required to be reported for LNG import and export facilities.
  6. Natural gas pneumatic devices and pumps will be required to use the “in service” hours to calculate emissions. In service is the time the device is supplied with natural gas.
  7. Changes to the emission factors for natural gas pneumatic controllers. Also, in anticipation of the proposes rules in NSPS OOOOb/EC OOOOc LDAR monitoring data may be used to calculate emissions for intermittent natural gas pneumatic devices.


Cimarron – Who We Are

Cimarron’s overall goal is to reduce greenhouse gas emissions for all industries as we work with our clients to create a cleaner environment.

The company engineers and manufactures environmental, production and process equipment for the upstream, midstream and downstream energy industries, as well as environmental control solutions for biogas at wastewater facilities, digester tanks and landfills.

Cimarron offers our customers the know-how and environmental expertise to meet the environmental standards of today and tomorrow. Cimarron is committed to bring value to the Energy industry and their shareholders based on our financial strength, experienced personnel, and engineering capabilities.

As a company, we thrive every day to make a difference through innovation (e.g. ESG), customer focus, and operational efficiency. In addition to being present in all major regions in the US, Cimarron serves more than 45 countries around the world, ranging from offshore to desert. From key operational centers in the United States, Italy and the United Arab Emirates, Cimarron offers ongoing service and support through its own field service personnel and strategic third-party partners, creating a cleaner environment for our customers and their shareholders.

Since its founding in the mid-1970’s in Oklahoma, the company’s product offering has expanded from production equipment to include the largest line of environmental solutions that capture or incinerate fugitive vapors. With the acquisitions of HY-BON/EDI in 2019 and AEREON (including Jordan Technologies) in 2020, Cimarron has added strong brands, products, and services to its portfolio.

Please contact us to learn more about our products and services and about all our ESG solutions at or visit our website

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