How to Meet and Maintain 98% Flare Destruction Efficiency under New Regulations

Cimarron’s solutions give operators a clear path to compliance with the DRE used for their flaring emission calculations.

1. Introduction

Operators of oil and gas facilities face a significant challenge: without upgrades to their flare systems, they may be forced to lower their flare destruction efficiency (DE) to 92%, which could increase their reporting of emissions and regulatory risks.

This is driven by recent changes to EPA regulations, which eliminate the option to assume a default DE of 98% for flares. Affected regulations include the GHG Reporting Program (40 CFR 98 Subpart W) and NSPS OOOOb rules. To maintain compliance and optimize environmental performance, facilities must now demonstrate actual flare DE or invest in flare system upgrades to meet the stricter requirements.

In the following paper, we present several solutions to help operators meet and maintain a 98% DE standard. These solutions include a combination of newer flare designs, enhancements to flare tips, real-time monitoring systems, and alternative testing methods such as the recently EPA-approved ALT156. Through the adoption of these technologies, operators can reduce emissions, meet regulatory standards, and avoid costly non-compliance issues.

2. Definitions

Destruction Efficiency (DE), also known as Destruction and Removal Efficiency (DRE), indicates the percentage of hydrocarbons that are destroyed, while Combustion Efficiency (CE) reflects the percentage of hydrocarbons that are completely combusted to produce CO2 and water vapor. The current GHG subpart W reporting rules use CE values to calculate flaring CO2 emissions while DE is used to calculate flaring CH4 emissions.

Based on empirical testing, the DE of CH4 is defined as combustion efficiency plus 1.5%.

3. Typical Past Flare Destruction Efficiency (DE)

In recent years, most oil & gas operators have used a default of 98% DE for emission calculations of their flares. The default of 98% DE for flares was established based on meeting requirements in 40 CFR 60.18.

Per 40 CFR 60.18, a flare is assumed to achieve 98% DE if the following are met:

1. The flare has at least one continuous pilot or its equivalent.
2. The flare does not smoke more than 5 minutes in any two-hour period.
3. The flare gas has sufficient net heating value (minimum of 200 or 300 Btu/scf, depending on the type of flare).
4. The exit velocity of the flare does not exceed a threshold value computed from the net heating value of the flare gas.

Recent changes to Subpart W GHG reporting rules no longer rely solely on 40 CFR 60.18 and have made using a 98% DE harder to justify for flares.

4. The flare DE value is now used to calculate methane fees

DE values used for O&G flares are important for the following reasons:

1. GHG Emissions: DE values directly impact the calculation of greenhouse gas (GHG) emissions, particularly methane (CH₄). Lower DE values result in higher CH₄ emissions, increasing both facility-level and basin-wide GHG totals. This, in turn, can lead to increased fees under the Waste Emissions Charge (WEC) due to elevated CH₄
2. State Air Permits: Facilities use DE values to calculate flaring potential to emit (PTE) and actual volatile organic compounds (VOC) emissions. These calculations are required for air permits and for facilities that annually report criteria pollutants (e.g., VOCs) emissions. Higher VOC emissions from lower DE values can affect the type of air permit a facility receives (e.g., minor source, general permit, or Title V) and lead to increased annual emissions fees.

Moving forward, operators will need to use the default flare DE values in 40 CFR 98 subpart W reporting for 2025 GHG reporting, or use results of an approved alternative test method (i.e. ALT156 method) given in NSPS OOOOb (ref: 60.5412b(d)).

Be cautious of claims of destruction efficiency values greater than 95%, unless the supplier provides the necessary regulatory monitoring and testing to support the claim (Cimarron does)

5. Waste Emission Charge (WEC) fee simulations

The 2025 WEC of $1200/metric tonne CH4 applies to oil or natural gas production sites when an annual threshold is exceeded, and the facility emits more than 25,000 tonnes CO2e. The following chart shows a routine flare’s contribution to WEC fee charges if the site is above its allotted methane emission thresholds.

This demonstrates a significant difference in WEC fee amounts based on the Destruction Removal Efficiency (DRE) levels. Specifically, there is a 4x ratio in WEC fees between 98% DRE and 92% DRE, and a 2.5x ratio between 98% and 95% DRE. It clearly indicates the value of increasing the permitted DRE for a combination flare/enclosed combustor or a dual flare (low pressure/high pressure). The investment required for this upgrade is a fraction of the cost associated with paying the WEC charges at 92% or 95% DRE levels.

6. Cimarron “Measurement While Flaring” Solution (MWF)

How does a facility gain approval to use a DE greater than the default values given in subpart W (ref: Table 1 above)?

Cimarron has been active in developing and testing flare designs that meet or exceed 98% DE. Some of these designs have been partially funded by the U.S. Department of Energy’s Advanced Research Projects Agency – Energy (ARPA-E). This includes:

1. DreamDuo® flare (commercialized)
2. DRE-Max® variable frequency drive (VFD) controller (commercialized). DRE-Max Gen II includes compliance with 2024 regulations, including NHVdil (>= 22 Btu/sq ft), by measuring and automatically adjusting the NHVdil value.
3. Computer Vision System (in partnership with CleanConnect.ai)
4. EPA-approved alternative test method ALT156 to measure NHVdil and DRE using simplified VISR imaging spectrometer If the ALT156 method is used continuously, the flare can be permitted at 98% DRE. If it is only used for spot checks (i.e. when a well is started or for scheduled inspections), the flare can be permitted at 95% DRE instead of 92%.

 

Cimarron’s flare upgrades that demonstrate DE values of at least 98% include:

1. Mechanical and electronic upgrades:
   • Change the flare tip to a proven high DRE design (Cimarron DreamDuo®).
   • Add a reliable flare pilot with an auto-reigniter system (Cimarron ARC™).
   • Add air-assist or gas-assist to improve combustion mix
   • Optimize the combustion mix to prevent under or over-aerating, by adjusting blower air volume (Cimarron DRE-Max® Gen II).
   • Optimize the consumption of assist-gas by adjusting the volume as needed, rather than traditional continuous flow (Cimarron DRE-Max® Gen II).
   • Optimize the blower air volume to prevent the NHVdil from being below the required minimum (Cimarron DRE-Max® Gen II).
   • Add a source of enriched gas to prevent the NHVdil from being below the required minimum (Cimarron DRE-Max® Gen II).
2. Visual automation upgrade options:
   • Add autonomous vision for 24/7 & 360° real time visible emissions monitoring of the flare and the whole well site or compressor station facility (CleanConnect.ai)
   • Add EPA approved alternative method ALT156 simplified VISR imaging spectrometer for measuring DRE and NHVdil.
3. Measurement at the source upgrade options:
   • Continuously measure waste gas flow rates and pressure, pilot status (Cimarron SyteLink360® for remote locations without SCADA systems).
   • Continuously monitor the NHVdil of the gas to be above the minimal requirement (Cimarron DRE-Max® Gen II).
   • Visually continuously monitor the lack of smoke or cold venting (CleanConnect.ai)
   • Visually continuously measure DRE, NHVdil, flow rates (ALT156 method using simplified VISR imaging spectrometer).

These solutions meet all the requirements for EPA Alternative Performance (see below)

State environmental regulatory agencies will refer to USEPA guidance and regulations when determining compliance with OOOOb DE requirements for flares.

7. USEPA and States’ Roles

The USEPA is the primary agency for nationwide enforcement, interpretation, and reporting of GHG emissions in 40 CFR 98 subpart W. Additionally, the USEPA serves as the lead agency for regulatory interpretation of NSPS OOOOb. This includes the use of DE values for flares.

Enforcement authority for OOOOb has been delegated to most state environmental agencies by the USEPA. States enforce NSPS OOOOb and other federal regulations through their state air permitting regulations and programs. All state environmental agencies look to the USEPA for guidance on interpretation of the NSPS OOOOb rules. We can expect this for flare DE values used for air permitting and emission inventories.

8. Subpart W Flare Default DE and CE

The default destruction efficiency (DE) and combustion efficiency (CE) required to be used for subpart W reporting and NSPS OOOOb compliance are summarized in the Table 1 above.

Each Subpart W Tier has specific monitoring and testing requirements for flares:

1. Tier 1 (98% DE) follows testing and monitoring requirements in 40 CFR 63 subpart CC (Refinery hazardous air pollutant rules).
2. Tier 2 (95% DE) follows testing and monitoring requirements in NSPS OOOOb.
3. Tier 3 (92% DE) requires the least amount of monitoring, including pilot flame, gas net heating value (NHV), and visible emissions.

9. EPA Alternative Performance Testing

Alternative performance testing is available to demonstrate a DE greater than the three Tiers specified by subpart W.  Rules in NSPS OOOOb (ref:60.5412b(d) and 60.8(b)) specify alternative testing methods to obtain a DE greater than 95% for flares. Subpart W references the rules in NSPS OOOOb for alternative testing methods. An operator is required to submit a request to the EPA OAQPS for an alternative test method at Oil_and_Gas_PT@EPA.GOV. The testing results can be used for NSPS OOOOb compliance, subpart W GHG reporting and state air permits.

General requirements for the alternative testing include:

1. Demonstration Continuous Compliance:
   • Net Heating Value of Combustion Zone (NHVcz) of 270 Btu/scf or greater (based on set of gas analysis samples or spot testing using approved ALT156 method with simplified VISR camera, both can be provided by Cimarron).
   • NHV Dilution (NHVdil) of 22 Btu/sqft or greater if the method is for enclosed combustion devices or flares with perimeter assist air (Cimarron DRE-Max® Gen II).
2. Validation:
   • Validate alternative testing using EPA Method 301 in appendix A of 40 CFR part 63 for each type of control device or include performance-based procedures and indicators to ensure self-validation (list all Cimarron’s solutions in section 5).
   • Facilities using EPA-approved ALT56 must notify the responsible agency before use of this alternative method with a copy of the approval letter. They should also include a copy of the approval letter and method with each quarterly report presenting results using the ALT56 method.
3. Data Collection Frequency:
   • Supply readings for each successive 15-minute period (Cimarron Sytelink360® or SCADA).
4. Visible Emissions Monitoring:
   • The method must document periods when the flare or enclosed combustion device operates with visible emissions. If the alternative test method does not support this, then perform monthly Method 22 visible emissions monitoring or continuous video surveillance to monitor for visible emissions (CleanConnect.ai visual data).
5. Monitoring Systems:
   • If the alternative method does not directly measure combustion efficiency (CE) but instead measures metrics like NHVcz and NHVdil, a pilot or combustion flame monitoring system must be installed (Cimarron DRE-Max® Gen II + ARC™ burner management system).
   • Incorporate the EPA-approved ALT156 method using simplified VISR imaging spectrometer for continuous measurement of NHVcz and NHVdil. If the ALT156 method is used continuously, the flare can be permitted at 98% DRE. If it is only used for spot checks (e.g., at the start of a new well, or once a year), the flare can be permitted at 95% DRE instead of 92%.

10. Conclusions

Recent changes to EPA regulations pose significant challenges for upstream operators (oil and gas facilities) and midstream operators (compressor stations, pipelines), particularly concerning flare destruction efficiency (DE). The elimination of the default 98% DE assumption under the GHG Reporting Program (40 CFR 98 Subpart W) and NSPS OOOOb rules means that operators may have to downgrade their flare DE to 92% unless upgrades are made. This change has far-reaching implications for GHG emissions, methane (CH4) reporting, and state air permit compliance. Facilities must either demonstrate actual flare DE through testing or invest in upgrading flare systems to maintain regulatory compliance and avoid elevated fees associated with increased emissions.

Without these actions, facilities may face increased methane and VOC emissions, leading to higher GHG totals, potential Waste Emissions Charges (WEC), and more stringent state air permits with elevated emissions fees.

Cimarron offers solutions to help operators meet and maintain a 98% DE standard through various mechanical and automation upgrades. These include new flare designs, enhancements to flare tips, real-time monitoring systems, and alternative testing methods such as the EPA-approved ALT156.  As regulatory enforcement becomes more stringent, operators need to ensure their flare systems meet both GHG and air permit requirements. By adopting these technologies, operators can reduce emissions, meet regulatory standards, and avoid costly non-compliance issues.

Please contact us at sales@cimarron.com to learn more about the changes to state and federal emissions regulations and how we help customers with emissions capture & destruction equipment, flare upgrades, field services and real time monitoring technology.