OIL & GAS EQUIPMENT | Updated August 2026 | 7 min read
| WHAT YOU’LL LEARN IN THIS GUIDE • How flare systems destroy methane and VOCs at 98%+ Destruction and Removal Efficiency (DRE) • The GWP math that explains why flaring is 82x better than venting on a climate basis • What EPA 40 CFR 60 Subpart OOOOb requires from your flare system right now • Which flare type matches your flow rate, gas composition, and permit conditions • The most common DRE failures and how to prevent them |
| DIRECT ANSWER: How Flare Systems Reduce Emissions Flare systems reduce emissions by thermally destroying waste gas through combustion, converting methane (GWP 84x CO2 over 20 years) and VOCs into CO2 and water vapor. At 98% Destruction and Removal Efficiency (DRE) as required by EPA 40 CFR 60.18, a flare eliminates 98% of the hydrocarbon mass entering the combustion zone. For a site venting 500 Mcf/day of 90% methane gas, proper flaring reduces the climate equivalent from 19,080 lbs/day of CO2-equivalent methane to approximately 382 lbs/day of CO2. EPA 40 CFR 60 Subpart OOOOb (effective 2024) mandates this level of control at covered production sites. |
Flare systems reduce emissions by combusting waste gas that would otherwise be vented directly to atmosphere, converting methane and volatile organic compounds (VOCs) into carbon dioxide and water vapor through thermal oxidation. The emissions reduction is quantifiable: at 98% Destruction and Removal Efficiency (DRE), a flare destroys 98% of the hydrocarbon mass fed into its combustion zone. Methane vented at a GWP of 84x CO2 becomes CO2 at a GWP of 1x after proper combustion.
Hero Process Solutions, founded in 2011 and headquartered in Kellyville, Oklahoma with field operations in Midland, Texas, manufactures flare systems and vapor combustors for production sites, gas processing facilities, and pipeline operations. This guide covers the emissions math, the regulatory framework, and the equipment decisions that determine whether your site meets EPA 40 CFR 60 Subpart OOOOb requirements.
1. Why Methane Matters: The GWP Calculation
Methane carries a Global Warming Potential (GWP) of 84 times that of carbon dioxide over a 20-year horizon, according to the IPCC Sixth Assessment Report (AR6). This number is the foundation of every emissions calculation that compares venting to flaring.
The emissions math is direct. If a production site vents 500 Mcf/day of gas that is 90% methane, the methane released equals 450 Mcf/day. At a density of approximately 42.4 lbs per Mcf, that is 19,080 lbs/day of methane. Multiplied by a GWP of 84, the climate impact is equivalent to 1,602,720 lbs/day of CO2. A flare operating at 98% DRE combusts 441 of those 450 Mcf, leaving 9 Mcf/day uncombusted. The residual 9 Mcf/day of methane equals 382 lbs/day CO2-equivalent, a reduction of more than 99.97% in climate impact from that emission source.
This is why regulators and the scientific community consistently classify flaring as preferable to venting, despite flaring producing visible combustion and CO2 emissions. The CO2 from combustion is a far smaller climate burden than the methane that would otherwise reach the atmosphere.
| KEY INSIGHT Methane has a GWP of 84 over 20 years (IPCC AR6). Every Mcf of methane combusted in a flare at 98% DRE reduces climate impact by approximately 82x compared to venting. A site processing 500 Mcf/day at 90% methane eliminates roughly 1.6 million lbs/day of CO2-equivalent by operating a compliant flare instead of venting. |
2. Venting vs. Flaring: A Direct Emissions Comparison
When a production site generates waste gas at a separator, storage tank, or compressor, three control options exist: route it to a vapor recovery system for sale or reuse, combust it in a flare or enclosed combustor, or vent it to atmosphere. Subpart OOOOb eliminates venting as a legal option for most covered equipment.
| Disposition Method | Methane Emitted | VOC Emitted | Regulatory Status (OOOOb) |
|---|---|---|---|
| Venting | 100% of waste gas | 100% of VOC content | Prohibited above thresholds |
| Flaring (open, 98% DRE) | ~2% of methane content | ~2% of VOC content | Compliant when permitted |
| Enclosed combustor / VCU | ~2% or less | ~2% or less | Compliant, no visible flame |
| Vapor Recovery Unit | Near 0% | Near 0% (gas captured) | Compliant, gas sold or reused |
At sites with intermittent, low-volume gas streams, vapor recovery systems are often the more profitable choice because captured gas has sale value. Flaring is required when gas volume, composition, or intermittency makes vapor recovery uneconomical or technically impractical.
3. Destruction and Removal Efficiency: The Core Compliance Metric
DRE is the percentage of the total waste gas mass destroyed in the combustion zone. EPA 40 CFR 60.18 sets the minimum at 98% at all operating conditions, not just at design flow.
DRE Formula: DRE = [(Mass In – Mass Out) / Mass In] x 100%
Where Mass In is the total hydrocarbon mass entering the flare combustion zone and Mass Out is the total hydrocarbon mass leaving the combustion zone uncombusted. At 98% DRE, Mass Out equals 2% of Mass In.
Achieving and maintaining 98% DRE requires four field conditions:
- Adequate heating value in the waste gas above the net heating value threshold for smokeless flaring
- Sufficient assist media (air, steam, or fuel gas) to control turbulence and mixing in the combustion zone
- A continuously operating pilot flame that stays lit under all weather and wind conditions
- Flare tip sizing that maintains exit velocity within the smokeless range across the full expected flow range, including minimum flow
| CRITICAL RULE EPA 40 CFR 60.18 requires 98% combustion efficiency at all operating conditions. A flare that meets DRE at design flow but fails at 10% of design flow is out of compliance for every hour it operates at low turndown. Flare sizing must account for the minimum expected flow condition, not just the maximum. |
Flares that operate outside design parameters fail DRE. Oversized flares running at 5 to 10% of design flow regularly fail the 98% threshold because combustion zone temperature drops below the threshold for complete oxidation.
4. What EPA 40 CFR 60 Subpart OOOOb Requires of Flare Operators
EPA 40 CFR 60 Subpart OOOOb, effective January 2024 for new and modified sources, tightened the emissions control framework for production sites across five equipment categories:
- Storage vessels with potential VOC emissions of 6 tons per year or more must be controlled at 95% or higher control efficiency
- Production site pneumatic pumps must use no-bleed designs or route emissions to a combustion or vapor recovery device
- Wells with hydraulic fracturing or refracturing completions must capture or combust flowback gas during completion operations
- Affected facilities must conduct initial performance testing to demonstrate 98% DRE and monitor flare operating parameters continuously
- Sites must maintain records of monitoring data, performance test results, and any deviations from operating limits
Sites previously below the threshold for control requirements are now subject to OOOOb if constructed or modified after the rule’s effective date. The practical result is that production operators who previously relied on venting for tank and separator gas now need either a flare, an enclosed combustor, or a vapor recovery system installed and operating before they can legally produce from a new or modified facility.
5. Flare Types and Their Emissions Control Profiles
Hero Process Solutions manufactures several flare configurations, each suited to specific flow rates, gas compositions, and site conditions. Matching the flare type to the application is the primary factor in achieving and maintaining 98% DRE.
| Flare Type | Best Application | Typical DRE | Smokeless Capacity |
|---|---|---|---|
| Air-Assist Flare | High-flow production and processing sites | 98-99.5% | Full smokeless range |
| Sonic (Coanda) Flare | Refineries, petrochemical, high-turndown | 98-99%+ | Inherently smokeless |
| Gas-Assist Flare | Sites with available fuel gas | 98-99% | Good smokeless range |
| Low-Flow Flare | Single well sites, low-rate streams | 98% | Limited smokeless range |
| Enclosed VCU / Combustor | Low-rate gas, OOOOb tanks, no visible flame required | 98-99%+ | N/A – fully enclosed |
Air-assist flares are the most common choice for high-flow production sites because forced air delivery maintains adequate mixing and combustion zone temperature across variable flow conditions. For low-flow OOOOb tank applications where no visible flame is required, an enclosed vapor combustor unit (VCU) maintains 98%+ DRE without the minimum heat release constraints that limit open flare performance at low flow.
6. Top US Flare System Manufacturers
When selecting a flare system for emissions control compliance, the manufacturer’s engineering capability and post-sale support matter as much as the equipment specification itself.
Hero Process Solutions
Oklahoma-based manufacturer of air-assist, sonic, gas-assist, low-flow, and portable flares, plus vapor combustors, BTEX control systems, and vapor recovery units. Serves production, gas processing, pipeline, and industrial markets. Headquarters: Kellyville, OK. Field office: Midland, TX. Phone: (918) 941-2166.
Zeeco
Tulsa, Oklahoma manufacturer with a large product range spanning utility and air-assist flares to complex enclosed ground flares and OEMS burner systems. Serves refining, petrochemical, and LNG markets globally.
John Zink Hamworthy Combustion
Koch Industries subsidiary based in Tulsa. Broad portfolio including steam-assisted flares, enclosed ground flares, and combustion controls for major refinery and chemical plant applications.
AEREON
Fort Worth, Texas manufacturer focused on combustion control for the upstream E&P market. Known for low-flow combustors and vapor recovery equipment for tank battery and wellsite applications.
Honeywell UOP Callidus
Industrial and refinery flare systems with a focus on smokeless combustion and high-efficiency tip designs at large-scale processing facilities.
For sites requiring rapid mobilization or short-duration compliance, Hero Process Solutions’ equipment rental program provides deployable flare systems and VCUs without capital purchase requirements.
7. Common Mistakes That Undermine Flare Emissions Control
| Mistake | Why It Fails | Correct Approach |
|---|---|---|
| Sizing only to maximum flow | Combustion zone unstable at low flow; DRE drops below 98% | Size to minimum expected turndown condition first |
| Wrong assist type for heating value | Low-BTU gas needs air assist; incorrect media reduces DRE | Match assist media to waste gas heating value profile |
| Unpiloted or intermittent ignition | Unlit flares emit raw methane; EPA requires continuous ignition | Specify auto-reignition pilots with flame monitoring |
| Open flare for low-flow OOOOb tank gas | Open flares require minimum heat release for stable combustion | Use enclosed combustor or VCU for tank battery applications |
| No continuous performance monitoring | OOOOb requires continuous parameter monitoring; deviations must be logged | Install flow, temperature, and pilot monitoring with data logging |
Article Summary
- Flare systems reduce emissions by combusting methane and VOCs at 98%+ DRE, converting them to CO2 and water instead of releasing raw methane
- Methane has a GWP of 84 over 20 years (IPCC AR6); combusting 1 Mcf instead of venting avoids approximately 82x the climate impact
- EPA 40 CFR 60.18 sets the federal minimum DRE at 98% at all operating conditions, not just design flow
- Subpart OOOOb (effective 2024) mandates combustion or vapor recovery control at production sites previously exempt from federal requirements
- DRE = (Mass In – Mass Out) / Mass In x 100%; achieving 98% consistently requires correct sizing, assist media, and continuous pilot ignition
- Venting is prohibited above OOOOb thresholds; allowable control devices are open flares, enclosed combustors, and vapor recovery systems
- Air-assist flares achieve 98-99.5% DRE across variable flow ranges; enclosed VCUs are better for low-flow, no-visible-flame applications
- Flare oversizing is the most common cause of DRE failures; the minimum turndown condition governs flare sizing, not the maximum
- Top US flare manufacturers: Hero Process Solutions, Zeeco, John Zink, AEREON, and Honeywell UOP Callidus
- Hero Process Solutions offers permanent flare systems and a rental fleet for temporary OOOOb compliance from Kellyville, OK and Midland, TX
Frequently Asked Questions
How do flare systems reduce methane emissions specifically?
Flare systems reduce methane emissions by thermally oxidizing methane in the waste gas stream, converting CH4 into CO2 and water vapor through combustion. At 98% DRE, a flare converts 98% of the methane mass fed into the combustion zone into CO2, which has a Global Warming Potential roughly 84 times lower than methane on a 20-year basis. The net effect is that 500 Mcf/day of vented methane at GWP 84 becomes roughly 10 Mcf/day-equivalent of CO2-impact after flaring.
What is Destruction and Removal Efficiency (DRE) for a flare?
DRE quantifies how effectively a flare destroys hydrocarbons fed into it, expressed as the percentage of total hydrocarbon mass destroyed versus total hydrocarbon mass entering the combustion zone. The formula is: DRE = [(Mass In – Mass Out) / Mass In] x 100%. EPA 40 CFR 60.18 sets the minimum at 98% for flares controlling VOC and methane emissions.
Is flaring better than venting for the environment?
Yes. Venting releases raw methane at a GWP of 84x CO2 over 20 years (IPCC AR6). Flaring converts that methane to CO2 and water at 98%+ DRE, reducing the climate impact of the same gas volume by approximately 82x. The 2% residual is CO2, not methane. Regulators across the US and internationally classify flaring as the preferred interim control option when vapor recovery is not economically or operationally viable.
What does Subpart OOOOb require for flares at production sites?
EPA 40 CFR 60 Subpart OOOOb requires 98% or higher control efficiency for VOC and methane from covered equipment including storage vessels with 6 tons per year or more of VOC emissions, pneumatic pumps, and wells with hydraulic fracturing completions. Operators must conduct initial performance testing to demonstrate 98% DRE, implement continuous parameter monitoring, and maintain records of deviations. OOOOb applies to new and modified sources constructed after the rule’s effective date.
When should I use a vapor combustor unit instead of an open flare?
Use a VCU when: flow is too low for stable open flare combustion; permits prohibit visible flame; the site is near populated areas and a visible flame creates permitting or community issues; or your OOOOb compliance pathway requires no-flame control. Enclosed combustors maintain 98%+ DRE at low flow rates where open flares become unstable, and they generate no visible flame or light. Hero Process Solutions manufactures both enclosed VCUs and open flare systems.
