On January 15, 2025, the U.S. Environmental Protection Agency (EPA) proposed amendments to OOOOb. Originally finalized in March 2024, New Source Performance Standard OOOOb (NSPS OOOOb) regulates methane (CH4) and volatile organic compound (VOC) emissions from the onshore oil and natural gas (O&G) sector. The rule applies to facilities constructed, modified, or reconstructed after December 6, 2022.
Overview of Proposed Changes
The proposed revisions focus on two specific areas:
- Net Heating Value (NHV) Monitoring and Testing Exemptions – Certain flares and Enclosed Combustion Devices (ECDs) would be exempt from NHV monitoring/testing under specific conditions.
- Temporary Flaring of Associated Gas – Expanded allowances for flaring duration in cases of malfunctions, safety incidents, repairs, and maintenance.
Key Changes:
- NHV Monitoring Exemptions: Unassisted flares and ECDs at new sources, along with unassisted, air-assisted, and steam-assisted flares at existing sources, would be exempt if their vent gas does not include streams that lower NHV. The blanket exemption for associated gas testing is removed.
- NHV Testing Modifications: The 14-day sampling requirement is updated to allow testing over 14 operating days, without requiring consecutive days.
- Associated Gas Flaring: The allowable flaring duration for malfunctions, safety incidents, repairs, and maintenance would increase from 24 to 48 hours per event. Other limits remain unchanged.
Public Comment Period
The EPA will accept comments until March 3, 2025. A public hearing will be held if requested within five days of publication. If scheduled, the hearing will take place 15 days after publication.
To submit comments, use Docket ID No. EPA–HQ–OAR–2024–0358 via:
- Federal Rulemaking Portal: www.regulations.gov (preferred method)
- Email: a-and-r-docket@epa.gov (include Docket ID in the subject line)
Current NHV Monitoring and Testing Requirements
Under NSPS OOOOb, flares and ECDs must meet specific NHV limits:
NHV Monitoring and Testing Exemptions
The proposal removes the blanket exemption for NHV testing of associated gas. To qualify for exemption, associated gas must not contain inert gases or other vent streams that lower NHV below required thresholds.
The EPA proposes NHV monitoring/testing exemptions for:
- Unassisted flares and ECDs at new sources.
- Unassisted, air-assisted, and steam-assisted flares at existing sources.
Exemptions apply if the vent gas does not include streams that lower NHV, such as:
- Acid gas removal (AGR) still columns.
- Glycol dehydration unit still column vent gas mixed with other streams without water removal.
- Acid gas service compressors.
- Enhanced oil recovery (EOR) facilities.
- High-water-content storage vessels.
NHV Testing Methods and Updates
For unassisted or pressure-assisted ECDs and flares that initially demonstrate compliance, continuous NHV measurement is not required. Instead, facilities must collect three inlet gas samples every five years. If NHV testing is required, current OOOOb rules provide three options and one approved alternative method:
- 14-day sampling/chemical analysis (every 5 years, minimum 28 samples).
- Proposed update: Testing can occur over 14 operating days (not necessarily consecutive), with no sampling day spaced more than 3 operating days apart.
- Continuous measurement using a calorimeter, gas chromatograph, mass spectrometer, or periodic grab sampling.
- Continuous monitoring of exhaust gas to ensure total organic carbon (TOC) concentration ≤275 ppmv (as propane).
- EPA approved alternative method ALT-156 simplified VISR imaging spectrometer for measuring NHV instantaneously instead of taking gas samples. Testing would also occur over 14 operating days.
Current and Proposed Limits for Temporary Associated Gas Flaring:
About Cimarron
With decades of experience and a legacy of innovation, Cimarron delivers advanced emissions management solutions for the global energy industry. Our technology-driven products and real-time monitoring systems help customers reduce emissions, optimize operations, and ensure regulatory compliance. We serve key sectors, including oil & gas production, energy storage & distribution, renewables & biogas, coal mine methane, and industrial applications. Our expertise spans tens of thousands of successful equipment installations worldwide.
Headquartered in Houston, Texas, Cimarron operates across more than 45 countries with 550+ employees and global engineering, manufacturing, and service locations in the U.S., Italy, India, England, and the UAE.
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