GHGRP Subpart W: What Oil & Gas Operators Still Need to Report, and When
Table of Contents:
What changed with the RY2025 GHGRP reporting deadline?
The reporting year (RY) 2025 Greenhouse Gas Reporting Program (GHGRP) deadline is now March 10, 2027. EPA signed the extension on October 8, 2026, and it was published in the Federal Register on October 14, 2026, taking effect the same day. It is the second extension this year. The deadline has changed, but the reporting obligation has not: Subpart W is still legally in effect.
Subpart W, which covers petroleum and natural gas systems, got the biggest rewrite in its history in 2024, but most of those changes first show up in RY2025 reports. About 18 months later, EPA proposed pausing nearly all of it. The question for operators is now which version of the rule will actually apply.
This article, based on Alliance's recent webinar with Trent Wade and Christoff Orr, covers where the rule stands, what changed for your equipment and how to prepare either way.
Subpart W timeline: 2009 to today
The RY2025 deadline has now moved twice since EPA proposed its rollback in September 2025.
Date | What happened |
2009–2023 | GHGRP established (2009); Subpart W added for oil and gas (2010); incremental revisions, including NSPS-aligned leak standards (2016) |
May 2024 | Comprehensive rewrite: empirical data methods, new emission factors and a new onshore transmission pipeline segment |
March 2025 | Congress disapproves the Waste Emissions Charge (WEC) rule under the Congressional Review Act |
July 2025 | The One Big Beautiful Bill Act delays the WEC until 2034 emissions |
September 2025 | EPA proposes suspending 9 of 10 segments until RY2034 and removing natural gas distribution. Still pending, with 53,000+ comments, including from API and AXPC arguing to keep reporting |
February 2026 | RY2025 deadline extended from March 31 to October 30, 2026 |
October 14, 2026 | Second extension, to March 10, 2027, published in the Federal Register and in effect |
Is Subpart W still in effect?
Yes. Subpart W remains legally in effect, nothing has been repealed, and RY2025 reports are due March 10, 2027.
The suspension is only a proposal. EPA has not finalized its September 2025 plan to pause reporting.
Only the deadline changed. The extension changes nothing else in Part 98. EPA says it needs time to finish reviewing comments and to get its e-GGRT reporting tool ready.
Litigation is likely regardless. The outcome could be challenged in court or reversed by a future administration, as happened with the NSPS OOOOa rollback.
Who has to report under Subpart W?
10 industry segments are covered.
25,000 metric tons CO2e per year is the reporting threshold. For four segments, including onshore production and gathering and boosting, the threshold applies to specific listed sources rather than the whole facility.
Reports are filed annually through EPA's electronic Greenhouse Gas Reporting Tool (e-GGRT).
Why is pausing Subpart W controversial?
EPA based the 2024 rewrite on five justifications: methane's priority under the Inflation Reduction Act, better measurement technology such as OGI, the weakness of generic emission factors, the link to the WEC's per-ton fee and a congressional mandate under Clean Air Act section 136(h). EPA now argues that with the WEC delayed, much of the reporting burden no longer serves a purpose. Critics say the other four justifications still stand.
What did the 2024 Subpart W rule change?
The 2024 rule pushes operators toward site-specific data and away from generic assumptions. It does that in three ways: better data (measured inputs and updated emission factors), more reporting (a new "other large release events" category and a new onshore transmission pipeline segment) and more QA/QC (heavier recordkeeping, documented assumptions and structured monitoring surveys). Here is what changed for the equipment operators manage most, and where Alliance can help.
Production well sites
Liquids unloading: methodology tiers, from continuous monitoring down to default factors, replace a flat per-event factor.
Associated gas venting and flaring: quantification now includes gas that isn't routed to sales.
Completions and workovers: updated venting calculations.
Threshold: the 25,000 mtCO2e test applies to listed sources, not the whole facility.
How Alliance helps: OGI surveys for every affected facility type, plus Subpart W reporting, recordkeeping and QA/QC documentation support across your well sites.
Gathering and boosting compressor stations
Applicability: a source-specific threshold means more stations may have to report.
Reciprocating compressors: rod packing vents shift to measured or monitored rates, in line with NSPS OOOOb.
Centrifugal compressors: wet and dry seal vents are handled separately, by control status.
Blowdowns and starts: updated methods for maintenance, emergency shutdown and pneumatic-start venting.
How Alliance helps: OGI surveys provide leak detection and quantification support tied directly to Subpart W and NSPS OOOOb, and our air compliance team supports reporting and QA/QC documentation.
Pneumatic devices
Pneumatics are the single biggest technical change, affecting nearly every segment. Operators choose among four methods, from most rigorous to most generic:
Method | Approach |
Method 1 | Continuous flow monitoring |
Method 2 | Manufacturer-specified emission rate × hours of operation |
Method 3 | Engineering equations |
Method 4 | Population default emission factors |
Facilities with 26 or more pneumatic controllers and pumps can phase in measurement over several years.
How Alliance helps: we support all four methods, so you can weigh where measurement lowers reported emissions (see the WEC example below).
Storage tanks
Flashing emissions require measured or site-specific inputs, such as gas-oil ratio sampling or process simulation, instead of default factors.
Bypassed or malfunctioning control devices must be reported as uncontrolled venting under "other large release events."
Assumed vapor recovery or combustor control must now be verified as actually operating.
A site run exactly as it was last year could report much higher emissions if it can't show its controls worked all year.
How Alliance helps: our field teams verify that tank control devices are operating, so your reported emissions reflect the controls you actually have.
Flare destruction efficiency tiers
The old rule let any properly operating flare assume 98% destruction efficiency (DE). Now the assumed DE depends on the monitoring you can document:
Tier | Assumed DE | Monitoring required |
Tier 1 | 98% | Refinery-grade monitoring per 40 CFR 63 Subpart CC |
Tier 2 | 95% | NSPS OOOOb-level monitoring |
Tier 3 | 92% | Pilot flame, gas heating value and visible emissions only |
Without records that prove your tier, you default to 92%. Unlit or malfunctioning flares count as 0% control in every tier. Alternative performance testing can support DE above 98%.
How Alliance helps: flare Tier 1–3 monitoring, DE optimization and the documentation to back up your tier.
Equipment leak quantification
Updated leaker emission factors come from recent field measurement studies.
OGI and Method 21 results now feed quantification, scaled by the rigor of the inspection. AVO inspections can find a leak but can't size it.
Survey frequency varies by segment.
How Alliance helps: OGI and Method 21 surveys, with field data managed in our SkyBridge software, cover both finding leaks and quantifying them.
Midstream: processing, transmission, storage and LNG
New segment: onshore natural gas transmission pipelines now have their own reporting obligation.
Compressor stations: the same compressor updates apply at transmission scale.
Transmission, storage and LNG: OGI findings tie to quantification, with updated leak survey and blowdown methods.
Midstream has fewer facilities than upstream, but each one carries more measurement and QA/QC work.
How Alliance helps: OGI surveys, emissions monitoring and air compliance support, including Subpart W reporting, recordkeeping and QA/QC documentation.
Why methodology choice matters: the Waste Emissions Charge
Once the WEC applies, the method you use to quantify emissions turns directly into dollars. By statute (CAA section 136), the WEC is $1,500 per metric ton of methane for 2026 and later. The One Big Beautiful Bill Act delayed it to 2034 emissions, with payments starting in 2035.
Example: one compressor station with 30 intermittent-bleed pneumatic controllers
Quantification method | Methane emissions | Basis |
Default factor (Equation W-1B) | 30.85 mtCH4/yr | 8.8 scf whole gas/hr per device, about 1.03 mt per device per year |
LDAR survey data (Equation W-1C) | 14.48 mtCH4/yr | 10% malfunction rate, about 0.48 mt per device per year |
Using survey data instead of the default factor cuts reported methane roughly in half. At $1,500 per metric ton, that is a $24,560 per year difference in WEC exposure, from methodology choice alone.
A second example points the same way. For a compressor station with 50 continuous low-bleed controllers, the Method 4 default factor gives about 1,264 mtCO2e per year. A measured value about 35% lower, consistent with published field studies, gives about 822 mtCO2e. Default factors are designed to be conservative, so in most cases they overestimate actual emissions.
The timing matters too. Whatever methodology a facility is using when the WEC clock restarts in 2034 becomes the baseline for what it pays. That makes now the time to decide where more rigorous measurement pays for itself.
How should operators prepare before March 10, 2027?
Treat the extra time before March 10, 2027 as time to prepare, not as relief from the requirement. Plan for three scenarios: the rule is finalized as proposed, it is narrowed, or it is vacated in court. Good documentation protects you against a future reversal of the reversal.
Improve equipment inventories and operational data collection now. If the 2024 rule takes effect, this data becomes far more valuable.
Document methodology assumptions while institutional knowledge is fresh. Don't let your calculation approach live with one person who may leave or retire.
Maintain QA/QC procedures regardless of federal deadline changes.
Standardize calculation tools across sites and segments as far as is practical.
If you export to Europe, track the EU methane intensity methodology, due August 2027.
Stay engaged with the EPA docket and public comment. EPA is taking comments on the deadline extension through November 30, 2026 (Docket EPA-HQ-OAR-2025-0186).
It's also worth starting an internal conversation now: if Subpart W goes away, is the data still meaningful to report? Would you keep using Subpart W methods, or build your own internal guidelines?
What should operators watch next?
Timing of the final Subpart W rule, and litigation over the rollback
Further NSPS OOOOb/OOOOc actions
The EU's methane intensity methodology (due August 2027) and state legislative sessions in 2027. See the beyond-EPA section below.
How can Alliance help with Subpart W compliance?
Whether you're preparing to file RY2025 reports, deciding where measurement pays off or building an internal GHG program, Alliance supports every step:
OGI surveys: leak detection and quantification support tied directly to Subpart W and NSPS OOOOb requirements, for every affected facility type. Learn more →
Emissions monitoring: instrumentation and data management for your highest-impact sources, including pneumatic device Methods 1–4, flare Tier 1–3 monitoring and destruction efficiency optimization, and tank control device verification. Learn more →
Air compliance support: Subpart W reporting, recordkeeping and QA/QC documentation, NSPS OOOOb/OOOOc compliance, and readiness for EU MRV and OGMP 2.0. We can also help you build a roadmap or an internal GHG and methane reporting plan. Learn more →
Want the full picture?
For related context on federal rollbacks, see our earlier article on the partial repeal of the Carbon Pollution Standards and capacity factor for new combustion turbines.
The common thread is that EPA, the EU and the market are all moving toward measurement-informed data instead of generic factors.
Sources
U.S. EPA, Extending the Reporting Deadline Under the Greenhouse Gas Reporting Rule for Reporting Year 2025 to March 10, 2027, Federal Register, October 14, 2026
Alliance Technical Group, "What's Next for GHG Reporting? Practical Guidance for Subpart W Compliance," webinar by Trent Wade and Christoff Orr
