The EPA’s Greenhouse Gas Reporting Program (GHGRP) under 40 CFR Part 98 requires facilities in the petroleum and natural gas sector that emit 25,000 metric tons or more of COâ‚‚ equivalent per year to report annual greenhouse gas emissions through the electronic Greenhouse Gas Reporting Tool (e-GGRT). Subpart W specifically covers petroleum and natural gas systems across all industry segments — production, processing, transmission, distribution, and gathering and boosting. Major amendments finalized in May 2024 added new calculation methodologies, expanded the universe of reporting facilities, and aligned Subpart W requirements with NSPS OOOOb monitoring data. Annual reports are due March 31 (or as extended) for the prior calendar year. A program audit evaluates whether your facility is correctly identifying all reportable emission sources, applying the proper calculation methods, maintaining required monitoring and records, and submitting complete and accurate annual reports.
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Download Checklist (.docx)Regulatory Requirements
40 CFR Part 98, Subpart W — Petroleum and Natural Gas Systems
Subpart W establishes GHG reporting requirements for the petroleum and natural gas source category covering nine industry segments: onshore production, offshore production, processing, transmission compression, underground storage, LNG import/export, LNG storage, distribution, and gathering and boosting. Facilities must calculate and report COâ‚‚, CHâ‚„, and Nâ‚‚O emissions from specified sources using prescribed calculation methodologies.
40 CFR Part 98, Subpart A — General Provisions
General provisions establish the overall framework including applicability thresholds (25,000 MT COâ‚‚e/year), reporting deadlines (March 31 annually), data verification, recordkeeping requirements (minimum 3 years), and provisions for confidential business information claims.
Clean Air Act Section 114 and Section 136(h)
The GHGRP is authorized under CAA Section 114. The Inflation Reduction Act added CAA Section 136(h), which directed EPA to revise Subpart W to improve accuracy of methane emissions data and ensure empirical data is used to the greatest extent practicable. The 2024 amendments implement these requirements.
Applicability and Source Identification
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Applicability determination | Facility has determined whether it meets the 25,000 MT COâ‚‚e reporting threshold based on prior year emissions or initial calculations. Determination methodology is documented. Facilities below threshold that previously reported have evaluated whether they qualify for discontinuation of reporting. |
| Industry segment classification | Facility is correctly classified within the applicable Subpart W industry segment(s): onshore production, offshore production, processing, transmission compression, underground storage, LNG, distribution, or gathering and boosting. Classification aligns with facility operations and SIC/NAICS codes. |
| Emission source inventory | All reportable emission sources within the facility boundary are identified and documented. Sources include: pneumatic devices, equipment leaks, storage vessels, compressors, dehydrators, acid gas removal units, flares, combustion equipment, well completions, blowdowns, and other venting sources as applicable to the industry segment. |
| Facility boundary definition | Facility reporting boundary is correctly defined per Subpart W definitions (e.g., well-pad site, gathering and boosting site, processing plant). All equipment within the boundary is included. Boundary definition is consistent year over year or changes are documented. |
Calculation Methodologies
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Method selection | Correct calculation methodology is selected for each emission source type per 40 CFR 98.233. Methodology selection considers available data, monitoring equipment, and regulatory requirements. Any use of optional new methodologies (effective RY 2025) is documented. |
| Pneumatic device calculations | Emissions from pneumatic controllers and pumps are calculated using the applicable method: population count with emission factors (Method 1), direct measurement (Method 2), or engineering estimation. Device inventories are current and categorized correctly (continuous bleed high/low, intermittent, zero-emission). |
| Equipment leak calculations | Fugitive emissions from equipment leaks are quantified using the applicable methodology: component counts with emission factors, OGI-based survey data, or direct measurement. Leak survey data from NSPS compliance can be used where methods align. |
| Combustion and flare calculations | Emissions from stationary combustion sources, flares, and engines are calculated per Subpart C and/or Subpart W methods as applicable. Gas composition data, fuel usage volumes, and operating hours are documented. RICE and gas turbine emissions use updated methane emission factors where required. |
| Storage vessel and dehydrator calculations | Emissions from storage tanks are calculated using simulation software or engineering methodology with throughput data, API gravity, Reid vapor pressure, and ambient conditions. Dehydrator emissions use appropriate method based on throughput and whether software modeling (GRI-GLYCalc or equivalent) is required. |
Monitoring and Data Collection
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Gas composition analysis | Natural gas composition is analyzed at required frequency using appropriate analytical methods. Results include CHâ‚„, COâ‚‚, Nâ‚‚, and Câ‚‚+ components. Sampling locations represent gas at the point of emission. Annual or more frequent analysis is conducted as required. |
| Activity data collection | Activity data (fuel consumption, throughput, operating hours, vent volumes, component counts) is collected systematically throughout the reporting year. Data sources are identified and consistent. Meters and measurement devices are calibrated per applicable standards. |
| Emission factor documentation | Emission factors used in calculations are documented with sources. Default EPA emission factors, manufacturer data, or site-specific measured factors are applied correctly. Any updates to emission factors from 2024 amendments are incorporated. |
| Missing data procedures | Procedures for handling missing data are documented and follow Subpart W requirements (40 CFR 98.235). Substitute data methods are applied consistently. Duration and reason for missing data periods are documented. Missing data is minimized and reported in the annual report. |
Reporting and Recordkeeping
| Audit Item | Expected Finding / What to Evaluate |
|---|---|
| Annual report completeness | Annual GHG report submitted through e-GGRT includes all required data elements for each emission source. Report covers the full calendar year (January 1 – December 31). All applicable sections of the reporting form are completed including source-level detail. |
| Report submission timeliness | Annual report is submitted by the March 31 deadline (or extended deadline if applicable). Verification status is checked and any resubmission requests from EPA are addressed within the required timeframe. |
| Record retention | All records supporting the annual report are retained for a minimum of three years including: gas composition analyses, activity data, calculation worksheets, monitoring records, calibration records, and missing data documentation. Records are organized and readily retrievable for EPA verification. |
| Data verification and QA/QC | Internal quality assurance and quality control procedures are implemented for emission calculations. Calculations are reviewed for accuracy before report submission. Year-over-year comparisons are performed to identify anomalies. Any EPA verification inquiries from prior years have been addressed. |
| Confidentiality claims | Any claims for confidential business information (CBI) are properly filed and documented. CBI claims align with EPA’s confidentiality determinations for Subpart W data elements. Public reporting of non-CBI data is understood. |
Corrective Actions
Common Issues and Responses
- Missing emission sources: Conduct a comprehensive facility walkthrough to identify all reportable sources. Compare equipment inventories against Subpart W source categories. Add any missing sources to the next annual report and document the correction.
- Incorrect calculation methodology: Review method selection criteria for each source type. Recalculate emissions using the correct methodology. If material errors are found in prior reports, submit revised reports through e-GGRT.
- Insufficient gas composition data: Establish a gas sampling and analysis program that meets Subpart W frequency requirements. Contract with an accredited laboratory for analyses. Implement tracking to ensure samples are collected on schedule.
- Late or incomplete annual report: Submit the report immediately with all available data. Implement calendar reminders and assign report preparation responsibilities. Begin compiling data quarterly rather than annually to avoid year-end backlogs.
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Air Emissions Software
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LDAR Software
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Inspection Software
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Environmental Data Management
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Corrective Actions
Track and resolve Subpart W reporting deficiencies, EPA verification requests, and data quality improvements.
