Subpart W Methane

Subpart W refers to the U.S. Environmental Protection Agency’s (EPA) greenhouse gas reporting requirements for petroleum and natural gas systems, under the EPA's mandatory Greenhouse Gas Reporting Program (GHGRP), 40 CFR Part 98, Subpart W. It requires operators to quantify and report methane and other greenhouse gas (GHG) emissions from specified oil and gas facilities each year.

This rule applies to a wide range of petroleum and natural gas industry segments, including production and processing, transmission, storage, and distribution. In September 2025, the EPA proposed permanent removal of some emissions reporting obligations through Subpart W and suspending other elements until reporting year 2034.

Why Do Subpart W Methane Requirements Matter?

Subpart W is one of the most widely applied methane reporting requirements for U.S. oil and gas companies. These requirements:

• Apply to owners or operators of many types of oil and gas system facilities that emit 25,000 metric tons of carbon dioxide equivalent (CO2e) or more annually
• Establish standardized methods for calculating GHG emissions for each source type
• Entail annual reporting of methane and other GHGs to the EPA
  
  

How Do Subpart W Methane Requirements Work? (Brief Technical)

Facilities subject to Subpart W methane requirements must:

• Collect activity data and emission factors, or direct measurement data in some cases, for methane and other GHGs
• Calculate emissions using the EPA’s prescribed methodologies
• Submit annual reports through EPA’s electronic reporting system

Although Subpart W has historically relied on emission factors, engineering calculations, software models, and some direct measurement techniques depending on the component type to calculate emissions, a future pathway could allow the use of advanced methane detection technology. Advanced technology such as aerial LiDAR emission detection and quantification can improve the accuracy and credibility of emissions data.

Key Applications in Oil and Gas

• Meeting EPA’s mandatory GHG reporting under Subpart W
• Standardizing emissions reporting using specified methodologies for calculating GHG emissions
• Supporting investor and ESG disclosures tied to regulatory data
• Benchmarking site-level emissions performance across assets

Related: EPA OOOOb Methane Rule, Methane Quantification, Methane Emission Rate, Aerial Methane Detection, OGMP 2.0

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