Regulations last checked for updates: Mar 14, 2025

Title 40 - Protection of Environment last revised: Nov 14, 2025
All TitlesTitle 40Chapter IPart 98Subpart WAppendix - Table W-5 to Subpart W of Part 98—Default Methane Population Emission Factors
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Appendix - Table W-5 to Subpart W of Part 98—Default Methane Population Emission Factors
Industry segment Source type/component Emission
factor
(scf methane/hour/
component)
Population Emission Factors—LNG Storage Compressor, Gas Service
LNG storageVapor Recovery Compressor 14.17
LNG import and export equipment
Population Emission Factors—Below Grade Transmission-Distribution Transfer Station Components and Below Grade Metering-Regulating Station 2 Components, Gas Service 3
Natural gas distributionBelow Grade T-D Transfer Station0.30
Below Grade M&R Station0.30
Population Emission Factors—Distribution Mains, Gas Service 4
Natural gas distributionUnprotected Steel5.1
Protected Steel0.57
Plastic0.17
Cast Iron6.9
Population Emission Factors—Distribution Services, Gas Service 5
Natural gas distributionUnprotected Steel0.086
Protected Steel0.0077
Plastic0.0016
Copper0.03
Population Emission Factors—Interconnect, Direct Sale, or Farm Tap Stations 2 3
Onshore natural gas transmission pipelineTransmission Company Interconnect M&R Station166
Direct Sale or Farm Tap Station1.3
Population Emission Factors—Transmission Pipelines, Gas Service 4
Onshore natural gas transmission pipelineUnprotected Steel0.74
Protected Steel0.041
Plastic0.061
Cast Iron27

1 Emission Factor is in units of “scf methane/hour/compressor.”

2 Excluding customer meters.

3 Emission Factor is in units of “scf methane/hour/station.”

4 Emission Factor is in units of “scf methane/hour/mile.”

5 Emission Factor is in units of “scf methane/hour/number of services.”

[89 FR 42326, May 14, 2024]
authority: 42 U.S.C. 7401-7671q.
source: 74 FR 56374, Oct. 30, 2009, unless otherwise noted.
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