Small methane emissions from large populations - natural gas industrial/commercial customer meters are an important source

Abstract:

Characterizing methane emissions from all components of the U.S. natural gas (NG) system is important for understanding where improvements can be made to have the greatest benefits for reducing overall greenhouse gas emissions in the U.S. The purpose of this project was to gather information on methane emissions from commercial and industrial natural gas customer meters represented in the U.S. EPA Annual Greenhouse Gas Inventory (GHGI). These meters have the potential to greatly influence nationwide methane emissions estimates from the natural gas distribution system. According to the GHGI for 2018, the NG production and exploration segments made up 58.6% of all methane from NG systems, followed by 24.2% from transmission/storage, 8.7% from processing, and 8.4% from distribution. Methane emissions from the distribution segment have received increased scrutiny recently despite the overall small percentage contribution to overall emissions. In 2018, the three largest sources of methane from the distribution segment were residential NG customer meters (17.4%), mishaps (dig-ins, 14.5%), and commercial/industrial NG customer meters (11.9%).

A comprehensive field sampling project was conducted across the U.S., visiting 337 commercial and 186 industrial meter sets across six regions to investigate and quantify methane emissions. This information was used to estimate nationwide population and “leaker-only” emission factors (EFs) for commercial and industrial natural gas customer meters nationally and by the six geographical regions. The population EF calculated in this study for industrial and commercial meters combined was 6 - 8 times higher than the current EF used in the GHGI. Broken down farther, the EF for industrial meter sets was 2 times higher than commercial meter sets. If the single EF for industrial/commercial meters or if individual EFs for each industrial and commercial meter sets are introduced into the GHGI, then the calculated methane emissions from the natural gas distribution segment could increase by 60 – 85%, driving emissions closer to those from the NG transmission/storage segment.