Majority of US urban natural gas emissions unaccounted for in inventories Journal Article uri icon



  • Across many cities, estimates of methane emissions from natural gas (NG) distribution and end use based on atmospheric measurements have generally been more than double bottom-up estimates. We present a top-down study of NG methane emissions from the Boston urban region spanning 8 y (2012 to 2020) to assess total emissions, their seasonality, and trends. We used methane and ethane observations from five sites in and around Boston, combined with a high-resolution transport model, to calculate methane emissions of 76 ± 18 Gg/yr, with 49 ± 9 Gg/yr attributed to NG losses. We found no significant trend in the NG loss rate over 8 y, despite efforts from the city and state to increase the rate of repairing NG pipeline leaks. We estimate that 2.5 ± 0.5% of the gas entering the urban region is lost, approximately three times higher than bottom-up estimates. We saw a strong correlation between top-down NG emissions and NG consumed on a seasonal basis. This suggests that consumption-driven losses, such as in transmission or end-use, may be a large component of emissions that is missing from inventories, and require future policy action. We also compared top-down NG emission estimates from six US cities, all of which indicate significant missing sources in bottom-up inventories. Across these cities, we estimate NG losses from distribution and end use amount to 20 to 36% of all losses from the US NG supply chain, with a total loss rate of 3.3 to 4.7% of NG from well pad to urban consumer, notably larger than the current Environmental Protection Agency estimate of 1.4% [R. A. Alvarez et al., Science 361, 186–188 (2018)].

publication date

  • November 2, 2021

Date in CU Experts

  • October 26, 2021 2:13 AM

Full Author List

  • Sargent MR; Floerchinger C; McKain K; Budney J; Gottlieb EW; Hutyra LR; Rudek J; Wofsy SC

author count

  • 8

Other Profiles

International Standard Serial Number (ISSN)

  • 0027-8424

Electronic International Standard Serial Number (EISSN)

  • 1091-6490

Additional Document Info

start page

  • e2105804118

end page

  • e2105804118


  • 118


  • 44