Majority of US urban natural gas emissions unaccounted for in inventories

Details

• Journal Title:
  Proceedings of the National Academy of Sciences
• Personal Author:
  Sargent, Maryann R. ; Floerchinger, Cody ; McKain, Kathryn ; Budney, John ; Gottlieb, Elaine W. ; Hutyra, Lucy R. ; Rudek, Joseph ; Wofsy, Steven C.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; CPO (Climate Program Office) ; GML (Global Monitoring Laboratory)
• Description:
  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 198 ± 47 Gg/yr, with 127 ± 24 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)].
• Keywords:
  Air Quality Methane Air Quality Greenhouse gas emissions
• Source:
  PNAS 118 (44) e2105804118
• Series:
  44
• DOI:
  https://doi.org/10.1073/pnas.2105804118
• Document Type:
  Journal Article
• Funding:
  Grant no. NA17OAR4310086 ; Grant no. NA20OAR4310303
• Place as Subject:
  United States
• Rights Information:
  Other
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha256:9565609a48464aeacee46c67027d914f0083b5a8c30faf5f00c8cd83b01f7250
• Download URL:
  https://repository.library.noaa.gov/view/noaa/45565/noaa_45565_DS1.pdf
• File Type:
  [PDF - 1.17 MB ]