Winter-Summer comparison of fugitive methane emissions from Metering and Regulating stations in Ohio, U.S.

Abstract:

The natural gas industry is one of the main sources of anthropogenic methane emissions, which is a concern as they contribute to greenhouse gas emissions and cause loss of product in the natural gas supply chain. While substantial research has been based on the methane emissions from the natural gas production and transmission sectors, less research been done in the distribution sector. Metering and Regulating (M&R) stations are one of the sources of fugitive methane emissions in natural gas distribution sector and as reported in the recent Environmental Protection Agency (EPA) Greenhouse Gases Inventory (GHGI), they were responsible for emission of 42.6 kt of CH₄ to the atmosphere, which is about 0.8% of total methane emissions from the natural gas industry and 9% in the distribution sector. Research shows that the emission factors determined for these sources in the EPA GHGI are based on field surveys of a small sample size in the Summer season, and there is no evidence that the fugitive methane emissions from the M&R stations in the Winter season are similar. This study focused on measuring CH₄ emissions from 25 M&R stations in Winter and Summer seasons in the state of Ohio by utilizing a cavity ring down spectrometer loaded in a sport utility vehicle (SUV) to collect CH₄ emissions downwind of the M&R stations. Inverse Gaussian Plume dispersion modeling was applied to calculate emission rates and identify the necessity of including seasonal observations to maintain accurate and representative emission factors in the GHGI for M&R stations. The emission rate for M&R stations in the 2018 GHGI was 4.06 g CH₄ /min while the average emission rate for M&R stations surveyed in this study was 12.47 g CH₄ /min for the Winter season.