Research Scientists NETL/Leidos Pittsburgh, Pennsylvania, United States
The United States natural gas (NG) distribution sector has around 123,869 metering and regulating (M&R) stations according to the recent Environmental Protection Agency (EPA) Greenhouse Gas Inventory (GHGI). These stations contribute about 10% of total methane emissions from the NG distribution system that is at least $6.3 million loss per year. This loss could be in the form of fugitive emissions primarily from pneumatic devices and is dependent on the type of station, inlet pressure, and location of the station as well as the demand hours and seasonal fluctuation. The current emission factors (EF) developed by GHGI for the distribution sector are based on measurements from 59 M&R stations and do not account for the seasonal variability. National Energy Technology Laboratory is quantifying the fugitive emissions from M&R stations in winter and summer seasons using OTM 33A, a ground-based vehicle survey that uses EPA’s GMAP-REQ-DA (Geospatial Measurement of Air Pollution, Remote Emissions Quantification – Direct Assessment) technique to estimate methane emissions. This study will be used to verify the influence of weather on EF quantification by collecting both summer and winter data from the selected M&R stations. Here, we present the fugitive emissions from 22 M&R stations in Ohio in the winter season. The M&R stations were identified using a commercially available database. The GMAP vehicle was mounted with a 3D Ultrasonic Anemometer, Weather station, high resolution GPS and a Cavity Ring-down Spectroscopy instrument to measure methane concentration downwind of the stations. The emission rates were calculated by using an inverse Gaussian plume dispersion model. A first winter field visit was conducted from December 2019 to February 2020. Initial average emission rate excluding the outliers was estimated to be 12.47g/min and the emission factor used for the M&R station in the 2015 GHGI is 4.06g/min. Note that the current estimation is based on the data collected from small size of stations sampled, narrow geographical range, low temporal variation, and consideration of winter season only. A field campaign in Summer 2021 will be conducted to compare the seasonal variation.
