Methane Emissions from United States Natural Gas Gathering and Processing

Abstract

New facility-level methane (CH4) emissions measurements obtained from 114 natural gas gathering facilities and 16 processing plants in 13 U.S. states were combined with facility counts obtained from state and national databases in a Monte Carlo simulation to estimate CH4 emissions from U.S. natural gas gathering and processing operations. Total annual CH4 emissions of 2421 (+245/-237) Gg were estimated for all U.S. gathering and processing operations, which represents a CH4 loss rate of 0.47% (±0.05%) when normalized by 2012 CH4 production. Over 90% of those emissions were attributed to normal operation of gathering facilities (1697 +189/-185 Gg) and processing plants (506 +55/-52 Gg), with the balance attributed to gathering pipelines and processing plant routine maintenance and upsets. The median CH4 emissions estimate for processing plants is a factor of 1.7 lower than the 2012 EPA Greenhouse Gas Inventory (GHGI) estimate, with the difference due largely to fewer reciprocating compressors, and a factor of 3.0 higher than that reported under the EPA Greenhouse Gas Reporting Program. Since gathering operations are currently embedded within the production segment of the EPA GHGI, direct comparison to our results is complicated. However, the study results suggest that CH4 emissions from gathering are substantially higher than the current EPA GHGI estimate and are equivalent to 30% of the total net CH4 emissions in the natural gas systems GHGI. Because CH4 emissions from most gathering facilities are not reported under the current rule and not all source categories are reported for processing plants, the total CH4 emissions from gathering and processing reported under the EPA GHGRP (180 Gg) represents only 14% of that tabulated in the EPA GHGI and 7% of that predicted from this study.

Comparing facility-level methane emission rate estimates at natural gas gathering and boosting stations

“…Dual-tracer release measurements of gathering stations were made previously in a national study by Mitchell et al (2015); however, no on-site or aircraft measurements were made. These measurements were used by Marchese et al (2015) to develop a national estimate of CH 4 emissions from gathering stations, which indicates an average emission rate of 53,066 scf/day (43 kg/h) per station. The influence of tank venting on the average FLER for 31 gathering stations measured by tracer in this study was evaluated in S8.…”

Quantifying methane emissions from natural gas production in north-eastern Pennsylvania

“…Data for compressor station locations and emissions come from a data set used in Marchese et al (2015). A total of 489 compressor facilities are listed for Pennsylvania, with 87 % of the listed facilities also containing location data.…”

“…Emissions for each compressor station are calculated through two different methodologies. In the simplest case, a flat emission rate of 32.35 kg h −1 is applied to each station, which is the mean emission rate of a gathering facility in PA found in Marchese et al (2015). In the more complex scenario, the same emissions total is used as in the flat rate case but is distributed among the compressor stations linearly as a function of their energy usage.…”

Estimating greenhouse gas emission level of a natural gas transmission pipeline from point A to B in West Java based on INGAA and IPCC guidelines

“…Methane, the main component of natural gas, is a more potent GHG gas than CO 2 as methane produces 21 times of trapped heat in the atmosphere when compared to CO 2 [2]. Several methane emissions studies have been reported as direct measurements from different natural gas supply chain facilities (exploration, production, gathering, processing,transmission, and distribution) with a variety of CH4 emission sources including fugitive, venting, and combustion emissions for objects in United States [3,4,5]. These studies basically estimate and calculate new emission factors based on direct measurements and mostly refer to The Environmental Protection Agency (EPA) Greenhouse Gas Inventory (GHGI) in comparing their calculation results.…”

“…The assessment result was then developed to extrapolate emission factors of Russian long distance gas transmission pipeline. However, these studies [3,4,5,6] had not assessed the variation of natural gas throughput and its contribution to emissions level, both fugitive and venting emissions.…”