Natural Gas Midstream Projects
Characteristics of Gathering and Boosting Stations Last Reviewed December 2017


The objective of this project is to develop: (1) nationally-representative, activity-weighted, methane emission factors for each type of equipment located at typical gathering compressor stations, suitable for use in the Environmental Protection Agency (EPA)'s Greenhouse Gas Inventory (GHGI) and other policy discussions; (2) develop estimates of episodic emissions; and (3) test new methods to characterize intermittent device emissions.

Colorado State University, Fort Collins, CO 80524

From 2013 to 2015, CSU conducted the first comprehensive national study of methane emissions from gathering compressor stations and processing plants as part of an EDF-organized emissions study. The CSU study included facility-level methane emissions measurements at 114 gathering compressor stations and 16 processing plants in 13 U.S. states. Methane emissions from gathering facilities were higher than expected, with 20 percent of the facilities exhibiting methane loss rates greater than 1%. The measurement results were used, along with a national estimate of gathering facility counts, to estimate total methane emissions from all U.S. gathering operations. The results showed that methane emissions from gathering was under-represented by a factor of eight in the GHGI. The GHGI was updated in 2016 (2014 data) to reflect the results of the CSU study, and included a revised gathering station count (4999 stations) and facility-level emission factor (43 kg/h) from the study. With these updates to the GHGI, gathering operations are now estimated to account for 27% of methane emissions from the natural gas supply chain.

Unfortunately, constraints on the CSU gathering and processing (G&P) study did not allow for on-site measurement of individual emission sources. Because the GHGI utilizes per-device emission and activity factors to back-cast emissions, there is a pressing need to complement the prior study with detailed on-site, point-source measurements. Further, detailed knowledge of emission sources provides critical information for policy discussions related to emissions reductions, such as development of the Section 111(d) reporting requirements. Industry groups can utilize per-device emissions measurements to develop emissions reduction strategies, such as work currently underway by ONE Future™, a sponsor of this project. New emission measurements will inform new methane monitoring technologies.

Results of this study will identify device-level emission factors for the EPA GHGI, to support estimates of current methane emissions and to contribute to back-casting to GHGI’s 1992 baseline year. Additional elements of the study will provide data suitable for a broad range of emission modeling efforts. Emissions and activity data may also support modeling of non-methane emissions (such as volatile organic compounds), including life-cycle analyses, and (if regional differences are seen in activity data) regionalized models of emissions. The project will extend measurement science in the characterization of intermittent device emissions. Facility-level and device-level emission models will serve as a guide for methane mitigation efforts, such as utilizing low cost methane sensors for LDAR applications.

Accomplishments (most recent listed first)

  • Field measurement campaign (19 weeks) has been completed, not counting additional ongoing effort for long-term pneumatic recordings.
  • Stack testing for methane entrained in exhaust emissions was accomplished using a novel in-stack tracer protocol. The study team extended and refined a historical method, which will likely be documented in an additional paper. Testing was completed on 129 engines including 81 lean-burn 4-stroke and 48 rich-burn 4-stroke engines. Due to lack of population, no turbines or 2-stroke engines were measured. Measurements included 426 individual tests.
  • The field campaign was able to sample across a broad diversity of facilities nationally, including substantial variation in location, gas composition, facility age, and facility configuration.
  • Component counts were completed on 776 pieces of major equipment, including over 500 compressor units, resulting in field counts of over 85,000 components.
  • Long-term pneumatic recordings were completed on 80 pneumatic devices, averaging 76 hours of recording per device.
  • Data has been compiled and is in the process of QA/QC.
  • A first review of the field campaign results was completed with the study partners "technical review committee" on December 14, 2017.
  • The project established a solid group of nine industry partners, some with midstream and some with upstream operations. These companies represent a national cross section of gathering facilities, and operate approximately 1,600 gathering compressor stations (of an estimated 4,500 nationally). All partners agreed to provide access to their stations for the field measurement campaign.

Current Status (December 2017)
Major field campaign operations are complete. However, additional long-term pneumatic recordings are continuing through January and February 2018. Initial compilation of data has been completed, and QA/QC processes have been started. Reviews will be completed with the scientific advisory panel and steering committee in January 2018. Final report on track for September 2018.

Project Start: October 1, 2016
Project End: September 30, 2018

DOE Contribution: $1,872,016
Performer Contribution: $474,727

Contact Information
NETL – Eric Smistad ( or 281-494-2619)
Colorado State University – Dan Zimmerle ( or 970-581-9945)