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

DE-FE0029068

Goal
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.

Performer
Colorado State University, Fort Collins, CO 80524

Background
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.

Impact
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)
Solid progress has been made on the protocols, with active participation by industry partners and the study team. Protocols for the measurement campaign have been created, discussed with industry partners, and modified to satisfy the needs of the partners and to maximize the productivity and value that the campaign will deliver.

CSU has established relationships with nine industry partners for the field sampling campaign. To date, six of nine partners have provided requested data for campaign planning purposes and the remaining three partners are in the process of having these agreements approved and will thereafter provide data.

Current Status (August 2017)
Site access agreements are currently in progress to support site access during the field campaign. Partners have agreed to request methane-specific emissions data from existing exhaust stack testing for use in the study. Partners have assisted in designing a multi-day pneumatic measurement system that will be accepted for use at field sites.

Data received thus far indicates that partner sites (over 1,350 in number) will provide a nationally representative sample of gathering and boosting stations from which to draw. Sites also provide representative samples in terms of different gas types (wet and dry) and size variation (number of compressors).

The field sampling campaign began June 12, 2017, with 16 weeks of the campaign planned with current partners. The remaining 3 to 4 weeks will be scheduled with additional partners to round out available sites for sampling.

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

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

Contact Information
NETL – Eric Smistad (eric.smistad@netl.doe.gov or 281-494-2619)
Colorado State University – Dan Zimmerle (daniel.zimmerle@colostate.edu or 970-581-9945)