Natural Gas Midstream Projects
Integrated Component-Specific Measurements to Develop Emission Factors for Compressors and Reduce Uncertainties in the Greenhouse Gas Inventory Last Reviewed
December 2017


GSI Environmental Inc. (GSI), with project partners Utah State University (USU) and Houston Advanced Research Center (HARC), are employing a robust field measurement methodology to quantify methane product leaks (unplanned releases) and losses (venting) from above-ground natural gas gathering pipelines and compressor components in the gathering and boosting (G&B) segment to reduce uncertainty of methane emissions in the EPA’s Greenhouse Gas Inventory (GHGI). This project has involved multiple sampling events to 1) collect accurate and defensible leak and vent rate data from components such as pneumatic devices, open ended lines, valves, meters, and flanges; and 2) develop refined emission factors that are disaggregated by component type and include activity data such as gathering line material type, compressor operational modes, and gas throughput. Methane emissions have been measured over the full range of expected field condi¬tions, including seasonal variability in climate and operations, to better understand true emissions from compressor and gathering line in the G&B segment.

GSI Environmental Inc., Austin, Texas 78759

The natural gas industry contributes jobs, economic growth, energy security, and global leadership to the U.S., while focusing on environmental stewardship for the communities in which they operate. Knowledge of methane venting from compressors and gathering pipelines is currently limited and not accurately represented in the GHGI. For the natural gas industry, methane emissions constitute millions of dollars annually of natural gas lost to the atmosphere.

This project is contributing valuable research needed to refine natural gas leak and vent estimates that will ultimately help the industry improve gas product delivery in a safe and cost-effective manner. GHGI estimates are used to drive environmental policy and regulations at the federal level, which can lead to economic impacts on businesses, individual natural gas customers, and rate payers. By reducing uncertainty and improving the characterization of methane losses from natural gas production, regulations will be better aligned with actual field conditions, and the cost of compliance will be reduced, resulting in savings being passed on to rate payers.

This research will have a significant impact on national estimates of methane emissions from the natural gas industry and will support operators’ targeted leak repair programs that reduce product venting from their operations. The technical team working on this research has an intimate understanding of the challenges posed by air emissions impacts, and is keenly aware of the relationship between economic development and protection of natural resources. It is therefore understood that to minimize product loss, the industrial process must first be measured and leak/loss rates must be carefully characterized. This project utilizes existing technologies in an innovative approach to i) establish methane product leak and vent frequency at natural gas G&B stations, and ii) develop component-specific emission factors that are based on field measurements and not prior estimates.

The findings from this study will identify specific leak/vent metrics that can be tracked at a company-level so operators can better prioritize repair of non-hazardous leaks and maximize the reduction of product loss. Studies have shown that fat-tailed emissions can be responsible for up to 50% of total emissions. That is, a small number of leaking and/or venting components are responsible for much of industry-wide emissions. By characterizing the larger leaks, operators can more efficiently reduce the environmental impacts of their system. A reduction on leaks also improves the safety for customers and the public.

Accomplishments (most recent listed first)
Technical Advisory Steering Committee (TASC) calls were held with representatives from industry, academia, regulatory, non-governmental, and governmental organizations to discuss field investigation activities and preliminary results.

Preliminary, component-specific emission factors were developed to align with existing regulatory standards set forth in 40 CFR Part 98 Subpart W.

Field campaigns were completed in March, June, and October of 2017. Leak/vent sampling was conducted on compressor units, receiving and discharge gathering lines, separators, coalescers, slug catchers, dehydrators, liquid dump/holding vessels, methanol injection units, tanks, and fuel-gas skids.

TASC calls were held to discuss overall project strategy and proposed field investigation methodology.

The project was awarded on October 1, 2016. Project workplans (health and safety, project management, data management and technology transfer) and a Data Source Status Report were developed and submitted to DOE NETL.

Current Status (December 2017)
The spring field investigation will be performed in March 2018. Preliminary analysis of data is underway.

Project Start: October 1, 2016
Project End: July 31, 2018

DOE Contribution: $800,480
Performer Contribution: $201,000

Contact Information
NETL – David Cercone ( or 412.386.6571)
GSI Environmental Inc. – Dr. Susan Stuver ( or 512.346.4474)