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Integrated Component-Specific Measurements to Develop Emission Factors for Compressors and Reduce Uncertainties in the Greenhouse Gas Inventory
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GSI Environmental Inc. (GSI), with project partners Utah State University (USU) and Houston Advanced Research Center (HARC), will employ a robust field measurement methodology to quantify methane product leaks (unplanned releases) and losses (venting) from natural gas gathering pipelines and compressor components in the gathering and boosting (G&B) segment to reduce uncertainty and potential overestimation of methane emissions in the EPA’s Greenhouse Gas Inventory (GHGI). The project will involve multiple sampling events to 1) collect accurate and defensible leak and loss rate data from components such as pneumatic devices, open ended lines, valves, 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 will be measured over the full range of expected field conditions, including seasonal variability in climate and operations, to better understand true compressor and gathering line emissions from G&B stations.


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 losses 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 of natural gas lost to the atmosphere annually.

This project will contribute valuable research needed to refine natural gas leak and loss 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 leads 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 loss 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 loss 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/loss 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 leaks and losses 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)

The first of four field campaigns were completed on March 3, 2017. Leak/loss sampling was conducted on compressor units, receiving and discharge gathering lines, separators, coalescers, slug catchers, dehydrators, liquid dump/holding vessels, methanol injection units, and fuel-gas skids.

Proposed compressor station and gathering pipeline components were identified for measurement. Multiple gathering and boosting facilities were selected for field evaluations.

Technical Advisory Steering Committee (TASC) calls were held with representatives from industry, academia, regulatory, non-governmental, and governmental organizations 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

The summer field investigation will be performed in May 2017. Preliminary analysis of data is underway.

Project Start
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DOE Contribution


Performer Contribution


Contact Information

NETL – David Cercone ( or 412.386.6571)
GSI Environmental Inc. – Ann Smith ( or 512.297.0347)


Additional Information

Final Project Report [PDF-5.00MB]