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Collecting Emissions Data for Shale Gas Facilities

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Article Posted On 3/21/2016

How do you monitor and quantify methane and other volatile organic compound emissions from the natural gas industry, which has thousands of small facilities spread over multiple states? This is a fundamental challenge to understanding the impact of the shale gas industry in the Marcellus Shale.

To address this issue, regulators and public policymakers are interested in both the aggregate emissions across a shale basin as well as emissions at each facility (well, compressor, etc.). Obtaining emissions data is complicated, however, by several factors: the sheer number of facilities, potential variations in emissions over time ("temporal variation") at a given facility and large site-to-site variations in emissions.

A PITA-funded project between Carnegie Mellon University's Center for Atmospheric Particle Studies (CAPS) and RJ Lee Group is addressing this challenge by focusing on understanding the emissions produced by "super-emitter" facilities.

"Finding super emitters and quantifying their emissions is critical to maintaining compliance with EPA regulations and to limiting overall emissions from each shale basin," explained Carnegie Mellon Assistant Research Professor Albert Presto, who is the principal researcher on the project. The team also includes Raymond J. Lane Distinguished Professor of Mechanical Engineering Allen Robinson.

While most facilities have low emissions, a small fraction of super-emitter facilities can provide the bulk of the emissions (e.g., 10 percent of the sites by number can cause more than 50 percent of the emissions). The research team is developing sample methods and analysis tools that will quickly diagnose super emitters as well as better characterize temporal variations in emissions from shale gas facilities.

They have used a pair of mobile laboratories -- the CAPS mobile lab and the RJ Lee Group's mobile lab -- that are equipped to measure methane and volatile organic compounds (VOCs). In one set of tests, the mobile laboratories parked downwind of known shale gas sources (one well, one compressor station and one gas processing plant) to observe temporal variations in emissions from these facilities. In a separate set of experiments, CMU performed mobile measurements to identify incidental plumes of methane and other VOCs that may have originated from shale gas facilities.

As well as quantifying temporal variations in emissions, these measurements have helped RJ Lee to validate their mobile platform and equipment for use in shale gas regions. Also, real-time measurement of methane and VOC concentrations can provide industry with a means to identify the specific emission sources, so the cause of the emissions can be corrected.

In the coming months, the team will use dispersion modeling tools, along with Google Earth images and databases of well pad locations, to estimate emission rates and facility locations that could describe the observed plumes.