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Editor’s note: With this issue, Henry Terrell resumes authorship of this column, and David Blackmon begins authoring a quarterly round-up of U.S. federal and state regulatory issues and actions.
Most of the heat-trapping or “greenhouse,” gas (GHG) released by our species is carbon dioxide (CO2). However, of late, more attention has been focused on the number-two GHG source, methane. In tonnage terms, CH4 accounts for 9% of total heat-trapping gasses released due to human activity, but it has received disproportionate blame. This is because: 1) it is associated with the energy industries; and, 2) pound-for-pound, it possesses about 21 times the heat-trapping potential of CO2. These higher greenhouse properties are offset, partially, by methane staying in the atmosphere for a much shorter time than CO2.
A very significant share of man-caused methane has its origins in agriculture, specifically in the guts of ruminants. According to EPA, 32% of released CH4 is from livestock, 23% “enteric” (go ahead, look that up) and 9% from “manure management.” The energy industries, including coal, contribute about 43% of the total methane emissions, again according to EPA. The remainder is attributed to wastewater treatment, landfill leakage and other minor causes. The oil and gas industry comes in with a 30-share.
Dubious estimates. Quoting from the EPA document, Overview of Greenhouse Gases, “Some CH4 is emitted to the atmosphere during the production, processing, storage, transmission and distribution of natural gas. Because gas is often found alongside petroleum, the production, refinement, transportation and storage of crude oil is also a source of CH4 emissions.” Many attempts have been made to quantify the amounts of methane released, though their accuracy has been hindered by the inherent difficulty of the measurements. This has provided understandable frustration to those trying to write regulations, as well as those trying to follow them.
Groups attempting to stop or sharply limit hydraulic fracturing have cited methane emissions as a primary reason. Last February, two professors from Cornell University asserted that “fracking” releases large amounts of gas, which consists mostly of methane, directly into the atmosphere—far more than EPA estimates. Robert Howarth and Anthony Ingraffea said they believe that fractured wells “leak 40% to 60% more methane than conventional natural gas wells.” If this were true, then improvements in CO2 reduction, derived from an industrial switch from coal to natural gas, could be cancelled out by a sharp increase in CH4 emissions.
Go to the source: One thing missing from all the estimates was direct measurement. Fortunately, a step toward clarity was made last month by The University of Texas at Austin’s Cockrell School of Engineering. A year-long study of fraced wells at 190 gas production sites around the U.S., which included direct measurement of emissions at the well pad, showed that, in many cases, EPA estimates were significantly exaggerated on the high side. The UT team of researchers, along with scientists from the testing firms URS and Aerodyne, published the study, entitled “Measurements of methane emissions at natural gas production sites in the United States,” in the Proceedings of the National Academy of Sciences.
The team studied 150 production sites, 27 well completion flowbacks, nine well unloadings and four workovers and concluded that:
- Most fractured wells had equipment in place that reduced CH4 emissions 99%. This is 97% lower than EPA estimated in April 2013.
- Emissions from pneumatic devices are actually higher than EPA estimates at an average 70%.
- CH4 emissions from gas production were close to EPA estimates.
The study represented an almost unprecedented collaboration of government, energy company and Environmental Defense Fund (EDF) experts. Because geological differences can mean differences in operating practices, sample sites were spread out among four U.S. regions. Nine companies gave access to well sites, and assisted in developing sampling methods. This allowed the research team to make, in many cases, the first-ever direct measurements of methane emissions at the source. Samples were also taken downwind, where the local topography allowed it.
Sample bias? The study has been received positively by policymakers, industry and many environmental groups. Mark Brownstein of the EDF said it “shows that when producers use practices to capture or control emissions, such as green completions, methane can be dramatically reduced.” However, critics have accused the researchers of “cherry-picking” only the best well sites to sample, thus passing over what they call the “super-emitters.” The authors point out that they studied 489 wells over several large regions of the country. The participating companies did not have control over when the teams would arrive. Since only a small number of wells are in a completion stage at any given time, it was the schedule that determined which wells were sampled.
True, companies volunteered rather than submit to random selection, so it is possible that the worst offenders avoided scrutiny. The authors conclude that the next step is a series of much larger studies with bigger sample sizes.
The most important results of the UT study are that areas needing improvement, such as pneumatic controllers, have been identified, and technology used in so-called “green” completions has been shown to be effective. This gives future policy a firmer footing. 
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