EPA Pauses Methane Rule as NOAA Study Finds Overstated Emissions from Oil and Gas

Thursday, June 01, 2017

Methane emissions from oil and natural gas development may be far lower than previously thought, according to a new peer-reviewed study. Researchers led by Dr. Stefan Schwietzke with the National Oceanic & Atmospheric Administration (NOAA) found that previous high emissions estimates were based on measurements taken during peak events, and do not necessarily reflect average emission rates.

The new research comes as the U.S. Environmental Protection Agency announced a 90-day stay on federal rules targeting methane from oil and natural gas production. The stay is intended to give EPA time to reconsider the regulations, which were implemented during President Obama’s final year in office as a key part of his administration’s climate action agenda.

The study, published in the journal Environmental Science & Technology, explains how previous assessments finding so-called methane “super-emitters” relied on data collected during episodic and other events that contributed to peak emissions. Those studies, which suggested methane emissions were as much as 50 percent higher than EPA estimates, incorrectly used the anomalous emissions data as reflective of normal operations.

“Operator reported hourly activity data show that midday episodic emissions from manual liquid unloadings (a routine operation in this basin and elsewhere) could explain ~1/3 of the total emissions detected midday by the aircraft and ~2/3 of the West-East difference in emissions,” the study’s abstract reads.

Aircraft measurements of methane emissions (also called “top-down” measurements) typically occur around noon to get the best readings. But this is also when episodic emissions events, which are typically scheduled by operators as a part of routine operations, will have their greatest influence on overhead readings. Thus, even though they are not reflective of average operations, measurements taken during this time can suggest emissions from oil and natural gas development are much higher than they really are.

As the study’s abstract also states, “episodic sources can substantially impact midday methane emissions and…aircraft may detect daily peak emissions rather than daily averages that are generally employed in emissions inventories.” 

The study is the first of a series of papers looking to reconcile “top-down” measurements with data collected directly from well sites.

EPA, meanwhile, announced last April its intention to issue a stay of its fugitive methane emissions rules, which it did earlier this week. The agency is planning to propose a new rule, though no firm timeline has been set.

 

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