The Environmental Defense Fund (EDF) has released a myriad of studies on natural gas system methane emissions over the past six years that have found low leakage rates between 1.2 and 1.5 percent of production. Five such studies are featured in the EID graphic shown above.

So the fact that a new EDF study released today finds methane leakage rates of 2.3 percent — well above what EDF-led research has previously found and “60 percent higher than the U.S. EPA inventory estimate,” according to the report — begs the question: What changed with regard to EDF’s methodology for this study that yielded a much higher leakage estimate than its past research has shown?

Turns out, quite a lot changed, and most of the changes raise red flags regarding the study’s conclusions. Not only did the authors of the new EDF study — which includes no new measurements and instead calculates national methane emissions based on past studies — opt not to use past EDF research as a basis for their emissions calculations, it relies exclusively on five far less comprehensive facility-level studies that lacked industry participation to arrive at its conclusion of higher U.S. emissions than previously reported. In contrast, an “alternative” calculation, based partially on EDF’s past studies, that finds emissions in line with current EPA estimates is buried in the study’s supplemental data and is not even mentioned in the report.

These are just two of several key issues regarding the manner in which EDF conducted this study that appear aimed at producing the most extreme emissions estimate possible ahead of the 27th annual World Gas Conference (WGC), which begins Monday in Washington, DC. Here is a deeper look at each issue.

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