Toward a Functional Definition of Methane Super-Emitters:
Application to Natural Gas Production Sites
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Abstract
Emissions from natural gas production sites are characterized by
skewed distributions, where a small percentage of sitescommonly
labeled super-emittersaccount for a majority of emissions.
A better characterization of super-emitters is needed to operationalize
ways to identify them and reduce emissions. We designed a conceptual
framework that <i>functionally</i> defines superemitting
sites as those with the highest proportional loss rates (methane emitted
relative to methane produced). Using this concept, we estimated total
methane emissions from natural gas production sites in the Barnett
Shale; functionally superemitting sites accounted for roughly three-fourths
of total emissions. We discuss the potential to reduce emissions from
these sites, under the assumption that sites with high proportional
loss rates have excess emissions resulting from abnormal or otherwise
avoidable operating conditions, such as malfunctioning equipment.
Because the population of functionally superemitting sites is not
expected to be static over time, continuous monitoring will likely
be necessary to identify them and improve their operation. This work
suggests that achieving and maintaining uniformly low emissions across
the entire population of production sites will require mitigation
steps at a large fraction of sites