"Over the course of three years, NASA flew a plane carrying gas-imaging equipment above California and made a discovery that surprised even the state’s own environmental agencies: A handful of operations are responsible for the vast majority of methane emissions.
In a report published in Nature on Wednesday, scientists estimated that 10% of the places releasing methane -- including landfills, natural gas facilities and dairy farms -- are responsible for more than half of the state’s total emissions. And a fraction of the 272,000 sources surveyed -- just 0.2% -- account for as much as 46%.
The report doesn’t identify these “super emitters,” but notes that landfills give off more methane than any other source in the state. NASA’s equipment found that a subset of these landfills were the largest emitters in California and exhibited “persistent anomalous activity.”"