Roughly 50 sites generate one-third of California methane emissions

A small number of methane emitters generate a disproportionate amount of California’s methane emissions, and landfills are the biggest culprit, according to a NASA Jet Propulsion Laboratory study. The work determined that some 50 point-source methane emitters—defined as individually identifiable sources of methane—generate more than half the state’s point-source methane emissions and one-third of the state’s overall methane emissions (Nature 2019, DOI: 10.1038/s41586-019-1720-3). The key point-source methane emitters in California are oil and natural gas fields, large dairies, and landfills. Nonpoint sources include, for example, natural gas leaks from homes that, though small by themselves, may collectively add up to a large amount. Over a 2-year period, a research team flew a plane equipped with infrared imaging instrumentation over nearly 300,000 facilities in California and identified 564 individual point sources emitting high concentrations of methane. The researchers found that 10% of those emitted 60% of measured methane emission. They further