Methane is a much stronger greenhouse gas than carbon dioxide and binds much more heat. Point source methane emitters are typically small – typically less than 10 meters in diameter – but they emit clouds of highly concentrated methane. So, if we want to reduce the amount of methane we throw into the air (which we should of course do, though we do not), these would be big potential targets. If only we could identify her.
To model such point emissions, scientists in California flew over the state with an airborne imaging spectrometer and used it to measure methane emissions. They focused on a long list of potential sources: oil and gas production, processing, transmission, storage and distribution; refineries; Dairy Management Offices; Landfills and composting plants; sewage treatment; Gas power plants; Installations for liquefied and compressed natural gas.
Most of the plants, especially the dairies and the oil fields, were located in the valley of San Joaquin. Researchers measured emissions from 564 different sources in 250 different facilities. These spotlights have not really been studied since they often emit their methane only sporadically or intermittently. To catch them, the researchers have repeated the overflights five times between August 201
They conclude that around 40% of Californian methane emissions come from these point source emitters and not from larger, more diffuse sources such as paddy fields. More than half of the point source emissions come from just 10% of the sites.
The worst was landfills, followed by dairies and the oil and gas sector. An earlier analysis using atmospheric measurements instead of aerial imaging spectrometry reversed the relative contributions from landfills and dairies, leading the authors of this recent work to conclude that other emission sectors in this earlier assessment may also have been misjudged. The authors also highlight that, perhaps not shockingly, "large discrepancies between many of the self-reported emissions from participating facilities and [this airborne imaging study] and independent airborne estimates are observed."
Plant operators who had methane super-emitters, could often reduce these emissions. Four of these cases were due to the leakage of LNG tanks. This study found the leaks and told the servers that they then repaired. Further overflights confirmed that the repair stopped emissions. This constant monitoring of both the spot emitters and the widespread low-level emitter could definitely help reduce methane emissions. How could you feed cows with kelp?
Nature, 2019. DOI: 10.1038 / s41586-019-1720-3 (About DOIs).