Methane is a very potent greenhouse gas from carbon dioxide, capturing much more heat. The point source methane emitters are typically small – usually less than 10 meters in diameter – but they emit highly concentrated methane plates. So, if we want to reduce the amount of methane we spit in the air (which we obviously should, though we don't), they will be great potential targets. Only when we could identify them.
To map such emissions at points, scientists in California flew across the state with an airborne spectrometer, using it to measure methane emissions. They focused on a long list of potential sources: oil and gas production, processing, transmission, storage and distribution equipment; refineries; dairy manure sites; landfills and composting facilities; wastewater treatment plants; gas stations; and facilities for liquidated and compressed natural gas
Most facilities, especially dairies and oil fields, were in the San Aokin Valley. The researchers ended up measuring emissions from 564 different sources at 250 different facilities. These dot emitters have not really been investigated before, as they often control methane intermittently or sporadically. To capture them, the researchers repeated the drones five times between August 2016 and October 2018.
They conclude that about 40% of California's methane emissions come from these emitters from multiple sources, rather than from larger, diffuse sources, such as rice fields. Over half of point-source shows come from only 10% of the pages.
The landfills were the worst, followed by the dairies and the oil and gas sector. An earlier analysis that used atmospheric measurements instead of airborne spectrometry returned the relative contributions of landfills and dairies, which led the authors of this newer work to suggest that other emission sectors could also have been improperly estimated at that earlier estimate. The authors also point out that, perhaps not shockingly, "Big differences have been observed between many self-reported emissions from participating facilities and [this airborne imaging study] and independent assessments of the air. "
The good news is that when scientists simply told facility operators that they had methane super-emitters, they were often able to reduce emissions. Four such cases are due to leaks in liquefied natural gas storage tanks; this study found the leaks and told the operators, who then repaired them. Further flights confirmed that the repairs had stopped the emissions. This constant monitoring of dot emitters and widespread low level emitters can definitely help mitigate methane emissions. As you can feed the algae on cows.
Nature, 2019. DOI: 10.1038 / s41586-019-1720-3 (For DOI).