The world’s largest facility to draw carbon dioxide out of the air began operation three weeks ago. It’s hoped to be the first of many carbon-capture plants that could be key for slowing down global warming.
And it’s now time to get serious about doing the same with methane, say researchers from Stanford University. Reducing methane in the atmosphere by 40 percent could reduce warming 0.4°C by 2050, and prevent over 50,000 premature deaths annually, they report in a modeling study published in Philosophical Transactions of the Royal Society A.
In an accompanying paper, they lay out a blueprint for a concerted research agenda for technologies to capture methane directly from air. “The time is ripe to invest in methane removal technologies,” said Robert Jackson, an author on both studies and a professor of energy and environment at Stanford. “Carbon dioxide removal has received billions of dollars of investments, with dozens of companies formed. We need similar commitments for methane removal.”
Methane emissions come mainly from livestock, rice farming, extracting oil and natural gas, and waste disposal in landfills. It remains in the atmosphere for a shorter time than CO2, but it is 81 times more powerful as a global warming gas over the first 20 years. So removing methane from ambient air could cut temperatures even faster than CO2 removal. Plus, methane is linked to harmful ozone formation in the atmosphere.
All together, because of its direct warming effects and ozone formation, methane has contributed nearly half of the global warming of CO2, say the researchers. Yet most climate research and policy has focused on CO2.
Using a model developed by the UK’s national weather service, Jackson and his colleagues measured the climate and air quality impacts of methane removal from the atmosphere. They construct different scenarios based on the amount of methane removed and the timing of removal.
The high-emissions scenario gave a temperature reduction of 0.4°C, while a low-emissions scenario in which temperature peaks during the 21st century, the same 40% methane removal could reduce the temperature by up to 1°C. In any scenario, “methane removal should be viewed as a complement to, not a substitute for, carbon dioxide removal and mitigation,” the researchers write.
But first, we need effective methane capture technologies. Researchers have developed a handful of techniques, such as the use of special catalysts or microbes to oxidize methane and convert it into CO2or methanol for industrial use.
While these technologies have been tested on a small scale in laboratories, none have been tested out in the field or on a large scale yet. The researchers call for deeper studies of these technologies in terms of cost; scaling up; technical efficiency; energy, land and water usage; social barriers of implementation; and potential negative effects.
In the end, regardless of the technology used, the team cautions that the volume of air that would need to be processed would be enormous. A system would have to treat 2 million teragrams of air to remove one teragram of methane. And as more and more methane is pulled from ambient air, further capture will require even more work and energy.
Just like for CO2, capturing methane near its sources where its concentration is higher than in ambient air would be much less expensive and energy-intensive, they say. This could be done at oil or natural gas wells, abandoned coal mines, landfills and farms. For instance, methane emissions might be difficult to eliminate at dairy farms, where methane concentrations can be 1000 times the average atmospheric concentration, so and strategically employing methane oxidation technologies could be effective.
Abernethy et al. Methane removal and the proportional reductions in surface temperature and ozone. Phil. Trans. R. Soc. A, 2021.
Robert B. Jackson et al. Atmospheric methane removal: a research agenda. Phil. Trans. R. Soc. A, 2021.