Methane is the second most important gas disrupting the climate, and concentrations are rising faster than ever. There are a lot more holes in our understanding of the sources of methane than for carbon dioxide, which interferes with efforts to slow the threat. It's got to the point where a team at Stanford University have proposed turning atmospheric methane into carbon dioxide, a truly last-gasp effort to prevent climate catastrophe.
Carbon dioxide is the largest source of global heating, simply because we emit so much of it. However, molecule for molecule, many other gasses are worse. In 20 years, methane does 84 times as much damage as the same weight of CO2, 28 times as much over a century.
The National Oceanic and Atmospheric Administration (NOAA) reports that 2018 saw a 10.8 parts per billion (ppb) jump in methane levels in the atmosphere, the second largest this century. This follows large increases every year since 2007, after an 8-year lull made some people think methane was in balance.
Methane is released from burping cows, flooded rice fields, warming permafrost, and badly managed drilling operations, among others. Identifying the relative contributions of each is key to controlling the problem. The contribution via fracking of unconventional natural gas deposits is hotly debated and could be controlled if recognized as serious enough.
In other cases, however, there is little we can do to stop the methane from escaping. If we are seeing the first firing of the clathrate gun, where methane frozen in the Arctic for millions of years is escaping as the world warms, we'll find it hard to reverse the problem.
That's why Professor Ed Solomon has suggested a counter-intuitive idea: he proposes collecting methane from the atmosphere and converting it to carbon dioxide for re-release. At first, this may make little sense – after all, carbon dioxide in the atmosphere is the primary threat. However, in light of the greater warming effect of methane, turning a molecule of methane to carbon dioxide is a major net win.
In Nature Sustainability, Solomon suggests using zeolite – a crystal of silicon, aluminum, and oxygen – as a sponge to store atoms that break methane down. “The porous molecular structure, relatively large surface area and ability to host copper and iron in zeolites make them promising catalysts for capturing methane and other gases," said Solomon in a statement.
The idea is a long way from a prototype, let alone a working model, but Solomon and co-authors suggest building giant fans that force air over powdered zeolites. These would capture the methane and turn it to carbon dioxide on heating in oxygen. Even after allowing for the electricity required to make it happen, this could be a net win for the climate, theoretically capable of bringing concentrations down from 1,860 ppb today to pre-industrial levels of 750 ppb.
To be profitable, it would require a price on carbon pollution 10-20 times higher than those in use today, which certainly suggests we'd be better off preventing any emissions we can.