Scientists Propose Methane Removal As Quick Fix For Climate Change

Removing a few billion tons of methane — a potent greenhouse gas (GhG) — from the atmosphere might reduce short-term global warming much faster than what can be achieved by removing far larger amounts of carbon dioxide.

This unusual idea spelled out in a paper published in the online monthly journal Nature Sustainability proposed developing systems that attain this aim. The study said that molecule-for-molecule, methane traps 84 times more heat than CO2.

“Methane removal would buy us considerable time to address the [larger] problem of carbon dioxide emissions,” Rob Jackson, a professor of earth system science at Stanford and lead author of the paper, said.

The study noted that we’d only need to eliminate 3.2 billion tons of methane to get back to earlier or preindustrial levels of this GhG. On the other hand, it will be necessary to remove hundreds of billions of metric tons of CO2 to return to preindustrial levels.

Success in eliminating this much methane will reverse one-sixth of the total warming effect of all GhGs in the atmosphere, according to the study.

To remove methane, the study proposes using zeolites, a class of minerals with very tiny pores commonly used as industrial catalysts. Zeolites are used as alkane-cracking catalysis in oil refining, for example.

Scientists note methane reacts poorly with most substances, and this is the reason why it’s physically difficult to trap this GhG. Another reason is that removing methane is a lot more difficult than capturing CO2, mainly because it’s far more dilute in the atmosphere.

While removing CO2 means plucking one molecule from among some 2,400 molecules in the air, capturing methane means snatching one nested amid more than 500,000 molecules.

One scenario proposed by the study is to use giant electric fans to suck air into tumbling chambers, where powdered zeolites will cling to methane molecules.

While this method is likely to cost more than carbon capture on a per-ton basis, “it could yield greater climate and economic value because of methane’s greater potency as a greenhouse gas,” said the study.

In April 2013, researchers from Berkeley and the Lawrence Livermore National Laboratory tested more than 87,000 zeolite structures and found a few candidates with enough sorption capacity to be technologically viable.

Their study said zeolites and other technologies should be evaluated and pursued to slash methane concentrations in the atmosphere from 1,860 ppb to preindustrial levels of some 750 ppb. Such a goal of atmospheric restoration provides a positive framework for change at a time when climate action is desperately needed.

It’s not the first time this idea has been floated. But Jackson and his co-authors took a closer look at what the climate benefits would be and how it could be done.

Most scientific models now show the world will need to remove vast amounts of CO2 to prevent exceeding dangerous warming thresholds, given how much has already been emitted and how little has been done to shift away from fossil fuels.

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The methane trapped in zeolites will be converted into CO2 and released again by heating the trapped molecules. When burned, methane emits only half the CO2 coal does. When released freely into the atmosphere, methane is 20 times more powerful than CO2 as a GhG.

This process, puzzling as it sounds, will still provide very significant reductions in warming. The captured methane could also be stored and converted into other products, but these processes will add a lot of cost and complexity to the process

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