Q&A: Getting serious about atmospheric methane removal

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Carbon dioxide, the most important man-made greenhouse gas, gets most of the attention in efforts to stem the effects of climate change. While methane is considered a much more potent greenhouse gas, it breaks down into carbon dioxide and water in the atmosphere within 12 years or so.

Still, the warming it causes during this time is significant enough that the National Academies of Sciences, Engineering and Medicine are exploring the merit of pulling methane out of the atmosphere—similar to the carbon dioxide capture demonstration projects already underway.

Margaret Wooldridge, a professor of mechanical engineering, recently collaborated on a new report calling for increased research into atmospheric methane removal to help combat the impacts of climate change.

What makes methane a worthy target for research efforts aimed at removing it?

Wooldridge: The bad thing about methane is that it's really effective as a greenhouse gas—even more effective than CO₂. It's better as an infrared absorber and it has more than 80 times the warming potential of CO₂ in the short term (less than 20 years).

But methane also presents us with the opportunity to get more bang for your buck in terms of how big an impact removal can have and how quickly that impact can be felt. Methane removal at any time is good, but earlier removal is even better than later. Less methane in the atmosphere frees up OH to remove more methane from the atmosphere; this amplifies methane mitigation and removal efforts.

There has been a lot of work done on identifying the sources of methane, resulting in good understanding about the five primary sources. And there are some easier solutions—lower-hanging fruit, like fixing leaks in natural gas pipelines.

Methane sources are both manmade, like landfills and pipelines, and natural, like wetlands and permafrost, and combinations of both, like animals and their manure. So reducing methane emissions presents a lot of opportunities for intervention and impact.

So what's the catch? Why haven't we focused on atmospheric methane removal before?

In part, methane is harder to capture since it's not as prevalent in the atmosphere as CO₂. CO₂ is 400 parts per million in the atmosphere and methane is two orders of magnitude lower at 2 parts per million.

Methane is also a really funny and interesting molecule. It's small, symmetric, non-polar, and not polarizable, coupled with the low concentration, makes CH₄ much harder to capture compared with CO₂.

So, for atmospheric methane removal, we have to find those two parts per million of methane in the air and then separate them. And doing that is hard. Part of what we're saying in this report is that, in this area, we don't know what we don't know about how to remove methane molecules from the atmosphere.

We know the general categories of removal, like membrane separation or surface treatments. These are the broad ideas right now, and this report provides directions for a research agenda.

Even with CO₂ removal, the technology is not commercialized yet, but the Department of Energy recently funded its first CO₂ direct capture hub to try to show CO₂ air capture can be done in a way that's cost effective.

What are some of the intriguing research areas for atmospheric methane removal out there?

One of the interesting ones is catalytic paints. You could paint a building with these specialized materials. The paints could reflect heat which reduces the energy footprint of the building while also capturing methane and, possibly, other pollutants and gases as well.

In any approach where you're having to move air, even with a direct capture facility, you're talking about very high energy costs. That's another area that could use investigation—methods where you have air movement that's passive, or natural, so you're not using that same level of energy.

Low temperature catalysts are always a goal. You want catalysts that don't use as much of the active materials, and you want them to operate with low energy inputs. There are all sorts of areas like this that need more research.

With the release of this report, what are you hoping for?

I'm hoping that this report will energize fundamental research on atmospheric methane removal. But I am also hoping this momentum generates renewed and sustained interest in methane mitigation because mitigation has obvious benefits. What we're trying to understand is does atmospheric methane removal also have obvious and significant benefits?

An example would be large farming operations that produce methane. If you produce enough of it, there are possibilities for using it as an energy source. In the right circumstances, farmers could sell their methane. There may be ways to take that waste and turn it into something valuable while simultaneously helping address climate change.

More information: A Research Agenda Toward Atmospheric Methane Removal (2024). DOI: 10.17226/27157

Provided by University of Michigan