The Case for Methane Removal

Excerpted from Pull the "undo methane" lever by: K Young

You may be aware of CDR—the idea is to remove CO2 from our atmosphere in order to slow and reverse atmospheric warming. This article is about doing the same thing, but with methane. If we remove 400 MT (megatons) of methane from our atmosphere every year by 2040, we can hope to shave ~1oC off peak global warming. This would be a huge deal; no other comparatively safe approach that I'm aware of gets anywhere near this level of impact.

CO2 is not enough

To keep our world mostly stable, we must not let it warm more than 1.5oC (above pre-industrial levels)—warmer temperatures would mean the accelerated unraveling of systems. But we're already at 1.2oC, and according to the U.N., there is no credible pathway to stay within the 1.5oC limit. Even with all our progress with CO2 emissions reductions, it seems we are on track for a calamitous 2.6oC of warming.

Methane to the rescue

But! In addition to emitting CO2, we’ve also been emitting a lot of methane. Humans have more than doubled the amount of methane in our atmosphere since pre-industrial times. That excess methane is responsible for more than ? rd of our current warming. The good news is: it may be much more efficient to reduce methane in the atmosphere than CO2. (Note: though this article doesn’t focus on methane emission reductions, rapid, deep, reductions are absolutely critical. The projections that follow depend on them).

The scenarios below represent net human-caused emissions, meaning emissions minus any removals. Each scenario starts at today's 400 MT/year of human-caused methane emissions and then diverges. They range from the black, current-business-as-usual trajectory which never drops much below 200 MT, to the dark blue, exceptionally ambitious reduction trajectory which hits zero (meaning net-zero methane emissions) in 2032, and -250 MT in 2040. For reasons that are too in-depth for this brief article, I don’t believe that we'll reduce emissions to zero. If we follow the dark blue line, we may succeed in getting our human-caused emissions down to 150 MT/year, which will leave us with another 400 MT/year to remove from the atmosphere by 2040.

The next graph (below) shows just how much each of these net methane emission scenarios (above) would affect global temperatures. Again, the black line shows our current optimistic warming trajectory: 2.6oC above pre-industrial levels in about 70 years.

Whether our ultimate peak temperature is 1.4oC or 1.5oC... or 2.6oC really matters. Once we hit certain temperatures, parts of our ecosystem will change forever or die. Reducing global temperatures back to current levels in the future will not restore our world any more than putting out a house fire will restore a home.

An aside about CO2 removal

CO2 removal is a key front in our fight to repair the climate. But CO2 removal will not dramatically affect surface temperatures in the next 10–20 years. It's a technology whose effect will bloom a bit later. Why? Because each 1,000 MT of CO2 removed will reduce temperatures by just 0.0005oC. I think of CO2 removal as the next runner in this climate-stabilization relay race; it is now speeding up and gaining momentum so that methane removal can hand off the baton in a few decades.

Methane removal

All this brings us to why atmospheric methane removal would be so effective. Removing 1,000 MT of methane from the atmosphere today would reduce global temperatures by 0.1oC 10 years from now—approximately 200 times more effective for cooling the atmosphere than CO2 over that timeframe, pound for pound. To be clear, over much longer periods of time, the effect of current methane removal would drop to zero because it would have naturally degraded anyway. For example, after 20 years, methane removal would only have 100 times the effect of CO2 removal and would continue to drop from there.

Methane does not need to be captured, transported, or stored. Instead, it can be rapidly aged and destroyed (oxidized into CO2) on the spot. Of course, the CO2 could then be captured, but even if it were not captured, oxidizing methane reduces its warming effect by about 200x over the following 10 years, as described above.

Strategies

Some research has been done on methane removal, but there is still a lot to discover. Several promising strategies need more attention and research, including aerosolized chemical catalysts (iron-salts, photocatalysts, and hydrogen peroxide), methanotrophs (microorganisms that consume methane for energy), and to a lesser degree catalyzing materials (photocatalysts and zeolites).

What to do

If you want to help, here are some things you could do. If you're a:

• Funder: Please fund primary research. Despite the huge impact of methane removal, very little work is happening in this area.?
• Founder: Dig in, then start a company in this area.
• Researcher: Thank you. Keep at it or start a company.
• Policymaker or elected official: Thank you, as well. Please help route funding toward methane reduction and removal, and create or enforce methane-emission policies.
• Everyone else: Find an organization that is currently working on reducing global methane emissions, and join them.

Thank You

Special “thank you” to all the researchers' work I reference, plus reviewers: John Matson, Erika Reinhardt, and Sam Abernethy.