It’s Time to Delete Carbon From the Atmosphere. But How?

And more crucially, these experts say, aiming for zero isn’t aiming low enough. We’ll have to remove some of the carbon that’s already in the atmosphere. “We’re almost certainly going to pass 1.5 in the next few decades,” says Hausfather. “And so the only way to get back down to 1.5 C is to actively suck carbon out of the atmosphere. There’s pretty much no other way to do it.”

“The reality is that we didn’t do what we should have done 30 years ago, which is to reduce our emissions back then enough so that we wouldn’t be in the situation where we are today,” agrees Pasztor. “Now it’s too late simply to reduce emissions.”

Carbon-Capturing Technologies

The US government seems to have gotten the message: On Tuesday, the White House announced the Carbon Negative Shot (a play on a “moonshot”), an initiative for accelerating the development of carbon removal technologies. In a new report, the White House acknowledges that certain industries will stubbornly resist decarbonization—think manufacturing and rail transportation. “Because of this,” the report says, “removals of CO2 from the atmosphere will be critical to enable the United States to reach net-zero by 2050 and to achieve net negative emissions thereafter.”

Carbon-capturing technologies come in two main varieties. Carbon capture and storage, or CCS, means grabbing the emissions from fossil fuel power plants and storing them. Carbon dioxide removal, or CDR, involves free-standing machines that suck in air and pass it over membranes that pull out the CO2. (This technology is also called direct air capture.) Basically, capture and storage methods would sequester the emissions a nation is currently producing, while the air removal methods would sequester legacy emissions already in the atmosphere.

But what happens with that CO2 once it’s been captured? One option is to dissolve it in water—sort of like the world’s biggest glass of soda—and pump it underground into highly reactive basalt rock, which absorbs the carbon and locks it away. Injecting captured CO2 underground is a fairly permanent solution. (Unless a supervolcano blows all that material sky-high.)

Another option is to turn it into fuel for airplanes and cargo ships. Both are hard-to-decarbonize parts of the transportation industry, given the size of the machines. This strategy isn’t actually carbon-negative, but carbon-neutral: The carbon is pulled out of the air, burned again, and returns to the atmosphere. It’s better than digging up more fossil fuels, and it reduces the demand for new fuel sources, but it’s still not an overall reduction.

Removing carbon from the atmosphere is not going to be cheap—far from it. Earlier this year, researchers called for a wartime-style investment in CDR technology, calculating that it’d take between 1 and 2 percent of global gross domestic product to build enough machines to pull 2.3 gigatons of CO2 out of the atmosphere a year. But at the moment, humanity is spewing 40 gigatons a year. We’d need 10,000 of these plants by the end of the century to even sequester 27 gigatons a year. 

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“We are so far from that, it is just not funny. So it requires acceleration, the kinds of things that governments can do by funding innovation, funding research,” says Pasztor. “Of course, the most important one to help financing would be a carbon price.” That is, to slap a tax on emissions from businesses, especially utilities and oil and gas companies, and use the proceeds to develop systems for sucking that carbon out of the air. But the financial onus of funding carbon-eating devices should not fall on economically-developing countries, says Pasztor, given that ultra-polluting powers like the US got us into this mess in the first place.

Some might wonder if upgrading fossil fuel plants to capture carbon will ultimately suppress investments in renewables, like solar farms. But the cost of those once-pricey green alternatives is now crashing. “Even somewhere like China, if they have to choose between retrofitting coal plants and increasing their cost by 25 percent, versus building new clean energy, I think the latter is going to be cheaper going forward,” says Hausfather. “I think the economics of coal are getting to be bad enough these days.”

Green and Blue Carbon

There is another way to sequester carbon: The planet is already doing it, and all we have to do is help it along. Forests inhale CO2 and exhale oxygen. The storage of carbon in plant matter, or even landscapes like Arctic peat, is sometimes called “green carbon.” Conservationists are also increasingly turning their attention to “blue carbon,” or coastal vegetation like kelp forests, seagrasses, and mangroves. 

Protecting environments like these not only helps more plants sequester carbon, but it can lead to beneficial knock-on effects: More biodiversity, more tourism, and more vegetation that prevents erosion or absorbs the water from storm surges, which will be particularly useful in places affected by sea-level rise. “Sometimes the other advantages of the nature-based approaches—for sustainability and local employment—may be much more than the actual carbon saved,” says Pasztor.