Expert Panel Points to Breakout Potential in Direct Air Capture for Carbon

Direct air capture (DAC) techniques to pull carbon dioxide out of the atmosphere may be on the cusp of the same drastic cost reductions that have brought solar, wind, and battery storage into the mainstream over the last decade, according to the chair of a recent U.S. expert panel on negative emission technologies.

“It’s very important to understand that there has been a revolution in the available technology to solve this problem in the last 15 years, with no historical precedent,” said Princeton University ecologist and evolutionary biologist Stephen Pacala, in a recent interview with veteran journalist and author Elizabeth Kolbert.

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“Fifteen years ago, if you asked me how to solve the carbon and climate problem, I would have said, ‘I don’t know. We don’t have the technology to do it,’” he added. Now, “I’ll tell you exactly what we have to build as a species to do it.”

Pacala traces potential and progress in a range of other negative emission technologies—from the United States directing 61 million tons of CO2 into underground reservoirs this year, to “afforestation, reforestation, changes in forest management, rebuilding the carbon backbone that maintains the fertility in our agricultural soils, and biomass energy with carbon capture and storage using waste biomass.” But direct air capture (DAC) is an area where he sees rapid gains in the immediate future.

“Imagine a scenario where you fly over to Germany and burn aviation gas on the way over, but we have a direct air capture machine that for $100 a ton takes CO2 out of the atmosphere and puts it in the ground to compensate,” he said. “And the question is, how much did that cleansing of the atmosphere cost in terms of the fuel? The answer is an extra dollar a gallon. So it’s going from, say, $2.50 to $3.50 a gallon”—far less than the cost aviation biogas, without tying up large expanses of land that are needed for other purposes.

“If you could get [the carbon capture price] down to 50 cents a gallon to solve the carbon and climate problem, how great is that?” Pacala asked Kolbert. “Our panel thinks direct air capture could be brought into the marketplace in a heavy way within 10 years’ time.”

That assessment, he added, has nothing to do with technology and everything to do with economics.

“It’s an exact analogy to wind and solar,” he said, an area of “remarkable achievement” where government subsidies triggered a competitive market that drove prices down. With DAC, “the government should create a market by subsidizing the activity, and then have every super-ambitious person in Silicon Valley who wants to save the world and become the richest person in it, compete with every other such person and drive the costs relentlessly down, and we’ll all be the beneficiaries.”

The expert panel report also suggested a clearer differentiation between carbon capture and storage methods and negative emission technologies.

“It’s very much the difference between solving the root cause and trying to compensate for symptoms,” Pacala told Kolbert.

“Negative emissions technologies solve the root cause of the climate problem—too much CO2 in the atmosphere. It simply takes out that CO2,” he said. By contrast, “geoengineering says, ‘Oh, that CO2 in the atmosphere is changing the climate, so let me try to change the climate in compensating ways, like by injecting sulfate aerosols high in the atmosphere to intersect some of the sunlight to cool the planet down.’ The problem is, of course, that we can’t compensate exactly for the C02, so we create other problems when we do that. Moreover, if you keep putting more and more CO2 in the atmosphere, you have to keep adding these geoengineering compounds to the atmosphere to compensate.”

The expert panel addressed earlier concerns that there won’t be space to store all the carbon dioxide that humanity is now becoming more intent on pulling out of the atmosphere.

“I would have bet a large amount of money 20 years ago…that there wouldn’t have been enough storage capacity, but now I think there is,” Pacala said. “It just turns out that there’s a lot, like injection of CO2 into saline aquifers, which is a kind of formation of salty water deep down under the ground. It’s where you get oil and gas from. Now there are some pretty strong indications that CO2 inside the salt reacts and turns into rocks really quickly.”

Kolbert asked Pacala about the risk that the availability of viable carbon capture techniques will encourage fossils and their supporters to party on, rather than addressing the roots of the climate crisis.

“There are two responses,” he replied. “The claim that we can wait is not made in any seriousness, because we don’t have enough negative emissions technologies to do even 10 or 20% of the job. And the moral hazard argument itself creates a moral hazard that is even more serious. So a technical group like the one that I chaired would have to decide that this is too dangerous for the public to know, that they can’t be trusted to make their own decisions, that we have to keep this information and ability from them. That strikes me as a road to ruin. That’s a real moral hazard.”