Pulling carbon dioxide directly from the air with giant vacuum-like devices is an enticing solution to the climate crisis, with governments and industry funneling billions of dollars into direct air capture (DAC) technology. But this would-be heavy-industry geoengineering solution remains mired in controversy as it faces real-world questions of cost, scale and viability.

At its most basic, direct air capture works by passing vast quantities of air through a series of filters and membranes to trap atmospheric carbon dioxide. DAC differs from other carbon capture approaches that aim to trap CO₂ directly at the source.

Once captured, CO₂ can be funneled into the earth, stored in geological formations for hundreds or thousands of years, or used by other industries to produce products ranging from plastics to hydrogen to synthetic aviation fuels.

DAC is just one of many carbon dioxide removal techniques (including technological and nature-based solutions) that many experts say may be needed by countries desperate to achieve their carbon reduction targets under the Paris climate agreement. Carbon dioxide removal (CDR) may also be needed to mitigate the worst impacts of global warming, as the world continues releasing record carbon emissions skyward.

Proponents argue that DAC can help achieve these climate goals, especially tackling emissions from hard-to-abate industries, and they underline its potential to remove CO₂ at industrial scales, possibly even capturing billions of tons each year.

“The reason why direct air capture is such a unique and important part of the carbon removal portfolio is because it gives extremely high levels of permanence,” says Kajsa Hendrickson, director of policy at Carbon180, an NGO that backs DAC as a climate solution. “We can store that captured CO₂ underground for thousands of years.”

But the technology is contentious, with DAC development tied closely to oil and gas interests. And with critics skeptical about DAC’s effectiveness along with the mammoth challenge of finding sufficient sources of renewable power to run energy-guzzling DAC facilities.

“I think [DAC] is intentionally distracting us from actually reducing emissions,” says Jonathan Foley, executive director of Project Drawdown, an NGO. “We’ve maybe at most removed a few seconds of the world’s emissions after spending billions and billions of dollars which would have been better spent elsewhere.”

DAC gains momentum but stays small scale

Earlier this year, a plant opened in Iceland that, for now, claims to be the world’s largest DAC facility. Operated by Switzerland-based Climeworks, the facility is technically capable of removing around 36,000 metric tons of CO₂ from the air annually and storing it underground, but this is more likely to be around 28,000 “net carbon dioxide removal,” according to Kate Dmytrenko, a Climeworks spokesperson. This plant builds on the work done at a smaller pilot facility in Iceland, dubbed Orca, that is removing around 3,000 metric tons of carbon yearly. As a point of reference, human activities released 35.8 billion metric tons of carbon dioxide into the atmosphere in 2023.

“There’s no other path forward other than really ramping down our reliance on fossil fuels and increasing our ability to access renewables,” Dmytrenko says. “But doing all of those things doesn’t address the fact that there’s [already] too much carbon in the atmosphere and all of [those fossil fuel cuts] isn’t going to solve that problem.”

Powered sustainably on Iceland’s abundant geothermal energy, Climeworks has provided proof of concept, showing that DAC can work, says Dmytrenko.

The company is now planning Project Cypress, a far larger U.S. project that aims to capture 1 million metric tons of CO₂ annually by 2030. Supported by industry partners and spurred on by millions of dollars in government funding, this project is part of an ambitious federal initiative to establish four DAC Hubs across the United States to drive technology deployment forward. Whether such a costly and ambitious climate goal will be backed financially by the incoming Trump administration is anyone’s guess.

Numerous other startups are moving into the DAC space. Some, such as France’s RepAir, are developing electrochemical approaches to carbon capture that try to sidestep energy-intensity issues, while others aim to produce valuable byproducts from the capture process, such as hydrogen, which can be sold at a profit.

China’s DAC technology is advancing with a 600-metric-ton unit under development, while global companies, including Microsoft, Google and Airbus, are making investments into DAC tech via future-based carbon credits.

Despite this momentum, direct air capture remains a nascent and expensive investment. As with other carbon direct removal techniques, DAC development costs are currently high — between $600 and $1,000 per captured metric ton. The U.S. government’s Carbon Negative shot is hoping to bring that price down to $100 per captured metric ton. Industry backers and analysts say scaling up hinges upon achieving these lower costs.

The most recent State of Carbon Dioxide Removal report, research led by the University of Oxford, estimates that 7 billion to 9 billion metric tons of CO₂ must be removed each year by 2050 to have any hope of meeting the 1.5° Celsius (2.7° Fahrenheit) global average temperature goal required by the Paris accord and scientific evidence to avoid catastrophic climate change. However, many experts say this CDR target is already well out of reach, particularly as fossil-fuel greenhouse gas emissions continue to soar annually.

Novel carbon removal solutions such as DAC account for a tiny fraction of an estimated 2 billion metric tons of carbon removal occurring today, according to the report. It’s estimated that the few dozen DAC facilities across the globe trapped a mere 10,000 metric tons of CO₂ in 2023. That’s dwarfed by other forms of carbon removal, including tree planting and biochar.

A fossil fuel industry fig leaf?

As various companies try to prove DAC’s viability, fossil fuel industry interest in the tech has sparked concern among experts and environmental groups.

Last year, oil and gas company Occidental purchased Carbon Engineering, a DAC company, and plans to develop two U.S. facilities backed by government funding. Occidental and BlackRock, the world’s biggest investment manager, are partnering on the Stratos facility in Texas, which aims to capture 500,000 metric tons of CO₂ annually and is scheduled for completion in 2025.

Occidental CEO Vicki Hollub is on record as stating that direct air capture is a route to preserving the oil and gas industry for decades to come. Other oil industry players such as ExxonMobil are actively researching DAC, eyeing it as a potential future investment.

These fossil fuel company-backed initiatives have prompted Project Drawdown’s Foley and others to describe DAC as a PR “fig leaf” employed as a smokescreen to allow the oil and gas industry to continue producing greenhouse gas-emitting fuels.

“Direct air capture is not only not just a waste of time, it’s very counterproductive. It’s creating a narrative that the fossil fuel industries really love,” Foley says. “If you look at the larger universe within which [DAC technology] operates, it creates a form of predatory delay … Fossil fuel companies will continue to operate, spewing billions of tons of CO₂ into the atmosphere while pretending to absorb a few thousand tons.”

Critics point to the history of carbon capture and storage with its costly failed ventures. In fact, carbon capture was originally created by the fossil fuel industry to extend the life of oil fields. In truth, about two-thirds of carbon captured via point source emissions today is still used for this purpose via a process known as enhanced oil recovery (EOR).

Some DAC companies, including Climeworks and RepAir, state that using their facilities for EOR is a “red line” they won’t cross. But at least some DAC plants may be used for this purpose.

“We think [DAC] is a massive distraction from the urgent task of phasing out fossil fuels and it serves as a cover up for industry expansion,” says Lili Fuhr, fossil economy program director at the Center for International Environmental Law. “Phasing out fossil fuels as rapidly and completely as possible is our only hope for actually limiting global warming.”

Hendrickson at Carbon180 notes that concerns over oil and gas influence are real, but also says DAC has a key role to play in addressing climate change as a public service, backed by government funds. But for that to happen, she says, stringent guidelines would need to be followed.

“We don’t want to see direct air capture go to enhanced oil recovery or be utilized in any way to offset or continue the existence of the fossil fuel industry,” she says. “Direct air capture needs to be accountable. It needs to be transparent and communities need to be involved.”

A clean energy crunch

For now, DAC is largely buoyed up by PR momentum, along with government and investor spending. But beyond the hype looms the very real challenges for achieving scale. For industry players, that means keeping ballooning research and infrastructure development costs under control, and especially requires finding clean energy sources.

Because DAC facilities are energy-intensive, their success hinges upon renewable energy availability. Climeworks, for example, is currently trying to source renewable energy for its Louisiana plant. But that DAC facility may need to run on “traditional energy” (i.e. fossil fuels) at first until renewables becomes available, says company spokesperson Dmytrenko.

This conundrum raises another red flag: To be successful, DAC will need to compete for renewables with other industries. In the U.S. and elsewhere, that competition is coming in part from the buildout of massive energy-consuming data centers, with AI on target to become a huge global renewable energy hog.

The data center dilemma “came out of left field” for direct air capture developers, says Josh Santos, founder of Noya, a U.S.-based DAC startup. Reports find that at least one DAC project has been canceled due to a lack of available clean energy.

“The sourcing of renewable energy is probably the biggest project-related hurdle that direct capture has to overcome,” says Santos. “Over time, it’s going to be relatively straightforward to source underground geologic wells. It’s going to be relatively straightforward to acquire permits for installing direct capture projects. The hardest part is going to be sourcing renewable energy.”

But others question the logic of developing clean energy to remove atmospheric carbon rather than just stop using fossil fuels altogether. Benjamin Sovacool, a climate scientist at University of Sussex, U.K., and his team produced expert-based recommendations for DAC use. While not advocating for the tech, the researchers aimed to optimize direct air capture projects. “Is the best pathway just to produce clean, low carbon electricity, full stop? Or is our best pathway to use low carbon electricity to run these [DAC] machines all the time?” Sovacool asks.

And he’s not alone in posing this question. In his view, investing in wind, solar and energy storage are likely “better investments” than direct air capture.

“In the best case, you use renewable energy to run the direct air carbon capture equipment, preventing that renewable energy from replacing a fossil source in the first place,” explains Mark Jacobson, a professor at Stanford University. “The other problem with carbon capture and direct air capture is it always needs pipelines.”

A 2023 report by the Oxford Institute for Energy Studies estimated that construction of carbon capture infrastructure on the “same order of magnitude as the existing refining industry” will be needed to draw down 1 billion metric tons of carbon by 2050.

It’s estimated that the amount of pipeline required for a large-scale carbon capture industry in the U.S. alone would require a colossal 96,000 kilometers (nearly 60,000 miles) of new pipeline. This construction challenge gets even bigger when you add in the infrastructure for the plants. DAC facilities would demand massive amounts of carbon emission-intensive building materials, including steel and concrete.

“These are some of the … material infrastructural constraints that, to me, scream that DAC will likely not be a significant source of emissions reductions in the near term,” says Sovacool.

He also questions what happens when DAC plants reach the end of their working lives. “This is a question we’re now just beginning to answer for wind turbines and solar, but I haven’t seen a single study talk about end-of-life recycling and reuse of DAC materials or DAC waste streams.”

Betting on the moon?

With an increasing number of DAC projects now in the pipeline, the effectiveness of the technology over the long run remains in doubt, and doubtful too are the industry’s highly ambitious growth projections.

Some analysts say the challenges posed by DAC make it a moonshot bet at best, though that has yet to deter investors. Those connected to the industry say they remain hopeful the sector will continue growing and eventually make a significant climate impact.

RepAir’s Jean-Philippe Hiegel, for example, says that technological carbon fixes including DAC could provide “complementary” pathways to decarbonization, and are “completely required to reach net zero.”

But achieving proof of concept via pilot projects and startups is a long, long way from scaling up DAC, which brings with it a host of concerns, says CIEL’s Fuhr. “Immediately, questions of energy and resource input into these technologies become extremely relevant,” she says. “What we’ve seen in reality is the fossil fuel industry really betting on this technology as a way to expand their business.”

Some experts argue that DAC projects must be developed with strict regulatory guardrails in place — banning its use for enhanced oil recovery and only operating using clean energy. That approach could help ensure DAC becomes a beneficial part of climate action. “I don’t want to say I’m pro direct air capture as the ultimate solution, because it isn’t,” says Dawid Hanak, professor of Decarbonisation of Industrial Clusters at the Net Zero Industry Innovation Centre at Teesside University, U.K. “I believe that it is part of the portfolio that we will need to deploy.”

But controversy seems bound to continue swirling around DAC’s oil industry connection, its viability and scalability. “There’s no truth in the claims that [DAC] is helpful. This is a greenwashing technology,” says Jacobson.

“Some limited forms of carbon removal will be very helpful in the future, and we undoubtedly will need some of this to balance the carbon budget in the future,” Project Drawdown’s Foley says. “I personally think nature-based carbon removal is the only conceivable, scalable, gigaton-scale way to do this. Direct air capture in the open atmosphere just doesn’t make any sense at all.”

Banner image: A Climeworks employee stands next to the company’s Mammoth facility in Iceland. To date, it’s the largest up-and-running DAC facility on Earth. Critics say scaling up the technology poses major infrastructure, energy and life-cycle challenges. Image courtesy of Climeworks.

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