Humanity has spent the past few centuries releasing ever greater amounts of carbon dioxide into the atmosphere – a state of affairs that must be reversed if we are to get to grips with climate change. Removing such CO2 in a process called direct air capture (DAC) has been on the cards for some time, but finally, after years of research and small-scale pilot projects, giant carbon-sucking facilities are becoming a reality. The question is, will the industry grow large enough, fast enough?

DAC got a big boost last week when Swiss company Climeworks switched on a new plant called Mammoth. This can extract up to 36,000 tonnes of CO2 a year from the atmosphere – living up to its name, at least when compared with its predecessor Orca, which boasted a maximum capture capacity of just 4000 tonnes per year.

The new plant instantly quadrupled global capacity for DAC and is a sign of a step change under way in the industry. Mammoth will only hold the title of world’s largest DAC plant until next year, when the Stratos plant, built by a subsidiary of energy firm Occidental Petroleum using technology from Canadian DAC company Carbon Engineering, comes online. It will be able to extract half a million tonnes of CO2 a year.

Steve Smith at the University of Oxford says Mammoth and Stratos are the start of a rapid expansion in global direct air carbon capture and storage (DACCS) capacity. “A dozen or so more DACCS projects are planned to go live in the next couple of years, by various companies,” he says. “If these all materialise, DACCS capacity could be nudging 800,000 tonnes per year.”

Overall, ambitions are high – both Occidental and Climeworks plan to be operating multiple plants with capture capacities of 1 million tonnes apiece by 2035.

This rapid expansion is being driven by two factors. The first is corporate interest in carbon removals, with the likes of Microsoft, Stripe and Coca-Cola buying DAC credits to help offset their own emissions. With the reputation of many traditional carbon offset schemes in tatters, DAC is seen by some large firms as one of the last respectable removal options.

Government policy has also been instrumental, particularly in the US. President Joe Biden’s administration is spending $3.5 billion to support four DAC “hubs” in the US, including Stratos, as part of measures passed in the Inflation Reduction Act to drive carbon removal efforts across the country. US federal tax credits also provide support of up to $180 per tonne of CO2 trapped and permanently stored via DAC, the first major policy of its kind anywhere in the world.

But voluntary carbon credits and generous government subsidies will only take the industry so far. Pathways to limit warming to 2°C will require billions of tonnes of carbon to be removed from the atmosphere by mid-century. For DAC to make a meaningful contribution to that, “some form of regulation by governments” will be necessary to drive the growth of this sector, says Smith.

For example, in February European Union officials outlined plans to create “a European single market for industrial carbon management” by 2050, to ensure all residual emissions from sectors such as livestock farming are balanced with equivalent removals. But the plans are still in their infancy and are yet to be approved by member states.

Another major hurdle is cost. For the DAC industry, the race is on to cut removal costs before government subsidies and corporate budgets run dry. Operators are hoping that by scaling up the size of facilities, the sky-high price of sucking carbon out of the air will come down rapidly, from around $600-$1000 per tonne today to $100-$200 per tonne within the next few decades. That price point would make DAC capable of delivering globally significant levels of carbon removal, most experts agree, but few are sure such a dramatic price drop is possible.

“The science was done 50 years ago. This has always been about the ability to do things at industrial scale, cheaply,” says David Keith at the University of Chicago. “The challenge is whether you can do it at an interesting cost, and I don’t think we know the answer to that yet.”

There are also reputational challenges to consider. Big oil companies including Occidental, ExxonMobil and Shell are all eyeing DAC as a way to justify squeezing more oil from reservoirs, reducing the net carbon footprint of their fossil fuels business on an ongoing basis. Rather than extending the lifespan of the fossil fuel industry, Smith stresses the focus should be on cutting global emissions and developing DAC as a way of tackling any residual, hard-to-abate emissions. He describes DAC as the “carbon equivalent of litter-picking: hard work, expensive, not the first-best way to deal with the problem, but necessary in our imperfect world”.

Some people doubt DAC will ever make a meaningful contribution to global pollution drawdown. Howard Herzog at the Massachusetts Institute of Technology Energy Initiative believes the technology is “overhyped”, citing uncertainty over its future costs and high energy demand.

Even Keith, who founded the DAC business Carbon Engineering, says that other methods of carbon removal, such as boosting the carbon storage capacity of soils or ocean waters, hold at least as much promise. “Direct air capture is one of many different carbon removal pathways,” he says. “I don’t see it as being unique.”

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