Angeli Mehta reports on how demand from corporates and government incentives are helping companies like Climeworks and Carbon Engineering remove carbon directly from the atmosphere

Travelling any road to limiting warming to 1.5 degrees Celsius requires us to suck carbon dioxide out of the atmosphere. The various climate scenarios suggest as many as 6 billion tonnes may have to be sequestered by mid-century, because some industries will still emit CO2, and residual emissions need to be mopped up.  Getting there is going to require many solutions, even as emissions are slashed. 

A decade ago, direct air capture (DAC) was dismissed as unproven and far too expensive to have in the armoury. But things look different as 2030 looms large.   

“We are in a tight spot, in terms of our climate goals. This type of technology gives us the opportunity to just make it, but we have to pull everything together,” says Christoph Beuttler, head of climate policy at Climeworks AG, a Swiss-based leader in the technology. 

In Iceland, Climeworks has opened the world’s largest DAC plant, capable of capturing 4,000 tonnes of CO2 a year

Direct air capture does what it says on the tin: it takes carbon dioxide directly out of the atmosphere. While carbon dioxide levels this year will reach 50% above those in pre-industrial times, CO2 accounts for only 0.04% of our atmosphere, which means huge volumes of air must be processed to capture it, requiring large amounts of renewable energy. 

DAC is to be distinguished from carbon capture and storage, which captures carbon from the flue gases of, for example, a power station, where CO2 is more highly concentrated. 

In Climeworks’ system, air is drawn by fans onto a solid filter material, which the carbon dioxide sticks to. Once saturated with CO2, the collectors are heated to release the gas. The resulting pure stream of carbon dioxide can be stored underground, or used by industry. 

In Iceland last year, Climeworks opened the world’s largest plant, capable of capturing 4,000 tonnes of CO2 a year. The gas is mixed with water and injected at pressure into basalt rock, by Climeworks’ Icelandic partner Carbfix. The CO2 becomes rock within a few years, and thus is locked away. The entire process is powered by geothermal energy. 

As well as demonstrating the technology at scale, Climeworks has stimulated a market for carbon removals, costing over 800 pounds sterling per tonne (although that figure depends on volume). 

It counts Microsoft, reinsurer Swiss Re, and payment software platform Stripe amongst its customers.

Ultimately, you’re only going to have a direct capture industry at scale when there’s regulation that requires it

Such has been the demand for carbon removals, Climeworks has brought forward plans to have a plant 10 times larger up and running in the next few years, and is confident of reaching million-tonne scale in the second half of this decade. For some idea of the potential impact, recent research suggests the Amazon basin (which covers around 7 million square kilometres) is sequestering around 100 million tonnes of carbon each year.  

While Climeworks is storing the CO2 its modules collect, others plan to combine it with green hydrogen to make e-fuels, to be used in aviation, for example. The CO2 will be released again when the fuels burn, but the climate impact of aviation could be reduced by 60% using e-fuels. 

Siemens Energy, Porsche and other international partners expect a pilot e-fuels plant to come on stream in Chile later this year, while British Columbia-based Carbon Engineering and its partners are planning to start producing 100 million litres of synthetic fuels in 2026, at a plant in Canada.  

Scaling DAC is going to require policy, says Amy Ruddock, vice-president Europe at Carbon Engineering. While the voluntary market “sends a signal to governments that this is something serious, ultimately, you’re only going to have a direct capture industry at scale when there's regulation that requires it.”

Carbon Engineering recently won funding from the UK government to help develop its processes for a project with Storegga Geotechnologies in north-east Scotland. It could potentially tap into carbon transport and storage infrastructure Storegga is developing through the Acorn carbon capture and storage project. 

Ruddock is talking to the UK government about its business model for greenhouse gas removals. One option is to create a Contracts for Difference funding mechanism for carbon, similar to those used to develop wind and solar in the UK. “With first plants, the cost can be higher than future plants. So, the conversation we’re having is around, if the UK wants leadership, how do we bridge that gap?” 

You need to really look for those markets, which can support direct capture to get going down that cost curve

At European Union level there are discussions about integrating DAC into its carbon market, and detailed work on carbon-removal certification is under way.  

In the United States, there’s talk of government procuring carbon removals for its own emissions. DAC plants can attract support through the 45Q tax credit for carbon storage; under discussion now is a package that could quadruple that from $45 to $180 a tonne. California’s low carbon fuel standard also provides revenues for direct air capture and sequestration. 
 
Indeed, the first commercial plant to come online using Carbon Engineering’s technology  will rely on those funding streams. It is being built in the U.S. Permian basin by 1PointFive, a joint venture involving Occidental’s subsidiary, Oxy Low Carbon Ventures. Some of the CO2 captured will be used for enhanced oil recovery, providing additional revenue. Ruddock defends the approach, saying that getting to scale means “you need to really look for those markets, which can support direct capture to get going down that cost curve”.

Beuttler at Climeworks is encouraged by the backing now being given to DAC. A major fillip came from President Biden’s infrastructure bill last November, which authorised $3.5 billion to create four DAC hubs. 

“We have to build an industry first. Reducing capex (capital expenditure) is one of the big objectives here and that means we need to build an industry that has suppliers, and the individual (components) of the technology become cheaper.” 

Carbon Engineering, by contrast, has selected equipment and solvents that have been used in other industries, modified to suit direct capture, meaning it has a ready-made supply chain. “You don’t have to wait for a supply chain to scale up behind you. You have people that know how to do the basics, and you work with them on the specifics of direct air capture,” says Ruddock. The company is also working with the oil and gas industry to take advantage of skills and experience in building and running large plants.  

You will need more energy than you get out. But it’s the only way to get off fossil CO2

Storage for the CO2 that DAC plants will collect will need to be developed. Climeworks is exploring locations in Norway and in Oman, where there is both availability of renewable energy and geologic storage.

DAC joins a long list of other energy-hungry industries of the future, such as green hydrogen. “You will need more energy than you get out. But it's the only way to get off fossil CO2. That's the reality of it, unfortunately,” says Beuttler.

Climeworks hasn’t disclosed the energy consumption of its Orca plant, but the biggest demand is heat for releasing the CO2. “We could look at things like solar thermal and heat pumps, but again, that would require improvements in solar thermal. So that's what I mean by building an industry. That there are many, many things that have to be improved.” 

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How a two-person tent in the Australian outback could capture CO2

 

While Climeworks and Carbon Engineering pursue scale, there are promising developments emerging from the lab. Last year a team of students at the University of Sydney won a share of the $5 million student XPrize, for scalable carbon removal concepts.

Their innovation was to design a material with a very large surface area that will absorb CO2 rather than any other molecule. “If we took one teaspoon of one of these materials, it would have a surface area of a football field,” says academic supervisor Deanna d’Alessandro. “That means that we can use a relatively small amount of one of these absorbants to capture a very large amount of carbon dioxide.”

Its industrial partner, Southern Green Gas, has designed DAC units the size of a two-person tent to be powered solely by solar PV panels and which would be set out in array like a solar farm. Each unit is capable of capturing two tonnes of CO2 a year. “A very significant aspect of this technology is the fact that we don't have to scale up in terms of making units bigger. We’re making so many of these units that it helps to bring our costs down.” 

The system also has the advantage that it doesn’t have to be connected to the grid, offering the prospect of using some of Australia’s vast tracts of non-arable land, and where geologic storage is available. However, she cautions, “It’s a significant technical challenge, and we have a very significant road to go with commercialisation.”

Promising as the technology is, mindsets will have to shift too. “There’s a very long and if I can say dirty history of conversation and work around carbon capture (in Australia), because people believe that it really hasn't delivered,” says d’Alessandro.

“So, there's a very significant piece of policy and legislation, (as well as) communication and education around helping everybody to understand that direct air capture is distinct from carbon capture and storage, that it doesn't involve users or producers of fossil fuels, and it doesn’t enhance fossil fuel recovery.”

Angeli Mehta is a former BBC current affairs producer, with a research PhD. She now writes about science, and has a particular interest in the environment and sustainability. @AngeliMehta.

 

Direct air capture  Climeworks  carbon capture and storage  e-fuels  Carbon Engineering  1PointFrive  Southern Green gas