How the largest direct air capture plant will suck CO2 from the atmosphere

The largest industrial plant yet to suck tons of global warming carbon dioxide out of the air was commissioned yesterday in southwest Iceland. Direct air capture plants like this have recently been highlighted by world leaders and giant corporations – including Microsoft – looking to erase their legacy of greenhouse gas pollution.

This particular operation is ideally located for testing emerging technology. The new plant, built by Swiss company Climeworks, is powered by renewable energy from a nearby geothermal power plant. Climeworks also plans to lock in CO2 captured in basalt rock formations just three kilometers from the geothermal power plant. It’s a storage plan that likely bypasses the need for controversial new carbon dioxide pipelines.

“It will be, I think, an interesting test case,” says David Morrow, research director at the Institute for Carbon Removal Law and Policy at American University. “But it’s also kind of a small step in the grand scheme of things.”

Climeworks’ new direct air capture plant, called Orca for the Icelandic word for energy, will be able to remove 4,000 tonnes of carbon dioxide per year. That’s roughly how many 790 passenger vehicles could pump in a year – not a huge amount, even though this is the largest operation of its kind in the world.

The new plant is surprisingly compact. Imagine a shipping container opened on one side to reveal twelve giant fans. The plant basically only has eight of these containers, stacked two by two.

Climeworks uses a method called direct solid air capture to trap CO2. Here’s how it works: Fans suck in air. The air passes through a special solid absorbent filter which traps carbon dioxide. Climeworks wouldn’t go into too much detail on how its filters work in an interview with The edge, other than saying it uses a base to attract CO2, which is slightly acidic. When the filter is completely saturated, it’s time to move on to the second step of the process. The unit heats the filter to approximately 100 degrees Celsius (212 degrees Fahrenheit), which releases the trapped carbon dioxide.

Once the CO2 has been separated from the air, it travels through pipes to an adjacent building where it can be prepared for permanent storage. Here it is mixed with a lot of water – about 27 tons of water for every ton of carbon dioxide. This mud then travels a few hundred meters (about a quarter of a mile) before being injected deep into the ground. Carbonated water reacts with basalt rock, creating carbonate minerals. Within two years, what was once a kind of sparkling water turns into solid rock.

Climeworks has partnered with the Carbfix company to keep CO2 safely captured in Iceland’s basalt rock formations. The two companies have already tried this in a pilot project, but Orca is the couple’s first commercial-scale operation.

Image: Climeworks

Climeworks’ other two commercial-scale direct air capture plants convert carbon dioxide into a product for use as fertilizer or in soft drinks. This CO2 escapes relatively quickly into the atmosphere. But trapped in rock, Carbfix believes the CO2 captured by Orca can be safely sequestered for thousands of years. While basalt rock is relatively common around the world, volcanic activity Iceland is particularly suitable for storing carbon dioxide because it has a relatively younger basalt. Fresh basalt is a better home for captured CO2 because it is more porous, giving the carbon more nooks and crannies to fill.

By installing Orca in the same remote location where the CO2 will be stored, the operation avoids one of the potential pitfalls of carbon removal: the creation of a new network of pipelines to transport the captured carbon dioxide. There are already pipelines that move CO2 so that it can be projected into the ground to expel oil reserves, a process called enhanced oil recovery. One of those pipelines ruptured last year in Mississippi, hospitalizing residents of a small, predominantly black community.

The other advantage of the plant’s location is its proximity to a geothermal power plant, which ensures the plant a constant supply of waste heat and renewable energy. That, along with Climeworks’ strong direct air capture process, gives Orca an edge over other competitors. Even larger direct air capture plants are expected to be commissioned in Texas and Scotland in the coming years, but these use a different filtration process that requires significantly more heat and energy. As a result, they will likely depend on a combination of renewable energy and natural gas.

“If your business is removing CO2 from the air, you want to emit as little CO2 as possible from fossil fuels. Otherwise, the process is not net negative or net eliminatory, ”explains Christoph Beuttler, Climate Policy Manager at Climeworks.

Cost is another hurdle that still keeps the direct air capture industry from growing enough to significantly reduce global greenhouse gas emissions. Microsoft, which pledged last year to capture all of its historic emissions by 2050, is both investor and client of Climeworks. Microsoft and other companies can buy captured CO2 from Climeworks for around $ 600 a tonne, offsetting a tonne of their own pollution. In its 2020 fiscal year alone, Microsoft was responsible for the equivalent of 11,164,000 metric tonnes of carbon dioxide. Multiply that by $ 600, and Microsoft would face a bill of almost $ 6.7 billion for just a year of pollution.

Unless the price drops significantly, it might not make a lot of financial sense to tackle climate change in this way. And some environmentalists fear that focusing on implementing this technology will take resources away from other climate solutions, while relieving companies of the pressure to stop burning fossil fuels.

“One thing people worry about is that all of these companies that make these net zero commitments will just use direct air capture instead of cutting emissions,” Morrow said. “But it seems highly unlikely to me that direct aerial capture will become cheap enough anytime soon that it makes sense.”

So while direct air capture may play a small role in helping the world sequester some global warming emissions, it does not replace deep reductions in pollution from fossil fuels in the first place. “At most, it’s a supplement that can help us reduce climate change,” says Morrow. “But that cannot replace reducing emissions.”