This interview first appeared in our sustainability newsletter, Climate Tech — you can sign up here.

Vertical farming’s sustainability credentials are often lauded — it can increase the yield of crops and lower land and water use, as well as localising food supply chains. But the industry still has one particularly unsustainable dependency: CO2 is pumped into vertical farms to help plants grow and, at present, it usually comes from fossil fuel production.

One startup, Skytree, has developed a method to install localised direct-air-capture units next to vertical farms, so they can capture their own CO2, recycling it from the atmosphere.

How does it work?

Skytree’s tech came out of founder Max Beaumont’s work as an engineer at the European Space Agency. His team there developed a more efficient way of removing CO2 from spacecraft by scrubbing the air using plastic beads.

“They’re a few millimetres wide and made of ion exchange resin. They’re exposed to the air and after 15-20 minutes they’ve collected CO2 like a sponge,” explains Beaumont. “Then they’re heated up to 70-80C and that releases the CO2 again.”

Outside of space travel, industries that need CO2 could set up mini, localised direct-air-capture units with this technology to produce their own recycled supply. “Because right now,” Beaumont says, “the only source of carbon is basically fossil fuels.”

What other applications could it have?

Skytree’s tech is on a significantly smaller scale than the large-scale plants operated by companies like Climeworks. Each unit can capture between 3 and 20kg of CO2 a day, while Climeworks says its plant will capture 36k tonnes a year when it’s fully operational.

That said, Skytree says small, decentralised units can create impact when joined together. Skytree’s units are small enough to be able to bring captured CO2 directly to where it’s needed as a product — unlike bigger plants which operate farther from industry.

Beyond indoor farming, applications could include water filtration, which requires CO2, or air filtration, where CO2 could be scrubbed from indoor environments and used for other purposes.

“Ultimately the vision is to get to commodity level, and really scale up to a point where we can sequester a lot of CO2 from the air into things like cement production, fuel production, plastic production,” says Beaumont. “That’s where it can make an impact.”

Freya Pratty is a reporter at Sifted. She tweets from @FPratty and writes our climate tech newsletter — you can sign up here.