‘Mechanical tree’ farms show promise for carbon capture

After two years of design and engineering work, research partners from Ireland and the United States have introduced a “mechanical tree” they say is 1,000 times more efficient at capturing carbon from the atmosphere than natural trees are—and they say they’re ready to start scaling up the model to eventually create tree farms.

The MechanicalTree™ now stands 10 meters high on the Arizona State University campus in the U.S. It’s clad in a series of tile disks that capture carbon dioxide (CO2) from the air as the wind blows across the tower of tiles. The technology, developed by Klaus Lackner and the university’s Center for Negative Carbon Emissions, eliminates the need for blowers or fans that would add to its operational and energy costs.

As the tree columns collect CO2, they retract into a base where the carbon is removed from the tiles with a goal of transforming it into a product for other uses. When that’s not possible, it can be sequestered beneath the ground or sea.

Once the carbon is removed from the tiles, the mechanical tree extends back up to collect more of the greenhouse gas emissions that are driving global warming.

“We believe we have developed a real and scalable solution to combat the effects of carbon dioxide,” said Reyad Fezzani, the executive director of Carbon Collect, the startup firm in Ireland that’s working to take the mechanical tree to market.

“Our goal now will be to accelerate the global climate effort and to contribute to reversing carbon emissions over the next decade and beyond.”

Direct capture of CO2 from the atmosphere is one strategy that’s been deployed in the fight against climate change, including a much-touted facility in Iceland designed to remove 4,000 tons of CO2 per year. When the plant opened in 2021, critics noted that its capacity is dwarfed by the massive amounts of emissions across the globe that will only continue to grow in the near-term future.

The mechanical trees are designed to do more when deployed at scale. They capture a metric ton of CO2 per day when planted in clusters of 12, while a small-scale farm of 1,200 trees multiplies that to 100 metric tons per day.

A large farm of two or three square kilometers, with 120,000 trees in operation, can remove 10,000 metric tons per day. Carbon Collect says that’s the equivalent of the daily CO2 emissions of 800,000 cars.

The idea isn’t to remove carbon so that global societies can continue business as usual, though. The goal is to use the technology in line with circular economy principles, providing carbon-based products, like fertilizers needed in agriculture or the carbon needed for the beverage industry. The captured carbon also may help to reduce the outsized carbon footprint of cement, steel and other industries.

Lackner, a global pioneer in direct capture of carbon, makes clear that the best solution is not to put carbon into the atmosphere in the first place. But we have, and he considers carbon removal to be more of a waste management solution until a clean energy transition is complete.

“You can do it,” he says. “We can provide the energy the world needs and we can clean up after ourselves. We can have a society that functions, that has access to energy and can do all of the things which it needs to do in order to create a decent standard of living.”