Mantel raises $30 million for molten borate carbon capture

Mantel Capture, a start-up founded by researchers from Alan Hatton’s lab at the Massachusetts Institute of Technology, has raised $30 million in series A funding to develop a carbon capture technology based on a novel sorbent: molten borates.

The company says the system can reduce costs by more than half compared to the most mature carbon capture technology, which is based on amine solvents. Mantel will use the funding, which was co-led by Shell Ventures and Eni Next, to demonstrate the technology at a pulp and paper mill.

In industrial carbon capture, carbon dioxide is captured from an emission source in a sorbent; it’s later removed in an energy-intensive and expensive regeneration step. Reducing the cost of carbon capture is necessary to help the planet reach net-zero emissions by 2050, Mantel says.

Mantel’s technology takes advantage of the fact that carbon capture produces energy when CO₂ is removed from the emission source. At high temperatures, like the ones at which Mantel plans to operate, this energy can be recovered as convective heat and repurposed to create steam. The company says its approach is more energy efficient than lower-temperature carbon capture technologies since the heat they produce is harder to redeploy.

Scientists have tried to apply this concept in the past but have struggled to find sorbents that don’t degrade at high temperatures. Cameron Halliday, a chemical engineer and Mantel’s CEO and cofounder, said he and his colleagues were “playing with chemistry” in Hatton’s lab to solve the problem when they observed that a borate salt performed better than expected. The team learned that the material is a liquid at higher temperatures, meaning it can withstand conditions that might degrade solid sorbents.

The team launched Mantel in 2022. The firm uses a mixture of alkali metals to form an orthoborate salt. When CO₂ is captured, the orthoborate forms a metaborate salt and a carbonate salt. So far, the team has built a system the size of a shipping container, Halliday says.

“What we’re doing is a little bit outside of the box for this industry,” he says. “We have done all of the work to show that it works other than actually build the full thing.”

Mantel will begin building the demonstration project at a North American site later this year, Halliday says. It’s looking to partner with companies across different sectors, he says, including the cement, steel, chemical, and power industries.

Mukunda Kaushik, a senior analyst who leads carbon economy coverage for the consulting firm Lux Research, says he is intrigued by the approach. “As far as we’re aware, they’re the only company today that is developing the molten borate technology,” he says. “But that also comes with its own challenges because you don’t necessarily have a blueprint from anyone else to work out of.”