Western Hemisphere

Mantel Raises US$18M From Constellation and Azimut to Scale Industrial Carbon Capture

Boston Climate-Tech Startup Mantel Adds US$18M for Carbon Capture

Mantel, the carbon-capture startup based in Cambridge, Massachusetts, announced a US$18 million strategic investment from Constellation Technology Ventures (CTV) and Azimut Investments, alongside existing investors. The round brings the company’s total funding to US$50 million and will support commercial deployment of its molten-borate CO₂-capture technology for high-emitting industries.

Founded in 2022 by Cameron Halliday, Danielle Rapson, and Sean Robertson, Mantel is moving from technology validation toward commercial projects across power generation, oil and gas, pulp and paper, chemicals, and other carbon-intensive industries. CEO Cameron Halliday said the financing adds partners with experience in large-scale energy infrastructure as the company expands across North America, Europe, and other markets.

Market Context

The new financing builds on Mantel’s US$30 million Series A raised in 2024, which was co-led by Shell Ventures and Eni Next and included bp Ventures, Vale Ventures, Engine Ventures, New Climate Ventures, Hartree, Arosa Ventures, Newlab, and MCJ Collective, among others. CTV’s investment adds a strategic link to Constellation, which Mantel describes as the largest producer of clean, reliable energy in the United States, while Azimut brings global capital-markets access and project-finance expertise.

Mantel says its high-temperature liquid system can integrate directly into industrial operations, recover thermal energy, and avoid some of the energy costs associated with conventional amine-based carbon-capture methods. The company says its technology can reduce energy losses by up to 97%, produce CO₂ streams with more than 99.9% purity, and achieve costs below US$50 per metric ton at scale. Those are company-reported targets and metrics that still need to be validated through sustained commercial operations.

Key Signal

“This moment is about execution and how fast we can build. This round brings in partners who understand large-scale energy infrastructure as we move at the speed this transition demands.”
— Cameron Halliday, co-founder and CEO, Mantel

Regional Relevance

For the United States, the deal connects an MIT-linked startup with CTV, Constellation’s investment arm, at a time when industrial decarbonization and thermal-power assets need solutions that preserve grid reliability. Mantel has been selected as the carbon-capture technology partner for the 1.6-gigawatt TerraSpark Energy Campus in West Virginia, a U.S. Department of Energy-supported project that would integrate its system into a large-scale coal-fired power plant.

For Canada, Mantel’s pipeline includes two industrial deployment tests. The company is developing a front-end engineering and design study for a steam-assisted oil-recovery operation at a major oil-and-gas producer, expected to capture 60,000 metric tons of CO₂ annually. It also plans to begin an installation this year at Kruger’s Wayagamack mill in Quebec, which is expected to capture approximately 2,000 tons annually and would be its first operation inside a commercial industrial facility.