Mantel raises $18M to put carbon capture in real plants

Carbon capture startup Mantel has raised $18 million, including strategic investments from Constellation Technology Ventures and Azimut Investments, to push its high-temperature capture system into commercial deployments across heavy industry. The round brings Mantel's total capital to $50 million, and the company has already tied the money to a specific portfolio of installations.

Mantel says the capital will support work with one of Canada's largest oil and gas producers, its selection as the carbon capture technology partner for the 1.6-gigawatt TerraSpark Energy Campus in West Virginia, and a deployment at Kruger's Wayagamack Mill in Quebec. The projects span power generation, oil and gas, and pulp and paper—the kind of dispersed, hard-to-abate industrial sites where carbon capture has historically struggled to gain traction.

Founded in 2022 by Cameron Halliday, Danielle Rapson and Sean Robertson as a spinout from MIT's Department of Chemical Engineering, the Cambridge, Massachusetts-based company is developing a molten-borate salt loop designed to work at the high temperatures already present inside industrial plants. The system captures CO2 and recovers thermal energy as high-pressure steam, which can be reused on site, and Mantel says the approach cuts energy losses by 97% relative to conventional carbon capture and operates at less than half the industry-average cost per ton.

The company's argument is that previous generations of carbon capture failed on cost, scale and the difficulty of integrating a new chemical process into a live factory; Mantel is offering a modular, systems-engineering-led package that slots into existing infrastructure rather than a bespoke plant built alongside it. For facilities that run around the clock, a capture system that steals steam or pressure is a production problem, not a climate solution.

Constellation's Kate Norman, senior vice president for commercialization and market development, called the investment an example of supporting practical clean-energy solutions that balance sustainability and reliability. For transition finance, the shift in what gets funded is that carbon capture increasingly arrives with named hosts and a construction timeline, less like a laboratory breakthrough awaiting a market and more like a contracted industrial service.

The $18 million is a modest round by transition finance standards, but the deployment list is not, and Mantel is selling the argument that execution on site matters more than chemistry alone in determining which carbon capture technologies survive. It is a bet placed in an industry that has spent years promising more than it has installed.