Mantel Adds $18M as Carbon Capture Moves Into Industry

Mantel's project ladder jumps from a 2,000-tonne demonstration to a 60,000-tonne commercial design and a proposed 1.6 GW power campus. That is an engineering expansion, but it is also a financing problem.

Mantel announced an $18M strategic investment on August 24, 2026, from Constellation Technology Ventures and Azimut Investments, with existing investors also participating. Axios described the financing as a Series A extension, and the transaction brings Mantel's disclosed total funding to $50M.

The capital is intended to move Mantel's molten-borate carbon-capture system further into commercial projects across power generation, oil and gas, and pulp and paper. Constellation brings the perspective of a major power producer, while Azimut brings capital-markets and project-finance experience. Their involvement aligns Mantel with the infrastructure work ahead, but it does not turn project ratings or company targets into operating results.

What Mantel Raised

Mantel's official investment announcement calls the financing a strategic investment. Axios Pro calls it an $18M Series A extension, which is the more specific round classification used for the publishing record. Mantel did not disclose a valuation or identify the existing investors that participated alongside Constellation Technology Ventures and Azimut.

An SEC Form D filed on August 24 reports $18,336,764 sold in an equity offering with a first-sale date of July 10, 2026. The company uses the rounded $18M figure in its public announcement. Mantel previously raised a $30M Series A in September 2024, co-led by Shell Ventures and Eni Next, after a $2M seed round in 2022; those disclosed rounds reconcile to the company's stated $50M total.

From MIT Chemistry to Industrial Equipment

Mantel was founded in 2022 by CEO Cameron Halliday, COO Danielle Colson Rapson and CTO Sean Robertson as a spinout from the Hatton Research Group in MIT's Department of Chemical Engineering. MIT News traces the central material discovery to Halliday's 2019 experiments with lithium-sodium ortho-borate, a molten salt that absorbed more than 95% of carbon dioxide in laboratory testing while maintaining its behavior through repeated cycles.

The company built its system around a high-temperature, liquid-phase loop. Molten borate absorbs carbon dioxide from industrial emissions, further heating reverses the reaction to release a concentrated stream, and recovered thermal energy is converted into high-pressure steam that can return to the host process. That last step is central to the pitch because conventional capture systems typically consume steam during regeneration, imposing an energy penalty on the facility they are supposed to help.

Mantel reports 97% lower energy losses than conventional carbon capture, carbon dioxide output above 99.9% purity and a projected capture cost below $50 per tonne at scale. Those figures remain company-reported claims and design targets. Mantel still has to demonstrate commercial reliability, realized cost and repeatable performance across operating sites.

The Projects This Capital Must Advance

Mantel's most concrete near-term proof is the D-1 demonstration at Kruger's Wayagamack pulp-and-paper mill in Trois-Rivières, Québec. The company's project page says D-1 is rated to capture more than 2,000 tonnes of carbon dioxide per year and generate 1 MW of steam for the mill's main steam header. The installation is important because it moves the technology out of a dedicated research setting and into a commercial industrial facility.

The next scale is substantially larger. Mantel's M-10 project with an unnamed Canadian oil-and-gas producer is designed to capture about 60,000 tonnes of carbon dioxide and generate 150,000 tonnes of high-pressure steam per year inside a steam-assisted gravity drainage operation. Mantel is also the capture-technology partner for the proposed 1.6 GW TerraSpark Energy Campus in Grant County, West Virginia, a development selected for up to $18.5M in U.S. Department of Energy funding for engineering, permitting and early studies.

These projects should not be collapsed into one commercial-traction number. D-1 is a demonstration, M-10 is a designed commercial-scale project, and TerraSpark is a proposed campus still advancing through development. The distinctions matter because carbon capture has a long history of technically credible plans meeting slower construction, integration, permitting, transportation and storage realities.

Why the Investor Mix Matters

Constellation Technology Ventures is the venture-investing organization within Constellation. The parent company says CTV invests in energy hardware and software and works with portfolio companies on commercialization through Constellation's operating platform. That relationship gives Mantel access to a partner that evaluates technology through the demands of power assets, customer commitments and system reliability rather than through laboratory performance alone.

Azimut Investments adds a different part of the deployment stack. Mantel's announcement specifically points to Azimut's access to global capital markets and project-finance expertise as the company looks beyond North America. A capture company may finance its core technology with venture capital, but large industrial installations eventually confront project-level capital, contractual risk, construction schedules and customers that need confidence in the economics of a particular site.

The strategic value of these investors will be measured by what they help Mantel repeat. A first project can absorb custom engineering and founder attention; a commercial platform has to turn lessons from one site into standardized designs, supply agreements and commissioning practices that lower the cost and uncertainty of the next installation.

The Carbon-Capture Market Is Still an Execution Market

Carbon capture is moving into more sectors, but operating capacity remains small relative to the scale implied by announced projects and climate scenarios. The International Energy Agency reported in 2025 that the amount of capture capacity under construction was roughly equivalent to what was already operating, while noting geographic concentration and the need for more private capital. In another 2025 assessment, the IEA put global capture capacity across sectors and fuels at about 50 million tonnes per year and described much of the future pipeline as early-stage.

Policy can improve project economics without doing the engineering. The U.S. Section 45Q credit supports captured carbon that is stored or used, but an August 2026 Government Accountability Office review found administrative problems and weak federal measurement of results. For a developer such as Mantel, the commercial case still depends on site design, construction, the fate of the captured carbon and whether the host facility can maintain reliable operations.

That is why Mantel's steam-recovery claim matters as an operating proposition rather than a marketing statistic. Heavy industrial companies sell products into competitive markets with little patience for equipment that raises energy costs, constrains output or creates new failure modes. A carbon-capture system earns adoption only when the emissions benefit arrives with an integration and cost profile the operator can carry.

What the $18M Has to Prove

The Series A extension gives Mantel more time and capital to cross the space between a working material and repeatable infrastructure. The immediate evidence will come from commissioning D-1, advancing M-10, supporting TerraSpark's development work and turning modular supply relationships into equipment that can be fabricated and installed with less reinvention.

The unresolved questions are practical. Mantel has not yet published audited commercial uptime, realized capture cost across multiple sites or a completed record at the 60,000-tonne scale. It also does not control every downstream part of the carbon chain, which means transport, utilization or storage can determine whether a capture project works economically even when Mantel's equipment performs as designed.

The $18M round therefore finances an execution test rather than a victory lap. Mantel has credible chemistry, strategic investors and a project ladder that increases quickly in size; the company now has to show that its molten-borate system can become an industrial installation that operators will build again after the first one starts running.