Industrial pollution has led to global carbon levels crossing 420 ppm.1 Cement, steel, and chemicals are heavy industries that emit nearly one-third of total global carbon dioxide (CO₂) emissions.2 Most of these processes cannot be electrified or substituted by renewables in the near term.
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Mantel, a Boston-based startup, has developed molten-salt-based carbon capture technology. Founded in 2022 as a spin-out from MIT's Department of Chemical Engineering by researchers Cameron Halliday (CEO), Danielle Rapson (COO), and Sean Robertson (CTO), the company's work originated in the Hatton Research Group at MIT. The research team's experiments with high-temperature sorbents identified molten borates as carbon capture agents.3
Mantel's Approach
Industrial activities account for approximately 30% of worldwide CO₂ emissions, with steel, cement, and chemicals being among the hardest industries to decarbonize due to their severe operating conditions.2 Mantel's approach utilizes molten feedstocks in carbon capture, over 600 °C, in industrial equipment such as kilns and furnaces.3
The technology employs molten salts of borate specifically designed for high-temperature applications. Typical carbon capture systems require cooling flue gases before capture, which reduces efficiency overall.
How the Technology Works
A molten borate salt, a liquid-phase sorbent that is stable at more than 600 °C, forms the core of Mantel's technology. The process involves three steps:
- Capture: Flue gas from industry passes through a tank containing molten borates. The salts selectively react with CO₂ to form thermally stable carbonates.
- Regeneration: In another reactor, the salts with high CO₂ content are moderately heated to release pure CO₂. The salts return to the capture vessel.
- Recirculation: The regenerated salts are reused continuously, providing a closed-loop system.3
This design eliminates the need for external cooling and steam facilities upon which amine-based systems depend and is appropriate for high-temperature industrial applications. As it works on waste heat from the process itself, it also provides higher overall energy efficiency.3
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The molten borate mixture was specifically formulated to possess maximum CO₂ solubility while being chemically stable under harsh industrial conditions.
The molten salt is most suitable in temperatures between 500 °C and 800 °C, the very temperature range in most industrial furnaces and boilers. Equipment development has focused on corrosion-resistant materials that can withstand molten salt conditions. Special steel alloy and ceramic components have been designed in collaboration with industrial equipment manufacturers to ensure long-term operating reliability.4
Applications in Hard-to-Abate Industries
Mantel's molten-salt technology is engineered for direct integration into industrial sectors where high-temperature process emissions have posed a major barrier to decarbonization. The system is designed to operate within existing infrastructure, requiring minimal plant modifications.
- Cement Manufacturing: Accounting for roughly 8% of global CO₂ emissions, cement kilns operate at approximately 1450 °C.5 By capturing CO₂ at these source temperatures, the technology avoids costly heat recovery systems and preserves the thermal efficiency essential for cement production economics.
- Steel Production: In modern steel plants, blast furnaces reach temperatures of 1500 °C. Mantel's system can target these hot flue gases directly, bypassing the extensive cooling infrastructure and significant energy penalties that conventional capture methods would require.
- Chemical Processing: Many chemical processes, such as ammonia and methanol production, emit CO₂ at 500–1000 °C. The system's ability to handle high-temperature, complex emission streams allows for effective, site-wide integration.
- Pulp and Paper: The technology's real-world viability is currently being demonstrated in a pilot project at a North American pulp mill set up to capture 1800 tons of CO₂ annually.6
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Industrial Sector
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Operating Temperature (°C)
|
Global CO₂ Share (%)
|
Implementation Status
|
|
Steel Production
|
800–1500
|
7–9
|
Development phase
|
|
Cement Manufacturing
|
900–1450
|
8
|
Pilot planning
|
|
Chemical Processing
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500–1200
|
3–4
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Assessment phase
|
|
Pulp and Paper
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600–1100
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1–2
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Active pilot
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Technology Specifications and Competitive Advantages
Mantel's carbon capture technology offers cogeneration potential, as the exothermic reactions in the capture process produce usable heat, which can be reintegrated into the industrial system. This approach delivers 30–50% energy consumption reductions compared to traditional amine-based systems, potentially reducing capture costs by $30–$50 per ton of CO₂ for industrial plants.4
Eliminating gas cooling requirements represents a significant operational advantage. This energy efficiency translates directly into lower operational costs and improved project economics for industrial operators. The technology creates opportunities for carbon utilization pathways that enhance project economics.
Pure CO₂ streams generated through molten salt capture can be converted into valuable chemicals, fuels, or materials, creating additional revenue streams.3
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Technology Comparison
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Molten Salt (Mantel)
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Traditional Amine
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Direct Air Capture
|
|
Operating Temperature (°C)
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600–800
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40–80
|
80–120
|
|
Energy Requirement (GJ/tCO₂)*
|
2.1–2.8
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3.2–4.1
|
5.5–8.0
|
|
Capture Rate (%)
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90+
|
85–90
|
85–90
|
|
Integration with Industrial Heat
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High
|
Low
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None
|
*Data sourced from4, 8
Environmental and Economic Impact
The technology offers significant environmental and economic advantages. It addresses a critical source of emissions by enabling cost-effective capture in high-temperature industries. Based on its high capture rate of over 90%, lifecycle assessments project that net CO₂ reductions could exceed 85%, supported by the long operational lifespan of the molten salts, which minimizes replacement waste compared to conventional capture media.3
Economically, models indicate industrial abatement costs could fall by 40–50% due to greater energy efficiency and reduced infrastructure needs. The system also generates a pure CO₂ stream suitable for conversion into valuable products, enhancing project viability. Furthermore, deployment is projected to create regional jobs in manufacturing, engineering, and operations.
Future Outlook and Industry Significance
Mantel schedules commercial demonstrations in 2025–2026 and full-scale deployment from 2027. A $30 million Series A round of financing in 2024, co-led by Shell Ventures and Eni Next, will be used for this scale-up.7
Policy programs such as the U.S. Inflation Reduction Act and EU Carbon Border Adjustment Mechanism (CBAM) provide investment incentives for industrial carbon capture.8 Mantel targets mid-to-large emitters, where high-temperature opportunities are limited. The company will focus on minimizing cost and integration with other clean energy systems, with growth into markets with pervasive carbon pricing, such as Europe.
Mantel's high-temperature molten-salt carbon capture technology presents a solution to industries like cement and steel that are constrained by conventional methods. With pilot installations in progress and funding, the technology is well placed to offer solutions to companies that must comply with carbon regulations.
References and Further Reading
- CO2.Earth. (n.d.). Daily CO₂. Retrieved October 19, 2023, from https://www.co2.earth/daily-co2
- Hertwich, E., Steinberger, J. K., Suh, S., et al. (2022). Industry. In P. R. Shukla, J. Skea, R. Slade, et al. (Eds.), Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (pp. 1157–1256). Intergovernmental Panel on Climate Change. https://www.ipcc.ch/report/ar6/wg3/chapter/chapter-11/
- Mantel. (2024). Technology. Retrieved from https://mantelcapture.com/technology
- Ainsworth, S. J. (2024, September 18). Mantel raises $30 million for molten borate carbon capture. Chemical & Engineering News. https://cen.acs.org/business/investment/Mantel-raises-30-million-molten/102/i32
- Lacina, L. L. P. (2024, September 16). Cement production accounts for 7% of global CO2 emissions. Here's how to make it more sustainable. World Economic Forum. https://www.weforum.org/stories/2024/09/cement-production-sustainable-concrete-co2-emissions/
- Business Wire. (2024, September 5). Mantel Secures $30 Million to Bring Low Cost, Energy Efficient Carbon Capture to the Heavy Industrial Sector. https://www.businesswire.com/news/home/20240905005184/en
- Casey, T. (2024, September 5). Shell, Eni lead funding round for carbon capture firm Mantel Capture. Reuters. https://www.reuters.com/sustainability/climate-energy/shell-eni-lead-funding-round-carbon-capture-firm-mantel-capture-2024-09-05/
- International Energy Agency. (2023). World Energy Outlook 2023. https://www.iea.org/reports/world-energy-outlook-2023
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