At first glance, the idea of using industrial waste to fight climate change feels counterintuitive. Waste is usually something we try to eliminate — not manage as a solution. Alkaline industrial wastes such as steel slag, cement dust, and red mud contain high amounts of calcium and magnesium. When these elements leach into water systems, they can disrupt normal water chemistry and mobilize toxic trace elements, producing caustic runoff that leads to downstream risks for the ecosystem. However, calcium and magnesium minerals can naturally react with carbon dioxide to form stable carbonate minerals. Through this process, carbon dioxide is permanently converted into solid compounds from the atmosphere, where it traps heat by absorbing infrared radiation and re-emitting it back to Earth. In this way, transforming industrial waste into carbon-capturing materials becomes a “two birds, one stone” strategy: reducing the environmental risks posed by the waste while also helping mitigate climate change.

The reaction works in a way similar to how spiny stone “icicles” form in caves. Carbon dioxide dissolves in water to form carbonic acid, which reacts with calcium or magnesium to form solid carbonates — essentially locking carbon dioxide into the rock. However, this reaction happens very slowly under natural conditions. To speed it up, researchers use three main approaches. The first one is to turn mineral waste into fine particles, creating a larger surface area for direct reaction between carbon dioxide and the minerals. The second method is to dissolve carbon dioxide in water, allowing greater mobility for carbon dioxide to react with metal ions. The last reaction pressures metal ions from waste into the solution to precipitate readily with dissolved carbon dioxide.

For industrial waste, there are more chemical factors to consider. Since high-pressure reactors rely heavily on pH, temperature, and pressure, strong alkaline components in the waste hinder the reaction. When the condition is acidic, more metals dissolve, but the carbonate formation may not be stable. Hydrogen sulfide, an extremely toxic gas, could also form during reactions. Thus, solution chemistry, gas composition, and solid properties need to be carefully controlled before the reaction happens.

Although the reaction can occur without external energy, it becomes diffusion-limited when carbonate layers form, slowing further carbon dioxide access. Energy input for grinding, heating, or pressurizing materials can also reduce net climate benefits if not optimized. Yet the advantages are compelling: carbon dioxide is permanently stored as stable minerals; the process can produce commercially valuable calcium carbonate; and globally generated alkaline wastes are abundant enough to potentially sequester a giant scale of carbon dioxide. Unlike some carbon capture technologies that require continuous regeneration, mineral carbonation offers durable, long-term storage.

Researchers are therefore exploring ways to integrate mineral carbonation into existing industrial systems. Large waste streams such as steel slag and cement dust are generated each year globally, providing abundant feedstocks for carbonation reactions. Because many of these wastes are produced at industrial facilities that also emit carbon dioxide, integrating carbonation processes with waste management systems could help stabilize waste materials while capturing emissions. In addition, the carbonate minerals produced through these reactions may be reused in construction materials or other industrial products, potentially improving the economic feasibility of the process.

Using mineral waste to sequester carbon dioxide may seem unconventional, but it represents a promising convergence of waste management and climate mitigation. By accelerating natural mineralization reactions, industrial byproducts can be transformed into stable carbonate materials that permanently store carbon. While challenges remain, ongoing research demonstrates practical pathways to improve efficiency and control side effects. As global industries continue to generate alkaline wastes alongside carbon dioxide emissions, mineral carbonation offers a compelling strategy to address both pollution and global warming.