Carbon Mineralization: Locking CO₂ Away Forever

When we talk about carbon storage, permanence is everything. Trees can burn. Geological reservoirs can leak. But when CO₂ reacts with certain minerals to form stable carbonate rock, the carbon is locked away for millions of years — effectively forever on any human timescale.

How It Works

Carbon mineralization is a natural process. When rain dissolves CO₂ from the atmosphere, the resulting carbonic acid slowly reacts with silicate minerals — particularly those rich in magnesium and calcium — to form solid carbonate minerals like magnesite (MgCO₃) and calcite (CaCO₃). In nature, this process takes thousands of years. Captisme accelerates it to days.

Our approach uses finely ground reactive minerals — sourced from basalt formations and mine tailings — combined with concentrated CO₂ from our capture systems. By optimizing particle size, temperature, pressure, and CO₂ concentration, we achieve reaction rates 10,000 times faster than natural weathering.

Why Mineralization Matters

• Permanence: carbonate minerals are thermodynamically stable for geological timescales
• Verifiability: solid rock can be weighed, assayed, and audited — no monitoring wells needed
• Safety: no risk of sudden CO₂ release, unlike pressurized geological storage
• Abundance: suitable minerals are available in vast quantities globally
• Co-benefits: can remediate mine tailings and industrial waste streams

Scaling Up

The main challenge for carbon mineralization is the scale of mineral processing required. Storing one tonne of CO₂ requires roughly 1.5–3 tonnes of reactive mineral. At gigatonne scale, this implies a mining and processing operation comparable to the global cement industry. The good news: unlike fossil fuels, the minerals are not consumed — they are transformed into stable, benign products that can be used as construction aggregates, soil amendments, or simply returned to the ground.

At Captisme, we are currently operating a 10,000 tCO₂/year mineralization pilot in partnership with a major mining company. The results are promising — and we are engineering the next generation of reactors designed for 100,000+ tCO₂/year throughput.