This company uses limestone to capture CO₂ and store it permanently

Heirloom takes crushed limestone and heats it in a kiln powered by renewable energy. The reaction generates two products. These are CO2, which can be permanently stored underground or in materials like concrete and a powder, which is hydrated with water to make calcium hydroxide. When the calcium hydroxide is spread onto trays, it absorbs CO2 from the air to become limestone and the whole process can begin again.