A novel reduction process of CO₂ fixation by waste concrete treatment

A new process to fix anthropogenic carbon dioxide via treatment of waste concrete was proposed. The main reaction of the process is the extraction of calcium ions from waste concrete particles by use of pressurized carbon dioxide (several MPa in pressure). The extracted Ca²⁺ is deposited as calcium carbonate (CaCO₃) particles when the pressure is reduced to the atmospheric pressure. The CaCO₃ particles can either be disposed of directly or reused industrially for cement production. The former case is a direct disposal of CO₂; the latter case is an indirect disposal of CO₂, because the net mining amount of virgin limestone could be reduced. Energy consumption and cost for the fixation process of CO₂, emitted from a 100-MW thermal power plant by the proposed process was evaluated based on laboratory scale experimental results. It was found that energy consumption for the operation was 3.5 MW per 100-MW power generation, and the fixation cost was about JPY 2100 per metricton of carbon. This result indicates that the present process is highly competitive with the previous CO₂ fixation scenarios such as ocean sequestration.