"Georeactor": CO₂ mineralization in hydrothermal system

This paper is a short review of a new technology, "Georeactor", which sequesters and fixes CO₂ into geothermal fields by carbonate mineralization. In countries such as Japan, where have many active volcanic areas, one possibility is to sequester CO₂ into hydrothermal regions. The chemical reaction rates between CO₂-saturated water and rocks are usually faster than those at room temperature. For example, the following reaction (alteration reaction forming kaolinite from plagioclase): CaAl/₂Si₂O₈ (plagioclase) + H⁺ + HCO₃^- + H₂O = CaCO₃ (calcite) + Al₂Si₂O₅ (OH)₄ (kaolinite) is a good example that gives rise the carbonate precipitation. This reaction moves towards the right-hand side with increasing temperatures and CO₂ in aqueous phase (or HCO₃^- as a soluble species), suggesting a potential of CO₂ sequestration. The calcite- and kaolinite (clay)-rich rock produced through the reaction is expected to form a cap rock for the geothermal reservoir, with increasing storage safety. Furthermore, the high temperature of a geothermal field is favourable for immediate mineral carbonation, which would also contribute to the storage safety. In Japan, total rock volume in geothermal fields is estimated to be 4900 km³. The CO₂ storage capacity is calculated to be about 20 billion tons CO₂ (∼17 times Japan's total annual CO₂ emissions.