"Georeactor": CO2 mineralization in hydrothermal system

Abstract

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.