The technology of CO2 sequestration by mineral carbonation: current status and future prospects

Mineral carbonation (MC) has been extensively researched all over the world since it was found as a naturally exothermic process to permanently sequester CO2. In order to accelerate the natural process, various methods for carbonation of Mg-/Ca-silicate minerals have been studied. It has been found that the MC efficiency will increase with an increase in CO2 pressure, retention time, temperature, mass ratio of Mg/Ca to Si in minerals, specific surface area, and the slurry concentration in a specific range, and with the introduction of NaCl and NaHCO3 or carbonic anhydrase. However, there is still no successful industrial application because of high economic costs and slow reaction rate. It is not economic to exploit Mg-/Ca-silicate minerals deposits or tailings to sequester CO2 by the MC due to the cost of grinding and heat pre-treatment. In some cases, the whole sequestration process may result in more CO2 emissions than the sequestered CO2 due to the requirements of energy inputs. The process, however, may be profitable as a whole (with carbon credits). It is suggested to combine the MC with valuable metals recovery from ore deposits in order to reduce the cost of the MC by cost sharing for mineral recovery.