Fixation of carbon dioxide by producing hydromagnesite from serpentinite

Fixing carbon dioxide (CO2) as carbonates using silicate-based materials is an interesting alternative option for storage of carbon dioxide. Suitable magnesium-rich rocks are distributed throughout the world. The magnesium silicate deposits in Eastern Finland alone could be sufficient for storing 10 Mt CO2 each year during a period of 200–300 years. Rocks potentially suitable for carbonation are already mined, processed, piled, and stored at mines producing industrial minerals and metals. Two process schemes were constructed based on previous experimental results with producing magnesium carbonates from serpentinite, a serpentine ore. The thermal stability of the produced hydromagnesite was also assessed using thermogravimetric analysis. Although pure hydromagnesite can be produced that is thermally stable up to 300 °C, the process scheme studied requires recycling of large amounts of sodium hydroxide and acid. Since the current methods for recycling the spent chemicals are expensive and would presumably cause CO2 emissions due to power consumption, the process studied might be suitable for producing valuable mineral and metal products from serpentinite, but probably not for CO2 capture and storage.