Keywords: basalt rock, silicate minerals carbonation, CO2, carbon dioxide, carbon storage, geothermal energy, heat release, exothermic reactions, geothermal power plants, electricity generation, mafic rocks, ultramafic rocks
Heat as a by–product or sub–product of CO2 storage in mafic and ultramafic rocks
Since carbonates are at a lower energy state than free CO2, storage through carbonation of silicate rocks is thermodynamically favoured and proceeds spontaneously by releasing heat. In an in–situ CO2 injection site, the heat released in these exothermic reactions can be exploited in a geothermal power–plant, effectively contributing toward the economic viability of the storage process. Our calculations suggest the possibility of generating up to about 25 TWh of electrical energy while capturing permanently about 240 Mton CO2 per 1 km³ of peridotite or basalt rock. That broadly corresponds to exploring an electric power plant having up to 60 MW gross output during a period of 50 years. These results show that geothermal energy and CO2 storage, often portrayed as conflicting uses of the subsurface, can actually work together, enhancing the economic feasibility of each other in case mafic and/or ultramafic rock formations are used as reservoirs.