| Abstract |
This study investigates the CO2 mineralization potential within the geothermal energy sector, with focus on the Olkaria basalts in Kenya. CO2 mineralization is a carbon mitigation method that converts CO2 into stable carbonate minerals, providing long-term solution to carbon-emissions associated with geothermal power production. The Olkaria geothermal field has an installed capacity of 799 MW, which is a huge step towards Kenya’s renewable energy generation goals. However, geothermal production is not entirely emission-free. The geothermal power plants in Olkaria emit ~68,916 tCO₂e/yr. Although much lower emissions than fossil fuel alternatives, this still contributes to greenhouse-gas accumulation and global warming. This study aims to improve understanding of the subsurface lithostratigraphy, specifically the Olkaria Basalt unit, for CO2 mineralization potential. The study involves carrying out binocular, petrographic, whole rock analysis and porosity volume estimations. Rock cuttings from four reinjection wells, OW-204, OW-723A, OW-739 and OW-R12, were used to investigate the variation in chemical composition, porosity distribution and width, and ultimately to estimate the theoretical CO2 storage capacity. Results indicate that the Olkaria Basalt unit is comprised of layers of basalts intercalated with layers of tuff, rhyolite, basaltic trachyandesite, trachybasalt and trachyandesite. The unit varies in thickness from 70 m in OW-723A to 250 m in OW-204. Total concentration of divalent cation oxides ranges from <10 to 27%, in the rhyolites and basalts, respectively, and porosity values range from 1.3-3.8 %. The theoretical storage capacity is estimated to be 23-89 Mt, which is sufficient for mineralization of the local CO2 emissions within Olkaria |