Assessing the carbon capture and mineralization storage potential in the Olkaria Geothermal Field, Kenya: A geochemical, policy and financial framework study

Abstract

Kenya’s primary energy demand is expected to rapidly increase in the coming decades in line with its vision for accelerated economic and industrial development. Central to this is the development of Kenya’s geothermal sector, accounting for 48.4% of renewable electricity consumed in 2021. Associated with further geothermal development, geothermal-related CO2 emissions are expected to rise, such that the risk of a carbon lock-in increases if mitigation practices are not implemented. This study aims to determine the feasibility of carbon capture and mineralization (CCM) storage of Kenya’s most developed geothermal field; Olkaria, using the Olkaria IV Geothermal Power Plant as its case study. Reaction path models reveal that the Olkaria Trachyte has 0% carbon sequestration potential due to increased competition for divalent cations with epidote, chlorite and zeolite phases at high reservoir temperatures (270°C) whereas the Olkaria Basalt can sequester up to 84% of injected CO2, where the amount of CO2 potentially fixed is highly dependent on the chemical composition of the injection fluid and reservoir conditions. Assuming present-day carbon capture efficiencies from geothermal exhaust streams (56% CO2 captured) hold true for a Kenyan CCM case-study, ~35 ktCO2 yr-1 of Olkaria IV’s emissions can be stored in Olkaria basalts. Furthermore, a review of Kenyan geothermal-related environmental regulations and accessibility to international climate finance for mitigation projects, suggests that legislation and multilateral finance mechanisms could act to support the deployment of CCM activities in Kenyan geothermal industries.