Geologic H2 generation with simultaneous CO2 mineralization: A dual strategy for energy decarbonization

Ultramafic formations are ideal for generating geologic H 2 and mineralizing CO 2 . The prospect of combining both processes is examined using geochemical kinetic modeling. Simulations show that CO 2 promotes H 2 generation up to 31% at depths where the temperature is less than ∼150 °C by enhancing Fe(II) dissolution. A key feature of this model is that porosity, which controls water availability for H 2 generation, evolves with mineral assemblage. This reveals that adequate flow is critical in sustaining the positive effect of CO 2 . We also report that magnesium promotes H 2 generation by scavenging SiO 2 , which broadens implementation options given that ultramafic rocks are replete with Mg. CO 2 is mainly mineralized in magnesite, rather than as siderite, thereby keeping Fe(II) available for H 2 generation. Relative to the H 2 generation target proposed in the IEA net-zero-emissions scenario, the CO 2 -enhanced H 2 generation could significantly reduce needed reactive formation volume while contributing to the CO 2 capture goal.