UTILIZING ULTRAMAFIC ROCKS FOR H2 PRODUCTION AND CO2 SEQUESTRATION: A PATHWAY TO CLEAN ENERGY AND EMISSIONS REDUCTION IN KAZAKHSTAN

Permanent geological storage of anthropogenic CO₂ and the development of low-carbon energy resources, including natural hydrogen (H₂), have become two key components of carbon-neutrality strategies. Ultramafic rocks are increasingly recognized as promising geological media because they can support both mineral carbonation and natural H₂ generation. However, the relationship between these processes, and the extent to which similar reactions occur in mafic rocks, remain poorly understood. Mafic and ultramafic rocks from the Charsk Ophiolite (eastern Kazakhstan) and the Kempirsai Ultramafic Massif (western Kazakhstan) were investigated under experimental conditions to evaluate their potential for CO₂ mineralization and natural H₂ generation. Serpentine-rich ultramafic rocks displayed the highest carbonation potential. Dissolution of lizardite released Mg²⁺ ions that promoted secondary magnesite precipitation and efficient mineral trapping of CO₂. Carbonation was substantially weaker in magnesiochromite-rich ultramafic rocks. Natural H₂ generation followed a different pattern. The highest H₂ concentrations were measured in ultramafic (0.872 mol%) and mafic (0.721 mol%) rocks from the Charsk Ophiolite, whereas only trace amounts were detected in samples from the Kempirsai Massif. CO₂ mineralization and natural H₂ generation were controlled by different mineralogical factors. Serpentine-rich ultramafic rocks were most favorable for long-term CO₂ immobilization through mineral carbonation, whereas Fe-bearing mafic and ultramafic rocks with high reaction potential were more favorable for natural H₂ generation. Kazakhstan’s ophiolitic complexes therefore represent promising geological targets for both permanent CO₂ storage and natural hydrogen exploration.

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