Evidencing the influence of temperature and mineralogy on microbial competition for hydrogen consumption: Implications for underground hydrogen storage (UHS)

Understanding the environmental drivers of microbial H 2 metabolisms is crucial for evaluating the risks for geological hydrogen storage. This study investigates how mineralogy and temperature affect H 2 consumption kinetics and metabolic activity of a microbial consortium containing methanogens, homoacetogens and sulfate reducers, incubated at 25, 34 and 40 °C under H 2 /CO 2 (80/20, v/v; 2 bars) with different rock powders (basalt, calcite, gypsum, and sandstone). The presence of gypsum favors sulfate reduction over methanogenesis and homoacetogenesis, especially at 25 °C. Methanogenesis is dominant at 34 and 40 °C with all sulfate-free mineralogies. At 25 °C, homoacetogenic bacteria are favored over methanogens and acetate production varies with the mineralogy. This suggests interactions of the microbial community with the rock powders, which may serve as a surface to form biofilms. These metabolic shifts are associated with radical changes in microbial populations, highlighting that ecosystems plasticity towards H 2 also depends on the mineralogical composition of the reservoir. • Both temperature and mineralogy affect H 2 consumption kinetics. • Gypsum powder favors sulfate reduction over methanogenesis and homoacetogenesis. • Low temperature favors homoacetogenesis over methanogenesis. • Proportions of methanogenesis and homoacetogenesis vary with the substrate mineralogy. • Metabolic shifts are associated with radical changes in microbial populations.