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 H2 2 metabolisms is crucial for evaluating the risks for geological hydrogen storage. This study investigates how mineralogy and temperature affect H2 2 consumption kinetics and metabolic activity of a microbial consortium containing methanogens, homoacetogens and sulfate reducers, incubated at 25, 34 and 40 degrees C under H2/CO2 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 degrees C. Methanogenesis is dominant at 34 and 40 degrees C with all sulfate-free mineralogies. At 25 degrees 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 H2 2 also depends on the mineralogical composition of the reservoir.