Microbiological and Geochemical Perspectives on Sustainable Dihydrogen Storage in Deep Aquifers.

The successful integration of dihydrogen (H) as an energy vector relies on effective seasonal storage in underground facilities like deep aquifers. However, the viability of this storage remains uncertain due to the unclear behavior of indigenous microorganisms in the presence of H, which could influence the gas composition. While modeling can inform H dynamics, reactor-scale experiments are needed for validation. In our study, we used a high-pressure reactor to simulate injecting 2% H into a gas storage aquifer currently used for natural gas (CH, 1% CO), utilizing formation water and rock samples from the aquifer. Our research led to a kinetic model that analyzes the interactions among gas, water, rock, and microbial activities. We found that microorganisms consumed H and caused alkalinization, which inhibited further microbial growth and respiration. This suggests that after an initial decrease in H concentration, the gas storage may be stabilized in deep aquifers. Reducing CO levels is vital as CO can hinder alkalinization and enhance sulfate-reducing, methanogenic, and acetogenic activities. Notably, while H-utilizing microorganisms were predominant, both methanogens and sulfate-reducers showed significant activity. Overall, our findings provide insights into the potential for underground H storage in deep aquifers, guiding future research and energy storage applications.