Microbial Redox Reactions During Underground Storage of Hydrogen

Underground storage of hydrogen (H2) could be an alternative or important supplement to energy storage. However, there is still lack of knowledge about fundamental biogeochemical aspects of underground H2 storage. The BMBF-funded project H2_ReacT investigates fundamental petrophysical, geochemical and biogeochemical aspects of underground H2 storage. The work presented here addresses the microbial consumption of H2 and the involved microorganisms at potential underground storage sites.

Microbial reactions that consume H2 are still a major uncertainty factor for underground H2 storage. Microbial life is widespread in the crust of the earth and geological formations suitable for underground H2 storage often contain a deep subsurface biosphere. Thus, an underground H2 storage site needs to be seen as a habitat for microorganisms. Microbial activity at the H2 storage site might affect the stored H2 as well as the integrity of the storage site itself. A specific interest is to gain information about microbial activity that might result in a loss of stored hydrogen as well as the production of unwanted metabolic products e.g. H2S. The importance of specific conditions with relevance for underground hydrogen storage i.e. elevated pressure, high temperature and rock material, will be addressed.

Preliminary results showed the consumption of H2 by indigenous microorganisms from a porous rock reservoir fluid. Hydrogen was consumed at different temperature and pressure conditions relevant for underground H2 storage. Here, hydrogen consumption rates were strongly influenced by temperature and pressure. Currently effects of several geochemical parameters on microbial H2 consumption are studied in more detail. Furthermore, molecular biological approaches are used to identify the involved microorganisms.