Exploring the biochemical potential of the subsurface for UHS risk assessments

Subsurface microbial communities constitute a major part of the global biosphere and they play a crucial role in the cycling of several gases related to Underground Hydrogen Storage (UHS), such as carbon dioxide, methane, hydrogen sulfide and, certainly, hydrogen (Beaver & Neufeld, 2024; Cascone et al., 2025; Kieft, 2016; Magnabosco et al., 2018; McMahon & Parnell, 2014). The key reactions in these processes involve the transfer of electrons between chemical species, i.e. the coupling the oxidation of electron donors to the reduction of electron acceptors, and are catalysed by a specialized subgroup of enzymes: oxidoreductases (Hay Mele et al., 2023). Organisms can then capture the free Gibbs energy released in these reactions and use it to sustain themselves (Lane & Martin, 2012). By elucidating which oxidoreductases a given microbial species or community contains, we can infer the potential for these reactions to occur in the environment of interest. Despite recent efforts, there are few comprehensive and comparative studies targeting the presence of oxidoreductases in the subsurface and their implications for UHS, which is critical to understand the risks these operations may face (Dopffel et al., 2021; Escudero & Amils, 2023; Ranchou-Peyruse, 2024; Templeton & Caro, 2023; Thaysen et al., 2023). In this work, we expand on a previous bioinformatics pipeline to predict the presence of oxidoreductases employing publicly available datasets of subsurface microbial communities as a case study with relevance to UHS (Climent Gargallo et al., 2025). Preliminary results point to potential sinks for the stored hydrogen and sources for the corrosive and toxic hydrogen sulfide, as well as methane and other related gases, which could greatly impact the operation conditions of the UHS pipeline.

 

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