InterPore2026

Impact of rock-microbe interactions on methanogenic conversion of hydrogen

20 May 2026, 12:05

15m

Oral Presentation (MS04) Biological Processes in Porous Media MS04

Speaker

Dr Chaojie Cheng (Institute of Applied Geosciences, KIT – Karlsruhe Institute of Technology)

Description

Hydrogen-consuming microbial metabolisms are gaining increasing attention in the context of underground hydrogen storage (UHS), because hydrogen is a universal electron donor for a wide range of subsurface microorganisms. These processes can cause hydrogen loss and generate unwanted by-products, thereby compromising gas quality and storage integrity. Robust site assessment therefore requires a quantitative understanding of microbial activity and hydrogen consumption kinetics. Batch reactors are commonly used to quantify hydrogen-driven metabolisms using natural formation fluids [Dohrmann and Krüger, 2023], or pure cultures [Strobel et al., 2023] by supplying hydrogen to the headspace. However, recent studies suggest that microbial activity can be markedly enhanced in the presence of particles or rock fragments, which was considered due to the increased accessible surface [Khajooie et al., 2024]. This concept was further experimentally measured in column experiments by measuring hydrogen consumption rates in sand packs with different effective surface areas [Mushabe et al., 2025]. In addition, rock dissolution may supply essential major and trace elements that support enzymatic function and microbial growth [Dong et al., 2022].

Here we present an approach using batch incubations to quantify methanogenic activity with and without Buntsandstein sandstone. Bottles contained 25 mL of a pure culture of Methanothermococcus thermolithotrophicus and were charged with a CO2/H2 gas mixture (20/80 vol%) to an initial pressure of 2.5 bar. Experiments were conducted at 60 °C under three conditions: (i) bulk solution, (ii) solution + crushed sandstone (24.6 g), and (iii) solution + a cylindrical sandstone core (24.6 g, permeability: 70 mD, porosity: 17%). Headspace pressure was monitored continuously and used to calculate hydrogen consumption rates via the ideal gas law. When pressure decline ceased, the headspace was flushed and repressurized to ~2.5 bar, for up to four cycles. Element concentrations in the initial and post-incubation fluids (bulk solution, solution + crushed rock, solution + core) were measured by ICP-OES. The results indicate that adding sandstone did not substantially change the initial hydrogen consumption rate during the first two cycles, consistent with rocks being immersed in the solution and not strongly increasing the effective gas-liquid interfacial area. In contrast, rock-bearing assays sustained methanogenic activity considerably longer than the fluid-only controls, with crushed sandstone supporting the longest activity. Post-incubation fluids containing rock showed elevated concentrations of Mn, Ni, and Ca (and additional trace elements) than the bulk solution, indicating that rock-fluid reactions may replenish nutrients and/or metal cofactors required for methanogenesis. These results demonstrate that rocks influence methanogenic hydrogen conversion not only by providing colonization surfaces and potentially modifying gas-fluid interfaces, but also by supplying geochemically derived nutrients. Rock-microbe interactions and bio-geochemical processes should therefore be explicitly considered in UHS risk assessment and predictive models of hydrogen loss.