Speaker
Description
A significant barrier to underground hydrogen storage is that hydrogen serves as an excellent electron donor for many microbial metabolisms, leading to its consumption and contamination. Recent studies have shown that the hydrogen consumption rate can be accelerated by adding solid particles, such as pure quartz grains, into the bulk solution, indicating that solid phases can enhance microbial metabolisms. This raises concerns about the reliability of microbial activity data derived from pure incubation experiments, which may not accurately reflect natural conditions, where hydrogen and microorganisms coexist in rock pore spaces. Rock mineral grains can provide physical attachment sites for microbes, while iron minerals (e.g., hematite) can act as conduits for microbial metabolism, potentially increasing reactivity. Additionally, some minerals may supply essential elements to microbes through dissolution. Therefore, it is crucial to deepen our understanding of bio-geochemical reactions in porous rocks.
Microfluidic experiments offer significant potential for investigating microbial dynamics in porous media. However, microfluidic devices are typically constructed from artificial materials such as PDMS, glass, and silicon, which only replicate pore geometry and fail to capture the chemical and physical properties of natural minerals. We present an approach using real-rock micromodels that combine microfluidic fabrication and thin section techniques using natural sandstones. This method includes rock chemistry and grain surface morphology (e.g., roughness and clay/hematite coatings), features often absent in conventional microfluidics. Additionally, it enables flow-through and incubation experiments with real-time pore-scale imaging. Using these micromodels, we investigated the interactions between methanogenic archaea and rock minerals, focusing on microbial growth, spatial distribution with respect to different minerals, and the impact of biofilm formation on rock permeability and porosity. Preliminary results revealed correlations between gas consumption rates and microbial distribution in Triassic Buntsandstein sandstones.
Within the recently funded Horizon Europe HyDRA project (Diagnostic Tools and Risk Protocols to Accelerate Underground Hydrogen Storage), we aim to advance our understanding of microbial activity in storage sites across Europe. This includes extending the real-rock micromodel approach to incorporate natural microbial cultures from downhole solutions and realistic reservoir materials to study microbial responses when hydrogen is introduced into initially hydrogen-free environments. Key investigations will include changes in wettability, biofilm formation, and their effects on flow properties in natural rocks. Flow-through experiments with microbial communities, including archaea, acetogens, methanogens, and/or Fe³⁺-reducing bacteria from porous reservoirs, will elucidate the roles of rock minerals and grain surfaces in microbial activity and distribution. Accurate prediction of bio-geochemical reactions and their impact on rock properties will help better assess the risks associated with underground porous storage and develop mitigation strategies.
| Country | Germany |
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