# Assessment of Potential Microbial Hydrogen Consumption in European Hydrogen Underground Storage Sites

Kateřina Černá, Jakub Říha, Kristýna Fadrhonc, Petra Bombach, Sétareh Rad, Sylvain Stephant, Caroline Michel, Laura Fablet, Delphine Ropers, Arnaud Belcour, et al.

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## ► To cite this version:

Kateřina Černá, Jakub Říha, Kristýna Fadrhonc, Petra Bombach, Sétareh Rad, et al.. Assessment of Potential Microbial Hydrogen Consumption in European Hydrogen Underground Storage Sites. GET 2025 - Sixth EAGE Global Energy Transition Conference & Exhibition, Oct 2025, Rotterdam, Netherlands. pp.1-5, 10.3997/2214-4609.202521032. hal-05448781

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Submitted on 8 Jan 2026

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# Assessment of potential microbial hydrogen consumption in European hydrogen underground storage sites

Authors: K. Cerna¹, J. Riha¹, K. Fadrhonc¹, P. Bombach², S. Rad³, S. Stephant³, C. Michel³, L. Fablet³
D. Ropers⁴, A. Belcour⁴, J. Tremosa⁵, K. Kyaw⁶, N. Paltrinieri⁶, A. Biwen An-Stepec⁷ and N. Dopffel⁷

Affiliations: 1 Technical University of Liberec, 2 Isodetect GmbH, 3 French Geological Survey BRGM, 4 Inria, 5 Geostock, 6 Norwegian University of Science and Technology, 7 Norwegian Research Centre AS - NORCE

Publisher: European Association of Geoscientists & Engineers

Source: Conference Proceedings, Sixth EAGE Global Energy Transition Conference & Exhibition (GET 2025), Oct 2025, Volume 2025, p.1 - 5

DOI: https://doi.org/10.3997/2214-4609.202521032

Summary: Underground hydrogen (H₂) storage is a key technology for stabilizing Europe's renewable energy supply, but microbial activity in subsurface environments may lead to H₂ loss, gas quality degradation, and infrastructure damage. The CETP-funded HyLife project brings together four European microbiology laboratories and multiple industry partners to quantify microbial risks associated with underground hydrogen storage. Twenty-one brine samples from salt caverns, aquifers, and depleted gas reservoirs across ten countries were characterized so far using developed fully standardized anoxic sampling and analytical workflows, including geochemical analysis, enrichment cultures, qPCR, and 16S rRNA sequencing. Distinct microbial communities were identified at each site, even when brine chemistries were similar. Enrichment experiments revealed rapid H₂ loss within weeks in several porous-rock reservoirs at ≤ 50°C, while most salt-cavern brines showed negligible activity after 12 months. Hydrogen consumption was most commonly linked to methanogenesis. Kinetic parameters derived from these tests are being integrated into 3D reactive-transport models and an open-access database to support techno-economic assessments, mitigation strategies, and evidence-based guidelines for selecting safe and efficient hydrogen storage sites. The project actively engages industry partners and continues to expand its dataset through additional sampling across diverse geological settings.

© EAGE Publications BV
# Assessment of potential microbial hydrogen consumption in European hydrogen underground storage sites

## Introduction

Hydrogen ($H_2$) is expected to play a crucial role in Europe's green energy transition by balancing the fluctuating supply and demand of renewable energy. Surplus electricity from sources like wind and solar can be converted to $H_2$ (power-to-gas) and stored for later use. To ensure system stability, storage capacity equivalent to around 30% of energy demand is needed. Underground $H_2$ storage in salt caverns or porous rock reservoirs (e.g., depleted gas fields, gas storage sites, or aquifers) is promising due to its large capacity, flexibility, and low operational costs (Tarkowski, 2019). However, subsurface $H_2$ storage may trigger microbial redox reactions, as $H_2$ serves as an electron donor for various microorganisms in anoxic environments. These microbes can consume $H_2$ while reducing nitrate, ferric iron, sulfate, sulfur, or $CO_2$, producing byproducts like $H_2S$ or $CH_4$ (Gregory et al., 2019). This activity poses several risks: $H_2$ loss, gas quality degradation, biocorrosion, $H_2S$ leakage, and changes in reservoir properties (Dopffel et al., 2021).

Microbial activity is presumably site-dependent and influenced by environmental factors such as geology, electron acceptor availability, temperature, pressure, salinity, and $H_2$ concentration. Laboratory studies have shown significant variation in $H_2$ consumption rates based on these factors (Dohrmann and Krüger, 2023; Dopffel et al., 2023). Despite the risks, data on microbial $H_2$ consumption in subsurface environments remain limited.

In our Clean Energy Transition Partnership (CETP) funded R&D project HyLife, we aim to provide valuable insights into the types of microbes present and how they will influence the stored hydrogen through extensive sampling across Europe. The project has already produced aligned and tested methodologies to maximize comparability and microbiological data on community characteristics, growth, and kinetics. The obtained data within the broad range of storage site conditions will be accessible through an open database. We will also assess related environmental risks, test potential mitigation options, and produce insightful techno-economic business analyses. One major goal is to map microbial presence in the different European sites and pinpoint the most important factors for field screening to minimize risks when selecting sites. For the success of this project, we rely on field samples provided by operators, ranging through all relevant geological locations.

## Methods

Geological and environmental conditions at potential hydrogen storage sites vary widely, making it essential to study many sites to understand microbial impacts on storage performance. This is beyond the capacity of a single lab, so the HyLife project established a European microbiological network involving labs in Germany, France, Norway, and the Czech Republic. To ensure data comparability, all participating labs aligned their sampling and analytical methods at the outset and created a set of standardized methodologies.

HyLife uses a range of microbiological, chemical, and DNA-based techniques to assess microbial activity and diversity in brine samples. Standardized protocols were developed for sampling and enrichment cultures, focusing on key microbial groups like sulfate-reducing bacteria, methanogens, and acetogens. These methods were tested in round-robin experiments to ensure reproducibility and to support industry guidelines for microbiological risk assessment.

Hydrogen consumption depends on factors like microbial diversity, cell density, brine chemistry, pressure, and temperature, all of which can shift during storage. We investigate how these variables affect microbial activity through controlled lab experiments, helping to define kinetic models of hydrogen consumption. These models will be used to simulate storage scenarios and predict changes in hydrogen quality, enabling better risk mitigation.

At the reservoir scale, the project incorporates microbial kinetics into 3D models to evaluate gas, water, and mineral phase interactions during storage cycles. These models will help predict issues like methane formation or $H_2S$ contamination.
## Results

By the beginning of 2025, we had obtained 21 brine samples from 10 different European countries, including salt caverns, aquifers, and gas reservoirs (Figure 1).

<figure><img src="image_3.png" /><figcaption>**Figure 1** Sampling overview - brine samples obtained so far across Europe.</figcaption></figure>

All samples were taken by the operators using our developed sampling SOP, with the main aim of sampling anoxically and sterilely for microbiological analysis. Initial findings from the different sites revealed site-specific microbial activity. Salt caverns and gas reservoirs tend to have a unique microbial composition; aquifer samples are, on the contrary, relatively similar to the gas reservoirs. Each salt cavern, gas reservoir, and aquifer harbors a different microbial community, even when brine chemistry is similar (Figure 2).

<figure><img src="image_4.png" /><figcaption>**Figure 2** Venn diagram showing the unique and shared microbial genera among the three potential storage sites.</figcaption></figure>
Laboratory enrichment tests were prepared from the collected brine samples, with all participating laboratories following the same procedure and using identical additions. These growth tests aim to assess whether microbial communities are capable of utilizing hydrogen. However, it should be noted that such tests provide only indicative results, as many microorganisms may not grow under laboratory conditions.

$H_2$ consumption activity was observed in several gas reservoir samples within weeks, whereas until now, only one salt cavern brine has shown $H_2$ consumption activity after nearly 12 months of incubation. These initial results imply that immediate hydrogen consumption by the indigenous microbial community in underground storage sites is especially likely to occur in porous rock reservoirs with on-site temperatures up to 50°C, where we observed the highest $H_2$ losses (Figure 3). In such environments, $H_2$ consumption was primarily linked to methane ($CH_4$) production in our studied samples. However, more incubations are being conducted to investigate $H_2$ consumption in other potential storage rock formations and field temperatures.

<figure><img src="image_5.png" /><figcaption>**Figure 3** Hydrogen consumption and methane production in porous rock reservoir brine samples.</figcaption></figure>

## Conclusions

We are four microbiological laboratories collaborating across Europe to investigate how microbial communities influence hydrogen storage in various types of facilities. Our field studies have shown that each storage site hosts a distinct microbial community. In some cases, these communities were capable of consuming hydrogen under laboratory conditions, with methane identified as the main metabolic product.

As the demand for hydrogen storage grows, selecting suitable sites is essential to minimize risks to infrastructure and operations. Our research aims to provide guidelines and support the energy sector in identifying safe and efficient hydrogen storage locations. To strengthen our findings, we are actively seeking additional storage operators to join the project. Expanding our dataset across diverse geological settings and chemical-physical conditions will provide a more comprehensive understanding of microbial activity in potential storage environments. By understanding the biological processes involved, we can develop strategies to prevent and mitigate unexpected failures and ensure safe, long-term storage of hydrogen. This will help accelerate the transition to a more sustainable energy future in Europe.

## Acknowledgments

This research was funded by CETPartnership, the European Partnership under Joint Call 2022 for research proposals, co-funded by the European Commission (GA N°101069750) and funding organizations Research Council of Norway, Agence Nationale de la Recherche, Technology Agency of the Czech Republic and Staatsministerium, für Wissenschaft, Kultur und Tourismus of Free State of Saxony. We also want to acknowledge our industry partners Lanxess, OMV, Corronation BV, TotalEnergies, SLB and BP for their support of the project.
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