Microbial risks associated with hydrogen underground storage in Europe

To decrease emissions of greenhouse gasses into the atmosphere, we have to move away from fossil fuels into a green and sustainable society. Hydrogen can play a big role in this, as it is a universal energy carrier and can be used to fuel cars or ships, heat buildings, melt steel or make electricity. For this transition, we will need a lot of hydrogen throughout the year. But where can we store all this hydrogen during the summer days when we do not need as much? Underground hydrogen storage (UHS) offers us the possibility for storing excess hydrogen in different deep geological formations. Salt caverns, aquifers and depleted hydrocarbon deposits (gas reservoirs) can be used for this type of storage. There the hydrogen can stay for days, weeks or months, until it is needed. When it is pumped back, it can be either directly used or transformed into electricity later. However, the storage sites in the subsurface often contain microorganisms and there are some types known, which can feed on hydrogen causing many problems. We want to understand what types of microbes are triggered by hydrogen storage, their growth behavior and possible inhibition. In our HyLife project will sample, analyze and characterize many different potential storage sites all over Europe with a focus on the microbial effects at the different sites. We hope to find key factors to understand the microbial risks better and make safe and resilient UHS possible. Partners: NORCE, NTNU, BRGM, Inria, TUL, Isodetect

Many renewable energy systems utilize “Power-to-Gas” technologies, which use renewable electricity to produce hydrogen (H2), a universal energy carrier. To ensure a secure supply of H2 throughout the year, it is essential to have flexible, large-scale storage to balance expected fluctuations of energy-production and -demand. Underground/subsurface storage has been proposed as a favourable solution for mid-to long-term storage, due to the large available volumes that could hold up to 920 TWh; this would be sufficient for a mid-range scenario of 2,500 TWh of annual H2 demand in 2050 with at least 30% storage capacity (1, 2). It is a known fact that many of these potential underground storage sites harbour diverse microbial communities and that H2 is not only a perfect energy carrier for human industry but also for microbial metabolisms. While microorganisms consume the H2, they can induce microbial-triggered risks including loss of the stored H2, risks to operational safety and deterioration in quality by H2S production, biocorrosion and changes of the reservoir properties (3). As the demand for more H2 storage rises, it is therefore important to understand the extent of the microbial presence and activity within the different types of sites (salt caverns, porous media including aquifers and gas reservoirs). HyLife will produce valuable insights on what types of microbes are present and how they will influence the stored H2 through extensive sampling across Europe. Direct results will be a) aligned and tested methodologies to maximize comparability, b) an open database on detected microorganisms within the broad range of storage site conditions, c) microbial factors for field screening to minimize the risk when selecting sites. We will also assess related environmental risks, test potential mitigation options and produce insightful techno-economic business analyses.