Geology in the Hydrogen Era
Interest in the hydrogen economy occurs in waves. The last 3‒4 years have seen the resurgence of a strong hydrogen boom. The last boom dates back to the late 1990s, although there have been small ups and downs at other times. The most recent wave of interest seems to have the potential to remain a permanent ‘hydrogen era’, and the hydrogen economy is experiencing its strongest period yet. The reason is clear: the drive to mitigate climate change through low-carbon energy production.
Hydrogen makes up about 90% of the visible atoms in the universe. The remaining 10% consists of helium, which makes up about 9%, and other elements just 1%. If we ignore dark matter and energy, we are living in an enormous world of hydrogen and helium. Other elements and compounds are, from this limited perspective of the human environment, negligible. The Earth is therefore just a tiny grain of a special distribution of elements in the universe. That is why our habitat has a different elemental distribution to, say, the average in our domestic galaxy. Therefore, producing and using hydrogen on Earth is not as simple as the amount of the matter in the universe would suggest. On the contrary, it is quite complex and therefore requires the cooperation of experts from different fields.
A multi-disciplinary hydrogen team was established at the Geological Survey of Finland GTK this year. The hydrogen team’s expertise focuses on structural geology, geothermal energy, geochemistry, groundwater geology and environmental geology. Our aim is to promote the use of renewable energy sources and the use of hydrogen in industry to reduce greenhouse gas emissions.
Driven by strong national and international interest, we are in the midst of a green transition where the hydrogen economy finally has a chance to play a bigger role.
GTK’s services related to hydrogen are divided into two main themes: the geological studies of rock hydrogen storage and geological hydrogen studies.
Hydrogen storages enable hydrogen utilisation
Storing hydrogen in the bedrock will be necessary in the future, as growing industrial demand will require such large quantities of hydrogen that will no longer be economically viable just to store it in small tanks above ground.
Hydrogen storage in Finland’s crystalline bedrock needs to be in a lined cavern, as our fractured bedrock alone will not be sufficient to hold the highly mobile hydrogen with its small molecular structure. There is as yet little international experience of similar crystalline rock storages, but there is great interest in the subject.
In order to optimise the performance, construction, and operating costs, and safety of a rock storage facility, it is important to find stable blocks of rock for the storage facilities and to accurately identify the bedrock characteristics of the area. Even if it is possible to build in weaker rock, the pressure and temperature variations on the rock during its lifetime, which will stress the lining structure and the adjacent areas of rock, must be taken into account.
Issues to be investigated include the fracturing of the bedrock and how the rock is subjected to constantly changing pressure and thermal conditions, i.e. mechanical stress. Geochemistry and fracturing are key research topics when considering, for example, the durability of lining structures over their lifetime and possible leakage situations where hydrogen could pass into the rock structures.
Storage is generally divided into gaseous, liquid, and solid hydrogen types (Chalk & Miller, 2006; Midilli et al. 2005; Principi et al. 2009). In Finland, the rock storage of gaseous hydrogen is currently under consideration, as liquefaction requires very low temperatures and a lot of energy. Hydrogen storage is closely linked to hydrogen production, as there are likely to be periods of high production and periods of very low production in the availability of hydrogen from renewable energy. Storage is therefore needed to balance availability for industrial use. This is the case with energy produced by wind power, for example.
Hydrogen research projects are paying a lot of attention to different availability solutions. GTK is aiming to work specifically to promote the use of green hydrogen, i.e. hydrogen produced from renewable energy sources. Another production option that is both favourable to climate change and feasible is the use of nuclear power to produce so-called ‘pink hydrogen’.
Geological hydrogen from the Finnish bedrock?
Geological hydrogen means hydrogen that is emanated from the Earth’s crust. The processes involved in the formation of geological hydrogen are still under investigation, although several different processes have already been identified. Hydrogen is known to be formed mainly abiotically, but the influence of microbes, for example, on hydrogen production (i.e. biogenic hydrogen production) has not yet been thoroughly investigated.
Hydrogen is known to emanate from the ground in many geologically diverse areas. The first reports and measurements of such hydrogen formation are from a German salt mine in the 1910s (Ball & Czado, 2022). Welhan and Craig (1979) reported significant leakage of hydrogen in surveys of mid-ocean ridges. In 1997, the French found a hydrothermal fluid rich in hydrogen when studying black smokers in the mid-Atlantic (Wang et al. 2023).
Subsequently, geological hydrogen has also been found in continental settings such as fault zones, volcanic conditions, crystalline areas and areas where the Earth’s crust is thick. In fact, geological hydrogen is formed in both geologically active and passive environments.
The most frequently mentioned geological hydrogen formation process is serpentinisation. It hydrothermally transforms iron- and manganese-rich minerals such as olivine, pyroxenes and amphiboles, into serpentine minerals. In Europe and in regions outside the crystal shield, only ophiolites are often referred to as a source of geological hydrogen. It should be noted, however, that serpentinisation also occurs in other ultramafic rocks, and the search for geological hydrogen should not be limited to ophiolitic structures. Finland is an interesting country in this respect because we have a lot of ultramafic rocks ‒ for example, ancient komatitic lava structures.
Another common process of geological hydrogen formation is the radiolysis of water. This involves the decay of radioactive minerals in the bedrock, producing alpha, beta, and gamma radiation. Radiation ‘cleaves’ water molecules to produce hydrogen radicals (H), after which the two hydrogen radicals link together to form hydrogen (H2). Finland has many rocks containing radioactive minerals, so radiolysis is an interesting geological hydrogen formation process. Radiolysis can also be carried out industrially.
Other geological processes that produce hydrogen include rock fracturing caused by rock movement, for example in active continental plates, and the separation of gases from magma in volcanic areas. These hydrogen formation processes no longer occur in Finland, but both have occurred in our bedrock over previous geological periods.
Finland’s bedrock offers potential for the production of geological hydrogen. GTK has research results on geological hydrogen concentrations in different rock types, but not yet comprehensively enough to provide a clear overall picture. There are therefore many unanswered questions in the field of geological hydrogen such as whether we could artificially accelerate hydrogen production in the ultramafic rocks of Finland? The most fundamental question, however, is whether it is possible to produce geological hydrogen from Finland’s bedrock profitably enough for commercial use. At GTK, we are now trying to find answers to this question together with our partners and other stakeholders in the hydrogen economy.
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Teppo Arola, Chief Expert
Taina Karvonen, Team Manager
Geological Survey of Finland GTK
Energy and Construction Solutions
Thank you to Senior Specialist Markku Hagström for his comments and corrections
References
Ball, P., Czado, K. 2022. Natural Hydrogen: the new frontier. Geoscientist. Spring 2022.
Chalk, S.G. Miller, J.F. 2006. Key challenges and recent progress in batteries, fuel cells, and hydrogen storage for clean energy systems. J. Power Sources 2006, 159, 73–80.
Midilli, A. Ay, M. Dincer, I. Rosen, M.A. 2005. On hydrogen and hydrogen energy strategies. I: Current status and needs. Renew. Sustain. Energy Rev. 2005, 9, 255–271.
Principi, G. Agresti, F. Maddalena, A. Lo Russo, S. 2009. The problem of solid state hydrogen storage. Energy 2009, 34, 2087–2091.
Wang, L., Jin, Z. Chen, X. Su, Y. Huang, X. 2023. The Origin and Occurrence of Natural Hydrogen. Energies 2023, 16(5), 2400.
Welhan, J.T. Craig, H. 1979. Methane and hydrogen in East Pacific Rise hydrothermal fluids. Geophys. Res. Lett. 1979, 6, 829–831.
