Geological Hydrogen - an overlooked energy source?

Abstract

Geological hydrogen (molecular hydrogen formed in the Earth’s subsurface), may become a new energy source. The discussion paper by the initiative "Energy Systems of the Future (ESYS)" provides researchers, energy experts and policy-makers with a scientifically grounded assessment of this potential ressource that has so far received little systematic attention in the German energy community. Two forms of geological hydrogen are explored in the paper: Natural hydrogen forms through naturally occurring geological processes such as reactions between certain iron-rich rocks and water. Stimulated geological hydrogen is produced by deliberately inducing reactions in the subsurface through the injection of water or catalysts. Both concepts are currently receiving strong research interest in the geosciences, but stimulated hydrogen is at a much earlier stage. What does the discussion paper address? • How does geological hydrogen form, and under what conditions does it accumulate in the subsurface? • Do commercially exploitable deposits exist, and how can they be identified? • Which use cases are most promising in the short and medium term? • What regulatory framework is needed for exploration and extraction? • What research is required to make well-founded assessments of the potential? Promising – but many open questions Whether geological hydrogen exists in quantities sufficient for commercial extraction remains unclear. So far, there is only one documented case of sustained production – in Mali. The generation processes are understood in general, but the knowledge about migration, accumulation and consumption by microbes and chemical reactions in the subsurface is still very limited. Decentralised applications such as co-production with helium or geothermal energy are considered the most promising entry points. Targeted public funding for research should strengthen the scientific basis for policy decisions, and mining codes should be adjusted to facilitate exploration and extraction. Geological hydrogen could complement the energy transition, but few experts see it as a real game-changer.