1 Introduction 2 Geoscience and exploration: Where to look for natural hydrogen? 2.1 Generation and accumulation of natural hydrogen 2.2 How much natural hydrogen is there? 2.3 Known and presumed occurrences of natural hydrogen 2.4 Exploration methods: Research and development needs 3 Industrial-scale production of geological hydrogen 3.1 Production cost 3.2 Key factors for economic viability 3.3 Challenges for industrial-scale production 3.4 Environmental impact and risks 3.5 The path to industrial-scale production: Timeline and milestones Excursus: Stimulated geological hydrogen production 4 Promising use-cases 4.1 Co-production with helium 4.2 Decentralised energy generation for mining projects 4.3 Co-production with geothermal energy 4.4 The potential role of natural hydrogen in the transition to climate neutrality 5 Regulatory framework and societal decision-making 5.1 Mining law 5.2 Regulatory assessment of climate impact and emissions reduction 5.3 State funding 5.4 Public debate and community consultation 6 Conclusion and policy options 7 Appendix

For the transition toward a climate-neutral energy system and industry, large quantities of low-carbon molecular hydrogen will be required. With the development of "green" and "blue" hydrogen taking more time than initially hoped, another form of hydrogen has gained increasing attention: geological hydrogen...