Geological generation, global potential, and techno-economic assessment of natural hydrogen systems

Natural hydrogen is an emerging geological resource with significant potential to contribute to the global energy supply. This study integrates findings from over 150 studies to examine the generation mechanisms, global occurrences, experimental insights, economic feasibility, and environmental implications of natural hydrogen systems. Subsurface hydrogen is generated through processes such as serpentinization of ultramafic rocks, radiolysis of water by radioactive decay, thermochemical breakdown of organic matter, and mechanochemical water–rock reactions. Global case studies from six continents, spanning ancient cratonic shields, sedimentary basins, ophiolitic complexes, and volcanic regions, demonstrate that natural hydrogen occurrences are widespread and often associated with features like ultramafic exposures, circular depressions, and fault zones. Under favorable geological conditions, natural hydrogen could be produced at costs significantly below current green hydrogen prices, suggesting strong potential as a competitive clean energy source. Experimental studies reveal that hydrogen generation is optimized at temperature range of ∼ 200–315 °C and can be dramatically enhanced by techniques like CO 2 injection, while isotopic analyses ( δ 2 H, δ 13 C), when combined with geological context and gas composition, can provide insights into hydrogen system characteristics despite rapid temperature-dependent re-equilibration. While challenges in resource characterization, extraction technology, and regulatory frameworks remain, natural hydrogen could become a significant component of a sustainable energy future, a geological analog to discovering a new, carbon-free gas reserve. This paper provides a comprehensive overview of current knowledge and identifies key directions for future research and development in this nascent field.