Pre-Exploration Workflow for Natural Hydrogen Prospectivity Quantification

Natural hydrogen (H2) is emerging as a promising low-carbon resource for energy storage and for the decarbonization of hard-to-abate sectors. Recent accidental discoveries of subsurface H₂ accumulations in different geological settings such as Mali, Albania, and Australia demonstrate that H2 can be generated and preserved in economically significant concentrations. These examples highlight the need for systematic, geology-based, high-confidence exploration strategies to identify the most prospective regions and accelerate natural H2 exploration. Within the EU-funded NHEAT—Natural Hydrogen for Energy trAnsiTion—project, this study developed a novel semi-quantitative workflow for national-scale assessment of natural H2 prospectivity that consist into four-step procedure: 1) GIS-based integration of geological, structural, geophysical, and geochemical data in thematic maps; 2) identification of potential H2-generating mechanisms according to regional tectonic, geological, and magmatic contexts; 3) identification of the evidence and conditions associated with each mechanism; 4) weighted scoring of H2 prospectivity to rank and prioritize exploration targets. The workflow was tested on Italy, where H2 generation may be related to serpentinization of ultramafic rocks, hydrothermal alteration of Fe-rich igneous rocks, and thermogenic degradation of organic matter. The results identify the Tuscan geothermal region as the highest-priority target, where H₂ may be generated by hydrothermal alteration of granitoids. The Voltri Massif shows moderate potential linked to active serpentinization, whereas the Northern Apennines may preserve H₂ generated from fossil serpentinization events. The Po Basin may also sustain H₂ production related to organic matter degradation. This national-scale synthesis transforms complex geological constraints into decision-ready insights, reducing uncertainty in early exploration decisions and supporting the allocation of resource and field efforts. Because it is based on a reproducible and editable matrix approach, this semi-quantitative workflow is transferable to other case studies, contributing to the global energy transition by integrating natural hydrogen into broader decarbonization strategies alongside existing geothermal and gas infrastructures.