[en] This publication proposes abstracts of contributions presented during this conference. The contributions addressed the following topics: the absorption spectrum and optical detection of gaseous hydrogen and of its isotopes; hydrogen and the definition of governance for energy transition; biological production of hydrogen (from the control of the microbial metabolism to the bio-reactor); risk management and impacts of hydrogen underground storage; materials for hydrogen purification and storage; mineralogical transformations and localised production of hydrogen and of abiotic organic compounds during the low temperature alteration of ocean lithosphere; low temperature serpentinization; native hydrogen in ophiolite contexts and cratonic basins (possible expectations for large scale productions); mechanisms and biotechnological stakes of biological production of hydrogen by micro-algae; monitoring of a hydrogen system in continental environment; dihydrogen produced by water radiolysis on model systems such as titanium oxide and calcite in solution. The abstracts of about twenty posters are also provided.