Séminaire Laurent TRUCHELet's go targeting natural hydrogen, the carbon-free fuel of the 21th century

Let's go targeting natural hydrogen, the carbon-free fuel of the 21th century
par Laurent Truche, Professeur à l'Université Grenoble Alpes, ISTerre

The quest for sustainable energy supply at low environmental and economical cost is a major issue in the current context of the energy transition toward a low carbon society. Hydrogen (H2) is the carbon-free fuel par excellence because its combustion, or its use in fuel cells emits only water. However, up to now hydrogen was only regarded as an energy vector and not as a credible large-scale alternative to hydrocarbons as most of the production methods (e.g. methane steam reforming) currently in use only postpone CO2 or methane emissions. Its massive production through water hydrolysis using renewable alternative energy resources (e.g. wind, solar) is also very challenging as it requires both pure water resources (salty waters from deep aquifers are unsuitable in the electrolysers) and local storage infrastructures.
The discoveries of hundreds of natural hydrogen seepages generally connected with circulations of hydrothermal fluids through ultramafic rocks, both under the seafloors and on the continents, over the last twenty years, remove these obstacles but raise several questions of primary importance regarding the energy potential that these sources can represent. In addition, recent observations of intra-cratonic seepages and accumulation with no obvious genetic link with ultramafic formations challenge our understanding of hydrogen production and fate in the crust. Hydrogen natural system is a recent science, and little is known about hydrogen generation, migration, consumption and potential accumulation. Hydrogen mobility in the crust is so poorly constrained that even fundamental properties of the molecule such as solubility in deep geological fluids at elevated T and P or adsorption at the mineral-water-gas interfaces are unknown. To date, there is no exploration strategy or resource assessment, as practical guidelines for hydrogen targeting are missing.
In this presentation, I will provide a brief history of hydrogen exploration on Earth and present the current status of our knowledge of hydrogen behavior in the crust from its sources to its sinks. I will also demonstrate that geological evidences are now sufficiently robust to justify extensive exploration campaigns provided that new targeting methods are developed.