“The game of the moment is to find where it has been released, accumulated and preserved,” said Chris Ballentine, professor and chair of geochemistry at the University of Oxford. That game, according to a growing body of research, could change the trajectory of the global energy transition.
A new synthesis of geological and geochemical studies concludes that over the past billion years, Earth’s crust has generated enough hydrogen to supply current global energy demand for an astonishing 170,000 years. The challenge is not whether the hydrogen exists rather, it does but whether it can be located, accessed, and extracted economically at scale. To help do so, Ballentine and colleagues have developed a detailed “ingredient list” of geological conditions most favorable for the genesis and preservation of natural hydrogen reservoirs.
Hydrogen in this context is “white” or “geologic” hydrogen-molecular hydrogen generated naturally underground through processes such as serpentinization, where water reacts with iron-rich minerals like olivine, and radiolysis, in which natural radiation splits water molecules. Laboratory experiments have demonstrated that the crushing of rocks like granite, basalt, and peridotite under controlled conditions can produce measurable hydrogen through reactions involving surface defects in silicate minerals. Within a restricted range of temperatures, such reactions may also yield oxidants like hydrogen peroxide, which in turn affect subsurface microbial ecosystems and the fate of hydrogen in geological formations.
A viable natural hydrogen system would have three key components: a source rock capable of generating hydrogen, a reservoir rock in which to store it, and a seal rock capable of trapping it over geological timescales. Whereas early assumptions suggested that hydrogen’s small molecular size would enable it to escape through most rocks, it has been determined that it can actually be trapped in formations similar to those that preserve helium for tens of millions of years. This realization provides exploration opportunities in diverse geological settings, from the Midcontinent Rift in Kansas, which formed 1.1 billion years ago and is rich in reactive basalts, to ophiolite complexes where ancient oceanic crust has been thrust onto land and Archaean greenstone belts, some of Earth’s oldest rock formations.
Real examples are now coming to the fore. In Albania’s Bulqizë chromite mine, for instance, researchers have measured an outgassing rate of 84% hydrogen by volume from a deep faulted reservoir within a Jurassic ophiolite massif-one of the largest natural hydrogen flows recorded to date. In the Bourakebougou field in Mali, a near-pure hydrogen reservoir has fueled local electricity generation for decades. These findings validate the geological models and show that economically useful accumulations can occur.
Tectonic activity plays a very important role. Fault systems can serve as conduits that conduct water deep into reactive rock and initiate hydrogen-producing reactions at the optimal temperatures of 200-300°C. They can also provide means for the migration of hydrogen toward the surface, where it could accumulate in traps. But these conduits could also be avenues of loss when their seals are breached. Microbial consumption is another limiting factor; subsurface bacteria use hydrogen prodigiously, so reservoirs need to be in positions where biological activity would be small or nonexistent.
From an engineering standpoint, exploration for geologic hydrogen can draw on the same technologies developed for oil and gas-seismic imaging, well logging, and directional drilling-but with adaptations to counter hydrogen’s embrittling effects on steel. Production methods may involve tapping formations that are currently generating hydrogen or stimulating generation by injecting water into iron-rich rocks in a manner analogous to enhanced geothermal systems. Early cost estimates are encouraging: in Mali, hydrogen has been produced at roughly $0.50 per kilogram, a fraction of the cost of electrolytic “green” hydrogen.
The environmental case is solid. Compared to hydrogen produced from hydrocarbons, which has a heavy carbon footprint, naturally occurring hydrogen extracted without co-produced methane could have a carbon intensity as low as 0.4 kg CO₂e per kilogram of hydrogen. Even with minor methane contamination, it remains well within thresholds for clean hydrogen certification schemes. Still, scaling up will require rigorous resource mapping, pilot projects to validate reservoir performance, and infrastructure planning to connect production sites with demand centers.
If the geological “recipe” proves reliable, the implications are profound: a self-replenishing, low-carbon energy source, locked in the crust, capable of supplying humanity’s hydrogen needs for centuries. The hunt is now on to match the right rocks, structures, and seals and turn this hidden planetary reserve into a cornerstone of the clean energy future.
