In the Pyrenees, a single tectonic system may generate enough hydrogen annually to power a city of 500,000—a figure extrapolated from peer-reviewed models simulating mantle rock hydration. This process, termed serpentinization, occurs when water infiltrates iron-rich mantle rocks that have been pushed upwards to depths of 7-15 kilometers, producing hydrogen gas. However, less than 0.1% of global hydrogen investment targets natural deposits, despite projections by Rystad Energy suggesting recoverable reserves could offset 10% of current synthetic hydrogen production costs by 2035.
