Naturally occurring 'white hydrogen' could revolutionise clean energy, with vast reservoirs beneath the Earth's surface holding up to 10 trillion tonnes of the gas, according to a 2024 US Geological Survey (USGS) study. If just 2% of this resource is recoverable, it could meet global hydrogen demand for 200 years and contain twice the energy of all proven natural gas reserves.
Unlike 'green' or 'blue' hydrogen, white hydrogen is a low-carbon fuel produced naturally when underground water reacts with iron-rich rocks. It has attracted at least 60 companies and $1bn (£740m) in investment, says Eric Gaucher, a French geochemist who co-leads a white hydrogen expert group for the International Energy Agency (IEA). Exploratory drilling is already under way in Australia and the US.
Hydrogen stores three times more energy than oil and emits only water when burned, making it attractive for hard-to-decarbonise sectors like aviation, shipping and steel production. However, most hydrogen today is made from polluting methane or coal, with green and blue hydrogen accounting for just 1% of global production due to high costs and rollout delays.
The USGS study, led by geologists Geoffrey Ellis and Sarah Gelman, estimates between one billion and 10 trillion tonnes of hydrogen in the subsurface, though most may be too deep, offshore or small to recover economically. Still, the potential has sparked a modern-day 'gold rush', with prospectors hoping to replicate the 1859 Titusville oil discovery that launched the petroleum age.
White hydrogen forms when water encounters iron-rich rocks in a process called serpentinisation, but it often escapes through porous rocks or is consumed underground. Trapped under low-permeability rocks like salt or shale, it can accumulate in reservoirs that companies now seek to exploit commercially.
