Natural hydrogen: How energy resides
How rocks and water make hydrogen on their own
What this tab covers The physical form in which the energy is held or carried, where it comes from, the chain of transformations that put it there, and how concentrated it is.Natural (geologic) hydrogen stores energy in the chemical bond of the hydrogen molecule, formed underground when water reacts with iron-rich rock or is split by natural radioactivity. It can collect in traps like natural gas, or seep continuously to the surface.
Form Chemical energy in molecular hydrogen gas (H2) Origin Natural chemical (water-rock reactions) and nuclear (radiolysis by natural radioactivity)How it got there
Iron-rich (ultramafic) rocks and radioactive elements in the crust Water reacts with iron minerals (serpentinisation) or is split by radiation (radiolysis) Hydrogen gas released into pore space Migration along faults; some trapped beneath seals, much escapes or is consumed by microbes Accumulation or seepage at the surfaceHow concentrated it is
| Measure | Value | Note |
|---|---|---|
| Energy content of hydrogen (lower heating value) | about 121 MJ per kg2 | Converted from NREL's 52,217 Btu/lb (the commonly quoted value is 120 MJ/kg); very high per kilogram but very low per litre as a gas |
| Purity at Bourakebougou, Mali | 97.4% H23 | Initial well; all wells in the 2022 campaign at least 95% H2 |
| Seepage at Bulqize chromite mine, Albania | at least 200 tonnes H2 per year4 | About 84% H2 by volume; the highest natural flux recorded |
Hydrogen forms underground mainly by serpentinisation, in which water oxidises iron in minerals such as olivine and releases hydrogen, and by radiolysis, in which radiation from uranium, thorium and potassium splits water molecules. Unlike oil and gas, which formed over millions of years and are now a fixed stock, some hydrogen systems may be recharging today.
Hydrogen is a tiny, mobile molecule that leaks through rock and is eaten by microbes, so only some of it accumulates. Where it does, it can be produced like natural gas through wells, but it is often mixed with nitrogen, methane or helium and needs purification. Per kilogram it carries more energy than any fossil fuel, but as a gas it is bulky, so it is best used close to where it is produced.
Sources
- Hydrogen fuel properties fact sheet National Renewable Energy Laboratory, 2008
- The natural hydrogen field without pressure depletion GEO ExPro, 2023
- Discovery of a large hydrogen reservoir in an underground mine in Albania ISTerre, Universite Grenoble Alpes / CNRS, 2024