Oxford Uni: Earth is leaking clean energy – scientists publish guide to tap it for $0.50/kg
A team of scientists from the University of Oxford, Durham University and the University of Toronto has published the most comprehensive guide yet to finding natural hydrogen underground – a resource that could offer a low-cost, low-carbon alternative to conventional hydrogen production.
The review, published in Nature Reviews Earth & Environment, maps out the conditions needed for hydrogen to be generated, migrated, and trapped in the continental crust.
According to the authors, the Earth has produced enough hydrogen over the past billion years to meet global energy demand for the next 170,000 years – though much of it has been lost or consumed.
The findings offer a science-backed framework for exploration, providing industry with a starting point to locate and evaluate geological hydrogen systems.
Several of the researchers have now launched Snowfox Discovery Ltd, a new venture focused on prospecting for commercially viable accumulations.
“One successful exploration recipe that is repeatable will unlock a commercially competitive, low-carbon hydrogen source”, said lead author Professor Chris Ballentine of the University of Oxford. “We have the right experience to combine these ingredients and find that recipe.”
What is natural hydrogen?
Unlike hydrogen produced using electrolysis or fossil fuels, natural hydrogen is created underground by two key geological processes:
- Water-rock reactions – where water reacts with iron-rich rocks like peridotite, producing hydrogen as iron oxidises,
- Radiolysis – where radiation from naturally occurring uranium, thorium and potassium splits water molecules into hydrogen and other by-products.
These reactions occur deep within the Earth’s crust and have been ongoing for billions of years.
Over time, hydrogen can migrate through fractures in the rock and accumulate in geological traps – but only under the right conditions.
Ballentine and co-authors say this trapped hydrogen, if found in high enough concentrations, could be extracted with minimal emissions and no need for electrolysers or carbon capture.
Not renewable – but very low carbon
The authors are clear that natural hydrogen should not be considered renewable.
The reactions that produce it operate on geological timescales, and depleted reservoirs would not replenish quickly.
That said, the carbon footprint of extracting already-formed hydrogen from the crust is expected to be extremely low.
According to previous lifecycle estimates cited in the review, emissions could be as low as 0.4 kg CO₂ per kg H₂ – lower than blue hydrogen and potentially even green hydrogen, depending on how it’s produced.
While no peer-reviewed cost estimates currently exist, the authors note that projected production costs range between $0.5 and $1.0 per kg – significantly below current green hydrogen prices and competitive with grey hydrogen from fossil gas.
What is needed for natural hydrogen to form
For hydrogen to accumulate in usable quantities, four geological conditions must be in place:
- A source rock – rich in iron (for water-rock reactions) or radioactive elements (for radiolysis),
- Water availability – enough to drive the reaction, but not so much that it flushes the hydrogen away,
- A trap – a sealed geological structure to collect and hold the gas,
- Preservation – an environment that prevents loss through diffusion, dissolution, or microbial consumption.
If any of these conditions are missing or disrupted, the hydrogen either won’t form, won’t accumulate, or won’t stick around long enough to be useful.
“We know, for example, that underground microbes readily feast on hydrogen,” said co-author Professor Barbara Sherwood Lollar of the University of Toronto.
“Avoiding environments that bring them into contact with the hydrogen is important in preserving hydrogen in economic accumulations.”
Mali’s hydrogen field is real – but rare
Much of the recent interest in natural hydrogen has been driven by the Bourakebougou field in Mali, where wells have produced hydrogen at more than 97% purity (for reference a hydrogen fuel cell requires 99.999% purity).
While flow data remains limited, it’s one of the few proven examples of a hydrogen-rich gas field, and it shows the concept is more than just theory.
But the authors caution against over-hyping mantle sources or assuming widespread riches.
Mantle-derived hydrogen is largely ruled out – it arrives as water, not H₂ – and most crustal hydrogen is mixed with other gases like nitrogen and helium.
Finding large, pure accumulations is likely to be the exception, not the norm.
That said, helium may help point the way. Because it’s co-produced during radiolysis and doesn’t react or degrade, helium can act as a useful tracer – offering clues about hydrogen release, migration, and trapping potential.
Exploration strategy now possible
The paper identifies five key types of geological terrane that could host natural hydrogen systems:
- Archaean cratons and greenstone belts – old continental cores with radiogenic granites and iron-rich volcanic rocks,
- Ophiolites – slices of ancient ocean crust thrust onto land, rich in ultramafic rock,
- Large Igneous Provinces – vast continental flood basalt regions,
- Alkaline granite complexes – radiogenic formations producing hydrogen via radiolysis,
- Sedimentary basins overlying crystalline basement – where gas can migrate upward into porous rocks and be trapped.
These play types are globally distributed – including in parts of the UK, Canada, the US, Australia, and Africa – and several are already well-characterised from decades of hydrocarbon exploration.
Jon Gluyas, professor at Durham and co-author on the paper, previously helped pioneer helium prospecting. He says the same first-principles approach can now be applied to hydrogen.
Industry interest growing
The potential scale of natural hydrogen – and the relatively low cost and emissions associated with it – has prompted growing industry attention.
The paper notes that while hydrogen-rich fracture fluids have been observed for decades, exploration was limited by poor data and a lack of framework.
That’s changing. Companies like Snowfox Discovery, formed by several of the paper’s authors, are now actively pursuing targets.
Others, such as 45-8 Energy and HyTerra, are already drilling exploratory wells in Europe and North America.
The review provides the roadmap, and what comes next is fieldwork.
Don’t call it renewable – but don’t ignore it either
Natural hydrogen isn’t going to replace electrolysers. But it could become a valuable piece of the hydrogen supply puzzle – perhaps as a blended solution with other sources of hydrogen, but especially for industrial or off-grid use where simplicity, cost and carbon intensity matter.
The crust isn’t a limitless sponge of usable hydrogen, but it may contain enough to help meet demand during the transition – if the right geological conditions can be found.
Professor Ballentine puts it simply: “We’ve got the ingredients, the recipe, and the oven.” Now to see if it rises.
Professor Ballentine puts it simply: “One successful exploration recipe that is repeatable will unlock a commercially competitive, low-carbon hydrogen source. We have the right experience to find that recipe.”
