Clean hydrogen source could power Earth for 170,000 years

Hydrogen is essential for fertilizer production and is increasingly promoted as a clean fuel for decarbonizing industry and shipping.

Yet almost all of today’s hydrogen – about 90 million metric tons a year – comes from reforming oil and gas, releasing roughly 2.4 percent of global CO2 emissions in the process. Blue and green hydrogen remain too expensive to scale rapidly, despite advances in carbon capture and clean electricity production.

A new review highlights a third option: tapping naturally occurring hydrogen produced by geological processes over millions of years.

Hunting for clean hydrogen

Researchers from the University of Oxford, Durham University, and the University of Toronto calculate that Earth’s continental crust has produced enough hydrogen over the past billion years to meet humanity’s projected needs for at least 170,000 years.

Microbes have consumed much of it, and some has leaked away, but the rest could still form recoverable accumulations. To find it, scientists say geologists must pursue hydrogen like helium or gas – though it diffuses and reacts more easily.

“We have successfully developed an exploration strategy for helium, and a similar ‘first principles’ approach can be taken for hydrogen,” said co-author Jon Gluyas, a professor at Durham University.

The review outlines the critical elements of such a strategy and identifies where current knowledge is solid or still developing.

How does hydrogen form?

Hydrogen forms through several crustal reactions. One of the best known is serpentinization, where water reacts with iron-rich minerals underground, oxidizing iron and releasing molecular hydrogen.

Other pathways include radiolysis – where decaying uranium splits water molecules – and organic shale maturation, which can generate hydrogen alongside hydrocarbons.

Production rates vary widely by region, depending on temperature, pressure, rock type, and the availability of liquid water.

Holding hydrogen underground

After formation, hydrogen must migrate through fractures and porous rock layers until it meets a geological trap that prevents further escape.

Traditional seals like rock salt or claystone can work, but because hydrogen molecules are so small, maintaining containment over geological time may require exceptionally tight caps. Even a perfect seal is not enough if microbes lurk in the reservoir.

“We know, for example, that underground microbes readily feast on hydrogen,” said co-author 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.”

Sherwood noted that high temperatures, salty brines, or low nutrient levels can slow microbial consumption.

Targeting deposits in Earth’s crust

The review challenges speculation that mantle-derived hydrogen, sometimes touted as limitless, could be a major target. Analyses of isotopic fingerprints and gas ratios show that most mature accumulations originate from crustal rocks, not from deep-Earth plumes.

The good news is that suitable crustal settings are common: ancient cratonic shields, younger rift basins, iron-rich volcanic belts, and faulted sedimentary basins all provide the right mix of source, pathways, and potential traps.

Some systems are geologically young, forming hydrogen within the past few million years, while others date back hundreds of millions.

Scientists have found encouragement in real-world hints. A village water well in Bourakébougou, Mali, accidentally tapped a stream of 98 percent hydrogen in 2012. Similar incidents have been reported in Kansas, South Australia, and the Pyrenees.

Drilling for water, oil, or minerals has accidentally revealed many deposits – hinting that targeted exploration could find much more.

Searching for accumulated hydrogen

Turning theory into drill bits will require integrating geophysics, geochemistry, microbiology, and reservoir engineering.

Study lead author Chris Ballentine from the University of Oxford offered a culinary analogy. “Combining the ingredients to find accumulated hydrogen in any of these settings can be likened to cooking a soufflé – get any one of the ingredients, amounts, timing, or temperature wrong and you will be disappointed.”

“One successful exploration recipe that is repeatable will unlock a commercially competitive, low-carbon hydrogen source that would significantly contribute to the energy transition – we have the right experience to combine these ingredients and find that recipe.”

Identifying significant hydrogen fields

To pursue that recipe, the research team has launched Snowfox Discovery Ltd., aiming to identify “societally significant” hydrogen fields.

Early priorities include mapping iron-rich rock belts intersected by deep groundwater, quantifying how fast different microbial communities devour hydrogen, and testing seal integrity for a highly diffusive gas.

Seismic imaging and magnetotelluric surveys could reveal subsurface alteration zones where hydrogen-generating reactions are ongoing. Meanwhile, isotopic tracers will help distinguish fresh hydrogen from ancient residues or from contamination by methane.

A step toward greener fuel

If abundant, natural hydrogen could bridge blue and green hydrogen as a low-carbon feedstock during infrastructure scale-up.

However, extraction must avoid repeating the environmental mistakes of fossil-fuel development. Regulators will need to set standards for monitoring leaks, safeguarding groundwater, and managing co-produced gases.

Even partial success would diversify the clean energy portfolio and relieve pressure on renewables to shoulder all hydrogen demand.

With the window to limit global warming rapidly closing, exploring Earth’s hidden hydrogen could buy valuable time – and illuminate a new frontier where geology and the energy transition meet.

The study is published in the journal Nature Reviews Earth & Environment.

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