Richard Musgrove
Dr Richard Musgrove is a zoologist and science journalist. He writes for Cosmos and Double Helix.
British and Canadian geochemists have detailed the ingredients needed to pinpoint clean sources of natural hydrogen underground.
Reliable supplies of hydrogen are vital to the global community. Fertilisers produced from ammonia contain hydrogen and therefore , contribute to the food supply of much of the world’s population. It’s also used in steel production and in heat and power generation.
Global production is around 75 million tonnes per annum (mtpa) as pure hydrogen with an extra 45 mtpa as part of a mix of gases. The International Renewable Energy Agency says this is around 3% of global energy demand
That will increase to 540 mtpa by 2050 says geochemist Professor Chris Ballentine from the department of earth sciences at of the University of Oxford.
Around 96% of hydrogen is produced from hydrocarbons (gas, coal and oil) with about 4% from electrolysis. Only about 1% of the total is made using renewable energy, and waste gases contribute 2.4% of global CO2 emissions.
Hydrogen could also be one of the keys to a carbon-neutral future, essential to preventing the worst predictions of climate change.
Geochemists from the Universities of Oxford and Durham in the UK and the University of Toronto, in Canada, have now produced a recipe for securing deposits of hydrogen to answer increasing demand without adding much to greenhouse gas emissions.
Hydrogen sources are described in a rainbow of colours. Green denotes renewables; pink and purple, nuclear; blue or turquoise, natural gas; orange, carbon capture and storage; black, coal.
It’s not a renewable resource, says Ballentine, lead author of the paper published Nature Reviews Earth & Environment which describes where the hydrogen is produced.
The two dominant processes creating natural hydrogen gas in the continental crust are water–rock reactions with iron-bearing minerals, and radiolysis of water from the natural decay of uranium, thorium and potassium. They estimate the Precambrian crust alone has generated hydrogen volumes over the last billion years equivalent to approximately 170,000 years of present-day societal oil use.
While renewal does happen within the crust, it’s not at human timescales, Ballentine adds.
Figuring out how much hydrogen is in the crust and where to dig, has hampered efforts at commercial exploitation. Until now.
Co-author Professor Jon Gluyas of Durham University says, “We have successfully developed an exploration strategy for helium and a similar ‘first principles’ approach can be taken for hydrogen.”
This recipe covers what needs to be explored for different systems, says Ballentine. How much hydrogen, in which rocks and under what conditions.
Look for rust in the crust. Rusting is ‘oxidation’, which means iron in silica-containing rocks react with water, creating magnetite or other iron oxides and releasing hydrogen. Uranium-rich rocks do the same thing as their radioactivity breaks down water.
High temperatures are also important, says geoscientist, Professor Simon Holford, South Australian State Chair of Petroleum Geoscience at the University of Adelaide. As are the pore spaces, he says. Cracks in the rocks allow water to penetrate, enabling those reactions.
“Parts of Australia are geologically well endowed with iron-rich rocks, Holford told Cosmos. “South Australia is a hydrogen hotspot. It’s a combination of right types of geology, the evidence for there being subsurface concentrations in certain places, and then the proactive approach from the South Australian (SA) Government.
“About 2021, the SA government changed its petroleum and geothermal energy Act to include hydrogen is a regulated substance, which allowed folks to explore for hydrogen.” Holford was not involved in the study.
Then it’s a matter of working out how much is produced, how it migrates underground from these rocks, the conditions that allow a hydrogen field to form, and the conditions that destroy the hydrogen.
Co-author of the Nature Reviews paper, Professor Barbara Sherwood Lollar of the University of Toronto says, “We know for example that underground microbes readily feast on hydrogen. Avoiding environments that bring them into contact with the hydrogen is important in preserving hydrogen in economic accumulations.”
The right conditions are found around the globe, says Ballentine.
Ballentine concludes, “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”
Storing hydrogen underground
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