Researchers have detailed the geological ingredients required to find new sources of hydrogen underground.
Beyond its existing use in fertiliser and chemical production, hydrogen is also seen as a key energy source in many net zero scenarios.
But today, most hydrogen is produced from hydrocarbons, with waste gases contributing to 2.4% of global CO2 emissions. And as demand for hydrogen is expected to increase rapidly from 90 million tonnes in 2022 to 540 million tonnes by 2050, the hunt is on for sources of the hydrogen that do not mean more CO2 emissions.
Hydrogen can be generated from renewable energy sources like wind or solar but these are not yet commercially competitive. Another option is to access the hydrogen within the Earth itself, according to new research from the University of Oxford, in collaboration with Durham University and the University of Toronto.
This hydrogen is generated in the continental crust when water reacts with iron-rich volcanic rocks, forming iron oxide and hydrogen. It can also be generated when radioactive elements in rocks split water molecules into oxygen and hydrogen. These reactions operate on very different timescales, ranging from thousands to millions of years for water–rock reactions, to tens to hundreds of millions of years for water-limited water–rock and radiolysis reactions.
Over geological timescales both these processes can create significant amounts of hydrogen, but understanding where that hydrogen might be found in the crust has been part of the challenge.
“In the last billion years, enough hydrogen gas has been produced by the Earth’s continental crust to supply mankind’s energy needs for at least 170,000 years. Whilst a proportion of this has been lost, consumed, or is inaccessible today, the remaining hydrogen could offer a natural (and emission-free) source of this natural resource,” the university said.
The paper published in Nature Reviews Earth & Environment noted that natural hydrogen would have a low-carbon footprint, but it should not be considered a renewable resource.
Study co-author Professor Jon Gluyas from Durham University noted: 'We have successfully developed an exploration strategy for helium and a similar ‘first principles’ approach can be taken for hydrogen.'
The research outlines the key ingredients needed to inform an exploration strategy for hydrogen systems. The researchers said this includes how much hydrogen is produced and the rock types and conditions these occur in, how the hydrogen migrates underground, the conditions that allow a gas field to form, and also the conditions that destroy the hydrogen – like the presence of underground microbes that feast on the gas. The researchers said the ingredients for a complete hydrogen system can be found in a range of common geological settings within the crust.
The author have also formed Snowfox Discovery, an exploration company with a mission to find significant natural hydrogen accumulations. The spinout from Durham and Oxford Universities has early-stage funding from Oxford Science Enterprises.
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- 27 hydrogen projects shortlisted for government funding
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