Earth’s hidden hydrogen reserves can power society for thousands of years

Scientists have found evidence that naturally occurring hydrogen is trapped deep in the earth’s crust and can provide huge low-carbon energy resources, equivalent to 170,000 years of current global oil consumption. If we can figure out how to find and extract it economically, this revelation is detailed in the comprehensive comments published in Nature Review and Earth Environment Review.

The study, written by researchers at the University of Oxford, the University of Toronto and Durham, maps how hydrogen accumulates through the Earth’s continental crust that has been running for billions of years. Unlike hydrogen produced, which currently produces about 900 million tons of carbon dioxide (2.4% of global emissions) each year, natural hydrogen can be extracted with a minimal carbon footprint.

But can we actually take advantage of these reserves, or is it just a geological curiosity rather than a practical energy solution?

How the Earth produces hydrogen

This review identifies two main mechanisms that drive natural hydrogen formation in the continental crust. It happens first when water interacts with iron-rich rocks, especially ultramafites such as peridotite. In these reactions, iron iron (Fe2+) is oxidized to iron iron (Fe3+), and hydrogen molecules are released in the process.

The second mechanism, known as radiolysis, occurs when radioactive elements naturally found in uranium, th and potassium (such as crustal rocks), emit radiation that dismantles water molecules into their components, including hydrogen.

“These two generations of reactions have worked on very different time scales, with water rocks in highly fractured rocks reacting to a range of thousands to millions of years, to water-limited water-rock and radiodecomposition reactions tens of thousands to millions of years,” the researchers explained in the comments.

These processes create truly amazing hydrogen during the geological period. The researchers calculated that the hydrogen energy produced in archaea alone was equal to about 170,000 years of today’s global oil consumption – an attractive figure for energy strategists.

Four geological environments with hydrogen potential

This study identified four major geological environments where natural hydrogen could accumulate commercially:

• Continental margin ophiolite complex – Ocean crust slices of continental ocean during tectonic collisions
• Alkaline granite topography – Radioactive granite that can produce hydrogen through moisture dialysis
• Igorized rock province – a large amount of mafic rock that can produce hydrogen through water rock reaction
• Archaeobacterial greenstone belt and Tonalite-Trondhjemite granite (TTG) granite bath stone – ancient rock formations with both water rock and radioactive hydrogen sources

It is worth noting that these geological strata are widely distributed across all continents, suggesting that natural hydrogen may be a globally accessible resource rather than concentrated in specific regions.

The mysterious hydrogen in Mali

Although natural hydrogen has been recorded throughout the 20th century, interest in its commercial potential surged in reports on the Bourakebougou gas field in Mali in 2018. Although production data are still limited, the hydrogen produced at this site has a purity of more than 97%.

Mali found that it embodies the way hydrogen containing natural gas can accumulate in geological traps. In order to form extractable accumulations, four conditions must be met: hydrogen source, migration pathway, sealed traps, and preservation from microbial or chemical degradation.

The researchers point out that preserving hydrogen during geological periods poses unique challenges, because hydrogen is both fluid and vulnerable to the consumption of underground microorganisms. This explains why, despite the large amounts generated in geological history, only a portion of them may be recyclable today.

Non-renewable, but sustainable

This study makes a crucial difference that can affect the way natural hydrogen is regulated and sold: it has a low-carbon footprint comparable to the “green hydrogen” produced by renewable energy electrolysis, which is not a renewable resource for human time scales.

“The mainland system does not provide young regenerated hydrogen systems for the centenary time scale, nor should it be considered a renewable resource,” the research team concluded.

This places natural hydrogen in a unique category – a potential low-carbon energy source, like fossil fuels, has a limited amount, but has a large reserve base and a greater environmental impact during the extraction process.

The authors estimate that natural hydrogen production is about $0.50-1.00 per kg, which is about lower than “green hydrogen” ($2.50-6.50/kg) and “blue hydrogen” from natural gas with carbon capture ($1.50-4.00/kg).

Challenges and knowledge gaps

Despite the promise, there is still a large knowledge gap. The researchers identified several priorities for future research, including a better understanding of the fact that hydrogen on Earth is still trapped in the Earth’s crust, improved methods for calculating the rate of hydrogen generation from water rock reactions, and developing technologies to locate and evaluate economically viable hydrogen accumulation.

The authors of the study warn that while large amounts of hydrogen are feasible, high-purity hydrogen deposits, like those in Mali, may be anomalies. More commonly, natural hydrogen may be found mixed with other gases such as helium and nitrogen – still valuable, but requires different extraction and processing methods.

“For the exploration to be successful, it is crucial to predict the amount and time of hydrogen produced.” This will require the integration of geological, geophysical and geochemical data to understand where it might be trapped and how many quantities are.

As the world seeks avenues for decarbonization, such as fertilizer production, steel manufacturing and long-distance transportation, the discovery and development of natural hydrogen resources can provide transitional energy for transitional energy than current hydrogen production methods. While this is not a silver bullet for energy transition, this unexplored resource may soon be added to the solution’s portfolio, helping to reduce global carbon emissions.