Is the future hydrogen-powered? It might be, if a new study turns out to be correct: using longstanding geological models tweaked to include data about natural hydrogen, researchers have estimated an untapped reservoir of potentially trillions of metric tons of the element within the Earth’s subsurface.
For a while now, we’ve been told that the future of energy lies in hydrogen fuel. It’s clean, producing only water and heat in its use; it has a higher energy density than batteries; it can be produced, stored, and transported using existing resources; and, let’s face it, it’s not like the universe is going to run out of it any time soon.
The problem, however, is getting hold of it. Until now, the best option has been to create so-called “green” hydrogen – to use a renewable energy source like wind or solar power to split water molecules into their constituent oxygen and hydrogen atoms. In the race for net zero, it’s a powerhouse player, creating just one kilogram or less of CO2 per kilo of hydrogen produced, even at this early stage in the industry.
So, why aren’t we all already living off green hydrogen power? Unfortunately, there are some drawbacks: it’s expensive, and production times are limited. That’s why most hydrogen power, where it is used at all, is either “gray” or “blue” hydrogen – energy sources that are often advertised as being clean despite relying on fossil fuels to produce.
There is another option, though. Hydrogen can be produced via natural chemical reactions that occur when rocks come into contact with each other – but until recently, it was thought that this was pretty rare. That was, until geologists discovered huge reservoirs of the element in Bourakebougou, in Mali – triggering what has, over the past year or two, become something of a global gold rush in the hunt for hydrogen.
The search for natural wells of hydrogen has taken prospectors to France and Spain; to Nebraska, Arizona, and Kansas; to Australia; Morocco; Brazil, and elsewhere. According to the team behind the new paper, there’s good reason for that – as, according to their calculations, we’re sitting on up to 5.6 × 106 million metric tons of the stuff.
Now, there’s a lot of wiggle room in their values: “the estimated amount of in-place hydrogen in the Earth’s subsurface is highly uncertain, varying over seven orders of magnitude,” they admit in the paper, although “the predicted flux to the atmosphere is less variable (three orders of magnitude), with the most probable value roughly within a factor of 2 of current observations.”
On top of that, the pair readily acknowledge that most of what they suspect to exist is inaccessible: “Given what is known about the distribution of petroleum and nonpetroleum fluids […] it is likely that recovery of most subsurface hydrogen can be expected to be in accumulations that are too deep, too far offshore, or too small to be economically recovered,” they write.
But even with these caveats, it’s a vast amount of hydrogen that could be available. Just two percent of what they think is out there would be enough to fulfill the global demand for hydrogen needed to reach net-zero carbon emissions for the next 200 years – and even just that small amount would yield “roughly twice the amount of energy in all the proven natural gas reserves on Earth,” they write.
There are, admittedly, still a lot of unanswered questions. Where, exactly, is all this hydrogen, for example, and what would be the consequences of harnessing such a vast amount of a basically untested and non-renewable fuel type? And then there’s the crucial one: is all this hydrogen really there at all – or has it “leaked” out over time, as some experts suspect?
But for those whose hopes are pinned on a hydrogen-powered future, it’s a glimmer of hope – and with more data and interest in the topic, estimates will likely sharpen.
“Our model provides an initial framework for assessment of the global resource potential of natural hydrogen,” the paper concludes. “These findings indicate that further research in this field is warranted.”
The paper is published in the journal Science Advances.
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