Laurent Truche, a geochemist at Grenoble Alpes University in France, has been searching for naturally occurring hydrogen for nearly a decade. This year, in a chromite mine in Albania, he and his colleagues struck gold, or rather another element on the periodic table. Nearly a kilometer below the surface, they discovered a hydrogen seep so strong it turned a murky drainage pond into something resembling a Jacuzzi. Truche had never seen hydrogen bubbles that big. “It was really intense,” he says.
Natural hydrogen is hydrogen gas in its molecular form (H2) that is generated through natural processes. Formed deep within Earth, it may get trapped on its way to the surface, creating accumulations of gas. Confusingly also called “gold,” “white” or “geological” hydrogen, natural hydrogen could offer us an energy source cleaner than other types of hydrogen because there is no carbon involved in the process that generates it (although drilling and distribution would still involve some carbon dioxide emissions, of course). A recent study estimated the greenhouse gas intensity of natural hydrogen to be 0.4 kilogram of CO2 equivalent per kilogram (kg CO2eq/kg), far less than the 22-26 kg kg CO2e/kg of black hydrogen (produced from coal) or the 10-14 kg CO2e/kg of blue hydrogen (produced from natural gas).
The Albania discovery was the latest in a string of similar findings that have recently spiked interest in naturally occurring hydrogen. When last year geologists discovered natural hydrogen in old coal deposits below Folschviller, a dilapidated mining town in northern France, local media went abuzz with hope. Some called it “the new petrol.” Others called it “a game changer.” And the words “El Dorado” have been uttered, too. But Truche casts a cautionary note, calling the fervor over the discoveries a “hydrogen fever.” “In one sense, it is wonderful because it attracts attention, funding and lots of motivation to move forward, he adds. “But in another sense, it’s also kind of a Wild West—with lots of overstatements.”
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Three decades ago scientists thought that naturally occurring hydrogen deposits simply didn’t exist. What was known, however, was that hydrogen could be produced deep within our planet through a process called serpentinization, which occurs when water reaches iron-rich rocks from Earth’s mantle. The reaction transforms the rocks and liberates hydrogen from water molecules. Other processes, too, were known to produce hydrogen, such as radiolysis—the splitting of water molecules by radiation from uranium and other radioactive elements within Earth’s crust. Yet it was taken for granted that hydrogen, the lightest molecule, would seep through rock layers and escape into the atmosphere instead of pooling in reservoirs like petroleum does. Scientists recognized as well that hydrogen was easily consumed by microbes, which, the theory went, would make reservoirs even less likely. “I’ve spent 30 years doing oil and gas research and very much had this mentality that, yeah, hydrogen is out there, but you could never get accumulations,” says Geoffrey Ellis, a geochemist at the U.S. Geological Survey.
Then, in 1987, workers attempting to drill a water well in the Malian village of Bourakébougou noticed an unusual breeze emanating from the hole. When one of the workers lit a cigarette, the gas exploded into a bright flame—the breeze turned out to be almost pure hydrogen. For safety reasons, the well was soon cemented shut. In 2012 it came back to life when a Canadian company, now called Hydroma, began combusting the hydrogen to supply local residents with electricity, the first such production site in the world. A few years later, Hydroma took up drilling around Bourakébougou and found more deposits containing natural hydrogen.
While scientists consider the findings in Mali to be evidence that natural hydrogen accumulations are indeed possible, there were other signs of their presence. In Turkey a site called the Chimaera seep, located under a temple dedicated to Hephaestus, the Greek god of fire, has been emanating hydrogen since antiquity. In Australia wells drilled in search for oil on Kangaroo Island in the 1920s and 1930s were found to produce high levels of hydrogen—up to 84 percent of the total composition of the gas retrieved. Now, after Truche and his colleagues’ analysis of the geology of the Albanian site, their discovery adds to the growing pile of data indicating that natural hydrogen can be trapped underground. “They provided some really compelling evidence that gas accumulation has been there for quite a long time,” Ellis says.
So how did we miss it? How did we not see that hydrogen may be trapped in potentially exploitable deposits? According to Linda Stalker, a geologist at the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia’s national research agency, scientists simply weren’t looking for these reservoirs. Decades ago, before the threat of climate disaster had gained its current prominence, there wasn’t much incentive to search for a new energy source. And because many hydrogen accumulations appear to be located in more shallow layers than oil and gas, crews likely just drilled through them. “You’re speeding straight through to go way deeper. You’re not sampling; you’re not measuring; you’re not looking,” Stalker says.
Another reason for the oversight was far more prosaic: a common method employed by the petroleum industry to analyze gas reservoirs involves using hydrogen as a carrier gas, which masks natural hydrogen found in deposits. This is why scientists are now going back to reanalyze old data and recheck old wells. “People are starting to realize that we need to go out there and try and measure again—and look for hydrogen,” Stalker says.
When Truche and his colleagues sifted through a database of French drilling records, they found previously ignored evidence of high hydrogen concentration in boreholes along a fault line in the Paris Basin. Meanwhile on the Yorke Peninsula in Australia last October, the energy company Gold Hydrogen drilled a new well parallel to one that was discovered to contain hydrogen back in the 1930s. And the gas was still there.
Revisiting old sites is not the only way to identify potential reservoirs of natural hydrogen. Isabelle Moretti, a geologist at the University of Pau and the Pays de l’Adour in France, travels the world in search of “fairy circles”—elliptical depressions with sparse plant cover enclosed by lush vegetation. Such depressions can now be spotted with the help of Google Earth. From the U.S. to Namibia, Russia and Australia, fairy circles have been associated with hydrogen seeping to the surface, infusing the soil. The bizarre appearance of a fairy circle, Moretti says, is likely caused by the way hydrogen migrates upward and changes the soil microbiome, which then affects vegetation. “The circle is compatible with one leakage point at a certain depth, then the gas going up to the surface,” Moretti says.
While fairy circles may be signs of the presence of geological hydrogen, they don't guarantee the existence of underground reservoirs. “If there is no seal or an impermeable rock, it will all escape into nature,” Moretti said. This is why scientists are working to identify which types of rocks can effectively trap natural hydrogen. In Mali, such a rock appears to be dolerite—a dark magmatic rock similar to basalt. Salt can also potentially act as a seal for escaping hydrogen, and so can volcanic sills, horizontal magma intrusions between rock layers. “People realize that, in fact, a lot of rocks are able to stand up to some columns of hydrogen,” Moretti says. Once such a cap is in place, a reservoir may form.
Using current knowledge on natural hydrogen production, trapping and migration, Ellis and his colleague at the USGS have built an unpublished model to estimate how much hydrogen might be actually stored underground. They came up with an estimate of somewhere between thousands and billions of megatons, with the most probable number hovering at “about five million megatons,” Ellis says. With the 2022 global hydrogen demand standing at 95 megatons that seems huge. But, Ellis admits, “there is a lot of uncertainty about all the inputs that go into this model.” What’s more, most of these hydrogen deposits would be unusable from a commercial perspective. “It’s likely going to be too far offshore or just too deep or something that’s just too small, so that it would never be economic to be produced,” Ellis says.
Yet even with smaller numbers, hope is not quashed. In February the U.S. Department of Energy announced selections for grants representing the nation’s first-ever major funding for advanced technologies for extracting natural hydrogen from within deep rock formations. While natural hydrogen reservoirs may be different from those known to the oil and gas industry, Moretti says, they should appear quite familiar to people working in the geothermal industry. Some of the tools for natural gas drilling would find their place on natural hydrogen fields, too. Australia’s Gold Hydrogen has estimated that the quantity of hydrogen it might recover from sites on Yorke Peninsula and the nearby Kangaroo Island to be about 1.3 megatons. In Spain another company hopes to produce up to 70,000 metric tons per year, beginning in 2029. And in the U.S. two companies have drilled in Nebraska and Arizona—for now, they have kept their results private, says Viacheslav Zgonnik, natural hydrogen researcher and CEO of Natural Hydrogen Energy LLC.
Natural hydrogen could power our cars, light our houses and provide a cleaner alternative for all of the industries that are currently dependent on methane, from cement to steel production. Yet it could also prove to be another unicorn that keeps us distracted from implementing clean energy solutions that are less glamorous but more demanding. It may keep us deluded that a deus ex machina will save us from climate catastrophe, even if our industrial societies continue a business-as-usual approach. There are other risks, too. A 2022 study warned that once hydrogen escapes into the air, it may impact atmospheric chemistry, increasing the levels of methane and ozone, two potent greenhouse gases. That is why “it is crucial to prioritize the management of leakages throughout the extraction, transportation and storage processes,” says Matteo Bertagni, a biochemist at Princeton University and the study’s lead author.
So far, Stalker says, the natural hydrogen industry appears to be at a stage similar to where the oil and gas enterprises were 120 years ago. “It’s going to be high-risk, high-reward for the foreseeable future,” she says. For Ellis, meanwhile, one of the concerns is that people might give up too early—as soon as a few wells turn out to be dry. “It's impossible to say today whether this will be commercially viable,” he says. But “we may need to drill dozens or hundreds of wells before we understand how to make this work.”