Geologists have known for decades that processes deep beneath Earth’s surface produce hydrogen. It is the major energy source for microbes that dwell in those dark depths. This geological hydrogen has recently caught entrepreneurs’ attention as a clean energy source for manufacturing and transport. But estimates of how much hydrogen there is—some say trillions of metric tons—are “entirely theoretical [or] based on modeling,” says Barbara Sherwood Lollar, a geochemist at the University of Toronto.
After collecting data at a mining site for 10 years, Sherwood Lollar and colleagues now provide the first long-term hard data on geological hydrogen production (Proc. Natl. Acad. Sci. U.S.A. 2026, DOI: 10.1073/pnas.2603895123).
And the numbers look good. They show that metal mines in operation today could be large, untapped sources of economically viable hydrogen. An added bonus is that “large amounts of helium are always found with this hydrogen,” Sherwood Lollar says. The world faces a helium shortage, a problem exacerbated by the Iran war, and companies are scrambling for new sources.
Sherwood Lollar and her colleagues conducted measurements at the Kidd Creek Mine, which primarily produces copper and zinc and is one of the deepest and longest-running mines in North America. The groundwater in such metal mines contains dissolved hydrogen, methane, and other gases, which today are vented to the air. Two main processes produce hydrogen underground. In one process, water reacts with iron- or magnesium-rich rocks to release hydrogen. In the other, radioactive decay of uranium, thorium, and other elements splits water.
The researchers collected groundwater samples from 35 boreholes and measured the gas composition in the lab. They could sample most of them only once because of mining operations. But they sampled eight wells two to three times over 18 months and three wells regularly for 7–11 years.
Based on their measurements, the researchers extrapolated that the site’s nearly 15,000 boreholes produce a total of more than 140 metric tons of hydrogen per year, enough for an estimated 4.7 million kW h of energy.
Geoffrey Ellis, a geochemist at the US Geological Survey, says that this “rigorous quantitative data over a decade . . . is novel and important to have.”
Sherwood Lollar says her team’s work introduces a new way to look at the geological hydrogen buzz. Much of the research and investment on geological hydrogen is focused on drilling new holes to tap this hydrogen and then building new pipelines and infrastructure to ship it over long distances, which requires compressing or liquefying it.
But this study shows that hydrogen is produced in hard rocks, which comprise about 70% of the continental crust and are already the focus of mining operations. “The same kinds of rocks that produce copper, zinc, gold, diamonds, and critical minerals—these are the same rocks that produce hydrogen,” Sherwood Lollar says. “Local use is an underexplored opportunity here. This would get around the problem of having to duplicate infrastructure for hydrogen and of long-term storage and transport.”
Ellis agrees. “This is low-hanging fruit,” he says. Mines currently vent hydrogen into air, he adds, but “rather than vent it, why not utilize it?” Using the hydrogen energy for mining operations would help mines cut costs and offset carbon emissions.
Another big advantage is that the same types of rocks that generate hydrogen provide the ideal environments to convert carbon dioxide to carbonate minerals for long-term storage, Ellis says. “Once you have this infrastructure that you’re using to capture the hydrogen and you’ve exhausted all that hydrogen, then you can go back in and inject carbon dioxide and mineralize it there.”
Capturing and using hydrogen from mines will take technology development, Sherwood Lollar says, but any new energy source requires development. “It strikes us from our economic analysis that this is certainly worthy of investment and creative thought that we need to deal with the climate crisis.”
CORRECTION
This story was updated on May 22, 2026, to correct the spelling of Barbara Sherwood Lollar’s last name. It is spelled Sherwood Lollar, not Sherwood Loller.
