Rock-deep hydrogen with buried CO2: lab win, next test

generate hydrogen – Researchers at the University of Texas at Austin have shown in laboratory experiments that adding CO2 to iron-rich volcanic rock water can boost hydrogen production while also mineralising CO2 into carbonates. The team says they now want to move toward field t

In the race to cut climate pollution. one stubborn problem keeps resurfacing: where clean hydrogen is concerned. the current supply chain is still tied to fossil fuels. But a team at the University of Texas at Austin is betting that the answer may lie far below our feet—inside rocks—where hydrogen could be coaxed out and carbon dioxide could be locked away at the same time.

The idea starts with a climate double win. Burning hydrogen produces only water, so it doesn’t drive global warming. Yet almost all hydrogen today is made from fossil fuels, which means lots of CO2 is emitted during its production. One route around that is splitting water using wind or solar power to yield hydrogen and oxygen. That work is underway. but hydrogen made this way is more expensive. and scaling it up would require vast amounts of renewable electricity—energy that could otherwise replace coal-fired power plants.

That trade-off has helped fuel growing interest in “natural” or geological hydrogen. In some settings. hydrogen can generate in rocks and collect under the right conditions. then be extracted much like natural gas. Still, how much hydrogen is out there remains uncertain. Gelencsér—who is part of the UT Austin team—doesn’t expect unlimited resources.

She points to Bourakébougou. a village in Mali. as the nearly pure natural hydrogen case where extraction and exploitation is happening—yet only on a tiny scale. “I think it’s a very special case,” Gelencsér says. Hydrogen molecules are tiny, she explains, and they’re produced at low rates. That makes it harder for overlying rocks to seal well enough to let the gas accumulate.

That limitation is why many groups are now working on stimulated hydrogen production—trying to generate hydrogen in rocks rather than waiting for it to happen naturally. Several approaches are already being tested, including pumping water underground. In a process called serpentinisation. water reacts with certain rock types to form hydrogen. and that chemistry is a major source of natural hydrogen. Pumping in more water can speed the process.

The crucial shift, UT Austin researchers say, is what to add to the water.

A company called Carbfix is already mineralising CO2 in Iceland by adding it to water pumped underground at a geothermal power plant. Building on that, Gelencsér and colleagues ran lab experiments to see whether CO2 could both disappear into stable minerals and help produce hydrogen.

They used a type of volcanic rock rich in iron. In a pressured container, they set conditions meant to mimic depth: 1.2 to 1.7 megapascals and 90°C. The researchers added either water with CO2 or water with argon as a control. The CO2-rich water released more hydrogen than the argon water. The team says the most likely reason is chemistry at the mineral surface: CO2 can form carbonic acid. which dissolves part of the rock and allows more water to react.

As expected, there was CO2 mineralisation. And hydrogen production could be boosted further by adding nickel chloride as a catalyst, Gelencsér said in a recent meeting of the European Geosciences Union in Vienna.

The lab results weren’t a theoretical promise alone. The researchers were able to release around 0.5 per cent of the hydrogen they say could, in principle, be obtained from reacting water with the rock. To make the approach feasible, they think they need to raise that to 1 per cent.

One potential lever is depth. Going deeper would mean higher temperatures, which enhance serpentinisation, Gelencsér says. That would increase costs—but it also could open the door to pairing hydrogen production with geothermal power, turning the same underground heat into more than one output.

The team’s optimism is also grounded in what they say exists on a planetary scale: globally. there are huge volumes of iron-rich rock of this kind. Even if efficiency landed at 1 per cent. they argue it could potentially yield far more hydrogen than the 100 million tonnes currently produced around the world.

Independent scientists who commented on the work framed it as a promising direction, not a guaranteed solution. Barbara Sherwood Lollar at the University of Toronto called it “good work” and said there is “definitely growing interest in approaches that combine stimulated geologic hydrogen production with CO2 mineralisation.”.

Aliaksei Patonia at the University of Oxford in the UK also pointed to the same concept. saying “a number of groups and start-ups are exploring variations of this concept.” He highlighted the economic hinge: if companies can charge for locking away CO2 in the process—Carbfix’s model—then extra revenue could reduce project risk and make investors more willing. But he added that it’s still unknown whether any of these approaches will prove viable.

There is also the question of how quickly the world needs breakthroughs. Sherwood Lollar argues that the most realistic near-term path includes using the small amounts of natural hydrogen that are already known. alongside pursuing stimulated hydrogen production. Her team has just shown that a mine in Timmins. Ontario. is emitting around 140 tonnes of hydrogen per year. which she says could be exploited locally.

“There’s no silver bullet,” she says. “Every one of these potential approaches can contribute and should contribute – and we need to move quickly on them.”

For Gelencsér, the next step is clear. The lab work suggests the concept can work for one common rock type. Now the team wants to work with companies on field trials—testing whether the chemical gains seen at a bench can survive the complexity of real underground systems. and whether carbon dioxide can truly be locked away while hydrogen is extracted in meaningful quantities.

“We hope to demonstrate that we will be able to generate hydrogen economically while sequestering CO2,” Gelencsér says. And she adds an additional possibility: generating geothermal energy at the same time.

hydrogen CO2 mineralisation stimulated geologic hydrogen production serpentinisation iron-rich rock geothermal energy Carbfix nickel chloride European Geosciences Union Mali Bourakébougou