Lab tests show CO2-stored hydrogen from iron-rich rocks

stimulated hydrogen – Researchers at the University of Texas at Austin report that iron-rich volcanic rock can produce hydrogen when water is enriched with CO2, while also locking that CO2 into minerals. The team says the next step is working with companies on field trials—if the p

Deep underground, hydrogen doesn’t just have to be waited for—it might be coaxed into existence, while carbon dioxide is trapped along the way.

At the University of Texas at Austin. researchers have shown in lab studies that a common. iron-rich type of volcanic rock can generate hydrogen when it reacts with water that contains CO2. Their aim is straightforward: produce clean hydrogen while sequestering CO2 so the climate benefit doesn’t get erased at the start of the supply chain.

“We hope to demonstrate that we will be able to generate hydrogen economically while sequestering CO2,” says Orsolya Gelencsér, a team member on the work. She adds that it might even be possible to pair the hydrogen production with geothermal energy—turning the same deep heat into multiple outputs.

Hydrogen matters because it doesn’t behave like fossil fuels. Burning hydrogen produces only water, so it doesn’t directly cause global warming. Hydrogen could therefore help with “net zero” efforts. especially in industrial processes that are difficult to electrify—such as fertiliser production and steel-making.

But the problem has been stubborn: almost all hydrogen today is made from fossil fuels. meaning CO2 is emitted during its production. One way to avoid those emissions is to split water using wind or solar power, producing hydrogen and oxygen. That method is beginning to scale, but hydrogen made this way is still more expensive. Producing it at large scale would also require vast amounts of renewable electricity—electricity that might otherwise replace coal-fired power plants.

That pressure has helped fuel a surge of interest in “geological” or natural hydrogen. In some places. hydrogen is generated in the subsurface and can accumulate. then be extracted in ways that resemble natural gas. Yet nobody agrees on how much is really there. Some researchers argue vast quantities may be waiting. Gelencsér, however, believes natural hydrogen resources may be limited.

The clearest example of natural hydrogen being extracted at present is a tiny operation in a village in Mali called Bourakébougou. There, nearly pure natural hydrogen is being tapped—but only on a small scale.

“I think it’s a very special case,” Gelencsér says. She explains that hydrogen is typically produced at low rates. Because its molecules are tiny, it can be hard for the overlying rocks to act as a strong seal that lets hydrogen accumulate.

That is why many groups are now pursuing an approach known as stimulated hydrogen production: instead of waiting for hydrogen to build up naturally, they aim to create the right conditions underground.

One method is to pump water into the subsurface. When water reacts with certain rock types, it can form hydrogen through a process called serpentinisation, which is also the source of a lot of natural hydrogen. Pumping more water speeds things up.

What Gelencsér and colleagues realised is that if CO2 is added to the injected water. that CO2 should react with the rocks and get locked away as carbonates. A company called Carbfix is already doing this kind of CO2 mineralisation in Iceland by adding CO2 to water pumped underground at a geothermal power plant.

Building on that idea. Gelencsér and her colleagues carried out lab tests using a volcanic rock type rich in iron. They placed rock samples in a pressured container at 1.2 to 1.7 megapascals and heated them to 90°C to mimic conditions at depth. They then added either water with CO2 or water with argon as an inert control.

The CO2-rich water released more hydrogen. Gelencsér says the effect is likely because CO2 forms carbonic acid that dissolves part of the rock. allowing more water to react. The team also observed CO2 mineralisation, which was expected. Hydrogen production could be boosted further by adding nickel chloride as a catalyst. Gelencsér told a recent meeting of the European Geosciences Union in Vienna.

In the experiments, the researchers were able to release around 0.5% of the hydrogen they estimate is theoretically possible from reacting water with the rock. They believe the process needs to reach 1% to be feasible.

One route to that higher yield is to go deeper, where temperatures are higher. Higher temperatures enhance serpentinisation, Gelencsér says. The trade-off is cost, but it may also open the door to extracting the geothermal heat for power at the same time.

The appeal is scale. The researchers point to huge global volumes of iron-rich rock of this type. Even at 1% efficiency, they say it could potentially yield far more hydrogen than the 100 million tonnes of hydrogen currently produced worldwide.

Experts not involved in the work say the direction makes sense, even if hurdles remain. Barbara Sherwood Lollar at the University of Toronto called it “good work.” Aliaksei Patonia at the University of Oxford in the UK said there is “definitely growing interest” in combining stimulated geologic hydrogen production with CO2 mineralisation. with multiple groups and start-ups exploring variations.

Patonia also described what investors would likely need to see. If companies could charge for locking away CO2—similar to what Carbfix does—the extra revenue could reduce project risks and make proposals more attractive. Still, whether any of the approaches will actually be viable is not settled.

Sherwood Lollar argues for urgency on both fronts. Her view is that researchers should exploit small amounts of natural hydrogen they already know about while pushing stimulated production forward. She points to her team’s finding that a mine in Timmins. Ontario. is emitting around 140 tonnes of hydrogen per year—hydrogen that could be captured locally.

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

hydrogen CO2 mineralisation stimulated geologic hydrogen production serpentinisation geothermal energy Carbfix iron-rich volcanic rock University of Texas at Austin European Geosciences Union Mali Bourakébougou Timmins Ontario