US researchers looking at extracting hydrogen from rocks

The US Department of Energy last month awarded US$20 million in research grants to 18 teams from laboratories, universities and private companies to develop technologies that can extract hydrogen from underground.

It’s commonly thought that the most abundant element in the universe, hydrogen, exists mainly alongside other elements — with oxygen in water, for example, and with carbon in methane. But naturally occurring underground pockets of pure hydrogen are punching holes in that notion — and generating attention as a potentially unlimited source of carbon-free power.

Geologic hydrogen, as it’s known, is produced when water reacts with iron-rich rocks, causing the iron to oxidise. One of the grant recipients, MIT Assistant Professor Iwnetim Abate’s research group, will use its US$1.3 million grant to determine the ideal conditions for producing hydrogen underground — considering factors such as catalysts to initiate the chemical reaction, temperature, pressure and pH levels. The goal is to improve efficiency for large-scale production, meeting global energy needs at a competitive cost.

The US Geological Survey estimates there are potentially billions of tons of geologic hydrogen buried in the Earth’s crust. Accumulations have been discovered worldwide, and a slew of US startups are searching for extractable deposits. Abate is looking to jump-start the natural hydrogen production process, implementing ‘proactive’ approaches that involve stimulating production and harvesting the gas.

“We aim to optimise the reaction parameters to make the reaction faster and produce hydrogen in an economically feasible manner,” said Abate, the Chipman Development Professor in the Department of Materials Science and Engineering (DMSE). Abate’s research centres on designing materials and technologies for the renewable energy transition, including next-generation batteries and novel chemical methods for energy storage.

Interest in geologic hydrogen is growing at a time when governments worldwide are seeking carbon-free energy alternatives to oil and gas. In December, French President Emmanuel Macron also said his government would provide funding to explore natural hydrogen. And in February, government and private sector witnesses briefed US lawmakers on opportunities to extract hydrogen from the ground.

Today commercial hydrogen is manufactured at US$2 per kilogram, mostly for fertiliser and chemical and steel production, but most methods involve burning fossil fuels, which release Earth-heating carbon. Green hydrogen, produced with renewable energy, is promising, but at US$7 per kilogram, it is still expensive.

“If you get hydrogen at a dollar a kilo, it’s competitive with natural gas on an energy-price basis,” said Douglas Wicks, a program director at Advanced Research Projects Agency - Energy (ARPA-E), the Department of Energy organisation leading the geologic hydrogen grant program.

Abate and researchers in his lab are formulating a recipe for a fluid that will induce the chemical reaction that triggers hydrogen production in rocks. The main ingredient is water, and the team is testing ‘simple’ materials for catalysts that will speed up the reaction and in turn increase the amount of hydrogen produced, said postdoc Yifan Gao.

“Some catalysts are very costly and hard to produce, requiring complex production or preparation,” he said. “A catalyst that’s inexpensive and abundant will allow us to enhance the production rate — that way, we produce it at an economically feasible rate, but also with an economically feasible yield.”

The iron-rich rocks in which the chemical reaction happens can be found across the world. To optimise the reaction across a diversity of geological compositions and environments, Abate and Gao are developing what they call a high-throughput system, consisting of artificial intelligence software and robotics, to test different catalyst mixtures and simulate what would happen when applied to rocks from various regions, with different external conditions like temperature and pressure.

“And from that we measure how much hydrogen we are producing for each possible combination,” Abate said. “Then the AI will learn from the experiments and suggest to us, ‘Based on what I’ve learned and based on the literature, I suggest you test this composition of catalyst material for this rock.’”

The team is writing a paper on its project and aims to publish its findings in the coming months.

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