The next green energy revolution may begin below our feet.
That's the idea behind a new CU Boulder effort that will explore the possibility of coaxing hydrogen from rocks to provide clean energy around the globe. The three-year project is supported by a new grant from the Grantham Foundation for the Protection of the Environment.
Researchers will drill into the Earth to kick-start the production of a commodity known as "geologic" hydrogen, a potential source for sustainable power.
"There's been a huge growth of companies in recent years who are zooming around the globe looking for existing subsurface deposits of geologic hydrogen that they can tap into," said Alexis Templeton, a professor in the Department of Geological Sciences who leads the project. "We want to know: Can we stimulate the production of hydrogen from rocks, creating new gas at rates that are fast enough to one day be economical?"
She explained that when water mixes with iron-rich minerals deep within the planet's crust, the ensuing reactions can generate pockets of hydrogen gas. These deposits could, theoretically, become a gold mine for sustainable energy: When hydrogen is burned to produce energy, it does not emit greenhouse gases. The only byproduct, in fact, is water.
Alexis Templeton visits a "hyper-alkaline" spring in Oman where hydrogen gas bubbles up to the surface. (Credit: Alexis Templeton)
But first, scientists will need to determine if companies and nations can bring those deposits up to the surface without harming the environment or human communities in the process-and in large enough quantities to meet growing global energy demands.
Templeton and her colleagues will conduct experiments in the lab and then hundreds of meters below the Earth's surface to see if they can nudge the planet to make more hydrogen than it normally does.
"We're trying to do this in a way that is as close to how the natural subsurface system behaves as possible," Templeton said.
The team includes Eric Ellison, a research scientist at CU Boulder, and researchers Peter Kelemen and James Leong from Columbia University; Eric Boyd at Montana State University; Juerg Matter at the University of Southampton in the United Kingdom; and the start-up company Eden GeoPower.
"This project allows us to test our understanding of the chemical reactions that produce hydrogen," Ellison said. "If we can accelerate these reactions underground, we can turn rocks into a clean and abundant energy resource."
Life belowground
Geologists aren't the only ones hunting for hydrogen, Templeton added.
Engineers, for example, have succeeded in using solar or wind power to split molecules of water into oxygen and hydrogen gas-so-called "green" hydrogen. The growing global demand for hydrogen, however, has inspired scientists to also look below Earth's surface.
Geologists have long suspected that deposits of hydrogen gas lay hidden underground. But recent research has hinted that there may be a lot more of it than once thought. One 2022 report from the U.S. Geological Survey suggested that there may be enough geologic hydrogen below the ground to supply humanity's need for liquid fuel for hundreds of years.
Templeton, who has worked extensively in Oman and other locales around the world, is an expert on these dark and often overlooked environments. Her research, for example, has helped to reveal that Earth's subsurface expanses aren't dead and sterile, but are often teaming with life-filled with communities of bacteria and other single-celled organisms that feed off supplies of those same traces of hydrogen.
"We've gone to these environments on Earth where water is naturally circulating through these iron-rich minerals," Templeton said. "We've studied how hydrogen is produced right in those environments."
She suspects scientists may be able to give those environments a big boost.
Sustainable energy of the future?
To find out, the researchers will drill boreholes and inject water into formations of a type of iron-rich rock called peridotites-potentially kick-starting chemical reactions to make even more hydrogen. The group will simultaneously try to prevent bacteria living underground from eating up the supplies of new gas.
Anne Sheehan, chair of geological sciences, noted that the project is a showcase for the department's research that has real-world impacts for people living in Colorado and beyond.
"Dr. Templeton's pioneering project not only has the potential to unlock a vast source of clean sustainable energy but also perfectly aligns with our department's vision for the future-a future where science and innovation combine to harness the Earth's natural resources responsibly and usher in a new era of sustainable energy for generations to come," Sheehan said.
Throughout the study, Templeton and her colleagues will carefully monitor their results to make sure that these reactions don't lead to any unintended consequences.
"We want to find a way to make clean energy, but we also don't want to create other environmental impacts," Templeton said. "We're asking: Is geologic hydrogen really a viable source of energy, and if it is, how can we go about continuously producing it?"
