Hydrogen gas produced by geological processes beneath Earth’s surface has been touted as a promising clean energy source. A new study provides the first solid evidence that it could be a practical and commercially viable option for decarbonizing the grid.
Hydrogen is an energy-dense fuel that produces only water when burned. But today, the vast majority of industrial hydrogen is manufactured using fossil fuels in an energy intensive process, negating its green credentials. While there’s hope renewable energy could one day power the process and provide a reliable source of green hydrogen, that technology is still a long way from commercial viability.
Recently though, there has been growing excitement about the possibility of vast natural hydrogen reserves stored deep underground. Several large deposits have been discovered and estimates suggest that trillions of tons of the gas could be sitting beneath our feet.
So far, those estimates have been almost entirely theoretical, based largely on near-surface measurements, proxy data, and extrapolation rather than direct observations. Studies have also typically brushed over the complexities of storing and distributing hydrogen gas, which needs to be kept at high pressure or extremely cold temperatures.
A new study, published in PNAS, firms up the numbers. The authors track the release of natural hydrogen over an 11-year period from a mine in Canada and conclude the site produces enough hydrogen to generate 4.7 million kilowatt-hours of energy annually. That’s enough to power a few hundred homes or an industrial facility and suggests the most promising approach to natural hydrogen could be to use it where you find it, they say.
“We present an alternative vision for the hydrogen economy that can address some of the current challenges arising from the focus to date, that has been largely based on transportation of hydrogen over long distances from source location to markets,” the authors write. “Calculations from this study site show that the amount of locally generated energy has economic value for both industries and communities located on hydrogen-producing rock.”
The new study focused on the Kidd Creek mine near Timmins, Ontario where researchers had collected 11 years of hydrogen discharge data from 35 boreholes between two and three kilometers below the surface.
The authors found that, on average, these boreholes were pumping out between 1 and 3 liters (0.04 to 0.1 cubic feet) of the gas per minute. Across all of Kidd Creek’s nearly 15,000 boreholes, the researchers estimate the site releases more than 140 tons of hydrogen per year.
The hydrogen at Kidd Creek is primarily produced through a process called serpentinization, in which water reacts with iron-containing minerals deep in the crust. More than 70 percent of the continental crust has the potential for this kind of hydrogen generation, the researchers say, suggesting the mine, and its hydrogen output, may be far from unique.
Since the gas is already being vented during routine mining, capturing it would require relatively modest investment, the researchers say. And hydrogen isn’t the only resource on offer. Sites that produce hydrogen also tend to release methane and helium at predictable rates.
Based on the amount of hydrogen at Kidd Creek, the researchers estimate the site is probably producing 4,200 tons of methane and 140 to 280 tons of helium. The latter could be particularly valuable, given its critical role in cryogenic technologies. With recent supply crunches, further exacerbated by the Iran war, prices have been in the range of $100,000 per ton.
Capturing the gas isn’t always simple, the authors note. Underground microbes can consume it before extraction. It may also require significant investment after capture to separate the gases.
But many communities sitting on hydrogen-producing rock may have a valuable renewable energy source just beneath their feet. And the economic case for exploiting it is looking increasingly solid.
