The largest natural flow of hydrogen gas ever discovered has been detected seeping through a pool of water deep within a chromium mine in Albania. Reporting the find in a new study, researchers say the deposit could pave the way for new, cleaner ways of capturing hydrogen for use as a clean fuel.

Hydrogen gas has long been sought after as an alternative to fossil fuels as it can be burnt without releasing any greenhouse gases. However, until now, natural hydrogen flows have been hard to come by, and the resource was typically manufactured from natural gas via a process that consumes energy and emits carbon dioxide.

Furthermore, despite the fact that hydrogen is known to play a key role in supporting life deep within the Earth’s crust, scientists had generally assumed that the gas’s high reactivity prevented it from accumulating in large underground deposits.

All that began to change when a flammable gas was first detected in the Bulqizë mine in Albania in 1992. Large explosions in 2011, 2017, and 2023 fuelled suspicions that the odorless gas was indeed hydrogen, and researchers have now determined that the mine may sit atop a fault that contains between 5,000 and 50,000 tonnes (5,511 to 55,115 tons) of the precious resource.

Analyzing the gas as it bubbled through a pool in the mine, the study authors determined that it was indeed 84 percent hydrogen, along with smaller amounts of methane and nitrogen. Calculating the flow of gas, they concluded that the pool emits around 11 tonnes (12.1 tons) of hydrogen per year, which is equivalent to 34 kilograms (75 pounds) a day.

Combining this with other flows in a borehole and a shaft within the same mine, the researchers calculated that the total amount of hydrogen gas passing through the mine amounts to some 200 tonnes (220 tons) per year.

“Our study unveils a high emission rate of almost pure geologic H2, suggesting the potential for a new extractable primary energy source,” they write.

Intriguingly, the Bulqizë mine is located within a stretch of iron-rich rock known as ophiolite, which is known to generate hydrogen as it reacts with water and has been associated with other hydrogen flows elsewhere around the world. The study authors therefore speculate that further significant natural hydrogen deposits may be lurking beneath other ophiolite outcrops in other locations.

“We reveal that ophiolites, which are mantle rocks from the oceanic crust obducted onto continents, not only constitute effective source rocks, but also have the potential to host high-quality, H2-rich gas reservoirs,” they conclude.

The study is published in the journal Science.