Natural, or geologic hydrogen (H2) has recently gained widespread interest due to its potential as an extractable primary energy resource. This new study, published in Science magazine, specifically addresses this important question by showcasing a remarkably high hydrogen outgassing rate of at least 200 tons per year in a deep underground chromite (chromium ore) mine in Albania. This is the highest recoded natural H2 flux to date. One of its physical manifestations turns a draining pool inside a mine gallery into a breathtaking 30 m2 jacuzzi bubbling with almost pure H2 (84% by volume). This considerable natural outgassing raises the question of hydrogen's origin and potential economic prospects.

Although this flow is minimal compared to the global production of hydrogen by the petrochemical industry (100 million tons per year), in-situ observations and numerical simulations presented by the authors of this study reveal the presence of a deep reservoir located in a well-identified fault zone. Mining operations have perforated this reservoir, resulting in hydrogen leakage at several well-localized points in the deepest galleries.

This discovery lays the foundations for new models of natural hydrogen exploration. In this sense, the Bulqizë chromium mine, by offering a direct access to the subsurface, is a key scientific tool for studying the hydrogen system and understanding the conditions of formation and accumulation of this gas. Ophiolitic massifs - mantle rocks from the oceanic crust obducted onto continents - are proving to be potential hosts for these high-quality hydrogen reservoirs. These large, widespread geological formations on Earth have already been identified as hosting hyperalkaline sources where hydrogen bubbles. Historically, ophiolites have not been the focus of the oil and gas industry due to their unsuitability as environments rich in hydrocarbon resources. By several aspects these findings may be a game changer in our relentless quest for energy resources.

However, it's still too early to say whether natural hydrogen will take a significant place in our energy mix, or remain a niche curiosity. It is important to stress that geologic H2 is not renewable as the production time for H2 far exceeds the extraction time. Furthermore, these geological environments harbor a fragile deep biosphere that relies on H2 as an energy source. Therefore, we also deliver a message of caution to temper the passion, and even sometimes the “hydrogen fever”, that will undoubtedly be stimulated by our discovery. While geologic hydrogen exploration warrants great scientific efforts, we must also be mindful of its potential environmental impact.