Earth-Science Reviews journal has published in March 2020 the article entitled “The occurrence and geoscience of natural hydrogen: A comprehensive review”. It combines data and ideas from almost 500 scientific publications and books and conclusively shows that hydrogen is much more abundant in nature than it was previously thought. 

Picture of the continuously burning gas seep at Chimaera, near Antalya, Turkey. The gas contains 7.5–11.3% H2. These active vents have been known for more than 2500 years and are believed to be the source of the first Olympic flame.

The potential of natural hydrogen has not been recognized earlier “because of an existing prejudice that free hydrogen in nature is rare, and descriptions of the few known discoveries are anecdotal and for some reason garner very little notice. Therefore, if no one expects to find free hydrogen, no one samples for it. This prejudice influences the way gas samples are analyzed and sampled, but also the way detection systems are designed.” Because of this, hydrogen has mostly been studied in a fragmentary way which has resulted in the underestimation of its important role in natural processes. 

This gap is covered by the review paper, which summarizes and classifyes discoveries of hydrogen as a free gas in different environments, as inclusions in various rock types, and as dissolved gas in ground water. It has been detected in high concentrations, often as a major gas, in all types of geologic setting: sediments, metamorphic and igneous rocks, basement, orebodies and coal mines, oil and gas reservoirs and aquifers.

Many of the reported discoveries are located in Ukraine.