Naturally-occurring geologic hydrogen, often referred to as white or gold hydrogen, is the cleanest, most cost-effective, lowest-carbon emitting form of hydrogen available today, but its production is currently an under-explored industry. This article by U.S. Geological Survey (USGS) explores the potential for geologic hydrogen for next generation energy. According to the survey, even if a small fraction of the estimated volume of hydrogen underground could be recovered, it´s most likely enough to last for hundreds of years.
SOURCE: United States Geological Sur