A potentially important new source of low-carbon energy may be hiding deep beneath the Earth’s surface. Scientists are investigating geologic hydrogen, also known as natural or white hydrogen, which forms through geological processes and can accumulate in underground rock formations. Unlike conventional hydrogen production, which often relies on fossil fuels, natural hydrogen could potentially be extracted without the same carbon-intensive manufacturing process.
Research published in Science Advances by scientists at the U.S. Geological Survey estimated that Earth’s crust may contain approximately 5.6 trillion metric tons of hydrogen, although the uncertainty surrounding this estimate is enormous. Most of that hydrogen is unlikely to be economically recoverable. Nevertheless, the researchers calculated that accessing even a small fraction could potentially satisfy projected global hydrogen demand for many decades.
The scientific challenge is discovering where economically useful hydrogen accumulations exist. Hydrogen can form when water reacts with iron-rich minerals deep underground, and natural radiation can also break water molecules apart. Researchers must identify geological structures capable of generating, trapping and preserving the gas. The USGS has already published a map highlighting promising exploration regions across the United States, while exploration projects are expanding internationally.
If commercial extraction proves practical, natural hydrogen could eventually support industries that are difficult to decarbonize, including steelmaking, fertilizer production and certain forms of heavy transportation. However, the technology remains in an early stage, and extraction costs, leakage, purification requirements and environmental impacts must be assessed. Geologic hydrogen is not yet a guaranteed replacement for fossil fuels, but it represents a potentially significant new direction in the global search for cleaner energy.
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