Summary
Energy companies are exploring for naturally occurring hydrogen in nearly 30 countries, hoping to find a cheaper alternative to manufactured hydrogen. The scale and commercial value of these underground deposits remain open scientific questions.
Companies are drilling in nearly 30 countries to find hydrogen gas generated naturally inside Earth and trapped in underground deposits. The search has attracted nearly US$500 million in venture-capital investment since 2023, but exploration is still at an early stage: no one yet knows whether large, commercially useful reservoirs are widespread.
The possibility matters because hydrogen can generate electricity without producing carbon dioxide at the point of combustion. If naturally occurring deposits prove plentiful and inexpensive to extract, they could provide a new source of energy alongside manufactured hydrogen made by splitting water.
How geological hydrogen forms
Geological hydrogen is produced through natural chemical and radioactive processes below ground. One route occurs when iron-rich igneous rocks, including olivine, react with water. Another begins when alpha particles released by the radioactive decay of uranium or thorium strike water molecules and split them, producing hydrogen.
Some of this gas moves through rocks towards the surface and supports underground microbial communities. Microbes consume hydrogen, while other geochemical reactions also remove it. Hydrogen molecules are small, and geologists traditionally assumed that gas escaping these processes would pass through rock layers and dissipate rather than collect beneath impermeable formations.
That assumption changed after a substantial hydrogen deposit was reported in Mali in 2018. Evidence from deep mines has added to the case for natural accumulations. In 2024, researchers found that at least 200 tonnes of hydrogen was released each year from a chromite mine in Albania, one of the largest natural hydrogen flow rates recorded.
A 2024 analysis estimated that Earth’s subsurface could contain tens of trillions of tonnes of hydrogen. That estimate describes a possible geological resource, not a proven recoverable reserve. If even a small fraction could be extracted profitably, the analysis suggested that it might meet projected clean-energy needs for 200 years, potentially at or below the cost of fossil fuels.
Drilling will test the resource
Exploration is now moving across a wide range of geological settings, from northern Canada and eastern Africa to South Australia. The UK-based company H2Au began drilling in Kansas in August. Another company, HyTerra, explored in Nemaha, Kansas, but the site did not contain enough gas for commercial production.
Results from new wells expected over the coming months could help establish whether hydrogen forms and accumulates at commercially useful scales. Exploration must identify more than the presence of gas: companies need deposits with sufficient concentration, flow and persistence to support production.
Several geological processes still need to be measured under different conditions. Researchers are studying how quickly hydrogen forms, how it travels through rock, where it can accumulate and how long it remains trapped. Those factors will determine whether underground hydrogen is a significant energy resource or a collection of scattered deposits that are difficult to exploit.
Geological hydrogen is also not an unlimited source. Its natural formation is slow, making the resource relatively finite even if the total quantity underground is large. The next phase of drilling will therefore provide evidence not only about how much hydrogen exists, but also about whether it can be extracted reliably enough to change the economics of hydrogen energy.