In recent years there has been a notable increase in interest in a particular clean energy source present in rocks: thewhite hydrogenhydrogen gas found underground, of natural origin and produced by geological processes. It’s about free hydrogenthat is, not bound to other elements (on Earth, most hydrogen is found in the form of compounds, such as water and methane). White hydrogen could significantly contribute to the energy transition, replacing gray hydrogen derived from fossil fuels. Research is underway around the world to identify new deposits of natural hydrogen and to collect scientific data that can help better understand its formation and economic potential.
How White Hydrogen Is Formed and Where Is It Found?
White hydrogen is formed mainly during a process called serpentinizationwhich transforms the rocks of the Earth’s mantle, called peridotitesin serpentinites. At high temperatures and pressures, the waters circulating in the mantle react chemically with the iron-rich minerals that make up the peridotites (for example olivine) and transform them into other minerals (such as serpentine). During these reactions the iron is oxidized, releasing white hydrogen.
Natural hydrogen tends to migrate towards the surface, escaping at the faults and in particular along the margins between tectonic plates. During its journey it may encounter impermeable rocks that prevent it from rising further, trapping it: this creates a deposit. Free hydrogen can also be formed due to radiation emitted by radioactive elements present in rocks, capable of separating water molecules.
White hydrogen escapes through cracks in the Earth’s crust, but is also consumed by bacteria to produce energy, especially methane. It can also react with rocks and gases to form water, methane, and mineral compounds.
Extraction, transport and storage of white hydrogen
White hydrogen is trapped in reservoirs made of porous rocks, located underneath impermeable rocks, just like oil and natural gas: it is therefore possible to extract it through perforationsas occurs at the well of BourakébougouIn the Western Mali. Mud is continuously circulated in the pipes used in drilling to keep temperature and pressure under control. Once the deposit is reached, the pipes are lined with concrete to prevent the gas from migrating: leaks of white hydrogen at low depths are in fact very dangerous because they can originate flammable and explosive mixtures with oxygen.
In white hydrogen deposits, other gases such as nitrogen and methane are often found. In these cases, it is therefore necessary separation processes to obtain pure hydrogen, for example by using membranes. Transporting hydrogen over long distances is possible by transforming it into a liquid state and using Pipelines cryogenic. Studies are also underway on storage sites suitable for hosting white hydrogen. These are, for example, cavities originating in salt deposits, which guarantee insulation and prevent gas leaks.
White hydrogen deposits in the world
The only white hydrogen deposit currently exploited in the world is that of BourakébougouIn the Western Maliwhere 5 tonnes of gas are produced per year. However, other important deposits have already been identified in the United States, Australia and Europe, particularly in France (where the largest deposit in the world could be located, containing up to 46 million tonnes of white hydrogen) and Finland. The areas where it is most likely to find white hydrogen are located near the subduction zones between the plates, where large amounts of water reach iron-rich rocks, and the mountain rangesduring the formation of which rocks from the mantle were brought to the surface.
THE research projects are increasingly numerous throughout the world, with the aim of obtaining more information on this important resource. According to studies, white hydrogen would be produced continuously: unlike fossil fuels, it would therefore be a renewable resource. Although the amount of hydrogen naturally produced every year underground is currently unknown and careful assessments of extraction costs are needed, in the future we may have access to a amount of hydrogen sufficient to satisfy global demandwith a huge contribution to the energy transition. White hydrogen has the advantage of being a clean energy sourcewhich does not emit carbon dioxide unlike grey hydrogen produced from fossil fuels.
