Naturally
Hydrogen
Natural hydrogen, also known as white, golden or geological hydrogen, is molecular hydrogen (H₂) that is formed naturally in the earth’s crust or in geological processes – in other words, it is not produced industrially. It has great, so far untapped potential and, in combination with geothermal energy, can become a solid component in the transition to a low-carbon economy. Below you will find interesting facts about the formation and accumulation of natural hydrogen underground.
1. When was Natural Hydrogen Discovered?
As early as 1910, the chemist Ernst Erdmann in Germany demonstrated the release of hydrogen in the potash mine Leopoldshall near Staßfurt in Saxony-Anhalt. However, his discovery was forgotten. In the 1970s and 1980s, hydrogen leaks were documented in oil and gas wells, but not further investigated because the focus was on fossil fuels. In 1987, well drillers made another accidental discovery in Mali. While drilling for water, they came across a source of almost pure hydrogen (~98% H₂). However, it took more than 20 years for the value of the find to be acknowledged. Since 2012, the natural hydrogen from the well has been converted into electricity, which supplies the village of Bourakébougou.
2. When Did the Systematic Search for Natural Hydrogen Start?
In 2020, Viacheslav Zgonnik, a geochemist of Ukrainian origin, provided translations and summaries of Russian-language scientific literature. However, it was his own research that sparked particular interest in natural hydrogen and its potential as a renewable energy source. This work laid the foundation for the boom in the search for natural hydrogen worldwide, which has since led to an exponential increase in scientific work and the founding of numerous companies on all continents.
3. How Does Natural Hydrogen Form in the Subsurface?
Natural or white hydrogen can be formed under various geological conditions. The main factors include:
Serpentinization
Ultra-mafic rocks are converted into the mineral serpentine by water and the oxidation of iron. This geochemical reaction, known as serpentinization, generates natural hydrogen in large quantities in all young mountain ranges such as the Alps, the Dinarides or the Pyrenees. It also frequently occurs at mid-ocean ridges or in ophiolite zones. The latter are remnants of oceanic crust that have been subducted onto continents.
Radiolysis of Water
Radioactive elements such as uranium, thorium or potassium can split water molecules into hydrogen and oxygen through ionizing radiation. This happens deep in the subsurface, especially in crystalline rocks such as granite. However, this process is considered to be less important in terms of quantity than serpentinization.
Biological Processes
Some anaerobic microorganisms can produce hydrogen as a by-product of their metabolic processes. This often occurs in sedimentary basins in the presence of organic material. Methane can also be produced in this way.
Illustration by brgfx on Freepik
Primordial Hydrogen
Primordial hydrogen is the hydrogen that was created directly after the Big Bang. It was formed in the first few minutes after the universe was created during the so-called Primordial Nucleosynthesis. There are indications that some of this “primordial hydrogen” could be stored deep in the earth’s mantle or core.
4. Under What Geological Conditions Does Natural Hydrogen Acumulate in the Subsurface?
Our understanding of the accumulation of natural hydrogen in the subsurface is still subject to many unanswered questions. However, what is clear is that in order for hydrogen to be stored in usable quantities, it must be stored in geological formations that have certain geological characteristics. Such sets of necessary conditions are referred to as play concepts. At present, geologists assume the existence of a number of very different play concepts, but further research is required to determine their validity. The most important concepts are:
Natural Gas-Like Reservoirs
Porous and permeable rocks (e.g. sandstone or carbonate) that are sealed by an impermeable caprock (e.g. claystone or salt). Similar to natural gas fields, hydrogen can remain trapped there over geological time periods. Such reservoirs are also known for helium. The latter has a similar molecular size to the hydrogen molecule.
Ophiolites and Ultramafic Rocks
In regions where serpentinite is abundant, hydrogen can not only be produced but also stored in cracks and fractures. However, the pore spaces in such rocks are relatively small, so the storage capacity is limited.
Salt Domes and Caverns
Salt formations, e.g. salt dome structures, are particularly well suited for gas storage. Salt is impermeable, so even the small hydrogen molecule has difficulty migrating. We see examples of this in northern Germany and Poland.
Aquifers
In water-bearing layers, so called aquifers, hydrogen can be stored in dissolved form. Today, we know of such deposits in aquifers at different depths, for example in Mali in Africa, in the United States in Kansas and Nebraska, but also in Southern Australia. Many of the known deposits of natural hydrogen are found in such water-bearing formations.