Raw materials: Climate neutrality – hydrogen from the earth

The hydrogen industry is on the rise. The explosive gas could replace coke in steel production in the future and has long been an important raw material for the chemical industry. So far, it has met its needs by extracting hydrogen on a large scale from the main component of natural gas, methane. However, there is a catch: a methane molecule (CH₄) is made up of one carbon and four hydrogen atoms, so the manufacturing process results in significant amounts of carbon dioxide (CO₂). Hydrogen production is still anything but climate-friendly, because CO₂ remains in the atmosphere for several millennia and contributes significantly to the warming of the global climate.

An alternative to this is the production of “green hydrogen,” which is already being done on a very small scale using renewable electricity. The “oxyhydrogen gas,” as we know it from school lessons, is obtained from water via electrolysis. As is well known, the latter is a compound of hydrogen and oxygen atoms. The only waste product that is created is pure oxygen.

The advantage of this solution would also be that the manufacturing process could also be used to stabilize the power supply. On the one hand, by limiting electrolysis to the times when a particularly large amount of wind or solar power is generated. On the other hand, hydrogen is used as a storage medium and burned in gas power plants when there is not enough wind and the sun doesn’t have much to offer. However, this would not only require more electrolysers, but also more storage, according to the Energy Storage Initiative, a gas industry organization. Due to the lower density of hydrogen, the existing natural gas storage facilities would not be sufficient.

Apart from that, hydrogen has one significant advantage: when it is burned, only water vapor is produced. It is therefore more or less climate neutral as long as no coal or natural gas electricity is used to produce it. And as long as its use does not result in a sustained increase in air humidity on a large scale. Water vapor is also a greenhouse gas, albeit a short-lived one.

A disadvantage of electrolysis is that it involves significant energy losses. It would of course be better if hydrogen could be mined as a raw material like natural gas, coal or petroleum. And there are actually natural occurrences of hydrogen, although they have so far met with little economic interest.

Large occurrence in Lorraine

This is now beginning to change with the general hype about gas and the search for climate-friendly energy sources. This shows once again that our knowledge of the raw materials that the planet has to offer mostly depends on economic interests. Until now, hydrogen deposits were considered rare and little was known about their extent. However, there is now increasing evidence that there is significantly more of this “white hydrogen” than previously assumed.

In Lorraine, France, an estimated 46 million tons of hydrogen are stored deep underground, writes the Austrian newspaper “Der Standard”. For comparison: around 90 to 100 million tons are currently consumed worldwide per year, but according to the International Energy Agency, global electrolysis capacities would only be expanded to produce an annual production of 30 million tons of hydrogen by 2030 under the current planning status, according to the International Energy Agency. If all plans are actually implemented and not destroyed by rising capital and equipment costs. In view of this, the production of geological hydrogen seems attractive.

In the USA there are already the first signs of a real hydrogen boom. The US newspaper Colorado Sun recently reported that an unnamed private company has raised $250 million in bonds and loans to search for the promising energy source. Meanwhile, the US Department of Energy has distributed $20 million to various institutes, universities and private companies for the search for hydrogen. Larger deposits are also reported from Albania, Australia and Spain.

First found in 1987

In Mali, West Africa, where there is currently the only commercially used source of the gas, a hydrogen reservoir located relatively close to the surface was opened in the village of Bourakébougou in 1987 when a well drilling failed. However, at first it was closed again and ignored. It was only two decades later that the energy source was remembered, which today drives a small power plant and thus supplies the village with electricity. The operating company Hydroma has been searching for additional hydrogen sources for over ten years using test drilling and seismic methods and has already found one. None have been developed yet, but Hydroma is already exploring ways to export hydrogen in collaboration with German companies and institutes.

But how do hydrogen deposits actually form? Like conventional energy sources, hydrogen can be produced from dead biomass under high pressure and heat. However, there are often various geological processes in which hydrogen is usually produced many kilometers below the earth’s surface and then rises through cracks and breaks in the plates of the earth’s crust. Here and there it collects under impermeable layers, such as old salt deposits, or in porous sandstone and karst, as in Bourakébougou.

Byproduct of radioactive decay

One such geological process, for example, would be so-called radiolysis. In many rocks there are traces of radioactive isotopes of uranium or thorium 230, which in turn is a decay product of uranium. When the isotopes decay, high-energy radiation is emitted, which can break down water molecules into their components and thus also release hydrogen. The rate of decay is described by the term half-life. When this has passed, half of the isotopes originally present have decayed.

The half-lives of the various isotopes range from a few tens of thousands to several million years. In the case of uranium 238, it is over four billion years old, which is why it is by far the most common uranium isotope on Earth. Different types of atoms of an element are called isotopes, all of which have the same chemical properties but differ in the number of neutrons in their nuclei. Some types of isotopes, such as those mentioned above, are unstable. This means that they eventually decay and release radioactive radiation in various forms.

Other and probably more significant examples of the geological genesis of hydrogen are various forms of iron oxidation at high temperatures and in the presence of water. This also includes the so-called serpentinization, which occurs in mafic, i.e. volcanic, rock. The water molecules are broken up and the oxygen contained in the water combines with the iron in the rock while the hydrogen is released.

Iron-bearing rocks are widespread on all continents and should not be confused with iron ore. In this respect, geologists are convinced that they can detect hydrogen in many countries. Studies from Bourakébougou also show that the deposit there is very dynamic and is filled by inflows from deeper underground at the same rate as hydrogen is removed. This means that geological hydrogen could even be viewed as a renewable energy source, at least there.

In all of this, however, a few things should not be forgotten. The hydrogen reserves, for example, will not be inexhaustible in the long term, and it is still unclear how quickly consumption will exceed geological formation.

Co-occurring with methane

Above all, the safety for the climate and the environment would still have to be proven. In the Lorraine deposits, hydrogen occurs in a mixture with methane, which is not surprising. Conventional natural gas can also contain a few percent of hydrogen. However, from a depth of 3,000 meters in France the hydrogen content seems to be at least 90 percent. The specialist journal “Nature” reported last summer that the source in Mali had a methane content of one percent.

So the question remains what happens to this methane when it is mined. After all, it is a fossil energy source that can be burned to further enrich CO₂ in the atmosphere. Simply releasing it into the air wouldn’t really be a better alternative, because methane is much shorter-lived than CO₂, but a much more effective greenhouse gas. After 100 years it has largely disappeared, but during this time it is around 20 times more effective than CO₂if you compare individual molecules.

Despite all the euphoria that will soon spread around “white hydrogen,” especially among the old energy companies, a few of the old questions remain.