Translated from the original German version: Der Traum vom weissen Wasserstoff

There is a lot of hype about a future hydrogen economy. It is tempting to consider this clean energy source, which leaves nothing behind when it burns except water vapor, as a replacement for fossil fuels. Hydrogen (H₂) can be produced in various ways, primarily by electrolysis, the electrical splitting of water. However, it would be even more elegant to find hydrogen in its free form, called natural or geological hydrogen, and extract it directly from the earth’s interior, similar to natural gas. In my opinion, the probability of economically viable success is likely to be low. 

(In saying this, I am aware that fifty years ago, no one could have imagined that today every child would walk around with a high-performance computer in its pocket, be able to access global knowledge in seconds via chat GPT, and communicate around the world via video. So my negative view of geological hydrogen may well be wrong). 

I think it is perfectly legitimate to test the concept. (Stay curious, stay foolish) That’s how inventions come about. The idea of finding and producing free hydrogen underground has attracted exploration companies worldwide. If this is done with money from risk-taking entrepreneurs, that’s great. But when support is subsidized by activist governments, i.e., with taxpayers’ money, alarm bells start ringing in my head. It is my long experience that state administrations, even with the help of experts, are not able to properly assess the risks involved.

What are these risks? 

Free hydrogen exists in the subsurface. This is not surprising because it is the simplest and most abundant element in the universe. And that is precisely what makes it so seductive. Hydrogen can be detected almost everywhere in the earth’s crust and mantle in infinitesimally small quantities. Over the entire volume of the earth, this still amounts to gigantic quantities. But it is extremely diffusely distributed. There are several geological processes that produce hydrogen. The best known is the reaction of water with ultramafic^[1] rocks, such as peridotite. Such rocks are mainly found in the earth’s mantle, below the continental plates from 30 km and below the oceans from 5 to 10 km depth to about 2900 km depth.

As a reminder, it is not yet technically possible to drill deeper than 12 km. Although deviated wells can be longer, they do not go deeper. Natural gas wells usually do not reach much deeper than 3 km. And drilling costs do not increase linearly with depth, but exponentially. It takes lucrative deposits to drill that deep.

Iron-rich minerals transform into serpentine at the high temperatures and pressures found in the earth’s mantle, releasing hydrogen in the process. Hydrogen can also be formed underground by the radiation of radioactive minerals, a process called radiolysis. However, free hydrogen is highly reactive and very volatile. It is therefore unlikely that economically viable volumes will accumulate, as is the case with natural gas.

In the exploration projects that I follow, I have noticed that the hydrogen detected is always only trace amounts. And that in most cases, we can only speculate about the history of its formation and origin. For example, traces of hydrogen were found in cores of old exploration wells on the York Peninsula in South Australia. Incidentally, in Australia, it is called Golden hydrogen. Interestingly, the hydrogen is not evenly distributed in the rock samples found there. A certain concentration process seems to have taken place.

The hydrogen found on the York Peninsula probably come from the aforementioned serpentinization process because it is a geological province rich in iron ore. Iron ore is mined there on a large scale.

In contrast to natural gas (methane), hydrogen is a much more volatile and reactive gas. An accumulation of free hydrogen, trapped by impermeable layers, is unlikely. It can not only escape through the smallest fissures but also creeps through the least permeable shale formations, which do not allow natural gas to escape. Or the hydrogen forms hydroxide minerals with metal oxides that are formed during weathering processes. Dissolved in water, economically interesting accumulations can hardly occur. The solubility at 20°C under atmospheric conditions is already low (1.6 ml/l). It decreases further at higher temperatures, as is usually the case in the subsurface.

Hydrogen can be found trapped in the crystal lattices of amphiboles, micas, and serpentine. Or it can occur as a free gas in loose crystal lattices such as in zeolites. In hydrous minerals, hydrogen can also be weakly integrated into the structure via hydrogen bonds. The exploration seems to be focussed on such inclusions.

But in these forms of bonding, the extraction of free hydrogen would require a mechanical breaking up or a chemical dissolution of rock, which always involves a greater expenditure of energy. And to make production economical, a mineable deposit would have to show a substantial concentration of such mineralization.

As already indicated, I lack the imagination to see how white hydrogen can be produced in economic quantities. I am happy to be proven wrong. I remain curious. However, I would advise against spending taxpayers’ money on it.

^[1] This refers to rocks that are extremely rich in magnesium and iron but contain very little silicon dioxide.