What are the colors of hydrogen?
As we can imagine, the chemical element called hydrogen (one proton plus one electron, and atomic number 1) has no color, but from a practical point of view in industry, hydrogen is given a color chart depending on the way it has been obtained.
Hydrogen is the most abundant element in the universe. We may wonder why on our planet it hardly appears in free form and it is necessary to obtain it. The explanation is that on Earth hydrogen appears united with oxygen, forming water: H20. Water is the source, in practice inexhaustible, to which we have to resort in order to be able to release hydrogen and use its energy potential.
Depending on the industrial process by which it was obtained, we can distinguish the following types, or colors, of hydrogen.
It is the one that has been obtained by release through a non-polluting process, it can also be called clean hydrogen.
Using another terminology, which is very popular in the environmentalist world, we could also say that this hydrogen comes from processes in which only renewable energies have been used, such as wind or solar energy, to cite two examples.
Black or brown hydrogen
It comes from the gasification of coal. It goes without saying that it is the most hated by environmentalists, since it is clear that, even if this hydrogen is subsequently used in a clean way, it was born with a strong pollutant load and has a negative balance as an energy carrier.
It is obtained from methane, or natural gas. At the moment almost seventy million tons have this origin and we go back to the paradox that no matter how clean the use of this hydrogen is, it is born with the burden of the pollutant bill that previously involved the combustion of the gas: if there is no natural gas there is no gray hydrogen, so ultimately its cleanliness is very debatable.
This is the one that, whatever its origin, undergoes a complementary process of capturing the carbon released in its production. This is a happy but misleading ending, since the addition to the cycle of an environmentally very costly pollution process makes the final balance negative. More energy is expended than can be obtained later with the hydrogen released.
It is the one obtained from nuclear energy. Horror! some still say. Promising, say the truly progressive.
A necessary balance
We are approaching the final conclusions: hydrogen is an excellent means of obtaining industrial energy, but to obtain it from water it is necessary to develop costly processes, in some of which more is spent than is obtained; moreover, some of these methods can be very polluting.
To these components of the equation must be added a not insignificant factor: when hydrogen completes its processes as an industrial fuel, it will not release carbon dioxide, like fossil fuels, but water vapor, which is one of the gases with the greatest greenhouse effect. Let's see how the President of the Government explains this in his role as enemy number one of so-called "climate change" when he intends to become a world leader in the commercialization of green hydrogen.
Green hydrogen: solution or smoke and mirrors?
The European Union seems willing to encourage research into green hydrogen as an energy source for the future, but we are still far from considering these processes as a panacea for our industrial and environmental problems.
The unabashedly optimistic stance of our president in affirming that we will be "the main supplier of green hydrogen for Europe" is nothing more than a smoke and mirrors operation, even if that smoke is water vapor.
It's very simple for plants
Green plants constantly perform the miracle of clean decomposition of water to obtain hydrogen, in their case flawlessly clean: they do it using solar energy, which is why biologists call the process "water photolysis".
The conclusion was reached by experiments that have gone down in the history of science as particularly ingenious. Let us see how they developed.
It was known that if a green plant is kept in conditions of controlled atmosphere and water is supplied in irrigation, after a certain time its atmosphere will have been depleted of CO2 and will have gained oxygen.
The conclusions at first glance were misleading. It seemed logical that the plant would absorb all the CO2 in order to use its carbon and give off the excess oxygen, but this was not the real solution, as radioactive isotopes showed.
By enclosing a plant in a controlled atmosphere and irrigating it with water labeled with the oxygen isotope 18, it was found that this was the oxygen it gave off, not the oxygen contained in the CO2 absorbed by the leaves. It is curious that oxygen, which allows animal respiration, is for plants simply a by-product.
It was demonstrated that green plants absorb all the atmospheric CO2, thus converting inorganic carbon into organic carbon; what they need from water is hydrogen, which they release from it thanks to the solar energy captured by chlorophyll, their green pigment.
This is man's great challenge: to imitate the chlorophyll pump, that is, to capture the sun's energy and use it. Unfortunately, we animals do not have chlorophyll or anything like it.
In the meantime, we will continue researching; scientists with the modesty that characterizes them, politicians with the arrogance that in Extremadura they compare to a "hollow turkey".
So we will continue to sell green smoke... for the time being.
Miguel del Pino, Professor of Natural Sciences.