Colors of hydrogen: what is the difference?

Hydrogen is a low-polluting fuel with a great calorific value that makes it particularly efficient. It is a gas widely diffused in the universe and on our planet it is not present in its pure state, but only combined with other elements. To obtain hydrogen in its pure state, it is therefore necessary to produce it through certain processes and subsequently store it in a suitable manner to be able to transport it elsewhere.

Hydrogen has no color, it is a transparent element; however, a chromatic attribute is commonly assigned to classify it (gray, blue, green, pink ...) according to the way in which its extraction from different molecules is carried out and according to the environmental impact of this operation.

• Brown (or Black) Hydrogen: is produced by coal gasification. It is the most polluting process of all as it releases CO2 and carbon monoxide.
• White Hydrogen: is generated through a natural geochemical process within the earth's crust. Little carbon emissions are created during its production, but it can have other environmental impacts such as the production of radioactive nuclear waste.
• Gray Hydrogen: is produced from fossil energy sources through a steam reforming process, a reaction created by steam. This conversion process produces CO2 which is released into the atmosphere regardless of whether it starts from the transformation of natural gas or from the gasification of coal and is therefore highly polluting. However, it remains the most widespread production system worldwide (95% of total production).
• Blue Hydrogen: is produced in a similar way to the gray one by steam reforming from fossil sources. Categorized as blue to indicate a lower polluting impact than gray, as CO2 emissions are captured and stored underground or transformed into raw material.
• Turquoise Hydrogen: is produced by pyrolysis, the process that manages to break the chemical bonds of molecules by heating the gas in the absence of oxygen. This process does not produce CO2 emissions but similarly to the white one it can have other environmental impacts.
• Pink Hydrogen (also Purple or Red): is produced by electrolysis through the current produced by a nuclear power plant. Similarly to the green one, it is a totally decarbonised and zero CO2 emission process. Like the white one, however, it can involve other environmental impacts such as the production of nuclear waste.
• Green Hydrogen: is produced through electrolysis from renewable sources such as photovoltaic or wind power. Of all the processes on the list, the cleanest, totally decarbonised and without CO2 emissions, as the waste product is water from the splitting of the molecules.

From this analysis it is easy to understand that choosing green hydrogen is the way to go if we want to protect the environment.

But why is the green hydrogen market struggling to take off on a large scale?
Basically because the quantities of electricity from renewable sources necessary for the production of hydrogen is huge and, with current production systems, up to 40% of this energy is lost during electrolysis, 15% disappears in processing during compression and a further 25% in liquefaction to make it transportable.

All this means that research must continue its path to find viable ways for the production of truly environmentally friendly hydrogen.

Find out more about FERCAM's initiatives for Emission Free transport solutions!