Green, blue and grey: the colours for hydrogen classification

31 Oct 2022

Green, blue and grey, but also purple, white, turquoise and black are some of the colours used to classify hydrogen.

First of all, we would like to point out that hydrogen is a gaseous molecule and is therefore completely transparent.

This colour classification is used colloquially to identify, with immediate simplicity, the technologies used to produce hydrogen and how it is extracted from the molecules in which it is combined.

For its part, Europe sets clear rules for the classification of sustainable hydrogen.

Indeed, with the legislative package on hydrogen markets and decarbonisation, it wants to establish new rules for developing a hydrogen market in the EU.

At this point, let’s find out more about the colour division.

Colours for classifying hydrogen according to the level of emissions released to produce it

All hydrogen molecules are the same, but each has a different impact on the environment.

This is why there is a classification of hydrogen according to the level of emissions released to produce it.

In particular, some of the main colours that fall into the hydrogen classification are:

Green hydrogen

Today, green hydrogen is the most environmentally sustainable and totally zero-emission “type”, as the molecule is extracted from water.

Specifically, green hydrogen is produced through the electrolysis of water.

This technique allows water molecules to be split into oxygen (O) and hydrogen (H2) through electricity.

To achieve this classification, however, electricity must only be supplied by renewable plants, such as hydroelectric, solar or photovoltaic plants.

Purple hydrogen

Purple hydrogen is also extracted from water through electrolysis.

In this case, however, the electricity is not supplied by renewable plants, but is produced by a nuclear power plant.

Consequently, although there are few carbon emissions, other environmental impacts such as the production of radioactive nuclear waste cannot be excluded.

White hydrogen

White hydrogen is generated in the depths of our planet by a natural geochemical process and to use it, it must be extracted.

Its extraction process includes several steps:

  • prospecting and site selection
  • drilling of the earth’s crust
  • extraction and separation of products

Also the production of white hydrogen creates few carbon emissions, but, just like purple hydrogen, it could cause other environmental impacts.

Blue hydrogen

The term blue hydrogen refers to the hydrogen molecule that is extracted from fossil sources such as methane.

In this case, the extraction technique is steam reforming, a process that uses steam to separate hydrogen molecules from natural gas, with subsequent capture of the carbon emissions generated.

For this reason, blue hydrogen is often referred to as low carbon.

It must be remembered, however, that existing solutions only capture 90 per cent of the CO2 and that the extraction of natural gas always results in the loss of molecules to the atmosphere.

Turquoise hydrogen

We speak of turquoise hydrogen when the hydrogen molecule is extracted from methane by pyrolysis

Pyrolysis is a process that involves heating the gas in the absence of oxygen to thermally break the chemical bonds and obtain hydrogen and solid carbon.

This process does not produce direct CO2 emissions, but due to the heating of methane, it could produce high levels of greenhouse gases.

Grey hydrogen

Just like blue hydrogen, grey hydrogen is extracted from fossil sources by steam reforming.

However, unlike the other category, grey hydrogen production does not involve the capture of the carbon emissions generated.

Consequently, unlike the previous forms of production, it releases a high level of CO2 molecules into the air.

Unfortunately, to date, grey hydrogen accounts for more than 90 per cent of the hydrogen produced.

Black hydrogen

Black hydrogen is considered the most polluting.

This is because electricity from coal- or oil-fired power stations is used in the process of electrolysis of the water and, as a result, a lot of CO2 is generated.

Simplifhy is the first Italian supplier of hydrogen solutions

At Simplifhy we offer strategies and systems for the decarbonisation of industry through the use of technologies based on the use of hydrogen as an energy carrier and alternative fuel.

Specifically, we realise customised projects for each reality and for different sectors:

  • mobility and transport
  • industry and steelworks
  • waste treatment and water treatment
  • agriculture and remote sites
  • hospitals
  • ceramics
  • logistics
  • glassworks

Our company’s strength lies in offering customised solutions designed to meet the specific needs of each customer.

Our mission is to simplify the approach to the implementation of hydrogen-based technologies.

This is why we act as a single point of contact during the phases of:

  • design and feasibility study
  • engineering and execution of hydrogen transport projects
  • system installation and maintenance

This is possible thanks to the network of specialised companies we use.

In fact, together with our partners we have built a true hydrogen ecosystem.

Within this ecosystem, different competences interact and integrate in order to offer complete solutions.

Contact us for more information.

In Simplifhy we offer strategies and systems for the decarbonisation of industry, through deployment of Hydrogen-based technologies as an alternative fuel.

Our plants are tailoredaccording to the necessities of each specific project.

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