The colours of hydrogen

Hydrogen itself is has no colour. The colourless gas is an efficient, climate-neutral energy source for heating, as it has a much higher thermal value than, for example, fuel oil or natural gas, and its combustion does not produce any substances that are harmful to the environment or the climate. Hydrogen is also easy to store, allowing surplus electricity to be put to good use. Despite these positive characteristics and the major contributions that hydrogen makes to climate protection, hydrogen production needs to be examined more closely with respect to climate protection. The subdivision of hydrogen into different colours is intended to provide information about how the hydrogen is produced, the energy sources used and the climate neutrality of the hydrogen.

Green hydrogen is the term used to describe hydrogen that is produced on a CO2-neutral basis through the electrolysis of water. During electrolysis, water is split into its constituent elements of oxygen and hydrogen. The electricity this requires is generated from renewable energy sources, for example wind energy, hydropower or solar energy. Since neither the production of green hydrogen nor the end products hydrogen and oxygen are harmful to the environment or the climate, green hydrogen is climate-neutral. That is why EWE is focusing on this variant.

In order to produce large amounts of green hydrogen, we need considerably larger electricity generation capacities from renewable energies. In addition, electricity prices must be affordable so that green hydrogen is also economically competitive. An important lever for achieving this would be the reform of the charges and levies on electricity.

Turquoise hydrogen is created by a thermal process in which natural gas is broken down with the help of methane pyrolysis into hydrogen and solid carbon. If the carbon remains permanently bound and is not combusted during further processing, this process is also CO2-neutral. The reactors or blast furnaces used to split the methane would also have to be powered by renewable energies. Another factor in the analysis of turquoise hydrogen is that the extraction of the raw material, natural gas, often also produces emissions. As a result, turquoise hydrogen is usually not completely climate-neutral when it comes to the entire production process and the downstream processing of carbon as a by-product.

Blue hydrogen is generated from the steam reduction of natural gas. During this process, natural gas is split into hydrogen and CO2. In this steam reforming process, however, the carbon dioxide is not emitted into the atmosphere; instead, it is stored or processed industrially. Carbon Capture and Storage (CSS) technology can be used to store CO2 underground. This means that blue hydrogen does not produce any CO2 emissions either. However, the long-term impacts of storage are uncertain and leakage can still negatively affect the environment and climate.

Grey hydrogen is the exact opposite of green hydrogen, as it is not climate neutral. Grey hydrogen is obtained by steam reforming fossil fuels such as natural gas or coal. In this process, the waste product CO2 is released directly into the atmosphere. Ten tonnes of carbon dioxide are produced for each tonne of hydrogen extracted, so grey hydrogen is harmful to the climate. Grey hydrogen is also the term used when electricity from fossil fuels and non-renewable energy sources is used instead of eco-power for the electrolysis of water.

Sometimes other colours are ascribed to hydrogen, based on how it is produced. For red, pink and violet hydrogen, the electrolysers are driven by nuclear power. Yellow hydrogen refers to hydrogen production from a mixture of renewable energies and fossil fuels. Hydrogen that is merely a waste product of other chemical processes is referred to as white hydrogen. The use of coal as a fuel produces brown hydrogen.

Hydrogen is considered to be an efficient, climate-neutral energy carrier. Only water vapour is produced during combustion and no environmentally harmful substances are released. Hydrogen is also easy to store, so electrolysers can use surplus electricity, such as from renewable energies, for the viable production of hydrogen. This makes hydrogen a promising and sustainable energy carrier in terms of environmental and climate protection. However, we need to undertake a more sophisticated approach to the production and extraction of hydrogen.

The differing processes, by-products and energy sources used influence how climate-neutral hydrogen production actually is. The classification of hydrogen by colour into green, turquoise, blue and grey hydrogen makes it possible to draw conclusions about how climate-neutral the hydrogen is in each case. Both industry and companies should expand the use of renewable energies so that they can increasingly make use of green hydrogen in the future. This is the only option that is absolutely climate-neutral and serves to effectively protect the climate.