The colours of hydrogen

©Thomas Gorny - stock.adobe.com

Hydrogen has an important role to play in the debate on climate change. It is currently mainly used for the production of ammonia and for refining products, but in the future it will also be increasingly used in industry such as steel production and as a raw material for fertiliser production. However, it should also contribute to decarbonisation in the transport sector and in the space heating market. As a gaseous energy source, hydrogen can be transported and stored in the existing gas infrastructure. Gas Connect Austria deals intensively with this topic and is working on preparing its network for future hydrogen content.

To date, hydrogen is largely produced from fossil fuels. In the long term, however, ways are being sought to produce hydrogen from renewable sources in order to avoid CO2 emissions. Hydrogen is a colourless gas – depending on the production type, different colours are assigned to the hydrogen.

Green hydrogen is produced by electrolysis of water, using only electricity from renewable energies. Regardless of the selected electrolysis technology, hydrogen is produced free of CO2, since the electricity used comes 100% from renewable sources.

Grey hydrogen is extracted from fossil fuels and is currently the most widely used method. As a rule, natural gas is converted into hydrogen and CO2 (steam reforming) during the production of natural gas through heating. The CO2 generated during production is usually not used.

Blue hydrogen is grey hydrogen, but its CO2 is deposited and stored underground (in English, Carbon Capture and Storage or CCS). The CO2 produced during hydrogen production thus does not enter the atmosphere and hydrogen production can, be considered CO2-neutral on the balance sheet.

Pink hydrogen is obtained by electrolysis through an atomic current.

Turquoise hydrogen is produced by the thermal splitting of methane (methane pyrolysis). Instead of CO2, solid carbon is produced. Prerequisites for the CO2 neutrality of the process are the heat supply of the high-temperature reactor from renewable energy sources, as well as the permanent binding of the carbon.

In the future design of the energy mix of tomorrow, the EU has already set firm ideas on hydrogen. In its strategy, it focuses primarily on green and blue hydrogen, with the green one as the priority. The economic use of blue hydrogen depends heavily on how CO2 is priced in the future and requires an infrastructure for the transport and storage of CO2. The necessary expansion of infrastructure and supply chains is important in paving the way for an even more sustainable and thus green hydrogen economy. In this respect, the EU’s path is, in summary: first blue then green.

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