Spectral color

Colored Hydrogen: What Color Reveals About Origin

Hydrogen is the gas of the future – also for voestalpine. The Group plans to gradually increase the use of green hydrogen in the steel industry in order to produce CO2-neutral steel by 2050. Although hydrogen is in fact colorless, discussions about its origin are becoming very heated .

The world is turning to hydrogen; it is just as in demand as a means of energy storage or fuel as it is for industrial processes, such as the future climate-friendly steel production of voestalpine (greentec steel). The “H2FUTURE“The project launched at the Linz site proves that sustainable gas production is possible in continuous large-scale operation.

Where does hydrogen come from?

At voestalpine, hydrogen is produced in the most climate-friendly way: using electrical energy from renewable sources, the pilot plant separates water into its components by electrolysis. This produces “green” hydrogen (H2) and the by-product oxygen. Currently, however, the vast majority (approx. 96%) of the global hydrogen demand of approx. 100 million t per year are satisfied by the steam reforming of natural gas, which produces ten times more CO2 for each cubic meter of H2. This process is also known as methane pyrolysis. On the other hand, the pyrolysis of methane (Kværner process), a promising technology, produces solid carbon in addition to hydrogen. However, it also uses natural gas as a raw material.

Water or natural gas, nuclear energy or fossil fuels – the origin and source materials of the electrical energy used as well as color psychology determine the “color” of hydrogen.

The color theory of hydrogen

Because the gas, colorless by nature, has now become colored. Our overview shows the extent of the current spectrum:

  • green hydrogen: Produced with electrical energy generated regeneratively by electrolysis of water.

  • gray hydrogen: produced by steam reforming from fossil fuels; separate CO2 is released into the atmosphere. (We also speak of gray hydrogen when the energy of fossil origin is used for electrolysis).

  • Blue hydrogen: generated as gray hydrogen; however, the captured CO2 is stored (CCS: Carbon Capture and Storage) or processed (CCU: Carbon Capture and Usage).

  • turquoise hydrogen: Produced by pyrolysis of methane. Climate-neutral if the high-temperature reactor runs on renewable energy and the resulting solid carbon is permanently bound.

  • red/pink/purple, also brown hydrogen: produced by electrolysis, for which nuclear energy is used.

  • yellow hydrogen: produced by electrolysis with an energy mix of renewable and fossil sources.

  • white hydrogen: By-product or waste of other chemical processes, for example in the production of chlorine.

From a climate neutrality perspective, all non-green offerings should probably be blacklisted in the long run.

And the transport?

The idea of ​​producing green hydrogen in regions with a reliable and sustainable energy supply, such as North Africa or the Middle East, seems tempting. There remains the question of transport. Huge vessels, such as natural gas tankers with large pressure vessels, could be used. For this, however, the gas must be under high pressure and a large amount of energy is needed for compression – and huge transport fleets would have to be created first.

Hydrogen lines are being considered as another option. But since hydrogen has a low density compared to other energy carriers (e.g. natural gas), extremely large quantities would have to be transported at high pressure. A corresponding quantity of pipelines should be kept available; the speed with which trans- and intercontinental supply lines can become the plaything of geopolitical considerations is now clearly demonstrated.

The production of hydrogen from electrical energy from European wind and photovoltaic power stations would ensure security of supply and promote the use of gas as a temporary energy reserve. The prerequisite would be the willingness to build the corresponding power plants and provide the corresponding electricity networks.

Producing hydrogen closer to the industrial consumer could become a favorable variant – which brings us back to the starting point of H2FUTURE… Colored hydrogen remains an area of ​​research and development as well as various strategic considerations.