Grey, blue, green... understanding the rainbow of hydrogen colours

Hydrogen production: matching each colour with its impact

Grey, brown and black: hydrogen from hydrocarbons

By definition, hydrocarbons are compounds containing carbon and hydrogen atoms, which need to be separated in order to extract only the hydrogen. At the present time, nearly all of global hydrogen demand is fulfilled via processes that use hydrocarbons. "Grey" hydrogen is created from natural gas using steam reformation. "Brown" and "black" hydrogen is produced via a coal gasification process.

Blue: capture the carbon emissions from grey hydrogen!

"Blue" hydrogen is produced from a variant of the steam reforming process in petrochemical plants fitted with carbon capture, utilisation and storage systems (CCUS). The carbon emitted by the process is captured and either put into long-term storage or reused for industrial purposes.

Pink, yellow and green: hydrogen from water electrolysis

Hydrogen is abundantly available in water. Hydrogen can be produced on an industrial scale by means of a physically simple electrolysis process that involves passing a current through the water to "split" its H₂O molecule.

In the case of pink hydrogen, the electricity required for the process is supplied by nuclear power plants. In the European Union, nuclear energy was included as a sustainable energy production source in the EU taxonomy adopted in July 2022.

Yellow hydrogen is also produced through electrolysis using electricity from the local grid, which may therefore be produced from fossil, nuclear or renewable energy.

Green hydrogen is made from renewable electricity (solar, wind, hydropower, etc.).

What about "dark green" hydrogen? The special case of biomass

Just like hydrocarbons, the organic molecules in biomass are rich in carbon and hydrogen. As such, hydrogen can be produced by fermenting or gasifying agricultural, forest, agribusiness and household waste. This technology is said to be "carbon neutral". The carbon emitted by the process is equivalent to the carbon that would have been released into the atmosphere if the waste had been left to degrade naturally.

What challenges face low-carbon hydrogen production?

The reason why the "colour" of the hydrogen is so important is that this chemical element will play a key role in driving the energy transition. In its Net Zero Emissions by 2030 scenario, the International Energy Agency (IEA) is expecting global hydrogen demand to almost double to over 175 Mt a year. According to some predictions, that figure will top 1,200 Mt by 2050. Such explosive growth in demand can only be sustained if green and blue hydrogen is massively developed at the expense of grey hydrogen. To deploy enough CCUS facilities and electrolysers to achieve a pathway to net zero by 2050, a study by consulting firm McKinsey estimates that some $700 billion will need to be invested in hydrogen by 2030.

VINCI and low-carbon hydrogen production

Extract from the Leonard conference with Bruno Nicolas, Director of the Actemium brand (VINCI Energies), Hugues Seutin, Director of Hyfinity (VINCI Construction), and Pascal Baylocq, President and CEO of Geostock (VINCI Construction).