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Chasing colourless hydrogen’s renewable energy rainbow

Hydrogen has seen the proverbial alternative energy gold rush in recent years as many regard it as the clean energy fuel of the future. 

Its uses in the energy space includes the ability to generate electricity, power industry, provide heat for homes/businesses and power vehicles.

Other uses include:

  • To make ammonia for agricultural fertiliser;
  • To remove sulphur from fuels during the oil-refining process;
  • To hydrogenate oils to form fats, for example when making margarine;
  • As a protective atmosphere for making flat glass sheets; and
  • As a flushing gas during the manufacture of silicon chips.

It was first produced artificially in the 16th Century. The first fuel cells and electrolysers were made in the 19th Century.

It is a clean alternative to methane and is the most abundant chemical element, estimated to contribute 75% of the mass of the universe. Vast numbers of hydrogen atoms are contained in water, plants, animals and humans.

The Royal Society of Chemistry says most hydrogen is produced by heating natural gas with steam to form syngas (a mixture of hydrogen and carbon monoxide). The syngas is separated to give hydrogen. Hydrogen can also be produced by the electrolysis of water.

Hydrogen is a colourless, odourless gas and has the lowest density of all gases.

Despite it being colourless it has been assigned a myriad of colours within the energy industry to differentiate between the types of hydrogen that can be produced.

What are the different colours of hydrogen to be made out there?

Some of the colours include green hydrogen, blue hydrogen, grey hydrogen, brown hydrogen, yellow hydrogen, turquoise hydrogen and pink hydrogen.

There is no uniform naming convention and the colour definitions may evolve and differ between countries, but the general rule of thumb seems to be the lighter and brighter colours are assigned to processes that are less ghg intensive.

These are, however, generally accepted definitions as per nationalgrid


Green hydrogen is made by using clean electricity from surplus renewable energy sources, such as solar or wind power, to electrolyse water.


Blue hydrogen is produced mainly from natural gas, using a process called steam reforming, which brings together natural gas and heated water in the form of steam.


This is the most common form of hydrogen production. Grey hydrogen is created from natural gas, or methane, using steam methane reformation.

Black and brown

Using black coal or lignite (brown coal) in the hydrogen-making process, these black and brown hydrogen are the opposite of green hydrogen and the most environmentally damaging.


Pink hydrogen is generated through electrolysis powered by nuclear energy. It’s also been referred to by some as purple, or red. Though, if we’re really splitting atoms here, red hydrogen would be produced through the high-temperature catalytic splitting of water using nuclear power thermal as an energy source. And, then pink is technically generated through the electrolysis of water by using electricity from a nuclear plant. (Purple – combines nuclear power and heat into thermochemical electrolysis.)


This is a new entry in the hydrogen colour charts and production has yet to be proven at scale. Turquoise hydrogen is made using a process called methane pyrolysis to produce hydrogen and solid carbon. In the future, it may be valued as a low-emission hydrogen, if the thermal process is powered with renewable energy and the carbon is permanently stored or used.


Yellow hydrogen is a relatively new phrase for hydrogen made through electrolysis using only solar power (as opposed to green that uses multiple renewable energy sources).


White hydrogen is a naturally occurring, geological hydrogen found in underground deposits and created through fracking.

Hydrogen energy to play a crucial role in reaching net-zero and reducing fossil fuel reliance

“In the future, some hydrogen colours may fade in importance and others burn brighter.

“What’s certain is that the hydrogen rainbow will play a significant role in reaching net-zero, as we reduce our historical reliance on fossil fuels and look to green alternatives to power our homes, businesses and transport,” said nationalgrid.

Sunita Satyapal, Director of the US’s EERE (Energy Efficiency and Renewable Energy) Hydrogen and Fuel Cell Technologies Office, said hydrogen is the simplest and most abundant element on earth.

“It consists of only one proton and one electron. Hydrogen can store and deliver usable energy, but it doesn’t typically exist by itself in nature and must be produced from compounds that contain it.”

“Hydrogen is an energy carrier, not an energy source and can deliver or store a tremendous amount of energy. Hydrogen can be used in fuel cells to generate electricity, or power and heat.”

Due to their high efficiency and zero-or near zero-emissions operation, hydrogen and fuel cells have the potential to reduce greenhouse gas emission in many applications, she explained. ESI

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ESI Africa
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