The Colours of Hydrogen: What it means to be Green

green hydrogen

The potential of Hydrogen as an alternative source of energy is currently a hot topic for governments, energy suppliers, consumers and investors alike.

Hydrogen is the simplest element known to man, a major part of every aspect of life. It makes up around 75% of the sun, is of course a key ingredient in water and is a major component of gas, coal and other fuels.

Companies hope to power transport and industry with it, governments look to diversify town and city supply grids with sources of energy including hydrogen and at home, people are looking to potentially use hydrogen to generate power and water in an environmentally friendly way.

The UK is looking to invest billions in green and blue hydrogen in the race to be carbon neutral by 2050, with many other countries investing in large and small-scale schemes.

Whilst the first element is in fact a colourless gas, the industry refers to hydrogen of different colours, classified according to origin and the method by which it is obtained:

With the colourful array of hydrogens on the market claiming to represent the future of power, we thought it would be helpful to share a straightforward guide to the different types and what they mean for a green energy future.

The Hydrogen Spectrum

Probably of greatest interest are the blue, grey and green sources of hydrogen but there are plenty more up and down the energy supply chain.

White Hydrogen

White hydrogen is naturally-occurring, obtained from underground sources and by the controversial fracking of shale gas.

There is very little hydrogen in our atmosphere so it all comes from underground, but there is no current commercial application for it.

Grey Hydrogen

Globally, the most common form of hydrogen production which uses a steam methane reformation process to create and capture the hydrogen, but CO2 is released as part of the process.

Blue Hydrogen

Blue hydrogen is similar to grey hydrogen but additional steps in its production processes make it more eco-friendly than grey: It is extracted from common natural gas by a process of steam reformation, using hot water to create steam and hydrogen gas.

Carbon dioxide is also produced but this is then captured and stored underground to prevent CO2 emissions. This results in a lower carbon energy but with the considerations of greater expense and of course the carbon storage requirements.

Green (our favourite colour) Hydrogen

The current poster-child of the environmentally friendly movement, green hydrogen production results in net zero emissions: Using electricity from renewable sources and water, it can be produced using surplus energy from on or off the grid.

By electrolysing water, the H2O is split into hydrogen and oxygen.

As with early solar and wind power schemes, the process is currently expensive but it will come down in price as technologies develop and as business and consumer interest in zero-carbon grows.

If the power source for electrolysis in this instance is solar power, it is sometimes referred to as yellow hydrogen.

Red Hydrogen

Red hydrogen (sometimes called pink or purple hydrogen) can be generated using the same processes as green or grey hydrogen But the power source is nuclear energy or the steam from it.

Politically, nuclear remains a highly-charged option, but safe operation can deliver useful green power and byproducts like hydrogen for the wider economy.

Turquoise Hydrogen

An experimental entry on the list, this uses an industrial process that starts with methane to create hydrogen, pollution-free by removing the carbon from the natural gas.

It is a simple process, but one that is unproven at scale and requires carbon capture to make it eco-friendly. Keenly talked about in research circles, this could well prove popular in the future.

Black Hydrogen

As previously mentioned, natural hydrogen exists in coal, so by a process of gasification, the hydrogen can be extracted.

However, as the name suggests this is not an eco-friendly option and is used in high-coal economies. Also known as brown hydrogen, its source means it cannot be considered to be clean energy and it is likely to be phased out as we move away from the carbon economy.

Hydrogen from the sea

You may have noticed that hydrogen from seawater (perhaps to be called ‘deep blue hydrogen’) is missing from this list.

The reason for its omission?

Production is scarce, as yet, because of the requirement to first desalinate or use other methods to clean the water.

Scientists are working on ways of making it commercially viable using solar, wind or tidal power with Saudi Arabia looking to invest $5 billion in a plant.

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