H2 Hydrogen
What is hydrogen?
Hydrogen is a clean alternative to methane, also known as natural gas. It's the most abundant chemical element, estimated to contribute 75% of the mass of the universe.
Here on earth, vast numbers of hydrogen atoms are contained in water, plants, animals and, of course, humans. But while it's present in nearly all molecules in living things, it's very scarce as a gas – less than one part per million by volume.
Hydrogen can be produced from a variety of resources, such as natural gas, nuclear power, biogas and renewable power like solar and wind. The challenge is harnessing hydrogen as a gas on a large scale to fuel our homes and businesses.
What is the difference between blue hydrogen and green hydrogen?
Blue hydrogen is produced from non-renewable energy sources, by using one of two primary methods. Steam methane reformation is the most common method for producing bulk hydrogen and accounts for most of the world's production. This method uses a reformer, which reacts steam at a high temperature and pressure with methane and a nickel catalyst to form hydrogen and carbon monoxide.
Alternatively, autothermal reforming uses oxygen and carbon dioxide or steam to react with methane to form hydrogen. The downside of these two methods is that they produce carbon as a by-product, so carbon capture and storage (CCS) is essential to trap and store this carbon.
Green hydrogen is produced by using electricity to power an electrolyser that splits the hydrogen from water molecules. This process produces pure hydrogen, with no harmful by-products. An added benefit is that, because this method uses electricity, it also offers the potential to divert any excess electricity – which is hard to store (like surplus wind power) – to electrolysis, using it to create hydrogen gas that can be stored for future energy needs.
The hydrogen colour spectrum
From green to pink hydrogen, we reveal the rainbow of hydrogen colours and the different types of technology used to produce each.
But isn't hydrogen a colourless gas?
Yes, hydrogen is an invisible gas. So, somewhat confusingly and despite their colourful descriptions, there is no visible difference between the different types of hydrogen.#
Why is a colourless gas given so many colourful terms?
Green hydrogen, blue hydrogen, brown hydrogen and even yellow hydrogen, turquoise hydrogen and pink hydrogen. They're essentially colour codes, or nicknames, used within the energy industry to differentiate between the types of hydrogen.
Depending on the type of production used, different colours are assigned to the hydrogen. But there is no universal naming convention and these colour definitions may change over time, and even between countries.
We're currently used to a blue flame from gas, so what colour will a hydrogen flame be?
The industry has not yet reached a consensus on this, but it will be the most obvious difference for people who've been used to seeing a blue gas flame inside their boilers or when igniting their hobs. The flame colour for hydrogen would be specifically added. Are you ready for a green flame?
Here's our guide to unlocking the current hydrogen colour code.
Green hydrogen
In the kaleidoscope of hydrogen colours, green hydrogen is the one produced with no harmful greenhouse gas emissions. Green hydrogen is made by using clean electricity from surplus renewable energy sources, such as solar or wind power, to electrolyse water. Electrolysers use an electrochemical reaction to split water into its components of hydrogen and oxygen, emitting zero-carbon dioxide in the process.
Green hydrogen currently makes up a small percentage of the overall hydrogen, because production is expensive. Just as energy from wind power has reduced in price, green hydrogen will come down in price as it becomes more common.
Blue hydrogen
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. The output is hydrogen – but also carbon dioxide as a by-product. That means carbon capture and storage (CCS) is essential to trap and store this carbon.
Blue hydrogen is sometimes described as 'low-carbon hydrogen' as the steam reforming process doesn't actually avoid the creation of greenhouse gases.
Grey hydrogen
Currently, this is the most common form of hydrogen production. Grey hydrogen is created from natural gas, or methane, using steam methane reformation but without capturing the greenhouse gases made in the process.
Black and brown hydrogen
Using black coal or lignite (brown coal) in the hydrogen-making process, these black and brown hydrogen are the absolute opposite of green hydrogen in the hydrogen spectrum and the most environmentally damaging.
Just to confuse things, any hydrogen made from fossil fuels through the process of 'gasification' is sometimes called black or brown hydrogen interchangeably.
Japan and Australia announced a new brown coal-to-hydrogen project recently. This project will use brown coal in Australia to produce liquefied hydrogen, which will then be shipped to Japan for low-emission use.
Pink hydrogen
Pink hydrogen is generated through electrolysis powered by nuclear energy. Nuclear-produced hydrogen can also be referred to as purple hydrogen or red hydrogen.
In addition, the very high temperatures from nuclear reactors could be used in other hydrogen productions by producing steam for more efficient electrolysis or fossil gas-based steam methane reforming.
Turquoise hydrogen
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, turquoise hydrogen may be valued as a low-emission hydrogen, dependent on the thermal process being powered with renewable energy and the carbon being permanently stored or used.
Yellow hydrogen
Yellow hydrogen is a relatively new phrase for hydrogen made through electrolysis using solar power.
White hydrogen
White hydrogen is a naturally-occurring geological hydrogen found in underground deposits and created through fracking. There are no strategies to exploit this hydrogen at present.
The future of hydrogen as energy
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.
Is hydrogen already being used as a fuel?
Yes. There are already cars that run on hydrogen fuel cells. In Japan there are 96 public hydrogen refuelling stations, allowing you to fill up just as you would with petrol or diesel and in the same time frame as a traditional fuel car. Germany has 80 of these hydrogen stations and the United States is third with 42 stations.
Hydrogen is also an exciting lightweight fuel option for road, air and shipping transportation. The international delivery company DHL already has a fleet of 100 'H2 panel vans', capable of travelling 500kms without refuelling.
What are the potential brakes to speeding up hydrogen use as a clean energy?
For hydrogen to be a viable alternative to methane, it has to be produced at scale, economically and the current infrastructure needs to be adapted.
The good news is that hydrogen can be transported through gas pipelines, minimising disruption and reducing the amount of expensive infrastructure needed to build a new hydrogen transmission network. There would also be no need for a culture change in our home lives, as people are used to using natural gas for cooking and heating, and hydrogen energy equivalents are emerging.