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 colour names are assigned to the hydrogen. But there is no universal naming convention and these colour definitions may change over time, and even between countries.
So what does hydrogen look like?
Hydrogen is an invisible gas. So, despite their colourful descriptions, there is no visible difference between the different types of hydrogen.
Here’s our guide to unlocking the current hydrogen colour code.
Green hydrogen
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 carbon dioxide is also produced as a by-product. So, the definition of blue hydrogen includes the use ofcarbon capture and storage (CCS) 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. Grey hydrogen is essentially the same as blue hydrogen, but without the use of carbon capture and storage.
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.
Last updated: 23 Feb 2023
The information in this article is intended as a factual explainer and does not necessarily reflect National Grid's strategic direction or current business activities.
FAQs
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.
What is the color classification of hydrogen? ›
But isn't Hydrogen a colourless gas? Yes, but each colour corresponds to a different extraction process. The three most common types of hydrogen are grey, blue, and green hydrogen. Grey hydrogen is currently the most common, and the cheapest, form of hydrogen production.
Is hydrogen grey or brown? ›
Grey hydrogen is the most common form and is generated from natural gas, or methane, through a process called “steam reforming”. This process generates just a smaller amount of emissions than black or brown hydrogen, which uses black (bituminous) or brown (lignite) coal in the hydrogen-making process.
What color is hydrogen heated? ›
Hydrogen gas itself is colorless, and its normal state doesn't emit visible light when heated. To produce visible light, you would typically need to excite or combust hydrogen in the presence of other substances, such as in a hydrogen flame or as part of a chemical reaction.
What are the 3 main colors of the hydrogen spectra? ›
Although the gas only emits water when burned, its contribution to achieving net zero emissions by 2050 depends on how it is produced. This video looks at the three different types of hydrogen – gray, blue and green – and examines their environmental credentials.
Is hydrogen green or blue? ›
Green hydrogen is when the energy used to power electrolysis comes from renewable sources like wind, water or solar. Blue hydrogen is hydrogen produced from natural gas with a process of steam methane reforming, where natural gas is mixed with very hot steam and a catalyst.
What is the most common color of hydrogen? ›
Different production methods render colorful classifications of hydrogen, including gray, blue, green, pink, and black/brown hydrogen. Grey hydrogen is the most common and cheapest form of hydrogen.
What is the hydrogen energy spectrum? ›
What is Hydrogen spectrum? The hydrogen spectrum is an important piece of evidence to show the quantized electronic structure of an atom. The hydrogen atoms of the molecule dissociate as soon as an electric discharge is passed through a gaseous hydrogen molecule.
What color sphere represents hydrogen? ›
Ball and stick models are three-dimensional models where atoms are represented by spheres of different colors and bonds are represented by sticks between the spheres. Particular atoms are associated with different colors, for example, black is usually used to represent carbon and white to represent hydrogen.
What color is hydrogen and oxygen? ›
The colours of the various atoms within the molecules follow the standard CPK rules: Hydrogen = White. Oxygen = Red.
The hydrogen rainbow is a handy tool, used within the energy industry, which can be used to decipher the kaleidoscope of hydrogen sources based on the production used and the emissions created in the process.
What four colors does hydrogen emit? ›
This is why hydrogen's emission spectrum is the inverse of its absorption spectrum, with emission lines at 410 nm (violet), 434 nm (blue), 486 nm (blue-green), and 656 nm (red).
What are the 4 types of hydrogen? ›
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.
What color does pure hydrogen burn? ›
Hydrogen burns with a pale blue flame that is almost invisible during daylight hours, so fires are almost impossible to see with the naked eye. Hydrogen fires have low radiant heat, so you can't sense the presence of a flame until you are very close to it (or even in it).
What does hydrogen smell like? ›
In its normal gaseous state, hydrogen is colorless, odorless, tasteless, and is nontoxic which makes it different from every other common fuel we use. By comparison, all petroleum fuels are asphyxiants, and are poisonous to humans. No odorant is added to Hydrogen fuel.
What is the classification of hydrogen? ›
Hydrogen is a gas at room temperature. It has an atomic number of 1, meaning it has one proton in the nucleus. Hydrogen is also classified as a non-metal.
What is the classification of the element hydrogen? ›
Hydrogen is a chemical element with symbol H and atomic number 1. Classified as a nonmetal, Hydrogen is a gas at room temperature.
Which classification group is hydrogen? ›
| Hydrogen |
|---|
| Atomic number (Z) | 1 |
| Group | group 1: hydrogen and alkali metals |
| Period | period 1 |
| Block | s-block |
47 more rowsHydrogen is grouped with alkali metals because it reacts like they do in many compounds, specifically nitrogen, oxygen and halogens. Alternative periodic tables place it off by itself at the top of the table, and some separate H+ as an alkali metal and H- as a halogen, because it also reacts with metals.
