The Hydrogen Rainbow

by Julia Wild

In 2020 the EU leaders agreed to the Fit for 55 package, which aims at lowering emissions by 55% instead of 40% by 2030, taking 1990 as the base level [1]. The European Commission declared that this decade resembles a make-or-break era defining if the Paris Agreement, committing to keeping global warming at 1.5 degrees will be met [2].

As part of the Fit for 55 package the EU Energy Taxation Directive (ETD), which you can learn more about here, and the Renewable Energy Directive (RED) are revised. These revisions have an impact on the hydrogen (H2) industry [3]. The EU sees a lot of potential in hydrogen to maneuver Europe to its climate neutral state. Therefore, a Hydrogen Strategy has been developed, which focuses on boosting clean hydrogen production and prioritizing hydrogen investments [4]. Due to the strategic importance of hydrogen in the Green Transition of the EU this article will dive into what hydrogen is and what it is used for as well as it will unveil what is behind the hydrogen rainbow.

What is Hydrogen and Where Is It Used?

Around 75% of the mass of the universe consists of hydrogen. Hydrogen is almost exclusively chemically bound, mainly in the form of 1/2O2. Hydrogen is considered a cleaner alternative to methane. Methane is a gas, which is used a lot to produce heat energy, as it is cleaner than coal, however, the burning of methane also leads to carbon dioxide (CO2) emissions and water vapour. Here lies hydrogen’s potential as a cleaner source because when you burn hydrogen your by-product is merely water vapour. However, hydrogen is very scarcely found in the form of gas. Renewables powered by wind and sun, natural gas, nuclear power, biogas and fossil fuels are all suitable to produce hydrogen gas. Currently. the problem lies in producing hydrogen in gas form on a scale large enough to power society and industry [5]. 

Figure 1: the EU’s hydrogen path [4]

Figure 1 above describes the EU’s hydrogen strategy in 3 steps: step 1 scaling-up hydrogen production, step 2 integrating hydrogen in the energy system and step 3 wide-scale expansion of hydrogen. Currently within the EU 2% of the energy consumption is powered by hydrogen, mainly used for manufacturing [6].

The Colorful World of Hydrogen

Hydrogen does not exist alone, naturally it is almost always bound to other chemical elements. Pure hydrogen is produced via several processes, which require various types of energy and therefore come with various advantages and disadvantages. The different inputs and methods used to produce hydrogen give the hydrogen its colour code. However, there is no international codebook, hence definitions can change and differ from country to country [7]. Below we list common hues of hydrogen according to the Environment Journal:

Grey Hydrogen

By far the most used hydrogen worldwide is grey hydrogen with 95% of hydrogen being grey. Grey hydrogen is produced by using fossil fuels e.g., natural gas, therefore, producing a lot of CO2. For each tonne of hydrogen 9-12 tonnes of CO2 are polluted into the air. The cost of grey hydrogen is relatively cheap with 1kg costing around US$1.00 [8]. 

Black/Brown Hydrogen

Some specifically take the two fossil fuels lignite (brown hydrogen) and coal (black hydrogen) out of the grey hydrogen group because they produce even more emissions [9].  

Blue Hydrogen

Blue hydrogen is an attempt to make grey hydrogen more environmentally friendly by capturing and storing the CO2 that is produced. It is considered a transition solution towards the net-zero goal by 2050. However, the carbon capture and storage (CCS) projects are still in its baby shoes and further research is necessary on its efficiency [9]. Also its environmental friendliness is disputed, as the CO2 is stored in the earth’s surface [8]. 

Green Hydrogen

Green hydrogen is what could actually provide the solution for zero-carbon energy as it is produced from renewable energy sources such as wind and solar power. However, the supply of green hydrogen is extremely limited as of now, mainly due to a lack of investment since green hydrogen stood at US$6.00 per kg in 2020 [8].

Yellow Hydrogen

Yellow hydrogen is a rarely used subgroup of green hydrogen and refers to hydrogen generated through solar energy [9]. 

Pink Hydrogen

Pink hydrogen uses nuclear electricity to produce hydrogen [9].

Turquoise Hydrogen

Turquoise hydrogen is a new invention of potentially low-emission hydrogen still undergoing development. Under this process of methane pyrolysis, hydrogen and solid carbon are produced. Its future depends on whether the process is powered by renewables and if the carbon can be stored permanently or even used [10].


All the different shades of hydrogen always describe the same hydrogen; the output is always H2, the difference lies within the input (solar energy, fossil fuels, nuclear energy, etc.) and the transformational process into H2. To date 95% of hydrogen is produced from fossil fuels making it not a sustainable energy source to reach the EU’s emission targets. What we really need is green hydrogen for the Green Transition. Potentially green hydrogen can make the EU fit for 55, however, in practice the capacity to produce the level of green hydrogen needed is by far not given. Therefore, the actual role of hydrogen to combat climate change relies on the EU’s success in fastly developing green hydrogen production, infrastructure and dissemination. 

Reference List

[1] ‘“Fit for 55%”: What is it and what does WWF want?’, WWF, URL:, [Accessed 20.03.22]
[3] S. Matalucci, 2021, ‘The Hydrogen Stream: What the EU’s Fit for 55 means for hydrogen’, URL:, [Accessed 20.03.22]
[4] European Commission, 2020, ‘A Hydrogen Strategy for a climate neutral Europe’, PDF: [Accessed 17.04.22]
[5] ‘Hydrogen – what is it?’, nationalgrid, URL:, [Accessed 20.03.2022].
[6] European Parliament, 2021, ‘EU Hydrogen Policy hydrogen as an energy carrier for a climate-neutral economy’, PDF: [Accessed 17.03.22]
[7] ‘What is the hydrogen rainbow?’, Cummins Inc., URL:, [Accessed 21.04.2022]
[8] ‘Grey, Green, Pink and Blue: We can sing a hydrogen rainbow too’, Environment Journal, URL:, [Accessed 21.02.22]
[9] A. Jones, ‘The colours of the hydrogen rainbow’, URL:, [Accessed 21.02.2022]
[10] ‘The hydrogen colour spectrum’, nationalgrid, URL:, [Accessed 25.02.2022]

Categories EU - Policies

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