Hydrogen in the Energy Transition 

In this cover the basics article, we answer some frequently asked questions about hydrogen and we explore how it contributes to the energy transition.

In the energy transition debate, hydrogen represents an important talking point as it can heavily contribute to a future, carbon-free, energy system. With this article, we join the discussion by trying to answer six frequently asked questions about hydrogen: What is hydrogen? What is hydrogen used for? How is hydrogen produced? How is hydrogen transported and stored? Why is hydrogen deemed important for the EUWhat are the most relevant strategies and legislation to mainstream hydrogen in the EU? 


What is hydrogen?

Hydrogen is the most abundant element in the universe. At room temperature and atmospheric pressureit exists as molecules (H2) in the form of gas. Despite hydrogen existing in large amounts in the universe, hydrogen gas can be found only in small concentrations in the Earth’s atmosphere (one part per million)The reason is that hydrogen is very reactive with oxygen to form water. This reaction also releases energy and therefore handling hydrogen can be dangerous and requires high technical safety measures. 

As hydrogen rarely exists alone, it must be derived from its compounds (e.g., water or other fuels) through chemical conversion processes. Therefore, hydrogen can’t be called an ‘’energy source’’  like oil, coal or other combustibles but instead an ‘’energy carrier’’ similarly to electricity.


What is hydrogen used for?

Existing demand for hydrogen is mainly related to industrial “non-energy” uses in which the molecule is employed as a feedstockExamples are: 

  • Processes for impurities removal from crude oil in refinery stations, the main one being sulphur; 
  • Chemical plants producing a wide variety of molecules e.g. Ammonia (NH3) and methanol (CH3OH), and many others (methylene, ethylene, …) which serve as a feedstock for the production of other chemicals, including fertilisers, household products and industrial solvents, and; 
  • Steel production through the Direct Reduced Iron (DRI) technological route.  

More recently, hydrogen has gained popularity in the scientific and the public debate for the possibility of using it as an energy vector. As explained below in the article, the production of hydrogen for energy purposes must factor in the life-cycle greenhouse gas (GHG) emissions per unit of energy delivered by hydrogen. When produced through some specific technological processes, in fact, hydrogen can be considered as a renewable or low-carbon synthetic fuel.  

Four potential types of energy uses can be identified:  

  • Residential heat and services (e.g. space heating); 
  • Industrial high-temperature heat; 
  • Mobility (e.g. hydrogen for truck cargo transport, synthetic liquid fuels for aviation), and; 
  • Electricity production. 

Most technologies needed to enable these energy uses of hydrogen are still in the Research and Development (R&D) or demonstration phase. At the time of writing, only passenger cars powered by hydrogen, so-called Fuel-cell Electrical Vehicles (FCEV), have reached an early adoption phase.  

It must be noted that for mobility, residential and industrial energy uses, hydrogen competes (in terms of current demand technologieswith direct electrification as discussed in more depth under Question 5 (Why is hydrogen deemed important for the EU?). Also, for residential and industrial energy usesconsumers could also be delivered a mix of hydrogen and natural gas, in alternative to pure gaseous hydrogen. However, the latter would require hydrogen to be blended in natural gas networksa practice that has not quite reached the commercial maturity stage yet. 

Hydrogen and other synthetic fuels
Hydrogen is not the only synthetic fuel used to deliver final energy uses. Other examples of synthetic fuels are ammonia (NH3), methanol (CH3OH), synthetic methane (CH4) and different synthetic liquid fuels. Hydrogen is a common building block for these other synthetic fuels as well. Whereas Ammonia requires nitrogen in addition to hydrogen, methanol, synthetic methane and synthetic liquid fuels require CO2.
The lifecycle emissions of the synthetic fuels other than hydrogen depend on the GHG emissions footprint of the molecules from which they are derived. For example, the lifecycle GHG emissions from the use of methanol will differ whether the CO2 needed for its production is sourced from a Carbon Capture and Storage (CCS) unit or from biogas or from the air, and dependent on the technology used to produce the required hydrogen.
Because of the different energy densities and physical properties of these other synthetic fuels, they might suit different energy uses. Some of the underlying technologies are either already available (e.g., aviation engines based on oil-derived products can run on synthetic liquid fuels), while others could potentially become available soon and be cheaper than alternatives based on electricity (e.g., fuel cells based on ammonia for the marine sector).
Also, these synthetic fuels have different costs and might require different means of transportation compared to hydrogen (e.g., shipping of ammonia vs shipping of liquid hydrogen). Some existing transport infrastructure can be re-used for some of these synthetic fuels (e.g., natural gas pipelines for synthetic methane). The same reasoning applies to storage.

How is hydrogen produced? 

Hydrogen is obtained from other molecules through chemical conversion processes. It can be produced either through “dedicated” production facilities or as a “by-product” of other production processes (e.g., steam cracking).[1] 

“Dedicated” production facilities can be distinguished based on the production technology and the type of input fuel. To simplify, hydrogen molecules produced via some of the most common processes are labelled with a colour. The figure below illustrates the technology, input, process and emissions for four main examples of processes, together with their ‘’hydrogen colours’’.



Green hydrogen”, “blue hydrogen” and “turquoise hydrogen” are GHG emissions-free or are characterised by lower GHG emissions-intensity, whereas “grey hydrogen” is GHG emissions-intensive. Nowadays, most of the hydrogen production (>90%) is “grey hydrogen”.  

Another nomenclature currently in use also refers to “green hydrogen” as “renewable hydrogen”, whereas “blue hydrogen” and “turquoise hydrogen” are called “low-carbon hydrogen”. It is important to keep in mind that the lifecycle GHG emissionalso depends on the emissions due to the supply chain of the inputs. For example, the GHG emissions of the natural gas supply chain can be significant due to methane emissions, whereas those for electricity supply are negligible if the electricity is sourced from renewable energy sources. 

As a reference, in 2018, the worldwide production of grey hydrogen for industrial feedstock uses (circa 99% out of 117 Mt) resulted in around 830 Mof CO2 emissions, 2.5% of global CO2 emissions.[2] 

Note that hydrogen obtained with an electrolyser powered by nuclear power is sometimes referred to as ”pink hydrogen or yellow hydrogen.” Also noteworthy is that there exist other “dedicated” production facilities to which no colour code is assigned or for which there is not a clear convention regarding a colour code (e.g., hydrogen produced through an electrolyser using electricity obtained from the public grid). 


How is hydrogen transported and stored? 

 If not produced at the consumption site, hydrogen needs to be transported and stored to eventually be delivered to final users. Different means of transportation are available: 

  • Pipelines: used to transport either gaseous hydrogen or hydrogen converted into ammonia;
  • Trucks: used to transport either gaseous hydrogen, or liquid hydrogen, or hydrogen converted into Ammonia or into a Liquid Organic Hydrogen Carrier (LOHC);
  • Shipping: transporting liquid hydrogen at temperatures below -253°C (requiring a considerable amount of energy for cooling), or through an intermediate hydrogen carrier such as ammonia or a liquid organic hydrogen carrier. 

Based on the distances and volumes of hydrogen, transport costs can widely vary. Newly built pipelines are widely assumed to be the cheapest method to transport hydrogen per unit transported.  

Instead, no agreement has been reached on whether either building a dedicated hydrogen network, or repurposing the existing natural gas network, or doing a combination of both options would be the optimal solution. Sometimes, blending hydrogen into the natural gas grid is seen as an option, but then the resulting gas mix would only be used for “energy” uses. 

Hydrogen can be stored in different ways, depending on its state (gaseous, liquid or solid) Gaseous hydrogen can, for example, be stored in rock cavern storages or pressurised tanks. There are also storage options that use an intermediate hydrogen carrier. Based on the storage duration and volume of hydrogen, storage costs can widely vary. 


Why is hydrogen deemed important for the EU? 

A couple of important reasons can be identified, explaining why the development of (inter)national hydrogen strategies has seen a big take-off lately 

  • Environment-related reasons (in view of EU 2030 & 2050 energy-climate targets) 
  • Prospected international dimension of a new hydrogen (and other synthetic fuels) economy. 

First, environmental reasons imply both phasing-out current GHG emissions from “grey hydrogen” production and substituting fossil fuel-based energy vectors with “renewable or “low-carbon” hydrogen (and other synthetic fuels) to achieve the EU energy-climate targets while satisfying our energy needs. As discussed in more depth under Question 6 (What are the most relevant strategies and legislation to mainstream hydrogen in the EU?), hydrogen and other synthetic fuels are explicitly included in some of the relevant EU strategies and legislation towards achieving the 2030 energy-climate targets (originally described in the Clean Energy Package) and 2050 climate neutrality (within the European Green Deal). In this respect, hydrogen will complement direct (clean) electrification in decarbonising sectors which are currently mostly powered by fossil fuels. For some energy needs, electrification is already feasible and could result in a cheaper option compared to hydrogen and synthetic fuels. An example is electric cars for passenger transport  

Instead, for other energy needs such as aviation, maritime and high-temperature industrial heating (e.g. steel production), electrification is either (currently) not technically feasible or not cost-competitive. These sectors are called “hard-to-abate” or “hard-to-electrify” sectors. Hydrogen, and other synthetic fuels that are derived from it, can potentially play an important role to decarbonise these sectorsHowever, at current price levels“clean” hydrogen and other synthetic fuels are not competitive when compared with fossil-fuel equivalents.  

Secondlythe future hydrogen (and other synthetic fuels) economy is prospected to have an international dimension; hydrogen could shake up the geopolitical landscape of energy. On the one hand, the EU is not the only region that is actively developing hydrogen strategies (Japan and the USA are as well for example). On the other hand, it is not clear whether sufficient green hydrogen can be produced in Europe by local green electricity. Thus, hydrogen import might be necessary 

Also, even if domestic production of hydrogen was possible, importing it may be more cost-competitive. Considerations on the need for dedicated transport infrastructureinternational trade agreements and a structured international market are also included in regional EU strategies (e.g. German national hydrogen strategythe EU Hydrogen Strategy Communication).  

It is also important to note that not all concerns regarding the security of supply are completely gone when relying on clean hydrogen to replace imported fossil fuels such as natural gas and oil. That is because not all potential uses of hydrogen will be satisfied in a cost-competitive way through domestic production. Also, cost-competitive domestic production of hydrogen (and other synthetic fuels) might require imports of input fuels (for example low-cost renewable electricity and/or natural gas). Some hydrogen strategies, such as the HydrogenEurope “2×40 GW Green Hydrogen Initiative or the German national hydrogen strategy do not fail to take this into consideration.  

Finally, relying on hydrogen imports might also raise some environmental issuesas it can be unclear how “clean” in terms of lifecycle GHG emissions imported hydrogen is. 


What are the most relevant strategies and legislation to mainstream hydrogen in the EU? 

As part of the European Green Deal, both complementary documents A hydrogen strategy for a climate-neutral Europe” (COM(2020) 301 final) and An EU Strategy for Energy System Integration” (COM(2020) 299 final) identify hydrogen and other synthetic fuels as crucial to reach decarbonisation. 

The “hydrogen strategy for a climate-neutral Europe”, identifies cumulative investments needs and policies to promote the entire value chain of renewable and low-carbon hydrogen. A goal is set including three phases for the deployment of renewable hydrogen, of other synthetic fuels, and their uses. Here is a breakdown of these phases and targets:
  • The first phase (from 2020 up to 2024): the installation of at least 6 GW of renewable hydrogen electrolysers and the production of up to 1 million tonnes of renewable hydrogen; 
  • The second phase (from 2025 to 2030): the installation of at least 40 GW of renewable hydrogen electrolysers and the production of up to 10 million tonnes of renewable hydrogen in the EU; 
  • The third phase (from 2030 onwards and towards 2050): renewable hydrogen technologies should reach maturity and be deployed at large scale. 

The “EU Strategy Energy System Integration”  describes that ‘’use of renewable and low-carbon fuels, including hydrogen, for end-use applications where direct heating or electrification are not feasible, nor efficient or have higher costs is one of the important concepts for energy system integration. [3] Some examples are the use of hydrogen and other synthetic fuels in maritime, aviation and certain industrial processes. 

Also, in the previous set of 2050 EU long-term strategy scenarios (“A Clean Planet for All” COM(2018) 773 final), both hydrogen and other synthetic fuels were included as potential energy vectors. Two scenarios “H2” and “P2X” focus specifically on the underlying technologies.

Additionally, “renewable” and “low-carbon” hydrogen and other synthetic fuels will also be one of the main recipients of the €750 billion recovery package negotiated by EU leaders on 17-21 JulyPreviously in the Commission’s recovery plan Europe’s moment: Repair and Prepare for the Next Generation” document (COM(2020) 456 final) released in May 2020, clean hydrogen had been already identified as one of the “key technologies for the clean energy transition”, for which the “Strategic Investment Facility” will also reserve investments. 

Finally, many of the National Energy and Climate Plans by the Member States include hydrogen. More details can be found in this report by Trinomics. Additionally, dedicated national strategies are being adopted. 


[1] According to IEA “The Future of Hydrogen” (2019), globally 60% circa of hydrogen is produced through “dedicated” facilities and the rest as a “by-product”. 

[2] CO2 emissions from worldwide hydrogen production were sourced from IEA “The Future of Hydrogen” (2019).

[3] Energy system integration refers to the planning and operating of the energy system “as a whole”, across multiple energy carriers, infrastructures, and consumption sectors, by creating stronger links between them with the objective of delivering low-carbon, reliable and resource-efficient energy services, at the least possible cost for society” (“ EU Strategy Energy System Integration” – COM(2020) 299 final, July 2020).

If you still have questions or doubt about the topic, do not hesitate to contact one of our academic experts:   

Piero Dos ReisRonnie Belmans, Maria Olczak


Relevant links 

FSR Sector coupling platform 


Cost-effective decarbonisation study AUTHORS: Andris Piebalgs, Christopher Jones, Piero Carlo Dos Reis, Golnoush Soroush, Jean-Michel Glachant

Molecules : indispensable in the decarbonized energy chain AUTHORS: BELMANS Ronnie, VINGERHOETS Pieter

Hydrogen technology summary AUTHORS:  Ivana Čeković, Ilaria Conti, Christopher Jones, Andris Piebalgs

Green hydrogen : bridging the energy transition in Africa and Europe AUTHORS: Swetha RaviKumar Bhagwat, Maria Olczak


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