What are hydrogen fuel cells?

Hydrogen is a potential paradigm shifter that can play a major role alongside battery electrification and renewable fuels in creating the carbon-neutral societies of tomorrow. Hydrogen is an energy carrier with qualities that can help reduce the net sum of greenhouse gas emissions. However, while battery-electric vehicles and machines and biofuels can decarbonize transport already today, large scale hydrogen powered transports and infrastructure still belong to the future.

Hydrogen itself is a colorless gas but there are around nine color codes to identify hydrogen including Green, Yellow, White, Black, Brown, Pink, Turquoise, Grey, and Blue hydrogen. The colors codes of hydrogen refer to the source or the process used to make hydrogen.

Hydrogen that reduce CO₂Emissions

Volvo Group’s hydrogen and fuel cell initiatives

Fuel cells as a concept and the use of hydrogen as an energy carrier are nothing new, but the development of hydrogen fuel cell technology that is viable for use in commercial transport systems and infrastructures is now accelerating. However, we’re still some years away before it becomes commercially available. Fuel cells for commercial vehicles and machines have the potential to become essential for the future of transportation and infrastructure, where we strive to accelerate the development, production, and commercialization of hydrogen fuel cell solutions.

We’ve taken a three-pronged approach to enable decarbonization:

Already today, batteries are an ideal solution for shorter/medium-range applications, such as use within the city for buses, refuse collection, local distribution and regional haulage, with regular returns to a fixed depot, thereby allowing for easy recharging. As battery technology and charging infrastructure develops, it will be used also for longer and heavier road transports.
As a complement to battery electric solutions, hydrogen fuel cells will offer a solution for heavy-duty and long-haul truck transport, where good electrical charging infrastructure is hard to come by or the size of the battery required to power the machine would be too unwieldy. Unlike batteries, which store the electricity used, fuel cells make their own electricity onboard from stored hydrogen in an electrochemical process.
Combustion engines which run on fossil free fuels, such as biogas, renewable hydrogen and other options, are the third key to decarbonizing our industry. While we believe that the absolute majority of commercial vehicles will be electric going forward – a mix between hydrogen fuel cell and battery electric – there will still be applications where we will need combustion engines for a long time.

Joint venture - cellcentric

2021 we officially launched cellcentric, our cell joint venture with Daimler Truck, with the ambition to become a leading global manufacturer of hydrogen powered fuel cells. When green hydrogen based on renewable energy is used, fuel cell trucks can reduce carbon emissions to zero. Hydrogen can also offer a path to reduce CO2 emissions with a minimum of grid investment (expanding hydrogen infrastructure) and by then offer an opportunity to quickly scale Zero Emission Vehicles.

Learn how Volvo Group is planning for a hydrogen future

The Color Codes of Hydrogen

Hydrogen(H) is the very first element on the periodic table. It is both the lightest and the most common substance in the universe. It is almost always found as part of another compound, such as water (H2O) or methane (CH4), and therefore needs to be separated into pure hydrogen (H2) before it can be fully utilized in its pure form.

Hydrogen is not an actual source of energy, but rather an energy carrier - a very important distinction to make. What this means is that hydrogen needs a primary source of energy to be produced – e.g., solar, wind, electric, nuclear, bio, fossil et cetera. It is the specifics of the production process, and the energy source utilized, that determine whether the hydrogen will be dubbed Green, Blue, Grey, or another color.

The many colors of hydrogen

Green hydrogen

The definition of the term “Green hydrogen” is twofold:

Green hydrogen produced by electrolysis using renewable energy
Green hydrogen as a general term

Green hydrogen produced by electrolysis using renewable energy

Green hydrogen has become synonymous with producing hydrogen by electrolysis of water using renewable power such as solar, wind, water, et cetera, thus creating a fully carbon-neutral hydrogen production process. Today, Green hydrogen accounts for a very small percentage of the total hydrogen production. There are initiatives to support the production of carbon-neutral hydrogen, such as the European Commission’s hydrogen strategy for a climate-neutral Europe. These initiatives are important to scale up this technology to mass production and reduce costs.

Green hydrogen as a general term

However, the definition of “Green hydrogen” also covers other renewable pathways to hydrogen such as thermolysis of biomass or reforming of biomethane – any climate-neutral or climate-positive method to produce hydrogen. One potentially climate-positive way to produce hydrogen is using biogas by either the Blue (SMR) or Turquoise (pyrolysis) production method. Bio-Blue and Bio-Turquoise could be even more beneficial to the climate than Green hydrogen (electrolysis). This is because the carbon in the biogas, when upgrading the biogas to biomethane, won’t be released as CO2.

White hydrogen (Natural hydrogen)

In nature, hydrogen is most commonly found in different deposits in its gaseous form (H2). This is referred to as White hydrogen. There isn’t a viable strategy to use and extract this hydrogen as of today. Instead, to utilize the power of hydrogen, different processes to generate it artificially need to be applied, which is what the different color denominations represent. Test drilling is ongoing, and the available resources will most likely play an important role in the future.

Blue hydrogen

Blue hydrogen is produced in the same way as Grey hydrogen by SMR, but where excess CO2 is prevented from dispersing in the atmosphere using Carbon Capture and Storage (CCS). Blue hydrogen is often referred to as a carbon-neutral energy source. Considering that the efficiency of CCS units is currently not 100%, describing it as a low carbon energy source would be more appropriate.

Blue hydrogen will be necessary to solve the decarbonization quickly enough and are emerging in many parts of the world. The key to the success of blue hydrogen production is to minimize methane leakage throughout the production chain.

It is a cost-efficient process to reduce the carbon content with 95% (from the 9-12 kg of CO2 per kg H2), ending up with around 0,5 kg CO2 per kg/H2. If we had used Blue hydrogen in our society up until today, there wouldn’t be any climate issues at all. It provides a level that is far cleaner than the electricity energy mix by 2050+. Blue hydrogen has been estimated by IEA (International Energy Agency) to become the single biggest hydrogen source by 2050.

Turquoise hydrogen (Hydrogen produced by Methane Pyrolysis)

Turquoise hydrogen is a relatively new and novel way to produce hydrogen. Like Grey and Blue hydrogen, it uses the methane in natural gas as a feedstock but utilizes electricity rather than fossil fuels to generate heat through the method of pyrolysis, also known as splitting, or cracking. Similar to Blue and Grey hydrogen, the output from Turquoise hydrogen is hydrogen and carbon.

However, unlike when SMR is used, the carbon is in a solid form rather than CO2. As a result, CCS Units are not necessary and solid carbon (carbon black) can be utilized in other applications, for example as a soil improver or to produce certain goods such as tires and rubber hoses. The production of carbon black adds to the attractiveness of Turquoise hydrogen by producing a high-value raw material alongside the hydrogen.

When the process is fed with renewable electricity and biogas, it has the potential to be carbon negative. Bio-methane is already being used in test facilities in Sweden (Höganäs). In the US, this method will be used to reduce methane leakage for landfills and produce useful hydrogen and carbon. This is also the main track for Russian fossil hydrogen.

Pink hydrogen

Pink hydrogen often refers to hydrogen that has been produced through the process of water electrolysis powered by nuclear energy. This is an interesting path for several countries and produces clean hydrogen. Pink is a recent denomination originating from France, where nuclear-based hydrogen was previously included under the name of Yellow hydrogen.

Yellow hydrogen

Yellow hydrogen is one of the more confusing colors. It is used by some to refer to hydrogen that has been produced through the process of water electrolysis powered solely by solar power, while confusingly, others consider it as electrolyzed hydrogen made using the power of mixed sources (electricity mix) – e.g., solar, nuclear, bio, fossil among others. And in the US, Yellow is used for Nuclear only.

Bio could have been sorted into Green hydrogen to indicate that it is a good solution, but that is not yet the case. When using mixed sources, hydrogen becomes polluted by fossils. While the amount of pollution will shrink over time, Yellow hydrogen won’t be as clean as Blue hydrogen for a long time, not even by 2050.

Hydrogens from Fossils

Brown and Black hydrogen (Coal hydrogen)

The oldest way to generate hydrogen is by transforming coal into hydrogen. This generates what is called either Brown or Black hydrogen. The hydrogen is dubbed as either Brown or Black depending on what coal is used:

Lignite coal -> Brown hydrogen
Bituminous coal -> Black hydrogen

Brown and Black hydrogen are created by a coal gasification process that convert organic or fossil-based materials into carbon monoxide (CO) and carbon dioxide (CO2) at very high temperatures, without combustion, using a controlled amount of oxygen and/or steam. The carbon monoxide reacts with the water to form carbon dioxide and hydrogen. The hydrogen is then separated from the other elements using filters or special membranes.

Producing Brown and Black hydrogen is a highly polluting process since both the CO2 and carbon monoxide cannot be reused and are released into the atmosphere. This is an old process which originates from the 19th century and is historically known as “town gas”.

Grey hydrogen

Grey hydrogen is hydrogen produced using SMR (Steam Methane Reforming) where excess CO2 is released into the atmosphere. It accounts for most of the production of hydrogen today. Grey hydrogen emits between 9 kg and 12 kg of CO2 per kg of hydrogen production, compared with Blue hydrogen that emits 0,5-4 kg and Green hydrogen which is essentially emission-free.

Grey hydrogen should not be used as is in fuel cells due to impurities that would impact the lifetime negatively. It can however be cleaned through liquefaction – while this consumes additional energy, it would make the hydrogen clean enough.

Ways to produce hydrogen

To produce hydrogen, as previously mentioned, it must be separated from other elements in the molecules where it occurs. There are many different sources of hydrogen and ways of producing it to use as a fuel. The two most common production methods are steam-methane reforming and electrolysis, but researchers are exploring other methods.

Water Electrolysis

Water electrolysis is the process of using electricity to split water into oxygen and hydrogen gas, sending direct electric currents (DC) to cause a chemical reaction. It is the most widely discussed alternative to SMR and is currently the leading pathway to achieve carbon-neutral hydrogen production. This is the main track to establish the hydrogen economy with a maximized climate benefit.

Steam Methane Reforming

Steam methane reforming is the process in which methane from natural gas or other methane streams (such as biogas or landfill gas) is heated (using steam) in the presence of a catalyst to produce syngas (hydrogen, carbon monoxide, and a small amount of carbondioxide). Today, SMR is the most widespread technology for producing hydrogen from natural gas on a large scale.

Gasification of coal and other hydrocarbons

Partial oxidation (POX), also known simply as “gasification”, hydrogen is produced from a range of hydrocarbon fuels including coal, heavy residual oils, and other low-value refinery products. The coal or hydrocarbon is reacted with oxygen in a less than the stoichiometric ratio, resulting in carbon monoxide and hydrogen at very high temperatures (1200 to 1350°C).

Biological hydrogen

Hydrogen produced through the action of living organisms is referred to as biological hydrogen, or “biohydrogen”. Biohydrogen is produced using microorganisms (such as cyanobacteria) and sunlight to turn water, and sometimes organic matter, into hydrogen. The advantage of these methods of producing hydrogen is that they do not result in any direct greenhouse gas emissions. As of today, the biological hydrogen production processes are still in the early stages of laboratory experimentation, but researchers are trying to understand, copy, and optimize this process to hopefully industrialize it in the future.

Commercializing Green hydrogen - The challenges and opportunities

1. Need for clearer energy policies and cross-sector collaboration

Many countries around the world now have ambitious hydrogen strategies and hydrogen plays an essential role in the EU Green Deal. There is a great willingness to engage in cross-sector hydrogen usage and the industries are actively looking for potential synergies with, for example, trucks and construction equipment hydrogen usage.

However, there is a need for a certificate of origin system for hydrogen. This to be able to trace that climate friendly hydrogen has been used and thereby resulting in fulfillment of low emission. This can be used as a basis for the level of taxation. Volvo would encourage a CO2 declaration on hydrogen rather than talking about colors.

2. Development of infrastructure to support the energy transition

National and local governments, the industry, and investors will need to band together to develop the necessary infrastructure to support the energy transition to Green hydrogen and make it commercially viable. There are several hurdles we need to cross, for example the lack of infrastructure and hydrogen prices for end-users.

The biggest problem today is that new offtakes (users) are not yet present. There is a huge willingness to invest, but not without the assurance of customers. Trucks are seen as a practical level to practice upon before going really big scale, such as the cement industry.

3. Governments and industries need to work together

Governments and industries need to work together to ensure that both existing and new regulations won’t impede investment in Green hydrogen. The trade of hydrogen will benefit from a common international standard for both transporting and storing large quantities, and for tracking the environmental impacts different hydrogen supplies might have.