Processes for sustainable hydrogen production at a glance

The hydrogen industry is on the upswing. However, to meet the market demand for environmentally friendly hydrogen, H2 must be produced from renewable raw materials and without emitting greenhouse gases. Find out what the technical options and specific subsidies are for this in this blog article.

Hydrogen is being traded as the clean energy storage of the future, but so far it has been produced primarily from fossil raw materials and with the release of CO₂. In order to produce hydrogen in a climate-neutral way, production must be switched to sustainable raw materials and to greenhouse gas-free processes. To achieve this, green hydrogen production processes must be further developed and scaled up to the point where they can replace existing processes. This is where current R&D projects can come in and be advanced with funding. And this will be worthwhile: The industrial sector around hydrogen will undergo strong growth in the coming years. As part of this, scaling all hydrogen-related sectors - production, transport and storage, consumption, and control components (balance-of-plant components) - is critical. By investing at the right time, companies can gain a decisive market advantage.

Environmentally friendly hydrogen demanded: Problems with current production

How is hydrogen currently produced and what is the problem with it?

• Steam reforming: Gaseous or low-boiling fossil raw materials are reacted with steam at high temperatures (700-1000°C) and high pressures over a catalyst (usually nickel). This produces a gas mixture of carbon monoxide and hydrogen (synthesis gas).
• Partial oxidation: Heavy-boiling or solid fossil raw materials are reacted with oxygen at very high temperatures (1000°C). This reaction also produces a gas mixture of carbon monoxide and hydrogen (synthesis gas).
• Water gas shift reaction: In a follow-up to the reactions the carbon monoxide produced in the processes can be transformed with water, forming carbon dioxide and producing additional gray hydrogen.

These processes rely on fossil feedstocks and release approximately 16.1 kg CO₂ eq/kg H₂. Due to these high greenhouse gas emissions, decarbonization cannot be achieved based on gray hydrogen.

Figure 1: The different reactions for the production of hydrogen starting from pentane.

Green hydrogen: sustainable production with electrolysis

Which processes are used for the production of sustainable green hydrogen?

Electrolysis is considered to be the most important process for the production of hydrogen in the future. In an electrochemical process, water is split into hydrogen and oxygen. Provided the energy for electrolysis comes from renewable sources, no greenhouse gases are thus released and the hydrogen produced is accordingly climate-neutral. Even using electricity from fossil sources, the greenhouse gas release of approx. 1.5 kg CO₂ eq/kg H₂ is significantly lower than for gray hydrogen.

1. AEL (Alkaline Electrolysis): Alkaline electrolysis is carried out in a highly concentrated potassium hydroxide solution as the electrolyte. The membrane between the electrodes allows the transfer of hydroxide ions, which are formed by the elimination of protons from the water at the cathode.
   
   
2. PEM (Proton Exchange Membrane Electrolysis): Proton exchange membrane electrolysis is carried out under acidic conditions. A proton transfer membrane between the electrodes allows protons formed at the anode to travel to the cathode, where hydrogen is formed.
   
   
3. HTE (High Temperature or Steam Electrolysis): In high temperature or steam electrolysis, water vapor is split electrolytically. In this process, the electrodes are connected by a membrane, which allows the transfer of oxygen ions from the cathode to the anode.
   
   

Challenges and development areas for electrolyzers

• Efficiency: The efficiency, i.e. the efficiency with which the energy from electrolysers is converted into hydrogen, must be further increased in order to make the best possible use of the energy.
• Materials: Rare metals such as platinum are needed for the electrodes. The minimization of the demand or the complete independence, from strategic resources represents a central factor in the electrolyser development.
• Pressure: The output pressure of an electrolyzer is crucial for subsequent steps. High-pressure electrolyzers reduce the amount of energy that has to be put into pressure adjustment and thus indirectly increase efficiency.
• Current density: The maximum current density of the membrane limits the power that can be applied in the electrolysis. By using higher powers, the membrane area required can be reduced and so can the amount of material used, allowing for a more compact design for electrolysers.

Alternative processes for green hydrogen

What alternative processes can be used to produce green hydrogen?

Apart from hydrogen produced by electrolysis, there are also other methods to produce sustainable hydrogen. One possibility would be to process waste products into hydrogen. Biomass, such as sewage sludge from water processing or liquid manure from animal husbandry, is particularly suitable for this. Due to their high content of bound hydrogen atoms, plastic waste is also attractive for recycling.

 
Figure 3: Possible waste for the production of green hydrogen.


Biomass is processed in two steps: It becomes fertilizer and residues are fed to energy production, mostly via biogas production. By converting the biomass to hydrogen via gas reforming or partial oxidation, hydrogen can be produced with the generation of CO₂ as a co-product. In the same way, non-recyclable plastic or wood waste, for example, can be processed. In the energy recovery of all these materials, CO₂ would inevitably be produced. Carbon capturing methods or the material recycling of the carbon-containing intermediate products can completely eliminate the release of CO₂. The HyWaste network, managed by EurA AG's hydrogen experts and funded by the Central Innovation Program for SMEs (ZIM), deals with various topics related to the generation of hydrogen from problematic materials. If you are active or interested in this field, please do not hesitate to contact us.

Hydrogen as a co-product or by-product of other processes

In addition to processes for the specific production of hydrogen, hydrogen can also be produced as a co-product or by-product in processes. One of the biggest examples is chlor-alkali electrolysis, which is actually used for the production of chlorine (approx. 80 million tons per year), but releases high amounts of hydrogen (approx. 2 million tons per year). Hydrogen is also produced as a co-product in petrochemical processes, such as the production of ethylene or gasoline production. In these large-scale processes, hydrogen is already specifically extracted and further utilized. However, there are many smaller processes, especially in the field of electrolysis processes, in which hydrogen produced as a by-product is released or burned via a flare instead of being isolated.

You want to advance your projects in the field of hydrogen and are looking for suitable funding or want to learn more about the opportunities and advantages of hydrogen? EurA AG's Aachen and Herten sites have years of experience in successfully applying for funding and providing technical  advice on hydrogen. Contact us, we will advise you on the selection of the right funding program and will be happy to support you in the application process.

 Text: Georg Beckmann