Hydrogen is abundant on earth and often found in compound elements such as methane CH4 or water H2O.
Hydrogen can be produced from several energy sources such as fossil energy, biomass, renewable energy and electricity from water electrolysis, and this is probably one of its particularities. However, the technologies most used today are highly dependent on economic aspects (process cost, profitability, CAPEX, …). The main routes used to produce hydrogen are described below.
- Natural gas methane reforming
The main route used to produce the most common form of hydrogen is natural gas reforming, which is responsible for the production of about 75% of hydrogen. Steam methane reforming (SMR) represents the dominant hydrogen production technology. The production process starts with the reaction between natural gas and steam methane which produces syngas that is then processed to separate carbon dioxide and hydrogen.
The production of hydrogen via this process would not be carbon free as it generates almost 9 kgCO2 per kgH2 hence the need to subsequently use CCUS carbon capture and storage technologies.
- Coal gasification
The second technology used for hydrogen production is coal gasification, which accounts for 23% of the production of the current form of hydrogen. It is a more mature production technology than the others and has been in use for several decades. China is the country that uses the most this technology today.
In the process, coal in the presence of oxidizing agents is reacted to produce syngas, which is then used to produce hydrogen. However, this is the most CO2 intensive production process with 20 kgCO2/kgH2 released, hence the great need to include CCUS technologies in the process.
- Partial oxidation and Water electrolysis
Finally, partial oil oxidation and water electrolysis account for about 2% of the technology used for hydrogen production. In particular, water electrolysis alone would account for less than 0.1% of the overall hydrogen production. It is an electro-chemical process that uses electricity to split water into hydrogen and oxygen.
Electrolysis technologies have seen an acceleration in deployment in recent years, with several projects under construction that could bring installed electrolyser capacity to 3 GW by 2023.
Alkaline, proton exchange membrane (PEM) and solid oxide electrolysis cell (SOEC) are the three main types of electrolysers used in the world. The last one is the least developed and has the highest investment costs.
It should be noted that biomass gasification has not become commercially available due to technological barriers and feedstock limitations.