Steam reforming is currently probably the most common large-scale industrial process for the production of hydrogen from carbonaceous resources such as natural gas and biomass. What is steam reforming? What are the advantages of steam reforming? What is the role of steam reforming in fuel cells? This and more is described in the following article.
Steam reforming is a chemical process in which carbon monoxide reacts with water vapor. This type of hydrogen production is a long-established process, which is why special steam reforming plants with a capacity of up to 100,000 cubic meters per hour are now available for this purpose. The oxygen contained in the steam causes oxidation of the fuel, resulting in hydrogen (H2). Natural gas, but also methanol, light gasoline, biogas or biomass are primarily used as carbon-containing fuels or energy carriers. In this process, the water vapor required for the reaction can be added from the outside or can come from the respective feedstock itself." 
The chemical reaction of steam reforming is endothermic, which means that it consumes heat. It is often supported by a catalyst or the required heat is generated by the combustion of the fuel. Conceivable sources of external heat include concentrated solar thermal energy, high-temperature nuclear reactors, or waste heat from internal combustion engines. Steam reforming yields a gas mixture whose energy content significantly exceeds that of the fuel used.
First, the long-chain hydrocarbons are split to form methane, hydrogen, carbon monoxide and carbon dioxide. This is done with the addition of steam at a temperature between 450 and 500 degrees Celsius and a pressure between 25 and 30 bar. The methane is then reacted with water at constant pressure and a temperature of between 800 and 900 degrees Celsius. To obtain pure hydrogen at the end, pressure swing adsorption systems or caustic absorption gas scrubbers are used. These filter out by-products such as carbon monoxide, carbon dioxide and methane down to a few thousandths.
When natural gas – whose main component is methane (CH4) – is used, the following reaction thus takes place during steam reforming:
CH4 + H2O → CO + 3 H2
(methane + water vapor → carbon monoxide + hydrogen)
To increase the hydrogen yield in steam reforming, the resulting carbon monoxide can be converted to carbon dioxide and even more hydrogen by a second reaction. This procedure is called a water gas shift reaction:
CO + H2O → CO2 + H2
Although high-temperature heat must be supplied to implement steam reforming, it can be carried out autothermally. This is possible due to the partial oxidation of the hydrocarbon that takes place in parallel. The efficiency of steam reforming (when natural gas is used) is about 60 to 70 percent." 
Steam reforming is applied in large-scale industrial contexts to produce hydrogen – for example, for use in petroleum refineries. Steam reforming is the most commonly used process for hydrogen production. Fossil fuels such as natural gas and petroleum or coal are usually used as feedstocks. Under pressure and high temperatures, the hydrocarbons contained in the energy sources are then converted into methane, carbon monoxide and carbon dioxide. These substances are then catalyzed to form hydrogen.
As an alternative to fossil fuels, biomass can also be used for steam reforming. This improves the overall CO2 balance of the process. Because almost any type of biomass is suitable for the process, the hydrogen output is very high. The hydrogen produced by biogas steam reforming way is also referred to as biohydrogen.
Already around 70 percent of the hydrogen produced worldwide comes from steam reforming. This is also due to the comparatively low cost of steam reforming of hydrogen. More expensive processes lag behind: For example, the share of hydrogen produced by electrolysis is only about five percent. A kilogram of hydrogen obtained from natural gas costs just under two euros. The cost of hydrogen from electrolysis is more than three times that amount.
What about the use of renewable resources in steam reforming? The use of alternative fuels promises lower emissions in steam reforming. However, comparing the use of biogas and biomass with that of natural gas, there are several disadvantages compared to the fossil fuel. For example, the hydrogen produced has a significantly lower degree of purity. In addition, purification is very costly and offsets the emission advantage of biohydrogen. In addition, the production costs for steam reforming from biomass are very high. This is mainly due to the fact that biomass is still relatively little known as a feedstock and therefore the production volume is also quite low.
Steam reforming plays an important role for hydrogen and direct methanol fuel cells . This is because in order to use hydrogen as a fuel, it must first be produced from other fuels or energy sources. The most suitable and probably most important type of fuel cell for numerous applications is the proton exchange membrane fuel cell. This usually runs on hydrogen obtained from methane or methanol by steam reforming. Thus, the hydrogen fuel cell achieves an efficiency of about 60 percent.
EFOY fuel cells are based on direct methanol fuel cell technology. They generate electricity by combining methanol with oxygen from the air. The methanol is converted directly into electricity, and the only by-products besides waste heat are water vapor and carbon dioxide. EFOY hydrogen fuel cells, on the other hand, are hydrogen fuel cells based on polymer electrolyte membrane technology. The electricity they generate is produced by combining oxygen with hydrogen as a fuel. The hydrogen is converted directly into electricity. Both processes are very environmentally friendly ways of producing electricity.
The process of steam reforming to hydrogen usually uses natural gas or residues from the petroleum industry, which are enriched with steam. The mixture is then converted to hydrogen under high heat and pressure. A byproduct of the process is carbon monoxide, which, however, can also be converted into hydrogen. Due to the partial oxidation of the hydrocarbon, steam reforming can be carried out autothermally. The steam reforming efficiency is correspondingly high at 60 to 70 percent. Steam reforming is therefore a very important process, especially for fuel cell technology.