Hydrogen is available in practically unlimited amounts on earth. However, it is present almost exclusively in chemical compounds such as hydrocarbons (fossil fuels) and water. A large part (~40%) of today's hydrogen production originates from chemical processes where it is a by-product (e.g. chlorine-alkaline electrolysis or crude oil refining). In the case of industrial production of hydrogen, steam reforming of natural gas is the most widely applied method. Nevertheless, there are several different types of production technology: 

 - reforming (light hydrocarbons)
 - partial oxidation (heavy hydrocarbons)
 - electrolysis (water or chlorine-alkaline)
 - Kvaerner Black process
 - biomass fermentation
 - biological 

Reforming of light hydrocarbons (e.g. methanol, methane or natural gas) to hydrogen can be done either by steam or autothermal reforming techniques. Steam reforming involves two steps, first a catalytic conversion of the fuel (here methane) at high temperatures: 

CH₄ + H₂O 3 H₂ + CO

This is followed by a conversion of the resulting carbon monoxide and water to hydrogen in a reaction, which is often called the shift reaction:

CO + H₂O H₂ + CO₂

Partial oxidation of heavy hydrocarbons involves addition of oxygen as well as steam to the process. The amounts of oxygen and water are accurately controlled to adjust the oxidation rate of the hydrocarbons. In principle, the reaction involves the components mentioned below:

C_nH_m + H₂O + O₂ H₂ + CO +CO₂

Autothermal reforming applies both steam reforming and partial oxidation steps and can be used for somewhat heavier hydrocarbons. After the reforming step, a gas purification process is necessary to remove carbon dioxide, carbon monoxide and other by-products not desired in the hydrogen rich product gas. The complexity of the gas purification process depends on the reforming technique applied and the intended application for the produced hydrogen. Small reformer systems have also been developed for onboard production of hydrogen, for instance in automotive applications.

Water electrolysis is in principle a reversed fuel cell. From water and electricity we get hydrogen and oxygen:

H₂O H₂ + ½O₂ 

Just as in fuel cells, reduction and oxidation take place on two spatially separated electrodes. Hydrogen is produced on the cathode and oxygen on the anode. The electrolyte is ion-conductive, usually either for protons (H⁺) or hydroxyl ions (OH^-). Most common is the alkaline (OH^-) process, which has been used since the beginning of the 20^th century. Other types are based on a solid polymer electrolyte or operated at elevated pressures and/or temperatures. Water electrolysis accounts for about 2-3 % of the global production of hydrogen.

The Kvaerner Black process is a way to produce hydrogen from hydrocarbons and electricity with only solid carbon black as a by-product. At very high temperatures, the hydrocarbon (e.g. methane) decomposes:

CH₄ + energy 2H₂ + C

This pyrolysis process was developed by the Norwegian company Kvaerner in the 1980’s, and is especially interesting since it is CO₂ free. Carbon black is used in rubber production, for example.

Biomass fermentation is really an anaerobic digestion of biomass by bacteria, enzymes or other small organisms. From this process, a gas containing methane is produced, which can either be fed directly into high-temperature fuel cells or used to produce hydrogen. By modifying the process, it is possible to increase the hydrogen content of the product gas.

Biological production of hydrogen is also possible. Some micro-organisms (algae and bacteria) are able to produce hydrogen primarily from water and light (photosynthesis). Promising substances are selected and improved by genetic engineering.

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