Methane is the main component of natural gas; its concentration in it reaches from 77 to 99%. The high content of methane in associated petroleum gases is from 31 to 91%. Methane is actually a large hydrogen molecule that consists of one carbon and four hydrogen atoms. The chemical formula clearly indicates that methane is “highly enriched” with hydrogen. Consequently, hydrogen production from methane should be the most cost-effective.

The process of separating hydrogen from the carbon base in methane takes place in tube furnaces (chemical steam reformers) with an external heat supply at temperatures of 750 °C to 850 °C, through the pipe wall on catalytic surfaces (nickel, corundum, etc.):

CH4+H2O ↔ CO+3H2

then with carbon monoxide (CO), or simply “carbon monoxide,” there is a reaction:

CO+H2O ↔ CO2+H2

This is the cheapest and most cost-effective way to produce hydrogen. The cost price of the process is 1.5 to 3 EUR per 1 kg of hydrogen.

The main disadvantage of the method is the release of a large amount of greenhouse gases, mainly CO2.  1 kg of produced hydrogen accounts for about 10 kg of CO2!

The oldest industrial method for producing hydrogen is coal gasification, known since the 1940s. The question arises: what does coal have to do with it, after all, if it contains only about 6% of hydrogen? The production of hydrogen from coal is associated with the thermal decomposition of water, while coal itself is directly used as an energy source and a chemical reagent. Coal contains a lot of carbon, which will react with oxygen, water, and carbon monoxide.

By acting on coal simultaneously with water vapor and oxygen, the same steam methane reforming (SMR) is taken place.

The main reactions of the coal gasification process:

• C+O2 ↔ CO2
• C+2H2O ↔ CO2+2H2
• C+H2O ↔ CO+H2
• C+CO2 ↔ 2CO

There are many ways to gasify coal. They differ in thermodynamic parameters, in the size and principle of coal supply to a gasifier, as well as in the method of slag removal.

The cost price of the process is 2 to 2.5 EUR per 1 kg of hydrogen.

The main disadvantage of the method, as in the case of SMR, is the release of a large amount of greenhouse gases, mainly CO2.

By acting on distilled water with an electric current, it is possible to decompose it into its
components — oxygen and hydrogen:

2H2O = 2H2 + O2

The first electrolytic decomposition of water into oxygen and hydrogen was carried out in 1800; the industrial development of this method began in 1888, when DC generators became available.

Electrolysis of water is a rather expensive technology for producing hydrogen. In aggregate, it accounts for only about 4 to 5% of the total volume of produced hydrogen.

The electrolysis of water technology looks attractive due to the environmental friendliness of the production and the possibility of creating installations with a wide range of productivity.

The method is simple and convenient in operation, having a high purity of the produced hydrogen. Additionally, oxygen, a by-product of its production, is a valuable chemical.

There are 3 main industrial methods for the implementation of electrolysis technology for the
production of hydrogen, they differ in the type of electrolyte used and the conditions of electrolysis:
1) Alkaline electrolysis is the primary method used.
2) SPE electrolyzers (electrolyzers with solid polymer electrolyte) have similar characteristics to alkaline
electrolyzers, but 6 times more expensive.
3) High-temperature electrolysis of water vapor in cells with a solid electrolytе.

The cost price of the process is 5 to 7 EUR per 1 kg of hydrogen.

Regardless of the electrolysis method, the main contribution to the cost of hydrogen produced by these methods is made by the cost of electricity, about 70 to 90%. And this is the biggest drawback. To date, the bulk of electricity is not produced by environmentally friendly methods, therefore, in fact, electrolysis is far from being a “clean” method of hydrogen production (in aggregate, CO2 emissions even exceed other methods of hydrogen production). The situation will change only with the massive use of renewable sources of electricity generation.

Pyrolysis is a process of thermal decomposition of organic and many inorganic compounds.

During thermochemical processing of biomass, it is heated without oxygen to a temperature of 500 °C to 800 °C, resulting in the formation of hydrogen, methane, carbon monoxide, and other gases.

Production by pyrolysis of synthesis gas can also be based on the processing of biomass and industrial waste, which simultaneously contributes to solving many environmental problems.

Various methods are used to extract hydrogen from synthesis gas: adsorption, absorption, diffusion through membranes, electrochemical conversion, deep cooling, and catalysis.

The cost price of the process is 5 to 7 EUR per 1 kg of hydrogen.

Reduction–oxidation reactions (ORR), aka redox, are counter-parallel chemical reactions occurring with a change in the oxidation states of atoms that make up the reacting substances.

In 2007, a method for producing hydrogen from water using an aluminum alloy was developed in the United States. An alloy of aluminum with gallium is formed into pellets. The pellets are placed in a water tank. The chemical reaction produces hydrogen. The technology is relatively new and so far ineffective, but in the future, with the use of electricity from nuclear reactors of the 4th generation, the cost of hydrogen obtained during the reaction may become equivalent to the price of gasoline.

Biological production of hydrogen using algae is a process of the biological splitting of water, accompanied by the release of molecular hydrogen, which is carried out in a closed photobioreactor by unicellular green algae — chlamydomonas or chlorella. This technology for the formation of bio-hydrogen is based on adaptive switching of algal photometabolism in response to suboptimal environmental conditions and was proposed in the 1990s after the discovery of hydrogen emission from the Chlamydomonas reinhardtii culture, which was caused by a sulfur deficiency.