1. What is biogas?
2. Composition of biogas
3. Methane fermentation process
4. Diagram of a biogas plant
5. The use of biogas
6. Development perspectives
What is biogas?
Biogas is produced in the anaerobic fermentation of organic waste when organic
substances are decomposed by bacteria to simple compounds.
In the process of anaerobic digestion 60% of the organic matter is changed into
In accordance with the laws in force in the European Union, the storage of organic
waste can only take place in a manner that protects it from uncontrolled methane
Przebieg fermentacji metanowej
1. Hydrolysis - decomposition of the polymer, soluble organic compounds (proteins, fats, carbohydrates) into
simple compounds soluble in water (monosaccharides, amino acids and fatty acids) by means of enzymes
(amylase, protease, lipase) produced by the hydrolytic bacteria.
2. Acidogenesis (acidification phase): - distribution of hydrolysed substances into simpler substances by
anaerobic bacteria. The products of this stage are formed: short chain organic acids (formic, acetic, propionic,
butyric, valeric, hexanoic), alcohols (methanol, ethanol), aldehydes, ketones and carbon dioxide and hydrogen.
Some of them are a source of carbon and energy for acetate bacteria.
3. Acetogenesis – conversion of organic acids and alcohols to acetic acid, carbon dioxide and hydrogen. In
this process, the non-selective bacteria are involved, Ie. reducing sulfate ion to H2S and oxidizing hydrogen
4. Methanogenesis – methane formation from acetic acid or carbon dioxide and hydrogen, with the
participation of methanogenic bacteria. Methanogenesis process aggregated responses from different
CH3COOH → CH4 + CO2
4HCOOH→ CH4 + 3CO2 + 2H2O
4CH3OH→ 3CH4 +CO2 + 2H2O
The use of methane fermentation process
Practical uses of anaerobic digestion is a result of the following properties
is a whole range of organic compounds undergoes a complete degradation to form
methane, carbon dioxide and hydrogen
the resulting product, that is biogas, contains 50-80% methane, which can be used
as a source of electric power
the process can be carried out on a large industrial scale, as well as at home in rural
of the available industrial pollution distribution methods it is the least disruptive to the
environment due to the amount of biomass produced as waste that can be used as
biogas can also be used to heat residential homes
In Poland, the development perspectives of energy based on biogas are large.
The biogas plants can be build next to, eg.:
wastewater treatment plants
near larger farms
small biogas plants can be used on farms
nearby industrial plants producing organic waste
in Germany there are 4.5 thousand biogas plants. Poland has more than 100,
but in the construction at different stages there are 200.