Biogas

2. Contents
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

3. 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
biogas.
 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
emissions.

4. Composition of biogas
 Methane (from 40% to 70%)
 Carbon dioxide (about 40-50%)
 Nitrogen
 Hydrogen sulphide
 Carbon monoxide
 Ammonia

5. 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
into H2O
 4. Methanogenesis – methane formation from acetic acid or carbon dioxide and hydrogen, with the
participation of methanogenic bacteria. Methanogenesis process aggregated responses from different
substrates:
CH3COOH → CH4 + CO2
4HCOOH→ CH4 + 3CO2 + 2H2O
4CH3OH→ 3CH4 +CO2 + 2H2O

6. Diagram of biogas plant

7. Diagram of biogas plant

9. 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
households
 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
fertilizer
 biogas can also be used to heat residential homes

10. Development perspectives
 In Poland, the development perspectives of energy based on biogas are large.
The biogas plants can be build next to, eg.:
 landfills
 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.