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

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.

Composition of biogas

Methane (from 40% to 70%)

Carbon dioxide (about 40-50%)

Nitrogen

Hydrogen sulphide

Carbon monoxide

Ammonia

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

Diagram of biogas plant

Diagram of biogas plant

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

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.