Technology of organic materials conversion is made by means of biochemical decomposition (hydrolysis) of high-molecular compounds into low-molecular organic compounds (organic acids, salts, and alcohols).
Organic compounds + Н2О→ С5Н7NО2+HCO3.
Further conversion of obtained dissolved compounds like organic acids and alcohols (С5Н7NО2, HCO3) into gases – СН4, СО2. С5Н7NО2 + HCO3 + Н2О → СН4+СО2+NH4.
Biological process of consecutive (phasic) conversion of organic compounds take place in anaerobic environment i.e. in oxygen-free tank (biological reactor). At the first stage of fermentation substrate hydrolysis take place under acidogenic bacteria influence. At the second stage elementary organic compounds come through hydrolysis oxidation by means of heteroacidogenic bacteria with production of acetate, carbon dioxide and free hydrogen. The other part of organic compound including acetate forms C1 compounds (elementary organic acids).
Produced substances are the feed stock for methanogenic bacteria of third type. This stage flows in two processes of A and B type the character which depends on caused by different bacteria type. These two types of bacteria convert the compound obtained during the first and second stages into methane CH4, water H2O and carbon dioxide CO2.
Methanogenic bacteria are more particular to living environment to be compared to acidogenic bacteria. They require complete anaerobic environment and need longer reproduction period.
Speed and scale of anaerobic fermentation depend of bacteria metabolic activity. That is why the biogas plant chemical process includes hydrolysis stage, oxidation, and methenization stage. For that kind of substrate these processes take place in the same reactor.