The unit contains a methane-tank (1) housed in the ground, having:i) acid (2), regressive acid (3), and alkaline (4) fermentation chambers;ii) silt water collector (5); and,iii) chamber and housing covers (6,7)with formation of spaces (8,9) for biogas collection. Methane fermentation chamber (10) is connected to the silt water collector (5), and section (11) to the gas-space (8) under cover (6).    Regressive acid fermentation chamber (3) has a collector (12) silt water collector, and the bio-gas chamber (13) has a gas-valve (14) and is connected to sections (15) of the methane fermentation pre-chamber (16); with the upper part of the prechamber (16) connected to collector (12) of chamber (3).    The sections (15) of pre-chamber (16) contain:i) pipes (17) for biogas input;ii) radial injectors (18);iii) overflow pipes (19); and,iv) granular packing (20) for immobilisation of microorganisms-destruction agents of volatile fatty acids.    The unit also contains:i) mixer (21);ii) separator (22);iii) grinder (23);iv) dispersion device (24);v) microfilters (25-27);vi) disintegrators (28-30);vii) bio-cultivator (31);viii) heat-exchanger (32); and,xi) transport (33).    Outflow from stock-breeding farms and aviaries is directed to mixer (21) for dilution with water and separation of mineral admixtures, then to separator (22), and subsequently to other devices in line.    Biomass is separated in micro-filter (27), processed in disintegrator (30), heated to 90-95C in heat-exchanger (32), and in the form of liquid mass, outputted to transport (33) for use on farms as a protein-vitamin additive.    Biogas containing 95-98% of methane from chamber (10) is directed to reservoir space (9) for utilisation.    USE -   In units for production of biogas from animal and aviary outflow; useful in treatment plants of stock-breeding and poultry farms in agriculture.    ADVANTAGE -   Increased content of methane in biogas; the treatment of outflow and production of biogas can make the operation of treatment plants profitable.