NOVELTY - A plant comprises mixing tank (1), anaerobic fermentation vessel (2) of liquid biomass, gasholder (3), aerobic fermentation vessel (4), a device (5) for pumping of liquid substance after fermentation, a device (6) for liquid aeration, a solid mass residue removal system (7), a gas distribution device (8), a device (9) for utilization of heavy gases, a device (10) for ammonia adsorption by water, liquid-gas mixer (11), a cavity mixer (13), a system (12) of serves a superficial active and dispersant matters, cooler (14), hotwell (15), and a system (16) of removal a sulphuretted hydrogen.    USE - As a plant for producing the oxygen-containing additive as an ecologically beneficial component for liquid motor fuels, from from a liquid colloidal phase of the decomposition of the biological waste of farm animals, people biomass and of vegetable biomass; and from the biological waste of vegetable biomass, people biomass and of farm animals.    ADVANTAGE - The plant produces an inexpensive the oxygen-containing additive (OCA) as an ecologically beneficial component for all of the liquid motor fuels from a liquid colloidal phase of the decomposition of the biological waste of farm animals, people biomass and of vegetable biomass; and from the biological waste of vegetable biomass, people biomass and of farm animals. The plant uses the solid phase of the decomposition of the biological waste of farm animals, of vegetable biomass and of people biomass as fertilizers; and improves the environmental situation in Ukraine and other countries. The consumption of diesel fuel in its mixture with the OCA decreases by 22%. There is a complete absence of the coking of the fuel equipment elements, of carbon deposit and luster on the piston group elements in an internal combustion engine. The emissions of harmful substances are reduced substantially. The fuel mixture has stable physical properties. The assessed value of cost the fuel blend with the OCA added is lower by 15% than that of pure fuel. The use of the solid phase of the decomposition of the biological waste of farm animals and of vegetable biomass as fertilizers, and environment improvement due to recycling agricultural organic waste and of people biomass ensure wide opportunities of using the plant. The use of the cavity mixer and of the system of serves a superficial active and dispersant matters to the liquid substance after a saturation aerobically by an oxygen-containing gases enables this substance to be stabilized due to the cessation of chain reactions and the performance indices of its oxygen-bearing components to be improved. The use of a vibrating device in the cavity mixer allows the colloidal substance to be activated by ultrasonic frequency of vibrations with predetermined parameters this resulting in the final destruction of anaerobic and aerobic bacteria cells The use, in the biogas plant, of the cavity mixer and of the system of serves a superficial active and dispersant matters allows to provide aggregate transformations and physical stability of the performance indices of the oxygen-containing components of the colloidal substance to be ensured this in turn allowing a long-term storage of a mixture of liquid motor fuels with an OCA to be achieved. Equipping the biogas plant with the cooler (heat exchanger-distiller) makes it possible to condense the gases produced during the process of activating the colloidal mass by ultrasonic cavitation and to provide a plant for producing the oxygen-containing additive as an ecologically beneficial component for liquid motor fuels in the form of a high dispersion, physically stable colloidal substance.    DETAILED DESCRIPTION - A plant for producing the oxygen-containing additive as an ecologically beneficial component for liquid motor fuels, comprises a mixing tank (1), an anaerobic fermentation vessel (2) of liquid biomass, a gasholder (3), a system (16) of removal a sulphuretted hydrogen, a hotwell (15), an aerobic fermentation vessel (4) provided with stop and control valves, a device (5) for pumping of liquid substance after fermentation, a device (6) for liquid aeration with an oxygen-containing gas, a removal system (7) of solid mass residue after fermentation, a gas distribution device (8), a device (9) for utilization of heavy gases, a device (10) for ammonia adsorption by water, a liquid-gas mixer (11), a cavity mixer (13); a system (12) of serves a superficial active and dispersant matters and a cooler (14). All the components are connected to each other by pipelines. A bottom of the gas distribution device is connected to the aerobic fermentation vessel and to the device for utilization of heavy gases, and a top of the gas distribution device is connected to the cavity mixer through the device for ammonia adsorption by water and through the liquid-gas mixer.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of plant for producing the oxygen-containing additive.    Mixing tank (1)    Anaerobic fermentation vessel (2)    Gasholder (3)    Aerobic fermentation vessel (4)    Device for pumping of liquid substance (5)    Device for liquid aeration (6)    Removal system of solid mass residue (7)    Gas distribution device (8)    Device for utilization of heavy gases (9)    Device for ammonia adsorption by water (10)    Liquid-gas mixer (11)    System of serves a superficial active and dispersant matters (12)    Cavity mixer (13)    Cooler (14)    Hotwell (15)    System of removal a sulphuretted hydrogen. (16)