FIELD: agriculture. SUBSTANCE: method involves supplying into methane tank outer chamber of diluted organic wastes with following sequential anaerobic fermentation in outer and inner chambers of methane tank; heating and mixing mass under fermentation process; discharging heated fermented sediment from methane tank and withdrawing biogas from its inner and outer chambers; introducing mass fermented in outer or inner chamber of methane tank into newly diluted organic wastes prior to feeding the latter into outer chamber of methane tank; heating mixture in heat-exchanger with heat of fermented heated sediment discharged from methane tank. Apparatus has hermetically sealed reservoir with concentric partition wall, which is attached to its cupola so that it does not reach end of reservoir. Concentric partition wall is contoured in plan similar to reservoir and is adapted for dividing it into outer and inner chambers. Apparatus is further equipped with branch pipes for feeding diluted organic wastes and discharging heated fermented sediment, device for mixing and heating wastes under fermentation process and branch pipes for withdrawal of biogas from inner chamber and outer chamber, with outer chamber being connected through gas pipeline to injector, which is cooperating with pump and is connected to gas and liquid mixture pipeline communicated with flow dispersal device arranged at methane tank bottom. Branch pipe for feeding newly diluted organic wastes into methane tank and branch pipe for discharging from reservoir of heated fermented sediment delivered from overflow pipeline are connected to heat-exchanger inner and outer chambers, respectively. Heat-exchanger inner chamber is connected through pipelines to reservoir inner and outer chambers. EFFECT: increased efficiency and enhanced reliability in operation. 5 cl, 2 dwg
