The aim of this work is to increase the output of biogas and electricity power generation in biogas plants through the use of stimulating supplements in the form of vegetable oil sediment in the transition from periodic to quasi-continuous loading of the methane tank. To achieve this goal, the following tasks were solved: the biogas yield from cattle manure was defined at various temperature conditions with periodic loading of the methane tank; biogas yield was estimated during the cattle manure fermentation with the added vegetable oil sediment, using a mathematical, biogas yield was predicted for permanent loading of the methane tank. The research was carried out at the laboratory plant consisting of a methane tank useful volume of 30 liters and the gasholder of the wet type. The biogas yield was recorded for lifting of the cylinder-gauge is a wet gasholder with attached to it a scale, calibrated in centimeters. The biogas is burned on a gas stove. Calorific value of biogas was determined by its elemental composition, which was recorded by the gas analyzer. The most important results are according to the experimental researches of biogas in periodic mode, boot using this model provided prediction of biogas yield for quasi-continuous loading of the methane tank. As a result of experimental studies, it was established that during manure milling, the maximum yield of biogas was observed at 3-8 days of fermentation, and then it gradually decreased. When adding to the substrate 1.3% vegetable oil sediment the biogas yield increases and reaches a maximum value for 20 days and then it gradually decreased. The significance of the research results is that the use of vegetable oil sediment as co-substrate will allow almost three times increasing the yield of biogas and electricity generation, to reduce the payback period of a biogas plant with a capacity of 4 MW when using a green tariff to 5.1 years.