Preparing and further cutting of bovine dung which also contains straw, and of corn silage happens in special cutters, from which it is fed into the pre-fermentation tank. The primary mixing of liquid manure, and sewage water, including other fluids happens in a heated pre-container. The foodstuffs which are their expiration dates, and various other waste (household waste, greasy materials from washing, depleted frying oil, fats from grease-traps, etc.) are accepted in the pounder. This is where the cutting and separation of wrappings of boxed products happens as well, after which the thin parts are fed into an autoclave, and kept at 70oC for at least four hours to sterilise them.The profit-oriented biogas plants consider the static, calculable production of electric and heat energy a fundamental goal, which requires the gas production to be continuous and free of hindrances [1]. In case of these factories, the gas yield for time unit may be lowered by various operation factors, but mainly malfunctions (errors, the foam within fermentation tanks from time to time, etc.). Incorrectly mixing or homogenising the materials arriving in the fermentation tanks also counts as a hindering operation factor. Our work details the basic questions of how the stirring inside fermentation tanks happens physically.