Digesters need to be kept at a steady, warm temperature for optimum gas yield and stable system operation. Ideally Digester heat requirements can be met by capturing waste heat from other facility unit operations, such as a Combined Heat & Power (CHP) system. therefore desired fixed temperature range is constantly maintained inside the Biogas Digester in order to achieve optimal bacterial action.
The temperature inside of the biogas reactor is mesophilic, which is about 37°С. Reactor heating is done using the heating system. Inlet temperature of heating water is 80°С and the outlet temperature is 55°С. The heating system is a network of pipes placed inside the digester chamber or on the inner wall surface. If the biogas plant is equipped with a co-generator the hot heating medium is supplied from the cooling system of the engine. Boilers fuelled by biogas, natural gas or their mixture can be also used as heat power source for the biogas plant.
Sometimes, such as during start up, supplemental heat from a gas boiler is required to get a system up to operating temperature. Heat can be applied internally to the tank through a series of hot water pipes that are either embedded in concrete tank walls or supported on the inside tank walls.