Design of A Solar Thermophilic Anaerobic Reactor for Small Farms

A 10 m3 completely stirred tank reactor has been designed for anaerobic treatment of liquid cow manure under thermophilic conditions (50°C), using a solar heating system mounted on the reactor roof. Simulation models for two systems have been developed. The first system consists of loose components and in the second system the components are integrated. Each of the two systems includes a heat recovery unit to heat the influent by extracting heat from the effluent. The integrated system includes an extra chamber for the pumps and the heat recovery unit, which are in the same insulating cover as the reactor and the solar collector. The control system is based on simple on/off strategy. An auxiliary heater, operated with the produced biogas, can be used during cold months. The measured and calculated design parameters are presented. The simulation results show that the temperature fluctuation of the reactor during the night is less than 1°C, which is too small to harm the microbial activity. The results show that an annual net thermal energy production and overall annual energy efficiency of 100 and 95%, respectively, could be obtained from the integrated system.