Simulation of Heat Transfer for Biogas Production

A comprehensive, fundamentally-based mathematical model that predicts energy requirements to operate a digester at a specified temperature and the resulting gas production is developed. The model accounts for heat loss through the digester walls, floor and top cover material. The ground surrounding the digester walls could potentially freeze thus alleviating heat loss through the walls. Solar energy transmitted through the cover material is also accounted for in this model. The model can be used to calculate energy requirements on a daily, monthly and yearly basis. The lowest energy requirement to operate the digester occurs in July and the highest occurs in December and January. Significant energy could be saved if the influent manure can be pre-heated before entering into the digester. The energy in the effluent manure could be used to preheat the influent.