Abstract
There is a large amount of wet biomass in Japan ; however, it is difficult to utilize them as energy for retained water. Digestion is efficient process to produce energy from them ; however, sludge and wastewater treatment after digestion is expensive. Recently, mixed digestion of sewage sludge and kitchen waste is suggested in sewage treatment plants, where wastewater after digestion can be treated efficiently by advantage of aeration tank capacity. For efficient use of biogas and residue, biogas should be utilized as auxiliary fuel in dried and carbonization equipment or in electric power plants, or as boiler fuel for heating of digestion tank. On the other hand, residue should be dried and carbonized as solid fuel. This paper reports calculated material and heat balance of case studies for such various systems.
