Process schemes of municipal sludge treatment to reduce greenhouse gas emission in Nagaoka city were evaluated by conducting pilot-scale experiments and review of annual operational reports.(1) High-concentrated anaerobic digestion process with partial ozonation on digested sludge to improve biological degradability, (2) high-concentrateda naerobicd igestionp rocess without ozonation, a nd (3) conventionala naerobicd igestionp rocess, were compared its energy consumption and the amount of dewatered sludge cake to incorporate CO2 emission equivalent in the subsequent incineration processes. For beneficial use of biogas, an application of power generation and recovery as alternative natural gas for local sectors were assessed using Input-Output Model with dynamic LCA procedure. It appeared that the scheme of the partial ozonation process with power production gave minimal CO2 emission equivalent because the produced energy was expected to cover all of the energy demand for the plant operation and the production of dewatered sludge cake from the process was only 40% of that from the conventional, which minimizes the hauling and the needs of fuel at the incinerationp rocess. The scheme of the partial ozonationp rocess with alternativen atural gas was ranked second to contribute the reduction of CO2 emission equivalent.
