We evaluated the feasibility of waste-generated heat using a 100-kW digestion gas engine at the Karatsu City Water Purification Center by evaluating its disaster resilience through four indicators. We achieved the best outcome, i.e., a power generation rate of 1,122 kW and a power self-sufficiency rate of 22% when two or more digestion gas engines were installed to supply waste-generated heat to the absorption chiller/heater of a water-pool. Additionally, we evaluated the environmental and economic aspects of a Mechanical Biological Treatment (MBT) system installed in Karatsu City. The results suggested that by installing an MBT system, the annual cost could be reduced by ∼100 million Yen and the power generation capacity could be increased to 4,310 kW; this could also help reduce 19,000 tons of annual CO2 emissions with increased power generation. The environmental and economic feasibility assessment tool developed here is configurable; hence, applicable to other regions.

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Japan’s declining population has caused changes in the amount and characteristics of municipal waste. In order to optimize waste incineration plants as a countermeasure to this problem, we analyzed the performance of the integration of the plants with the Mechanical Biological Treatment (MBT) system. In the integrated system, food waste and sewage sludge from waste incineration plants, sewage treatment plants, and industrial facilities were mixed and fermented to produce methane gas. In this study, we evaluated the environmental and economic performance of the integrated system in four case scenarios. The integrated system is located in Ichihara City in Chiba Prefecture, where the Keiyo Coastal Industrial Zone is located and where petroleum and chemical industries are concentrated. The MBT system in which the heat generated from the incineration of waste was transferred to the Keiyo Coastal Industrial Zone was found to be the best. This method could reduce CO2 emissions by 1341 t-CO2/Y, and the annual cost was the lowest at 1.60 billion yen/Y. However, the results of the sensitivity analysis of the food waste ratio and the piping distance suggested that it may be impossible to obtain appropriate evaluation results without considering the regional characteristics.

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