Performance Evaluation of Japanese Eco-toilets for Realizing Nutrient Matter Cycle

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For realizing nutrient matter cycle based on night soil compost, the author focused on the household use of Japanese eco-toilets and made a series of their use experiment in terms of sanitary engineering and exergy analyes. As results, followings were found. High temperature fermentation to be expected against thermal death of pathogenic organisms was not realized without highly calorific material. Uncomfortable odor was not generated during whole use experiments. The clearer the environmental water is, the larger exergy of black water is, namely, the harder the purification work is. Therefore, clear water should be separated from excrement. A sorting-type composting tank can avoid use of flushing water and production of ureafertilizer, if urea from a composting toilet is utilized as inorganic fertilizer.Thereby, primary exergy input for operating equipments of a composting toilet becomes smaller than primary exergy input for flushing water and production of urea fertilizer.