An important perspective on urban management : the application of material flow balance model to the past recycling society in Japan

Since the industrial revolution, growing and active economic activities in urban area have disrupted sustainable material flow balance in the environment, and the imbalance has induced some serious environmental problems. In order to realize proper urban management, taking measures to keep well-balanced material flow between urban and rural area is necessary. It is considered by historians that Edo, the old name for Tokyo, was environmentally friendly with its material recycling system developed. This paper develops a material flow balance model to quantitatively investigate the impacts of economic activities on the quality of the environment and the effects of the recycling system of Edo. A simulation result by the model shows that the water quality of Edo-bay (present day Tokyo-bay) was 0.095mg/L in the water quality index of total nitrogen (T-N). This value is within the optimal range for the cultivation of Nori, a kind of seaweed essential for Japanese traditional food Sushi. This result means that the recycling system contributed not only to the environment of the Edo urban area but also to seafood production in Edo-bay, and implies the importance of material flow balance for optimal and sustainable urban management.