Night Soil to Chemical Fertilizer: Lessons from the Abolishment of the Circular Economy in Postwar Japan

To realize a circular economy in agriculture, it is crucial to determine whether and how agricultural fertilizers are sustainably used. Night soil has been used as a source of agricultural fertilizer in Japan by the 1960s. Night soil was bought and sold through a market in the Edo era in Japan. Since the 1910s, night soil supplied from urban areas has gradually transformed into an economic bad owing to the rapid population growth and urbanization; thus, local governments needed to administratively manage night soil. Except for several years after the end of World War II, night soil was an economic bad, and local governments had a legal obligation to manage it in postwar Japan. Nevertheless, many urban cities, including Tokyo, struggled to supply night soil to farmers in rural areas, and farmers in rural areas used night soil as a source of nitrogen fertilizer by the 1960s across Japan. This paper aimed to analyse the causal inference of why the circular economy of night soil was abolished in the 1960s in Japan using an empirical strategy. I concluded that the increase in the demand for artificial chemical fertilizers caused the abolishment of night soil delivery system to rural areas. To promote a circular economy in current society, it is important to establish an economic environment in which farmers can continue to use night soil as a fertilizer.