there is no need to mechanically pump air into the landfill.

Since the semi-aerobic landfill structure allows cheaper construction and faster waste stabilization than the anaerobic landfill system promoted in the West, and since it can even restrict methane generation, it has recently attracted the attention of many developing countries as a sustainable technology and a suitable technology with which to help prevent global warming.

# Conceptual image of the semi-aerobic landfill structure

Source : Fukuoka University and Fukuoka City Government

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## The hexavalent chromium problem and the amendment of the Waste Management Law

The Waste Management Law, enacted in 1970, provided a clear definition of industrial waste and positioned it within the legal framework. However, because of the lack of an appropriate mechanism to accurately keep track of activities concerning industrial waste disposal, the monitoring and directions provided by the authorities were incomplete, leading to problems such as the frequent occurrence of illegal dumping and other violations, along with failures by the waste-generating businesses in exercising their responsibility. In addition, as the shortage of final disposal sites worsened, a growing number of companies simply piled up their waste out in the open, within their factory premises.

In the summer of 1975, an inappropriate disposal site for slag containing hexavalent chromium was found at a Tokyo factory that manufactured hexavalent chromium compounds, such as bichromate of soda. Environmental pollution was also discovered in the area around this site, along with potential health hazards to local residents. This incident developed into an issue of major public concern since pollution from hexavalent chromium slag was identified in many other regions following this initial discovery.

In light of public concern over waste disposal problems, the government amended the Waste Management Law in 1976. This amendment was mainly aimed at tightening regulation and supervision in order to ensure responsible final disposal.

Specifically, these amendments included redefining final disposal sites as waste disposal facilities, instituting a registration system, and introducing prior assessments based on technical standards. To enforce appropriate outsourcing practices concerning waste disposal, the amended law set up standards for the outsourcing of disposal work and banned companies from subcontracting any disposal work they have undertaken to another company. To keep track of industrial waste disposal activities and provide appropriate supervision and instructions, the amended law obliged enterprises and disposal companies to create and maintain disposal records, and added provisions on restoration orders to be issued in the event of any incident harmful to the conservation of the living environment.

This hexavalent chromium problem awakened Japan to the need to take environmental effects into consideration when addressing the final disposal of any waste, including industrial waste. It was also the starting point for efforts that have since led to Japan’s success in reducing the amount of waste disposed of in final landfill sites by about 70% since the 1990s.