The Future of the Environment Built from Ash: Saitama Prefecture's Challenge to Recycle Sewage Sludge as a Resource (1995)

The Future of the Environment Built from Ash: Saitama Prefecture's Challenge to Recycle Sewage Sludge as a Resource (1995)

In the mid-1990s, Japan was faced with a "mountain of waste" piled up as the residue of its rapid economic growth. With the enactment of the Basic Environment Law (1993), the formation of a "recycling-oriented society" was set as a policy goal, and waste disposal was being reexamined throughout the country. Under such circumstances, Saitama Prefecture focused its attention on "invisible waste"-the sewage sludge generated from daily wastewater.

Sewage sludge is the muddy material that remains after sewage from homes and factories is purified at sewage treatment plants, and at the final stage of treatment it is incinerated into a large amount of ash. The "Comprehensive Plan for Sewage Sludge Treatment," formulated over a two-year period from FY1995, calls for the wide-area recovery of incinerated ash and the establishment of a prefecture-wide system for its reuse as a construction material.

Incineration had already been introduced at many sewage treatment plants in the prefecture, and the incinerated ash was recycled into lightweight fine granular materials, bricks, and permeable blocks. These have been used as pavement material for public facilities and sidewalks in parks, and in some cases in Tokyo, they have been adopted for parking lots at the Tokyo Metropolitan Government Office and platforms at Waseda Station on the Tokyo Metropolitan Electric Railway. Based on these precedents, Saitama Prefecture is building a "sludge network" across municipalities and developing a sales and distribution system for recycled products.

This move is not merely a technological innovation, but a revolution in the social structure that "finds value in waste," and is truly an "ideal picture of resource circulation" drawn by the government, technology, and industry working in unison. The sewage treatment system has changed from being "behind the scenes" of urban life to being a "creative site" where future construction materials are created. This was the dawn of a new era in which human activity itself would be in harmony with the environment.

Saitama Prefecture's challenge can be counted as one of the urban models of the 21st century, as a practical example of the concept of not wasting even urban "excrement. Value buried in the ashes of sludge has been revived here.