Utilization of Sewage Heat as Part of Environmentally Conscious Urban Development - October 1996 Namekawa City, Toyama Prefecture

Utilization of Sewage Heat as Part of Environmentally Conscious Urban Development - October 1996 Namekawa City, Toyama Prefecture

The 1990s was a time when Japan began to become increasingly aware of the need to conserve energy and introduce renewable energy. In particular, the need to reduce carbon dioxide emissions was clearly stated as a national priority by the "Outline for the Promotion of Measures to Cope with Global Warming" in 1993, and energy recovery and reuse began to be explored throughout the country.

Against this backdrop, the demonstration experiment of a "sewage heat utilization system" undertaken by Namekawa City in Toyama Prefecture was a pioneering example of an innovative urban energy policy. Urban sewage contains heat from domestic and industrial wastewater that has been discharged without being utilized. Focusing on this "unused energy," Namekawa City decided to introduce a system that recovers the thermal energy contained in sewage and reuses it for air conditioning and hot water supply in buildings.

The New Energy and Industrial Technology Development Organization (NEDO) participated in the project, which was a typical public-private partnership (PPP) type initiative involving local government and national technology development organizations. Namekawa City, despite being part of the industrial city of Toyama, is oriented toward regional development in harmony with nature, and local environmental awareness was high.

The sewage heat utilization system uses a heat exchanger to recover the temperature difference in sewage as a heat source, which is then utilized as practical heat energy using heat pump technology. Although the technology was relatively new at the time, and problems of capital investment and operating costs were pointed out, the system attracted nationwide attention as a model case for sustainable urban development in that it utilized heat that had previously been discarded as a source of local energy.

This experiment also influenced the later spread of "energy use in all areas" and "district heat supply systems," and showed a new direction in the fusion of urban infrastructure and environmental policy. It proved that advanced energy circulation models are possible even in regional cities, and provided inspiration to municipalities nationwide for their concrete implementation.