emissions in Japan, and so the measures addressing these sectors are also important tasks.

Japan is reducing its $ CO_{2} $ emissions with the cooperation of local government through their low-carbon programmes, such as developing an intensive urban structure, improving energy efficiency in regional units, and changing the regional strengthening measures to shift the regional structures to low-carbon.

One such effort is the “Challenge 25 Community Building Project.” Mitigation of global warming is a task that involves comprehensive actions in all fields, such as industry, transportation, private/commercial sectors, and community building, and it is becoming increasingly important for a wide variety of parties such as the national government, local governments, private commercial operators, NPOs, and regional residents to participate and make efforts in order to mitigate global warming. In light of this, the Ministry of the Environment began the Challenge 25 Community Building Project in FY 2009. This project invited and promoted proposals for actions effective for $ CO_{2} $ emissions reduction in the regions, facilitated the revitalization of the regions and enabled the realization of communities that have a small environmental load. This Challenge 25 Community Building Project offered subsidies for the projects in three areas, “establishment of plans,” “subsidized

Source: Ministry of the Environment

projects” and “verification projects”. In FY2009, 12 entries, 11 entries, and 5 entries were accepted for these three areas respectively. The verification projects

Efforts under the Challenge 25 Community Building Project - The Example of Nakatsugawa City

A project proposed by Nakatsugawa City was accepted as a “challenge by a small-or medium-size city” under the Challenge 25 Community Building Project. This project is to verify the effect of $ CO_{2} $ emission reduction by a heat transportation system (Trans Heat Container) that transports low temperature heat generated from waste incinerators using trailers, and by a geothermal heat pump system that employs the groundwater and provides a stable supply of heat throughout the year.

The Trans Heat Container is the system that stores the heat generated by waste incinerators in containers filled with latent heat storage materials, transports containers to separate facilities (e.g. offices) that use the heat for air-conditioning. One of advantages of the Trans Heat Container system is that they can collect low-temperature waste heat of $ 100^{\circ} $ C or less, which had conventionally been emitted into the atmosphere because it was difficult to recover using existing technologies. By using one container at a time it is possible to reduce emissions by a maximum of approximately 500kg of carbon dioxide equivalent. In Nakatsugawa City, they collect low-temperature waste heat generated by waste incinerators, transport it to publicly-operated hospitals in different locations where it is used as a heat source for air-conditioning and hot water, thereby reducing of carbon dioxide emissions.

When air-conditioning is used during the summer, exhaust heat that was air-conditioned by the heat pump is emitted into the soil (cool heat is absorbed). Source: Taisei Corporation

When heating is used during winter, the heat pump collects warm heat from the soil.

Nakatsugawa City is also conducting a verification experiment for the geothermal heat pump system. A geo thermal heat pump is a system that uses soil or groundwater, which experience fewer temperature changes as a heat source than the atmosphere. Since