2012 年 8 巻 4 号 p. 356-369
Objective. In hot spring areas, the water is generally heated by heavy oil boilers. However, substantial CO2 is emitted in the heating process, and the process is always affected strongly by oil prices. The Nagareyama Hot Spring, which is owned by the Hokkaido Railway Company, has recently introduced a waste oil boiler that is fueled by lubricating oil discarded by the railway company. Regarding a hotel with hot spring, used bath water is usually thrown away to the river and extra heat generated from a machine room is usually released to the outside. Given the current situations, we considered 2 possibilities: (1) using waste oil in place of heavy oil in Nagareyama Hot Spring, and (2) utilizing wasted bath water and released heat from the machine room for warming greenhouses in winter in Yubari Hot Spring. These modifications were designed to minimize the environmental burdens as represented by CO2 emissions and economic costs. The potential CO2 reduction was evaluated quantitatively by using a method of Life Cycle Assessment (LCA).
Results and Discussion. CO2 emission was reduced by 94.1 t-CO2 annually by using waste oil in place of heavy oil at the Nagareyama Hot Spring. The replacement of a heavy oil boiler with a waste oil boiler also contributed to reduce the annual running cost by 141,000 yen. By utilizing the heat of the used bath water in the Yubari Hot Spring to improve asparagus production in the greenhouses in winter, it was estimated that the annual CO2 emission is reduced by 7.26 t-CO2. However, the running cost was predicted to be 939,000 yen higher than in the present system.
Conclusions. The replacement of the heavy oil boiler with the waste oil boiler was expected to reduce both CO2 emissions and the running cost. In the case of the heat-use of old bath water, it was effective in terms of the reduction of CO2 emission. However, economic benefits were not expected because of the high price for installing a new equipment to transport the hot water into the greenhouses. Introduction of further carbon pricing such as a carbon tax and carbon credits is necessary to promote these alternative energy systems throughout local communities.