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(1) Material Circulation Analysis and Minimization of Environmental Loads
When you see environmental loads driven by urban activities, there are two types of loads, namely “direct” and “induced” loads. For example, CO2 emission driven by combustion of petroleum fuels is direct load, whereas CO2 emission from consumption activity is derived from production stage and it can be induced load. Huge amount of materials are consumed and disposed in urban areas and they induce various environmental problems. To build up sustainable society, reduction of virgin materials and wastes must be achieved through efficient consumption and reduce & reuse activities. Even if you connect individually effective processes, some contradiction and vainness can happen. For making a good system, seeing whole picture is very important. From the lifecycle viewpoint, we have evaluated various waste management scenarios.


Strategy for Unutilized Wastes
Organic wastes, such as garbage, sewage sludge, animal wastes, and food wastes, can be not only wastes but also carbon neutral biomass. They are generated in large amount and various technologies, such as methane fermentation and composting, are found. However, they are not effectively used so far. One possible reason is the gap between demand and supply. For example, large amount of food wastes are generated in urban areas but composts produced by food wastes cannot be consumed in urban areas only. Recycle of organic wastes is quite different from recycle of plastics in terms of their circulation areas. Long-range transport of heavy but low value organic wastes causes high transportation costs. Therefore, the circulation of organic wastes is limited within small areas. Hence, composting and production of feeding materials have demand limitation. To minimize the environmental loads, the optimum recycle system of organic wastes should be considered for each local area. Besides, further use of manufacturing industries may contribute to utilization of biomass. Cooperation between urban and agricultural areas or between urban and industrial areas can become more important from now.
Waste Management using Life Cycle Assessment
There are various waste treatment and disposal systems. Wastes can be used for energy production as well as be recycled. The estimation of environmental loads derived from recycling is complicated. For example, if “material A” is recycled as “material B” instead of disposal, the merits are: a) avoidance of “material A” treatment and disposal, and b) no need to produce “material B” from virgin material C. On the other hands, energy consumption and pollutants emission can be also derived from recycling. Detailed estimation of these merits and environmental loads can bring correct evaluation of recycling.
Evaluation of various waste management systems by Life Cycle Assessment
In this study, life cycle environmental loads derived from various waste management systems, such as combustion, methane fermentation, and composting, are compared in Tokyo and Sao Paulo. For evaluating environmental loads, the indexes such as global warming potential (GWP), acidification potential, and nutrient emission are used. When the lifecycle loads are compared, differences between the countries can be found. It is caused by differences of waste composition and carbon intensity.

Fig：Comparison of GWPs of various waste management systems between Tokyo and Sao Paulo
Evaluation of Seoul Waste Management Systems through midpoint and endpoint LCA approaches
In the case of waste management evaluation by LCA, how local people’s preferences can be involved in the evaluation? The basic procedure of current LCIA involves damage estimation at endpoints and integration using conjoint analysis or AHP. However, is it true that endpoint evaluation is better than midpoint evaluation? In this study, local midpoint impacts were shown to residents and compared with the evaluation using endpoint estimation results. And then methodologies to involve residents’ preferences into decision making are discussed.


(２) Measures to foster waste prevention behaviors
Reduction of household wastes is one of the key issues for building a sustainable society. Waste generation is closely related to product consumption, causing other environmental burdens such as greenhouse gas emissions. Currently, greenhouse gas emissions from the household sector account for 20% of all greenhouse gas emissions, and the amount of emission has been increasing. Based on these circumstances, the government has intensified activities to raise citizens’ awareness of “3R”, that is, reduction, reuse, and recycle. As defined by the Organisation for Economic Cooperation and Development (OECD), waste prevention can be positioned upstream from recycling. Recycling activities have become daily routine behaviors for residents, whereas waste prevention behaviors strongly depend on people’s purchasing behaviors which is relatively difficult to change. To faster people’s waste prevention behaviors, understanding the psychological factors that determine people’s behaviors may be effective.