廃棄物系バイオマスの利用に関するLCAの論点

抄録

Appropriate and effective use of waste biomass is anticipated because it is estimated that waste biomass accounts for a maximum ratio in biomass of Japan. Three salient issues related to the LCA of waste biomass use are presented herein: system boundary, uncertainty, and impact assessment. First, renewable resource collection and waste landfills are specifically addressed as issues in related to the boundary separating technological and nature systems. Forests and forestry should be included in evaluation of waste wood recycling; and attention must be devoted to the period of environmental impact when evaluating waste landfills. Regarding the boundary surrounding waste biomass use systems, selection of processes that would be replaced by the use of waste biomass is important. As an issue related to boundaries when comparing various recycling systems, some methods of system expansion to establish the same functional units are presented. Classification of recycling by association with existing industries is also presented in conjunction with system boundaries. Second, in conjunction with uncertainty, factors of uncertainty generally related with LCA, their specific examples, and coping methods for those factors are explained. As uncertainty factors in the LCA of the waste biomass use, we present the maturity of recycling technologies, variation of the amount of energy and waste composition, and preparation of databases for venous industries. As coping methods applied to those factors, acquisition of more data, adequate classification of technologies, presentation of the range of results, and clarification of uncertainty factors through discussion among the donors and recipients of LCA information are suggested. Furthermore, regarding impact assessment, we introduce existing methodologies and research and development trends and describe that impact categories at the midpoint and endpoint are applied in Japan and Europe, respectively, in LCA of waste management. As impacts related to waste biomass use, regional water pollution by discharge to the natural environment and inappropriate application of fertilizer to farmland, NIMBY problems related to facility location, and changes in bio-diversity by agriculture and forestry are considered. Finally, we describe the conduct of activities parallel to LCA and use of LCA results for planning waste biomass use.