A new scheme of hybrid life-cycle assessment (LCA) termed the waste input-output (WIO) model is presented that explicitly takes into account the interdependence between the flow of goods and waste. The WIO model has two distinguishing features. First, it expands the Leontief environmental input-output (EIO) model with respect to waste flows. It turns out that the EIO model is a special case of the WIO model in which there is a strict one-to-one correspondence between waste types and treatment methods. By relaxing this condition, the WIO model provides a general framework for LCA of waste management. Second, the WIO model takes into account the "dynamics of waste treatment," which refers to the fact that the input-output relationships of waste treatment are significantly affected by the level and composition of waste feedstock, by incorporating an engineering process model of waste treatment. Because waste treatment is expected to accept whatever waste is generated by industry and households, a proper consideration of this feature is vital for LCA of waste management. We estimated a WIO table for Japan and applied it to evaluating effects of alternative waste management policies with regard to regional concentration of incineration and the sorting of waste with regard to flammability. We found that concentrating treatment in a small number of large incinerators combined with an increased degree of sorting could decrease both landfill consumption and the emission of carbon dioxide.
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