4 巻 (2008) 4 号 p. 324-333
Background and Objective. In recent years, besides the domestics recycling, a part of Japanese post-consumer PET bottles are exported to and recycled in mainland China. In this study, life-cycle assessment was applied to the comparison of PET bottle recycling scenarios, including domestic recycling and transboundary recycling between Japan and China, from the viewpoint of CO2 emission and fossil fuel consumption.
Results and Discussion. The following 10 scenarios based on our field surveys were evaluated: Japanese post-consumer PET bottles are (i) recycled into polyester staples in Japan, (ii) recycled into polyester filaments in Japan, (iii) recycled into polyester clothes in Japan, (iv) chemically decomposed and recycled into bottle-grade PET resin in Japan, (v) chemically decomposed and recycled into polyester filaments in Japan, (vi) (vii) recycled into polyester staples in two different flows in China, (viii) recycled into polyester clothes in China, (ix) incinerated and partly recovered as electricity in Japan, and (x) directly landfilled in Japan. The results showed that all the domestic and transboundary recycling scenarios had smaller impacts than the incineration scenario, and that the chemical recycling scenarios had larger impacts than the other recycling scenarios. The robustness of the results was examined against variability of background parameters for electricity supplies and against specification of virgin products substituted by recycled products.
Conclusions. The differences of CO2 emissions and fossil fuel consumptions between domestic and transboundary recycling scenarios, other than the chemical recycling scenarios, were not large enough to be robust against the above-mentioned variability. In particular, the variability strongly influenced the results of the scenarios including cloth-manufacturing processes in their system boundaries.