社会エネルギー消費量を指標としたPETボトルリサイクルのLCA解析

抄録

Objective. The "bottle to bottle recycling" of PET bottle by chemical process, hydrolysis and re-synthesis of PET resin, was put into practical use in April of 2004 in Japan, and this method was regarded as one of the most promising routes of PET bottle recycle. There are, however, several options of PET bottle recycling that should be examined whether they are really useful or not. In this study, LCA analysis was tried to estimate the effectiveness of several alternatives of PET bottle recycling. A new concept of "Social Energy Consumption", defined as sum of energy inputs for production plus feed stock energy minus total energy loss in our society during the use and recycling of PET bottle, was proposed and used as criteria for estimating the effectiveness of the PET bottle recycling: in other words, energy equivalent of resource conservative quantity was used for estimation of recycling, that is a main characteristic of this study.
Results and Discussion. Several case studies were carried out to examine the adequacy of assumed values as well as the estimation procedure adopted in this study. As a result, the reliability of the values and method was confirmed. Results of the case studies indicated that the advantage of the chemical recycle for bottle to bottle is not so larger as was expected than that of material recycle for other products, because energy input for chemical recycle is rather large, however the difference in the quality of products is not taken into account. And it was also found that bottle reproduction from flakes obtained directly by crushing used PET bottle has a better potential advantage, meaning that this recycle route will be worthy of serious consideration although this is not practical in present-day Japan by the ministerial regulation from a hygiene point of view.
Conclusions. Thus, there should be more emphasis on the necessity of wide-ranging discussions on the recycle of PET bottle based on objective and quantitative LCA investigation from the stand point of, not only CO₂ emission, but the social utility of repeated use of petroleum resource.