Abstract
This study intends to propose a new approach to evaluate the utility of recycling used products made of Polyvinyl Chloride (PVC) . In order to determine whether or not these used products can be recycled, there must be some indicators that appropriately and quantitatively show the degree that the contribution of recycling these targeted used products has on society. It was indicated that the rights and wrongs of incineration and/or heat recovery using a material such as wallpaper or floor cover made of PVC could be judged by the concept of "Social Energy Consumption" originally proposed by the authors (Chap. 3 in the text) . On the other hand, in the case where the used products such as PVC pipes and joints are dug out from underground and recycled, this research shows the estimation of its utility should be accomplished by extending the concept: Specifically, the manpower converted to the value of the social energy consumption was added, because labor costs for digging out these used products occupy a large portion of the total recycling cost, although manpower is not taken into account in the usual energy balance calculation, which leads to the contradiction of the estimation results from the standpoint of energy balance and economy. In this study, the marginal cost for digging out PVC pipes and joints evaluated by this method was shown as an example of a trial calculation (Chap. 2 in the text) . As a whole, this research quantitatively demonstrated an example trial calculation showing whether or not these used products should be recycled disregarding if the economic efficiency should be evaluated as a result of the analysis based upon the concept of "Social Energy Consumption".
