Development of methodology for quantifying collection rate of post-consumer products based on material flow of steel

Abstract

Currently, some post-consumer products are not collected appropriately and remain or are disposed of by unknown ways. In order to conserve resources, the collection rate of such products should be increased. To date, few definitive methods to quantify the collection rate have been developed due to the difficulties in monitoring the amounts of the uncollected products. We have no other choice but to estimate the collection rate. In this paper, a new statistical method was developed to quantify the collection rate of post-consumer products. This method is based on the identification of dynamic material flow of steel used in several kinds of products. The steel-contained products were categorized into six categories: buildings, civil engineering, machines, automobiles, containers, and "others." The collection rates of buildings, civil engineering, and machines were estimated. As the denominator of the collection rate, the amount of discarded post-consumer products during a year was calculated dynamically from their lifetime distributions and production history in which steel was used prior to that year. As the numerator of the collection rate, the amount of collected steel scraps for recycling domestically and exports was obtained from statistics. Furthermore, uncertainty derived from the lifetime distributions was considered in the calculations. The estimated collection rates obtained with these methods were 1.00 for buildings, 0.00 to 0.22 for civil engineering, and 0.39 to 0.52 for machines. © 2007 The Japan Institute of Metals.