Recycling of Steel

Abstract

There have been a large demand of steel scraps in Asian countries, and Japan has been the main exporter of steel scrap since 1996. So, estimation of steel scrap generation in Japan in the future is of interest. For assessing scrap generation and materials’ stock in-use, Material Flow Analysis (MFA) has been of interest in USA, Europe and Japan, etc. Since steels are used for various products whose life-time distributions significantly differ, the MFA should have a dynamic aspect. The authors have conducted dynamic material flow analyses for steel to estimate the stock in-use and generation of scraps in Japan at a given time in the future by employing a population balance model (PBM). The PBM predicts the amount of post-consumer materials discarded in a particular year based on the year-by-year chronological data of the demand for material, as well as a lifetime distributions of the material according to each application. Obtained were the data about steel production, scrap consumption, and their import and export in the 20^th century in Japan as well as lifetime distributions of products and collection rates of scraps from end-of-life products (construction, machinery, automobile, container, other). It was estimated that the amount of collected obsolete scrap in Japan would increase up to 33.5 million t in 2030. It was found that quality requirements on steel scraps by other countries could have large influence on the quality of domestic steel. Finally, the author will discuss how the results of MFA can be used with Life Cycle Assessment for assessing the environmental impact of steels.