Toward the efficient recycling of alloying elements from end of life vehicle steel scrap

There has been a sharp increase in the production of automobiles over the past decade. In 2010, one billion automobiles were in circulation worldwide. The automobile industry is one of the largest metals consumers and plays an important role in their sustainable use. Steel materials, including alloy steels that contain alloying elements (AEs) such as manganese, chromium, nickel, and molybdenum, are the main component of automobiles. The recycling of end-of-life vehicles (ELVs) significantly affects the cycling of iron, steel, and AEs. Currently, ELV recycling is performed using the electric arc furnace (EAF). In this method, losses of AEs are likely to occur because their presence is rarely considered. This study evaluated the environmental and economic benefits of alternative ELV recycling schemes, which allow more efficient utilization of AEs found in ELV-derived steel scrap (ELV-dSS). The AE contents in ELV-dSS (as car-parts) were estimated by means of a waste input-output material flow analysis (WIO-MFA) model extended for the detailed analysis of automobile composition. Using Japanese data, it was found that sorting ELV-dSS by parts can result in a significant recovery of AEs; more specifically, a 10-fold saving in AEs was achieved by sorting exhaust parts. The recoverable mass of AEs from sorted ELV-dSS was found to correspond to 8.2% of the annual consumption of AEs in Japan, as virgin resources in EAF steelmaking. ELV-dSS sorting was found to be significantly effective in the conservation of AE resources.