Assessment of the Recycling Potential of Aluminum in Japan, the United States, Europe and China * 1 Hiroki Hatayama * 2 , Ichiro Daigo, Yasunari Matsuno and Yoshihiro Adachi Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan Global aluminum consumption has exhibited significant growth in recent years, because of aluminum’s useful properties. As this will result in a large amount of aluminum accumulation in ‘‘urban mines’’, the exploitation of these urban stocks will be an important issue in the future. To examine the recycling potential of urban stocks, a dynamic material flow analysis of aluminum was conducted focusing on Japan, the United States, Europe and China. The concentrations of the alloying elements were also investigated, because carryover of alloying elements during recycling can result in off-specification secondary metals and alloys. The recycling of aluminum scrap was optimized from the results of dynamic material flow analysis using multimaterial pinch analysis. It was estimated that Japan, the United States, Europe and China have the potential to reduce their primary aluminum consumption to 60%, 65%, 30% and 85% of their present levels, respectively. In 2050, it is estimated that 11400 kt of primary aluminum will be required among the four countries, while 12400 kt of obsolete scrap will not be able to be recycled because of high concentrations of alloying elements. [doi:10.2320/matertrans.MRA2008337] (Received October 1, 2008; Accepted December 12, 2008; Published January 28, 2009) Keywords: aluminum alloy, material flow analysis, pinch analysis, recycling, optimization 1. Introduction Aluminum is a versatile metal, owing to various properties such as its light weight, high corrosion resistance and good formability. Such advantages have resulted in increasing aluminum consumption, and today attention is turning to the large amount of aluminum scrap. To exploit these urban resources, an assessment of recycling potential by material flow analysis (MFA) becomes important. Using dynamic MFA, Melo 1) estimated aluminum scrap generation in Germany, and Martchek 2) estimated the in-use stock of aluminum in the world. However, to assess the recycling potential of aluminum, the chemical composition of the scrap should be taken into account. Aluminum properties are modified by adding alloying elements, including Si, Fe, Cu, Mn, Mg, and Zn. In producing secondary aluminum from scraps, the alloying elements in the scraps are usually reused in the recycled alloys, and at the same time, some new alloying elements are added, to satisfy standards on chemical composition. On the other hand, excess presence of the alloying elements would require additional primary alumi- num for dilution because some alloying elements cannot be removed at secondary smelters. Boin and Bertram 3) analyzed the aluminum flow in Europe, considering the different recovery processes by end use, because different products yield scrap of differing compositions. In their work, ‘‘quality of aluminum scrap’’ was taken into account in recycling. However, it is not sufficient to discuss the balance of respective alloying elements between scrap and secondary metal. The assessment of the influence of alloying elements on recycling should be achieved by considering the chemical composition of each aluminum flow; Hatayama et al. 4) analyzed aluminum flow in Japan allowing for chemical composition, and Yamada et al. 5) assessed the recycling of aluminum in Japan. This paper presents the assessment of aluminum recycling, focusing on Japan, the United States, Europe and China, for which dynamic MFA is used. 2. Methodology 2.1 Overview Figure 1 shows the structure of this study. Our MFA focused on Japan, the United States, Europe and China, which accounted for about 80% of the world aluminum consumption in 2003. The MFA estimated the amount of in-use stock and scrap generation in each end use. The concentrations of alloying elements in stocks and flows were calculated by counting the consumption in each end use by alloy type. Then, from the relation between the amount of in-use stock and per capita GDP in the past, future in-use stock change was predicted using GDP and population forecasts. Finally, a multimaterial pinch analysis estimated the recycling potential of scrap and requirements for primary aluminum for each region. The scrap trade in 2050 was optimized to achieve the best recycling in the four regions. 2.2 Data for aluminum consumption Aluminum consumption in each end use was obtained for the respective regions from 1960. Different alloy types were considered: wrought alloy and cast alloy for the three regions except Japan, while for Japan, die-casting alloy was counted independently from cast alloy. Consumption by both end use and alloy type were obtained from statistics 6) for Japan up to 2003 and the United States up to 2005. For Europe (including Austria, Belgium, Denmark, Finland, France, Germany, Italy, Greece, Netherlands, Norway, Spain, Sweden, Switzerland, the United Kingdom and Yugoslavia), consumption of each alloy type for 1974–2003 was obtained from statistics. 7) These consumptions were divided into respective end uses according to the shares given in the * 1 This Paper was Originally Published in Japanese in J. Japan Inst. Metals 72 (2008) 812–818. * 2 Graduate Student, The University of Tokyo Materials Transactions, Vol. 50, No. 3 (2009) pp. 650 to 656 #2009 The Japan Institute of Metals