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Table 3 Materials used in automobiles. Automobile sales in SEA (units) (a) Weight (=a*1.153) (tons) Metal weight (=a*0.920) (tons) Steel* weight (=a*0.773) (tons) (b) Steel use in SEA (tons) (c) Steel use fraction (=b/c) (%) Note: SEA stands for ‘Southeast Asia’. Table 2 Materials breakdown and weight of an automobile. Steel Non-ferrous metal (Al, Cu, etc.) Plastics Others (rubber, glass, fluids) Total weight Note: We referred to the data collected in the study by Tahara et al. (2001). Although not all the details on the data used in that study were indicated in the literature, we used those data in our study. The total weight (1,153 kg) does not include the weight of gasoline, although the ‘curb weight’ generally includes the weight of gasoline. 5) The CO2-saving effect was also estimated. Based on estimates of CO2-saving effects of automotive parts remanufacturing at the product level, and the amount of remanufactured automotive parts estimated in (4), the potential CO2-saving effects of automotive parts remanufacturing were estimated. The estimations in these processes involved uncertainties; therefore some of them can be regarded as assumptions rather than estimates. The processes are described in further detail in the following sections. and the share of remanufactured parts in the spare parts market was estimated. Based on these estimations and the material use for spare parts estimated in (3), the potential material-saving effects of automotive parts remanufacturing were estimated. Material resources are used in developing all types of artifacts infrastructure, transportation infrastructure and all kinds of products. Automobiles are one of the prominent consumers of material resources. Today, 90 million cars are sold annually (flow), and 1.3 billion cars are in use globally (stock) (Table 1). The stock has increased for over a century and its trend shows it is not likely to reach saturation in the near future. Southeast Asia comprises 4.5% of the global stock (Table 1). It has sales of 3.5 million cars (flow) and 58 million cars in use (stock) (Table 1). While the number of cars per 1000 inhabitants is around 600 in Europe and Japan, and 821 in the US, it is 88 in Southeast Asia, and the figure varies highly country-wise in the region, from 439 in Malaysia to 23 in Vietnam (Table 1). These figures and trends indicate that both the flow and stock in Southeast Asia are likely to increase significantly in the coming decades. including, buildings, urban An automobile typically weighs 1.0 to 1.5 tons. Of the curb weight, approximately 70% is steel (ferrous metals), 10% is non-ferrous metals (Al, Cu, etc.), 10% (or less) is plastics and 10% (or more) is other materials (glass, fluids, etc.). Several studies have investigated bills of automobile materials (e.g. Mayyas rubber, Estimating the Potential Material-saving Effects of Automotive Parts Remanufacturing Portion (%) Weight (kg) 773 147 89 145 1153 67.0 12.7 7.7 12.6 100.0 et al., 2017; Bobba et al., 2021; Tahara et al., 2001). We used the figures shown in Table 2 for the weight of an automobile and its materials breakdown. Assuming the figures in Table 2 represent the average figures for automobiles in Southeast Asia, we estimated the amounts of materials in vehicles sold in 2015 and 2030 in the region. Table 3 shows the results, where, in 2015, the vehicles (3.1 million units) are made up of 3.59 million tons of materials, of which 2.86 million tons are metals, of which 2.40 million tons are steel (Table 3). The amount of steel (2.40 million tons) accounts for 2.8% of the total steel used in the region (Table 3). In our estimation for the year 2030, we first estimated the car sales and steel use in the region in the year 2030. They were estimated in both cases by extrapolating the linear approximations of their trends in the years 2010–2019. The car sales in 2030 were estimated at 4.5 million units, and the steel use, at 130 million tons (Table 3). We assumed that the influence of increased numbers of electric vehicles (EVs) and other factors would be limited. Globally, more than 6.8 million battery EVs (BEVs) were on the road in 2020 (IEA, 2021), whereas in Thailand, only 7,250 BEVs were on road yet as of April 2021 (EVAT, 2021). EVs (total of BEVs and plug-in hybrid EVs (PHEVs)) are predicted to account for 7% of the car stock worldwide by 2030 (IEA, 2021). The ratio is expected to be lower in Southeast Asia. This study did not take the influences of car electrification into account. The materials, metal and steel used in vehicles in the region in the year 2030 were estimated at 5.19, 4.14, and 3.47 million tons, respectively, and the steel for cars was estimated to comprise 2.7% of the total steel used in 2030 (Table 3). The estimated fractions of steel used in automobiles in the region (2.8% and 2.7%) are smaller than those globally. According to Allwood and Cullen (2015), the steel used in cars and trucks in 2008 globally was 108 million tons, comprising 10.0% of total steel used globally that year. We then estimated the amount of materials used in 1) Source: (OICA, 2021a) 2) Source: (World Steel Association, 2020) 3), 4) Source: Authors’ estimation (or assumption). 2015 2030 3.11 M 1)3.59 M 2.86 M 2.40 M 84.8 M 2)2.8% 4.50 M 3)5.19 M 4.14 M 3.47 M 130 M4)2.7% 67 2.2 Flow and Stock of Automobiles 2.3 Material Use for Automobiles 2.4 Material Use in Spare Parts

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