Estimation of steel consumption and obsolete scrap generation in Japan and Asian countries in the future

In this paper the present flows of steel scraps in Japan, China, South Korea and Taiwan are clarified, and a dynamic model which analyzes future scraps flows is developed. To estimate the amount of collected obsolete scraps, a Population Balance Model (PBM) was used for Japan, South Korea and Taiwan. PBM is a model which estimates the amount of discards dynamically by taking into account the steel input to a society by end-uses and the lifetime distributions of each end-use. For China, a Leaching Model was used to estimate the amount of collected obsolete scraps. This model uses the amount of steel stocked in a society and the collection ratio of obsolete scraps. Three different methods were applied to predict future steel inputs for each country. The first method is applying the assumption that steel demand in the future remains constant at the present level. The second method is applying a logistic curve for future steel stocks. The third method is applying regression equations to future steel inputs by each end-use. GDP and population were used as variables. Finally the results of the steel input predictions by each method were substituted into the collected obsolete scraps estimation model. Under the logistic curve method, it was estimated that in 2030 the amount of collected obsolete scraps would be 29 million tons in Japan, 83 million tons in China, 20 million tons ill South Korea and 3.7 million tons in Taiwan.