著者

醍醐 市朗 五十嵐 佑馬 松野 泰也 足立 芳寛

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.93, no.1, pp.66-70, 2007-01-01

被引用文献数

2 17

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During the last two decades, the total material input in Japan has been about 2 billion tons, and approximately 50%, i.e., about 1 billion tons has accumulated as the net addition to stock in the form of buildings, social infrastructure, and various kinds of products. The amount of the net addition to stock is calculated annually from the differential between the input and the output. Therefore, the contents of the accumulated stock are unknown. It is said that these unknown contents include material that has already been discarded as invisible waste. In this study, dynamic material flow analysis was conducted to quantify the amount of stock that is not associated with social activities and cannot possibly be collected as scrap in the future. First, we defined some terms: in-use stock, hibernating stock, and overall stock. Hibernating stock comprises the steel used for the constructional material of land fill site, the steel dissipated by corrosion and erosion, etc. Furthermore, we defined the system boundary to account for the steel stock and constructed equations to calculate the three types of stock. To calculate the amount of in-use stock, a dynamic model-the population balance model-was adopted. The amounts of in-use stock and hibernating stock in Japan from 1980 to 2000 were calculated. The result shows that 0.96 billion tons of the in-use stock is included in the 1.22 billion tons of overall stock in the year 2000.

著者

平戸 崇博 醍醐 市朗 松野 泰也 足立 芳寛

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.95, no.1, pp.96-101, 2009-01-01

被引用文献数

2 16

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Recently, prices of natural resources have rapidly risen, so recovery of materials from the end-of-life products as secondary resources is of great interest. However, it is generally a challenging task to estimate the in-use stock of materials, especially in developing countries, because of lack of data. In this paper, two approaches, a top-down approach and a bottom-up approach, were adopted for estimating the in-use steel stock in end uses. A top-down approach uses time-series data of consumption and trade of materials and product lifetime data, whereas a bot-tom-up approach uses the numbers of units of a specified product in a designated area and its material intensities. In this paper, the steel stock in Japan divided into six end uses was estimated by the top-down approach. The steel in-use stock in Japan was estimated as approximately 1,000Tg in 2005. Steel stock in automobiles in 2005 was estimated as 105Tg by the bottom-up approach and compared with that estimated as 125Tg by the top-down approach. In addition, applying the bottom-up approach, steel stock used in automobiles in U.S. was estimated and compared with that obtained by the previous research using a top-down approach. Steel stock used in automobiles in 2000 in U.S. was estimated as 480-870Tg by the top-down approach and 754-767Tg by the bottom-up approach. Both approaches have some uncertainties in the parameters used in the estimation. Therefore, complementary use of the two approaches is helpful to estimate in-use stock of materials.