Steel flows and stocks in the Global South highlight development gaps

To strategically discuss how steel should be produced, used and recycled, understanding of current and future flow and stock of steel is of high importance. Because steel is used in the society for many years, records in the relevant industries including import and export from the past years are crucial as well as the current up-to-date statistics when illustrating flow and stock of steel in a year. Following the pioneering national flow and stock figures developed in Japan, this paper presents Taiwanese 2006 and 2007 versions of illustration of iron and steel flow, stock, and recycling, as well as list of data sources, estimation method for missing data, prediction method for the future flow and stock and recommendation for future refinement. The methodologies were modified basing on the Japanese method, due to differences in data availability, collection methods and social background of the data. Using a bottom-up approach, stock and obsolete scrap flows are estimated for three major household appliances, i.e. washing machine, refrigerator, and air conditioner. From comparison of the 2006 and 2007 versions, increasing importance of scrap materials in Taiwanese crude steel production and increase of importance of external market can be seen. Increasing the number of steel products covered by bottom up approach and its combination with top-down approach is recommended, as well as the refinement of assumptions from accumulating recorded data to increase completeness of the future versions.

Mapping provincial steel stocks and flows in China: 1978–2050

Steel stocks and flows of global merchant fleets as material base of international trade from 1980 to 2050

Steel is the most widely used metal in the world. Many studies analyzing the flow and stock of steels have been conducted for Japan, Asian countries and the world. While top-down and bottom-up approaches have been used in these material flow and stock analyses, the applicability of these approaches is dependent on data availability. To overcome this problem, we proposed a methodology to estimate steel stock based on satellite images. Previous studies have shown that satellite images of nighttime lights are closely correlated with human activities, such as electricity consumption, CO 2 emissions, and GDP, which can also be linked to the amount of steel stock. In this study, images of nighttime lights were used in conjunction with land cover data to estimate the building and civil construction steel stock in Japan and other Asian countries. Analysis was first performed for each prefecture in Japan, and then the results were applied to China, South Korea and Taiwan. Building steel stock was highly correlated with urban nighttime lights, while the steel stock used for civil construction structures correlated more closely with total nighttime lights. This work is considered as revised version of the authors’ previous study by updating some of the nighttime light data.

A model to estimate future steel stock and demand was developed under the assumption that the steel stock per capita saturates following a sigmoid curve for Japan, China, South Korea and Taiwan. Per capita GDP was used as the variable. Different sigmoid curves were assumed for each end-use, i.e. buildings, infrastructure and automobiles. As in a previous study on automobiles ownership forecast, country-specific saturation values were introduced for steel use in buildings and infrastructure. As an indicator of regional difference, net population density was introduced. The relation between the saturation value and net population density was examined using the Japanese prefectures as samples, and the relation was applied to the East Asian countries. Future population and GDP were substituted into the sigmoid curves and the steel stock and demand was estimated up to 2050. As a result, steel demand for buildings and infrastructure was estimated to reach its peak around 2020 in China, the amount approximately being 330 million tons and 200 million tons respectively. Steel demand for automobiles in China was estimated to continuously increase until 2050 exceeding 100 million tons.

We present a comprehensive analysis of steel use in the future compiled using dynamic material flow analysis (MFA). A dynamic MFA for 42 countries depicted the global in-use stock and flow up to the end of 2005. On the basis of the transition of steel stock for 2005, the growth of future steel stock was then estimated considering the economic growth for every country. Future steel demand was estimated using dynamic analysis under the new concept of "stocks drive flows". The significant results follow. World steel stock reached 12.7 billion t in 2005, and has doubled in the last 25 years. The world stock in 2005 mainly consisted of construction (60%) and vehicles (10%). Stock in these end uses will reach 55 billion t in 2050, driven by a 10-fold increase in Asia. Steel demand will reach 1.8 billion t in 2025, then slightly decrease, and rise again by replacement of buildings. The forecast of demand clearly represents the industrial shift; at first the increase is dominated by construction, and then, after 2025, demand for construction decreases and demand for vehicles increases instead. This study thus provides the dynamic mechanism of steel stock and flow toward the future, which contributes to the design of sustainable steel use.

Steel is the most widely used material in the world and numerous studies analyzing the material flow of steel have been conducted for Japan, Asia and the world. While top-down and bottom-up approaches have been employed in material flow analysis and steel stock accounting, the applicability of these approaches is largely dependent on data availability. To overcome this problem of limited data, we proposed a method for estimating steel stock based on satellite images. Previous studies have shown that satellite images of nighttime lights are closely correlated with human activities, such as electricity consumption, CO2 emissions, and GDP, etc., which are also linked to the amount of steel stock. Therefore, in this study, images of nighttime lights were used in conjunction with land cover data to estimate the building and civil construction steel stock in Japan and other Asian countries. We initially performed the analysis for each prefecture of Japan and then applied the combined result to Japan, China, South Korea and Taiwan. Building steel stock was highly correlated with urban nighttime lights, while the steel stock used for civil construction structures was more closely correlated with total nighttime lights.

Steel is known as the most consumed metal in the world. Especially the use of steel in building and civil engineering sector accounts for the largest share in the total steel consumption. The flow and stock of steel has been intensively studied by material flow analysis (MFA) methodologies. The steel intensity for buildings largely depends on building structure, which is further decided by various factors, e.g. local economics, environment, frequency of earthquakes, culture, etc. However, these factors were seldom considered in previous MFA studies when estimating building steel stocks. In this paper, the worldwide difference in building structural composition was compared, and average building steel intensity was calculated. The authors examined the influence of GDP per capita, frequency of earthquakes, and average people killed per earthquake on the building structural composition, and the average building steel intensity. As the result, Asia-Pacific countries show relatively higher average building steel intensity than European countries, which is attributable to the seismic frequency. However, countries like China could have low average building steel intensity even with high seismic risk due to their low GDP per capita. These countries indicate high potential in growth of steel consumption in building sector in the future.

Tools and data sources for illustration of flow and stock of steel in Taiwan and neighbor countries

Estimation of structural steel and concrete stocks and flows at urban scale–towards a prospective circular economy

In this work, a dynamic material flow analysis (MFA) was conducted to estimate the global flow and in-use stock of steel for 4 machines (engineering and construction equipment, agricultural machinery, fans and pumps, and conveyance machines) in 42 countries until 2050. Concerning 3 machines (engineering and construction equipment, fans and pumps, and conveyance machines), the growth of in-use stock and demand for steel was estimated based on the historical growth in Japan until now. For agricultural machinery, the growth of in-use stock and demand for steel was estimated based on the historical growth of steel in 42 countries until now. It was estimated that the in-use stock, demand and discard of steels for these machines would be 1.4-1.7 billion t, 100 million t and 80-100 million t, respectively.

This paper analyzed stainless steel stock and flow in Japan by using a dynamic modeling. Classifying different kind of alloys, stainless steel was subdivided into 13Cr, 18Cr, Ni–Cr, and Ni–Cr–Mo. Productions of heat-resistant steel, low-alloyed steels for machine structural use, cryogenic special steel, bearing steel, and spring steel were also taken into account as alloying steel including Cr and/or Ni in mass balances of Cr and Ni. In production processes, all raw materials for stainless steel were clarified by upholding mass balances of Cr, Ni and Fe. In-use stock of ferritics and austenitics at year 2005 were 4 Tg and 12 Tg, which could be converted to 3 Tg of Cr and 1 Tg of Ni. From the results of the model, collection rates as stainless steel scrap were estimated less than 35% for ferritics and more than 75% for austenitics. The collection rate of ferritics was estimated to be relatively small because some of ferritic scrap could be recovered as carbon steel scrap due to its magnetism. The dynamic model slso estimated that main source of ferritic scrap generation will be automobiles in the next decade. In order to promote recycling of ferritic scrap, recovery from automobiles would be important.