In-use Steel Stock Research Articles

Quantifying the spatiotemporal evolution of the in-use steel stock in countries along the Belt and Road

Urban development has advanced the accumulation of steel resources from the natural environment to urban structures, thereby aggravating the deterioration of the natural environment and increasing concern for the circular economy. Accurately understanding the spatiotemporal evolution of urban steel stocks is necessary to better maintain sustainable socioeconomic development. This paper constructs the consistency and continuity of multisource nighttime light (NTL) data and the results of modelled in-use steel stock (IUSS) in the Belt and Road (B&R) areas at a 1 km resolution. The multiscale IUSS spatiotemporal evolution in the B&R areas was quantified using geographic information analysis methods. The results revealed that the evolution of IUSS in the southern and northern parts of the B&R has significant differences. From 1992 to 2004, the evolutionary state of the IUSS showed drastic changes, while an overall trend of balanced development was maintained from 2004 to 2019. High-intensity IUSS is mainly concentrated in China, Russia, and India, and wealth level is the primary factor driving the development of IUSS. Combining the results of the development state analysis and spatial correlation analysis shows that central India and central and western China are potential hotspot areas for the flow of steel resources in the future. The results of this study can help develop differentiated and refined management strategies for the flow of anthropogenic steel resources.

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

Exploring the dynamic changes of steel from the ships is critical for developing sustainable strategies for waste management of shipping industry. However, the information of stocks and flows of ships and related steel is currently unavailable, hindering the sustainable development of shipping industry. By collecting dispersed information on production, use, material composition, and end-of-life management of five types ships, we first estimated the historical steel stocks and flows respect to global ships from 1980 to 2019, and further projected the amount of steel scraps from shipbreaking by 2050. The steel stocks of ships increased by 2.6 times from 208.4 Mt in 1980 to 542.9 Mt in 2019. The top 2 regional contributors, Asia and Latin America & the Caribbean, were together responsible for about half of the total increase. A transition from oil tankers to container ships and bulk carriers reduced the in-use steel stock due to the lower steel intensity of the latter. The rapid increase of ship stocks after year 1980 led to significant increase of steel scrap in the 2010 s, reaching 10.1 Mt/year in 2019. Our projections showed that the steel from scrapped ships worldwide will increase by around 4-fold to 40.4–47.3 Mt/year by 2050, which imposed a great challenge on coordination of recycling ship-related steel and require long-term planning on ship recycling facility development. By identifying the stocks and flows of ships and related steel, this study provides insights for the steel waste and recycling management of end-of-life ships worldwide.

Spatial and temporal disparity of the in-use steel stock for China

The in-use steel stock is an important indicator of urban metabolism. However, there is a big gap in the in-use steel stock level among different regions because of diverse driving factors and the mechanism of how the factors act on the in-use steel stock. This strongly aggravated the difficulty of accounting in-use steel stock. To identify the comprehensive disparity, this paper took China’s provinces as the empirical context and established a hybrid accounting model framework by considering the unique characteristics for the downstream steel-using sectors. The results show that China’s per capita in-use steel stock have increased by 1.96 times from 2002–2016, reaching 3.65 ton/cap in 2016. Therein, the building sector always contributes more than 50 % of the increase. Based on the change of per capita in-use steel stock and socio-economic factors, Chinese provinces can be divided into three clusters. The driving factors have different effects on the per capita in-use steel stock in three types of provinces. For example, an increase of 1 % in the urbanization rate would increase the per capita in-use steel stock for the infrastructure sector by 0.55%ö2.69% in these three types of provinces. In addition, foreign direct investment, the aging population and per capita income are the main factors affecting the in-use steel stock. From 2021–2035, it would be the peak period of scrap production in the building sector. The government is suggested to implement fiscal preferential policies to achieve effective recycling of scrap.

Feasibility of a new-generation nighttime light data for estimating in-use steel stock of buildings and civil engineering infrastructures

Regional scale estimation of in-use steel stock (IUSS) using satellite observation of nighttime lights (NTL) is essential for urban resource consumption management and resource recovery monitoring. S-NPP VIIRS (Suomi National Polar-orbiting Partnership’s Visible Infrared Imaging Radiometer Suite) NTL product is newly released in 2013, which has enhancements in both spatial and radiometric resolutions compared with the DMSP-OLS (Defense Meteorological Satellite Program’s Operational Linescan System) NTL products. To evaluate whether these enhancements can improve the estimations of IUSS of buildings (IUSSB) and civil engineering infrastructure (IUSSCE), the S-NPP VIIRS NTL products were used to estimate IUSSB and IUSSCE at both sub-national level of Japan and national level of world, and their performances were compared with those of using DMSP-OLS radiance calibrated (RC) NTL data. Our results indicate that the S-NPP VIIRS NTL data can offer more accurate estimates of IUSSB and IUSSCE (R2 values of 0.952 and 0.909) than those of DMSP-OLS RC NTL (R2 of 0.929 and 0.884) at prefectural level of Japan. Similar to DMSP-OLS RC NTL product, urban NTL of S-NPP VIIRS data has a stronger relationship with IUSSB, and IUSSCE was more closely related to total NTL. At national level, S-NPP VIIRS NTL also showed better estimations of IUSSB and IUSSCE. We confirmed that dividing the world into different regional groups is also required for estimating IUSSB and IUSSCE from S-NPP VIIRS NTL. For estimation of IUSSCE, two classifications including Asia region and Non-Asia region are appropriate when using S-NPP VIIRS NTL product, which is superior to DMSP-OLS RC NTL. For estimation of IUSSB, more classifications may be still required which is similar to DMSP-OLS RC NTL. Overall, our study indicated that S-NPP VIIRS data have greater capability in modeling IUSSB and IUSSCE than DMSP-OLS RC data. Our results are critical for ever-improvement of policy making on urban resource management.

Modeling In-Use Steel Stock in China’s Buildings and Civil Engineering Infrastructure Using Time-Series of DMSP/OLS Nighttime Lights

China’s rapid urbanization has led to increasing steel consumption for buildings and civil engineering infrastructure. The in-use steel stock in the same is considered to be closely related to social welfare and urban metabolism. Traditional approaches for determining the in-use steel stock are labor-intensive and time-consuming processes and always hindered by the availability of statistical data. To address this issue, this study proposed the use of long-term nighttime lights as a proxy to effectively estimate in-use steel stock for buildings (IUSSB) and civil engineering infrastructure (IUSSCE) at the provincial level in China. Significant relationships between nighttime lights versus IUSSB and IUSSCE were observed for provincial variables in a single year, as well as for time series variables of a single province. However, these relationships were found to differ among provinces (referred to as “inter-individual differences”) and with time (referred to as “temporal differences”). Panel regression models were therefore proposed to estimate IUSSB and IUSSCE in consideration of the temporal and inter-individual differences based on a dataset covering 1992–2007. These models were validated using data for 2008, and the results showed good estimation for both IUSSB and IUSSCE. The proposed approach can be used to easily monitor the dynamic of IUSSB and IUSSCE in China. This should be critical in providing valuable information for policy making regarding regional development of buildings and infrastructure, sustainable urban resource management, and cross-boundary material recycling.

The impact of climate targets on future steel production – an analysis based on a global energy system model

This paper addresses how a global climate target may influence iron and steel production technology deployment and scrap use. A global energy system model, ETSAP-TIAM, was used and a Scrap Availability Assessment Model (SAAM) was developed to analyse the relation between steel demand, recycling and the availability of scrap and their implications for steel production technology choices. Steel production using recycled materials has a continuous growth and is likely to be a major route for steel production in the long run. However, as the global average of in-use steel stock increases up to the current average stock of the industrialised economies, global steel demand keeps growing and stagnates only after 2050. Due to high steel demand levels and scarcity of scrap, more than 50% of the steel production in 2050 will still have to come from virgin materials. Hydrogen-based steel production could become a major technology option for production from virgin materials, particularly in a scenario where Carbon Capture and Storage (CCS) is not available. Imposing a binding climate target will shift the crude steel price to approximately 500 USD per tonne in the year 2050, provided that CCS is available. However, the increased prices are induced by CO2 prices rather than inflated production costs. It is concluded that a global climate target is not likely to influence the use of scrap, whereas it shall have an impact on the price of scrap. Finally, the results indicate that energy efficiency improvements of current processes will only be sufficient to meet the climate target in combination with CCS. New innovative techniques with lower climate impact will be vital for mitigating climate change.

Estimation of in-use steel stock for civil engineering and building using nighttime light images

To establish a sustainable society, it is necessary to understand the flows and stocks of materials. However, traditional material flow analysis requires large quantities of data relating to the consumption and trade of materials in the past and the lifetime distributions of end use. To overcome the problem that such data may not be available, we have proposed using nighttime light images to estimate the in-use stocks of materials in countries for which the data are unavailable. In the previous study, in-use steel stock for civil engineering and building in 2006 was estimated using nighttime light images. However, several aspects of the methodology must be improved, and time-series analyses using nighttime light images have not yet been performed. Therefore, in this study, we improved the estimation of in-use steel stock by using new geological information (i.e., LandScan population distribution data) and correcting the pixel area. We prepared radiance-calibrated nighttime light data for 2006 and 2010 and conducted time-series analyses of the in-use steel stock using the nighttime light data. The in-use steel stock for civil engineering and building in 2010 was found to amount to approximately 11.3Gt, which was approximately 21% higher than that in 2006.

Exploring and estimating in-use steel stocks in civil engineering and buildings from night-time lights

Steel is the most widely used metal in the world, and numerous studies have investigated its stock and flow. Two basic methods for analysing material flow and accounting for stock are the top-down and bottom-up approaches. Their applicability, however, largely depends on data availability. To overcome this limitation, we have contemplated using satellite imagery as a proxy for missing data. In a previous study, we confirmed the correlation between night-time light radiance and civil engineering/building in-use steel stocks in Japan. In this study, the scope of the investigation was expanded to a global scale, examining correlations in different regions of the world. We found that night-time light radiance and in-use steel stocks have region-specific linear correlations, which are influenced by construction styles, which in turn depend on climate, seismic activity, cultural preferences, etc. The results were then applied to countries in the various regions whose in-use steel stocks were previously unreported. This technique produced an estimate of the global civil engineering/building in-use steel stock of around 9 × 109 tonnes (9 Gt), with 1.24 Gt being previously unreported. As a further step, this study shows the spatial distribution of civil engineering/building in-use steel stock in each region.

Estimation of World Steel Demand and In-Use Stock for Ships

Recovery of materials from end-of-life products will contribute to the reduction in consumption of natural resources and global warming. For many decades, ships have been a major share of steel use, and used high quality steel products, mainly plates and high tensile strength steel. So, the steels contained in end-of-life ships should be useful for secondary resources. Therefore, it is important to estimate the in-use stock and demand of steel for ships from past to future. In this study, we conducted material flow analysis of steel for ships in global scale to estimate the in-use steel stock and demand in the future for ships. As the result, world in-use steel stock of ships was estimated as 540 million ton in 2009, and predicted to reach 900 million ton in 2035, 1.7 times in 2009. It was expected that future steel demand for ships would increase up to 41 million ton in 2035.

Estimating in-use steel stock of civil engineering and building in China by nighttime light image

China is dramatically changing due to rapid development in recent years. This can be observed from the change in landscapes, which most resulted from new or replaced constructions. The floor area of residential and commercial construction had increased fourfold from 1990 to 2005, and its speed does not show any sign of slowing down. The construction will also drive the demand of steel, which comprises half of the total national consumption. However, there were not many studies aiming to quantify the construction steel stock in China, which was mainly due to lack of statistical data. In order to overcome this obstacle, we proposed a methodology to estimate sub-national steel stock using nighttime light image. As a result, we found out that the Beijing municipality possesses the most construction steel stock. Most construction steel stock exists on the eastern coast, and is most concentrated in the Beijing municipality, the Tianjin municipality, the Shanghai municipality, and the Guangdong province.

Analysis of Global Demand for Iron Source by Estimation of In-use Steel Stock

The Utility of Stock hypothesis, which assumes that an in-use stock of constructional material is a function of GDP, was formulated and a clear correlation between the world steel stock and the world GDP led to the estimation that the world demand for iron ore (primary iron) depends not on the volume of GDP but on the variation of GDP, as already reported. In this study, the world steel stock in use is computed. Sensitivity analyses are conducted to show the effect of lower reliable data such as the usage period (lifetime) of iron-containing final products. Clear correlation is found between the in-use steel stock and the steel stock. Hence, the Utility of Stock hypothesis is verified.

Future Steelmaking Model by Direct Reduction Technologies

Steel production requires iron ore and coal, and accompanies greenhouse gas emissions. The annual production of the world crude steel increased from 0.9 to 1.3 billion tonnes since 2002, and is anticipated to increase due to the continuous economic growth in developing countries especially in Asia.About two thirds of the crude steel is produced by BF–BOF route whose ratio in the total crude steel production has gradually been increasing. The BF–BOF process is an excellent process in terms of productivity and energy efficiency, the process, however requires high grade iron ore and coal, and the large steel production by the BF–BOF route will accelerate the exhaustion of the high grade raw materials. The CO2 emissions are also anticipated to increase as does the steel production, since approximately 2 tonnes of CO2 is generated per tonne of steel by the BF–BOF process.On the other hand, world in-use steel stock has been increasing year by year due to the continuous large steel production, and will be recycled as a large amount of scrap to the market in the future.Steelmaking by feeding Iron Nuggets to EAF together with the scrap can significantly decrease the CO2 emissions while satisfying the steel quality by diluting the impurities containing in the scrap, as well as conserving the natural resources of high grade iron ore and coal. Steel production by using the direct reduction processes together with the scrap is a suitable and reasonable solution for a sustainable iron and steel making.

ストック効用仮説による世界の鉄源需要の解析

To forecast iron source demand, the Intensity of Use hypothesis, which assumes that material consumption per capita is a function of GDP per capita, is the most dominant theory in existing studies. However, this hypothesis is not effective for a world one-region model of iron sources. Therefore, we focus our attention on utility, and we suppose that economic growth is a major driver to increase the utility. As the utility of steel sustains for ages after purchase, we formulate the Utility of Stock hypothesis, which assumes that the in-use steel stock is a function of GDP. In this study, the world steel stock was computed and the Utility of Stock hypothesis was tested. Clear correlation is found between the steel stock and the GDP. It leads to the estimation that the world demand for iron ore depends not on the volume of GDP but on the variation of GDP. For the first time with total world figures, the result enables us to rationalize the recent decoupling between the world growth of iron source demand and the economic growth.

使用過程の鋼ストック量の推定による世界の鉄源需要の解析

The Utility of Stock hypothesis, which assumes that the in-use stock of constructional material is a function of GDP, was formulated and the clear correlation between the world steel stock and the GDP led to the estimation that the world demand for iron ore (primary iron) depends not on the volume of GDP but on the variation of GDP, as already reported. In this study, the world steel stock in use is computed. Sensitivity analyses are conducted to show the effect of lower reliable data such as the usage period (lifetime) of iron-containing final products. Clear correlation is found between the in-use steel stock and the steel stock. Hence, the Utility of Stock hypothesis is verified.

In-use Stock of Steel Estimated by Top-down Approach and Bottom-up Approach

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, the top-down approach and the bottom-up approach, were adopted for estimating the in-use steel stock in end uses. The top-down approach uses time-series data of consumption and trade of materials and product lifetime data, whereas the bottom-up approach uses the numbers of units of a specified product in a designated area and its material intensities. In this paper, steel stock in Japan divided into seven end-uses was estimated by the top-down approach. Steel in-use stock in Japan was estimated as approximately 1000 Tg in 2005. Steel stock in automobiles in 2005 was estimated as 105 Tg by the bottom-up approach and compared with that estimated as 125 Tg by the top-down approach. In addition, applying the bottom-up approach, steel stock used in automobiles in the United States was estimated and compared with that obtained by the previous research using the top-down approach. Steel stock used in automobiles in 2000 in the United States was estimated as 480–870 Tg by the top-down approach and 754–767 Tg 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.

トップダウン手法とボトムアップ手法による用途別鋼材蓄積量の推計

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 bottom-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 1,000 Tg in 2005. Steel stock in automobiles in 2005 was estimated as 105 Tg by the bottom-up approach and compared with that estimated as 125 Tg 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 480–870 Tg by the top-down approach and 754–767 Tg 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.

Analysis of Global Demand for Iron Source by Utility of Stock Hypothesis

To forecast iron source demand, the Intensity of Use hypothesis, which assumes that material consumption per capita is a function of GDP per capita, is the most dominant theory in existing studies. However, this hypothesis is not effective for a world one-region model of iron sources. Therefore, we focus our attention on utility, and we suppose that economic growth is a major driver to increase the utility. As the utility of steel sustains for ages after purchase, we formulate the Utility of Stock hypothesis, which assumes that the in-use steel stock is a function of GDP. In this study, the world steel stock was computed and the Utility of Stock hypothesis was tested. Clear correlation is found between the steel stock and the GDP. It leads to the estimation that the world demand for iron ore depends not on the volume of GDP but on the variation of GDP. For the first time with total world figures, the result enables us to rationalize the recent decoupling between the world growth of iron source demand and the economic growth.