Consumption-based accounting of steel alloying elements and greenhouse gas emissions associated with the metal use: the case of Japan
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Metal extraction and smelting cause considerable impacts on the environment. Consumption-based impact accounting highlights the responsibility of metal-consuming industries for the impacts and may drive a system-wide improvement in the structure of related supply chains. To drive the improvements, policies at national level coordinated for respective product types across the nations is needed. However, nationwide responsibility for specific use of metals is difficult to identify because metals are manufactured into composite products (e.g., vehicles) in a country that is in many cases, different from the country where mining is practiced. The final product environmental footprints would not reveal the location where the various impacts are caused. This study presents a method to support the policy coordination by identifying the magnitude of the responsibility of metal-consuming countries for environmental impacts occurred in mining countries so that the countries sharing large responsibilities can find partner countries to jointly work on reduction in environmental impacts effectively. An input–output-based material flow analysis model is used to track the flows of metals included in products made in Japan throughout the international supply chain. In 2005, Japanese industries collected steel alloying elements (manganese, chromium, nickel, molybdenum) embodying 3200 kt-CO2eq and distributed them as both intermediate and final products. For steel mill products, Asian countries were the main destination, while alloying elements contained in other products were relatively evenly exported to Asia, Europe, and North America. By consuming products made in Japan, South Korea, China, the USA, and Taiwan shared approximately 10% each in terms of share of responsibility for greenhouse gas emission embodied in alloying element collected by Japan. Japan shared 40% of the responsibility with domestic consumption of own products. These findings suggest that Japan, a collector and distributor of steel alloying elements, must work on its own resource use reduction policies coordinating with these countries to globally develop sustainable resource use system.
KeywordsMaterial flow analysis Input–output analysis International trade Steel alloying element Greenhouse gas emissions Consumption base
Metals are indispensable in our society. To obtain sufficient metals for economic development, huge amounts of ores and industrial minerals are extracted globally (United Nations Environment Programme (UNEP) 2011); on the other hand, metal mining and smelting cause negative environmental impacts (Nuss and Eckelman 2014). Because the impacts of these processes directly affect the environment of mining and material processing countries, metal-consuming countries have indirect responsibilities for the impacts occurred in metal-producing countries according to own consumptions (Peters 2008; Peters and Hertwich 2008).
Once metals have been mined, smelted, and refined, they are consumed in the mined country and/or exported. Countries that import metals use them to produce various value-added products, consume the products themselves, and/or export them. However, this supply chain is unevenly distributed among countries. Mined metals tend to be collected by industrialized countries and then redistributed in the form of finished products through the international supply chain (Wiebe et al. 2012; Nansai et al. 2014; Wiedmann et al. 2015).
As the UNEP International Resource Panel points out, decoupling resource use and negative environmental impacts from economic growth is important for the development of a sustainable society (UNEP 2011). Improving resource efficiency and/or productivity is one of the key concepts for decoupling, although countries have been tackling such improvements in their own ways, which may not be the best approach to reaching the overarching objective. Consumption-based impact accounting, which considers the responsibility for environmental impacts in upstream supply chains, is different in that it places the responsibility on those countries that benefit from the products (Peters 2008; Peters and Hertwich 2008; Shigetomi et al. 2015, 2016). For example, if demand in country A for the products of country B induces huge resource use in country B, country A would be obliged to contribute to the activities in country B for improving resource efficiency and/or productivity. In this regard, the need for decoupling should be tackled through international cooperation.
In this paper, we demonstrate how a country can identify the magnitude of the responsibility sharing with other countries and find out the target countries to jointly work on impact reduction. Moreover, the flow of metals accompanying with international trade is revealed and the environmental impacts on the countries in the supply chain are organized to discuss the nature of the international coordination. A case study is then demonstrated by using the case of Japan and its use of alloying metal in the steel industry.
As an industrialized country, Japan contributes highly to the international flow of metals; Japan, who has the second largest steel production and third largest automobile production in the world (International Organization of Motor Vehicle Manufactures (OICA) 2015; World Steel Association 2015) without having any resource deposits, has considerable responsibilities for metal mining countries in order to drive its large metal fabricating industries. At the same time, Japan exports more than 40% of the produced steel mill products (World Steel Association 2015) and around 50% of the produced automobiles (Japan Automobile Manufacture Association (JAMA) 2015) every year. Hence, Japan is passing on the responsibility for metal use to consuming countries as well as exporting metal-containing products (Kondo et al. 1998; Peters 2008). In terms of alloying elements, Japan consumes about 10% of the world’s steel alloying elements (Japan Oil Gas and Metals National Corporation (JOGMEC) 2008). Among steel alloying elements, we focus on manganese, chromium, nickel, and molybdenum whose consumption in steel industries is relatively great compared with those in other industries in Japan (JOGMEC 2007). Steel alloying elements add various properties to steel such as corrosion resistance, heat resistance, and toughness (Nakajima et al. 2013). Steel mill products containing alloying elements (so-called alloy steel) are utilized widely in industries requiring high-performance materials, such as the automobile and machinery industries.
The content of alloying elements in steel mill and other fabricated products is estimated by using the waste input–output material flow analysis (WIO-MFA) model (Nakamura et al. 2007; Nakajima et al. 2013; Ohno et al. 2014). By using the WIO-MFA model to identify the content of alloying elements, metal compositions in highly fabricated products are derived based on IO analysis, whereas the representative compositions must be carefully chosen in process-based bottom-up MFAs.
Nansai et al. (2009, 2012) evaluated the carbon footprints of 230 countries and regions induced by Japanese economic activities by using the global link IO model. Their approach of connecting Japanese IO tables with international trade information is well suited to the use of WIO-MFA. Nakajima et al. (2011a) and Nansai et al. (2014) calculated the flows of metals accompanying with Japan’s international trade by combining the WIO-MFA and global link IO models. Furthermore, Nakajima et al. (2014) addressed the global supply chain of nickel and examined its influence on the environment of mining sites.
The flow of steel alloying elements collected by Japan by distinguishing domestic use from exports;
The international flow of steel alloying elements accompanying with the exports of Japanese products; and
The responsibility for environmental impacts in mining and material processing countries, using greenhouse gas (GHG) emissions as a proxy for the environmental impact in mining and material processing countries.
2 Methodology and data
2.2 MFA of alloying elements in domestic final demand and export
2.3 Share of the responsibility
WIO-MFA was conducted based on the Japanese 2005 IO table (Ministry of Industrial Affairs and Communications (Japan) 2009). The sectors of materials and steel mill products in the original IO table were disaggregated in detail and converted into a monetary unit description based on several statistics (Ministry of Economy Trade and Industry (Japan) 2006; The Japan Ferrous Raw Materials Association 2006; JOGMEC 2007). For more detailed information on the definition and disaggregation of the sector, see previous works (Nakajima et al. 2013; Ohno et al. 2014). Commodities considered in this analysis are listed in Additional file 1.
The trade data were organized based on the trade statistics of Japan (Ministry of Finance Japan 2005) by connecting the Harmonized System (“HS”) codes (i.e., international standard trade category codes) with the corresponding goods sectors in the IO table. Because the definitions of the sectors in the IO table were sometimes inconsistent with the HS codes, we could not perfectly adjust the amount of trade between the trade statistics and the values of the exports and imports of goods compiled in the IO table. Consequently, the exports from the IO table were allocated based on the ratio of the amount of trade by partner countries calculated from the records in the trade statistics. For partner countries, Nansai et al. (2014) were referred to.
Inventories for GHG emissions in the production of alloying elements resources
3.1 Domestic flows of alloying elements
In 2005, 636, 635, 250 and 29 kt of manganese, chromium, nickel, and molybdenum were imported, respectively, in the form of virgin sources. These were mainly consumed in steelmaking to produce steel mill products from crude steel by employing alloying elements. Accompanying steel mill products, alloying elements are widely distributed through the international supply chain. Indeed, in addition to the imported alloying elements, alloying elements contained in domestically generated steel scrap are utilized in steelmaking. Consequently, the actual flow of alloying elements is greater than that in the imported masses. Given the above, this study discusses the balance of alloying elements in the flow based on the imported masses. The masses of alloying elements remaining in Japan were calculated by subtracting the total exported masses of alloying elements in Japan from the imported masses instead of subtracting the total exported masses from the total consumed masses.
3.2 International delivery of alloying elements from Japan
In total, 98 kt (manganese), 25 kt (chromium), 150 kt (nickel), and 4 kt (molybdenum) were exported as products excluding raw materials and steel mill products. In contrast to the case of steel mill products, the flows of alloying elements accompanying the exports of other products were relatively evenly shared by region (Fig. 7). This fact suggests that alloying elements are spread globally in the form of the products made in Japan. At the country level, the USA occupied the largest proportion of accompanying exports, approximately twice as large as those of other countries for all alloying elements. Panama followed the USA for accompanying exports of manganese with products just because of its trade in steel ships. For the other alloying elements, China came in second place followed by other Asian countries. For more results at the country level, see Additional file 2.
3.3 Responsibility for environmental impacts
Furthermore, because Japan not only imports but also domestically produces some raw materials such as ferroalloys and/or pure metals, the impacts associated with alloying elements passing through Japan would be much higher than the value estimated in this study. According to the IO-based emission inventories developed by Nansai and Moriguchi (2012), Japan emitted 3717 kt-CO2eq in its ferroalloy production in 2005. Therefore, GHG emissions embodied in alloying elements passing through Japan would be more than double the GHG emissions in origin countries in reality.
South Korea, China, the USA, and Taiwan are the most important partners in Japanese trade in terms of sharing the responsibility for GHG emissions in alloying element production. Therefore, when Japan tries to reduce the environmental impacts associated with its metal use, it may be able to ask these four countries to contribute to developments of new technology that reduces the environmental impacts in mining, smelting, and refining.
4.1 Improving resource efficiency
Alloying elements once collected by Japan are widely distributed across the Japanese economy as well as other countries embodying GHG emissions. Although the proportions of each country’s responsibility for GHG emissions are not large individually, demand for Japanese products from other countries has induced large imports of metal sources by Japan. However, reducing demand for Japanese products would be an unsuitable solution to reduce impacts on the metal mining and producing countries sustainably. Therefore, Japan must play a key role in the reduction in the impact of metal consumption in this supply chain. If it could maintain supply to other countries and reduce its imports of metal sources, the responsibility shared by each country would decrease. To achieve this, the utilization of urban mines in Japan (i.e., recycling) would be important. Currently, recycling alloying elements from scrap (except process scrap and stainless steel scrap) is rarely taken into account, whereas steel scrap is highly recycled (Ohno et al. 2014). In particular, although automobiles contain a large amount of alloying elements as shown in “Results,” most of alloying elements in end-of-life (EoL) vehicles tend to be losses by dissipating into steelmaking slag and/or contaminating into molten steel during the recycling of EoL vehicle-derived steel scrap (Nakajima et al. 2011b, 2013; Ohno et al. 2014). On the contrary, EoL vehicle-derived steel scrap can be a source of alloying elements to substitute 46–63 kt of ferroalloy production by appropriate treatment and sorting during recycling (Ohno et al. 2015). Because this substitutable mass corresponds to a 318–609-kt-CO2 reduction in embodied GHG emissions, it has a significant effect on the reduction in the responsibility. To obtain this benefit from EoL vehicle recycling, appropriate policy and scrap prices must be established (Ohno et al. 2015). For this need, Japan should ask the top four above-mentioned countries (i.e., South Korea, China, the USA, and Taiwan) each sharing around 10% of the responsibility to contribute.
Similarly, it would also be important to recycle metals in consuming countries themselves. However, the recyclability of alloying elements highly depends on the infrastructure and industries in each country. In the case of alloying elements in EoL vehicle-derived steel scrap, for instance, matured EoL vehicle correction and recycling policies are first required, as the EU (The European Communities 2000) and Japan have already established.
Nansai et al. (2014) characterized the international flow of metals by the technology level of countries. The authors categorized Japan as a “high-level production technology and material-use efficiency” country. If Japanese products containing alloying elements are exported to the countries categorized as the same level as Japan, flows are classified as “green flows,” which means that material-use efficiency is the highest because both producing and consuming countries have high levels of technologies. In this case, alloying elements would be well utilized and recycled with high technologies. By contrast, when Japanese products are exported to low-technology-level countries, the flows become “yellow flows,” which are defined as “moderately efficient.” In these flows, alloying elements in exported products may dissipate because of the lack of recycling technologies in the consumed countries. To reduce the flows in this category, as one potential solution, high-level countries should export their technologies and systems to low-level countries (Nansai et al. 2014). This kind of activity may reduce the need for both primary metal production and embodied environmental impacts not only in the Japan-oriented supply system discussed in this study but also in the global supply chain.
4.2 Limitations of the model and data
Because we conduct an MFA based on the IO table for one year, the result only represents a snapshot of the status of that year. Furthermore, this analysis focuses on only Japan-oriented international trade coming into and going out of the country, whereas research using multi-regional IO tables covers global trade (Lenzen et al. 2012; Dietzenbacher et al. 2013; Tukker et al. 2013). However, a detailed flow analysis for specific metals, especially non-base metals, requires a high-resolution IO and disaggregation of metal sectors to avoid the flow of metals being aggregated and unable to be distinguished from each other even for Japan who has one of the highest resolution of IO table. In this sense, multi-regional IO tables, which tend to have limited number of sectors for both metals and industrial activities owing to the necessity to homogenize the size of the IO tables for each region, or joint IO tables of a lot of regions with keeping the original sizes of tables, are unsuitable for our purpose. Therefore, to focus on the detailed flow of alloying elements, we selected this approach and demonstrated the trade of specific substances by using the presented snapshot.
In terms of data limitations, we cannot trace the flow of alloying elements associated with second-hand goods because of the lack of trade data for them. Consequently, in addition to the limitation in the adjustment of Japanese IO sectors and HS codes in the trade statistics, this data shortage may cause us to underestimate the real flows. In this regard, we just traced the flow of alloying elements in products produced in 2005, omitting the associated flow of second-hand products.
In this study, the flows of steel alloying elements in Japan and exports of Japanese products were obtained by means of the WIO-MFA model and by taking data from the trade statistics. Although the content of tiny metals such as alloying elements in highly fabricated products tends to be aggregated and/or ignored, this study covers the detailed content and flow of four alloying elements in order to consider the environmental impacts of the use of each metal separately and thus provide more precise implications. Based on the flow, the responsibility for GHG emissions during metal mining and production was estimated and its distribution among countries and regions in the supply chain calculated. Focusing on four alloying elements in the Japan-oriented supply chain allowed us to describe the role the country plays in the supply chain.
We found that Japan has been a large importer of metal resources as well as a distributer of metals through its product exports. However, this activity has also been driven by consumers of Japanese products. Therefore, the development of eco-friendlier systems and processes with the aim of reducing the environmental impacts associated with metal consumption should be discussed not only in Japan but also in other countries that share the burden of responsibility.
HO derived results and led the writing of this article. KM developed calculation method used in this study. KN supported the calculation and evaluation of the results of metal flows. KN provided the methodology and data for the analysis with a global scope. YF and TN planned the study and interpreted the implication of the results and the developed method. All authors read and approved the final manuscript.
This research was supported by a Grant-in-Aid for Scientific Research (A) from the Japan Society for the Promotion of Science (No. 15H01750) and the Japanese Society for the Promotion of Science Grant-in-Aid for JSPS Fellows (No. 258801).
The authors declare that they have no competing interests.
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