Consumption-based accounting of steel alloying elements and greenhouse gas emissions associated with the metal use: the case of Japan

Hajime Ohno,Kenichi Nakajima,Kazuyo Matsubae,Tetsuya Nagasaka,Yasuhiro Fukushima,Keisuke Nansai

doi:10.1186/s40008-016-0060-9

Abstract

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.

Highlights

IntroductionBecause 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)
Accompanying steel mill products, alloying elements are widely distributed through the international supply chain
5 Conclusion In this study, the flows of steel alloying elements in Japan and exports of Japanese products were obtained by means of the waste input–output material flow analysis (WIO-MFA) model and by taking data from the trade statistics

Summary

Introduction

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. This supply chain is unevenly distributed among countries. Mined metals tend to be collected by industrialized countries and redistributed in the form of finished products through the international supply chain (Wiebe et al 2012; Nansai et al 2014; Wiedmann et al 2015)

Methods

Results

Discussion

Conclusion