Materials flow analysis (MFA) is a method useful in accounting for the supply and demand structure of resources and wastes, as well as the international material balance. There are two classifications within the MFA approach : the bottom-up approach and the top-down approach. The top-down approach uses statistics data, such as input-output tables, while the bottom-up approach uses unit numbers for specific products and their composition. There is a weakness in the application of input-output analysis to MFA because it does not properly take into consideration the mass balance condition between inputs and outputs (physical inputs=physical outputs+process waste+emission) in the production of goods. To cope with this, a new hybrid approach to MFA has been developed, the WIO-MFA (Waste Input-Output Material Flow Analysis) Model (Nakamura and Nakajima, Materials Trans. 2005). This paper introduces the WIO-MFA model and its application to a detailed MFA for polyvinyl chloride (PVC).

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In this paper, the trade flows for typical metals are shown. Data was obtained from the United Nations COMTRADE statistics. Inter-country flow lines are shown with arrows, based on data from the importing countries. Countries that are importing or exporting in large quantities are also plotted with their values. With regard to the trade flow of metals, Japan is seen as one of the most important sites. The paper also reveals how the intensified position of China and its expanded flow of goods into eastern, northern and southern Europe, etc. has caused changes to the three-country framework comprised of the US, Japan and Germany in the late 20th century.

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Material demands around the world, especially in developing countries, have Recently seen a rapid rise. The recovery of scrap from end-of-life products plays an important role in the conservation of natural resources and the construction of a sound material cycle society. In order to investigate the potential in material scrap recovery for designated areas, an estimation of the amount of materials used in products, filled “Material Stock Accounting”, has recently gained attention. Material stock accounting two approaches, the top-down approach and the bottom-up approach : the top-down approach uses time-series data for consumption and trade of materials as well as distributions for product lifetimes,while the bottom-up approach uses the number of product units in the designated area and its material use intensities. This paper explains the methodologies for material stock accounting and introduces some case studies.

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Many base metals, such as iron, copper and aluminum, are being used in society and are accumulating in huge amounts. They contain alloying elements, except for some of the electric lead materials like copper wire. This situation strongly indicates to us that a contamination problem, whereby base metals by alloying elements or the loss of alloying elements during base metal recycling, is about to occur in the near future. In order to minimize this problem, information on the flow of alloying elements, or impurities, is crucial in designing effective recycling processes for base metals and for saving rare metals as alloying elements. This paper deals with some of the results found in the substance flow analysis of rare metals as alloying elements, together with the bulk material flow of steel products.

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This paper introduces an estimation method for end-of-life product flows using case studies on mobile phones and other home electric appliances. A case study on mobile phones estimates hibernating stock, and also reveals the difficulties of capturing international material cycles. In addition, the paper discusses resource potentials for metals found in end-of-life mobile phones. Though precious metals have higher resource potential when compared to other rare elements, the aggregated values for all metals might be much lower than the values expected by consumers.

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Plastics in Japan are all made from imported raw materials. Every year, a total of fourteen million tons of plastics are manufactured with a total of 10 million tons of waste plastics being discharged in Japan. Besides this discharge, 1.5 million tons of waste plastics are exported to foreign countries. The recycle ratio for waste plastics is currently at 73% but under such circumstances, this amount needs to be much greater.
Though there are plentiful forest resources in Japan, 77% of its timber supply is imported while half the remaining debris is abandoned. The iron and steel industry does, in fact, have the infrastructure and technologies to effectively make use of large amounts of these abandoned resources. A waste plastics recycling process using coke ovens by Nippon Steel Corporation is one such technology put into practical use in the year 2000. To date, the process has successfully recycled almost 1.2 million tons of plastics. It is projected that wood biomass can be used instead of large quantities of fossil fuel in the iron and steel industry, as well as waste plastics. However, due to certain problems that still exist regarding the establishment of a proper collection system and costing, this system has not yet been put into practical use. Utilization of waste plastics and wood biomass in the iron and steel industry could be a contribution toward the prevention of global warming and the establishment of a sustainable recycling society.

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This article discusses recent trends in material flow analysis and its future development based on six different viewpoints : subject material, spatial scale, time scale, material stock, data preparation methods, and policy use. Recent trends include the expansion of the subject to a variety of materials and products, diversification of spatial levels from local to global, extension of the time-scale focus, increased interest in material stock, application of input-output analysis for data preparation, gradual progress in policy use of macro-material flow information. Future research topics associated with resource recycling and waste management include analysis of composite materials such as metals in terms of material grade, estimation of indirect trade, prediction of future material flows, assessment of material stock in terms of waste management and resource reutilization, construction of a database based on common terminology, response to other issues regarding material flow indicators.

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