Environ. Sci. Technol. 2008, 42, 3843–3848
Hybrid Input-Output Approach to Metal Production and Its Application to the Introduction of Lead-Free Solders S H I N I C H I R O N A K A M U R A , * ,† SHINSUKE MURAKAMI,‡ KENICHI NAKAJIMA,§ AND TETSUYA NAGASAKA| Graduate School of Economics, Waseda University, Tokyo 169-8050, Japan, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan, National Institute for Environmental Studies, Tsukuba 980-8579, Japan, and Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan
Received October 19, 2007. Revised manuscript received February 27, 2008. Accepted February 29, 2008.
The production process of metals such as copper, lead, and zinc is characterized by mutual interconnections and interdependence, as well as by the occurrence of a large number of byproducts, which include precious or rare metals, such as gold, silver, bismuth, and indium. On the basis of the framework of waste input-output (WIO), we present a hybrid IO model that takes full account of the mutual interdependence among the metal production processes and the interdependence between them and all the other production sectors of the economy as well. The combination of a comprehensive representation of the whole national economy and the introduction of process knowledge of metal production allows for a detailed analysis of different materials-use scenarios under the consideration of full supply chain effects. For illustration, a hypothetical case study of the introduction of leadfree solder involving the production of silver as a byproduct of copper and lead smelting processes was developed and implemented using Japanese data. To meet the increased demand for the recovery and recycling of silver resources from end-of-life products, the final destination of metal silver in terms of products and user categories was estimated, and the target components with the highest silver concentration were identified.
Introduction Mutual interconnections and interdependence, as well as the occurrence of a large number of byproducts, which include precious or rare metals such as gold, silver, bismuth, and indium, characterize the production process of metals such as copper, lead, and zinc. With increasing concern about the sustainable management of rare and precious metals that are of vital importance for the production of products such as solar cells, fuel cells, LEDs, and catalysts, the need * Corresponding author phone: +81 3-5286-1267; fax: +81 3-32039816 ; e-mail:
[email protected]. † Waseda University. ‡ The University of Tokyo. § National Institute for Environmental Studies. | Tohoku University. 10.1021/es702647b CCC: $40.75
Published on Web 04/18/2008
2008 American Chemical Society
for proper consideration of the LCA (life cycle assessment) and MFA (materials flow analysis) of these interconnected aspects of metal production has attracted increasing recognition (1, 2). The hybrid approach, a combined use of process knowledge and input-output analysis (IOA), increasingly has become a conventional tool of LCA and MFA (3). Recent examples of the hybrid approach that explicitly address the issue of metal production are refs 4 and 5. Hawkins et al. (4) proposed a mixed-unit IO model that involved the flow of metals in mass and applied it to the flow of lead and cadmium in the U.S. The issues related to the interconnectedness of metal production among different metals and to the generation of byproducts, however, were not addressed explicitly. In particular, the fact that cadmium can be obtained as a byproduct of the lead smelting process (cadmium can occur in lead ores) was not considered. Because of the separate treatment of lead and cadmium, Hawkins et al.’s (4) study falls into the category of conventional MFA where one material is considered at a time (see ref 6 for a recent survey of the literature on MFA). Murakami et al. (5) were concerned with a simultaneous MFA of 19 metals under explicit consideration of the interconnected nature of metal production represented by the flow of intermediaries such as slime among different processes, the use of secondary materials such as scrap, and the generation of a large number of byproducts. The presence of a large number of diverse byproducts and of various types of scrap for recycling, however, turned out to be difficult to cope with within the framework of conventional IOA because this was based on the assumption of one activity-one product and excluded joint production. Consequently, instead of an integrated IO model that encompasses all the production sectors containing both metal production and other manufacturing sectors, two submodels were developed: one for metal production and the other for all other goods and services. The two submodels were not integrated fully because of the lack of feedback from the latter to the former. To cope with the conceptual weakness of the conventional IOA (viz., that it does not explicitly consider the flow of wastes and byproducts and the activity of waste management including recycling), Nakamura and Kondo (7) developed the waste input-output model (WIO) that explicitly addresses these points. WIO can therefore be regarded as an ideal hybrid framework for considering metal production processes characterized by the presence of many byproducts and residues. On the basis of the framework of WIO, we present in this paper a hybrid IO model including production processes and flows of copper, lead, zinc, silver, and gold for the Japanese economy. The model takes full account of the mutual interdependence among the metal production processes (including the generation of byproducts) and the interdependence between them and all the other production sectors of the economy as well. The combination of a comprehensive representation of the whole national economy and the introduction of detailed process knowledge allows for the detailed analysis of different materials-use scenarios under the consideration of full supply chain effects. For illustration, the proposed methodology was applied to a case study of the introduction of a Pb-free solder, the SAC solder, which is based on tin, silver, and copper. The Pb-free solder represents a well-known example of a shift in the use of metals that is driven by environmental concerns. This shift in materials poses an interesting question for industrial ecology because a sizable portion of silver was VOL. 42, NO. 10, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Flow of metals among non-ferrous metals production processes. A process is indicated by a box in black with white letters, a refined metal by a box with a bold frame, and a loss by a shaded box. The underlying data are available in the Supporting Information. obtained as a byproduct of copper and lead smelting processes (8): it might be the case that the shift from lead to silver decreased the very supply of silver as a byproduct of the lead smelting process.
Model Flow of Metals in Metal Production Processes. Figure 1 gives a representative flow of metals among the refinery processes of copper, lead, and zinc, where silver and gold are obtained as byproducts (Figure 1 is based on Japanese data for the year 2000 that are available in the Supporting Information). The generation of a lead source from the zinc smelting (electrolysis) and the generation of a copper source from the lead dross electric furnace suggest the interdependent nature of the production processes. Eleven processes can be identified in Figure 1: two for copper (smelting and electrolysis), four for lead (smelting, copper removal, electric furnace, and electrolysis), three for zinc (electrolysis, smelting, and separation), and one for silver and gold. Each process is defined by the “primary output”, which is its major output that enters into another process/ processes for further processing or treatment. This establishes a one-to-one correspondence between the processes and the primary outputs. The primary outputs coincide with the product with the largest amount except for the lead dross electric furnace, where the largest output is a loss that is not further fabricated but is disposed of as waste. The source of the metal consists of a primary source (metal concentrate) and secondary sources of diverse kinds, including scrap. It is important to note that the flows in Figure 1 refer to those of metals only. For instance, slag of copper smelting refers to the part of copper that ends up in slag and does not include other elements such as lime and gangue. Accordingly, the materials provided by the primary and secondary sources are of the same quality for metal production and are not distinguishable. Because differences in the source of origin do not matter, for each metal, its diverse sources can be integrated into a single one. This integration reduces the metal sources from 11 to five. 3844
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For the lead smelting process, the entire portion of its primary output “crude lead with copper” enters the removal of copper process to be transformed into “crude lead without copper” that represents the only source of metal input for the latter process. On the other hand, the byproduct of the latter process “dross” is entirely processed by the electric furnace for the recovery of copper sources. Here, too, “dross” happens to be the only source of metal input to the latter process. It then seems reasonable to integrate these three processes into a single process, which can be called the lead smelting process. The same applies to the zinc smelting process and the cooling and separation processes, where the entire output of the former is the exclusive input to the latter. We use the term zinc smelting for the integrated process. This “vertical integration” reduces the number of processes from 11 to eight. The major source of input for the production of silver and gold is the slime generated by copper and lead electrolysis. Through the use of information concerning the silver and gold content of the slime, the production of silver and gold from the slime can be traced back to their copper and lead origins. With silver and gold processes allocated to copper and lead electrolysis according to their origins in slime, the number of processes is further reduced from eight to six. This integration also cancels out the flow of slime and dross. Hybrid IO Model with an Integrated Metal Production Process. The previous operations transform the flow of metals in Figure 1 to a simpler one that consists of six processes with 10 outputs (eight metal products and two types of residues) and five inputs (metal sources), which can be represented by a 15 × 6 matrix of inputs and outputs. The array of numbers with the columns named M in Table 1 gives this matrix in the form of IO coefficients. To make the matrix square with regard to the primary outputs and the processes, the matrix is augmented with two columns referring to the primary production process of silver and gold from concentrate and five columns referring to the production processes of five types of metal concentrate. Slag and loss have no corresponding column sector because there
TABLE 1. Matrix of Input Coefficients of Integrated Metal Production Processes with Byproductsa M
M
P C
crude copper el. copper crude lead el. lead dist. zinc el. zinc el. silver el. gold copper source lead source zinc source silver source gold source slag loss
P
C
primary
concentrate
crude copper
el. copper
crude lead
el. lead
dist. zinc
el. zinc
silver
gold
copper
lead
zinc
silver
gold
0 0 0 0 0 0 0 0 1 0 0 0 0.011 0.011 0
1.247 0 0 0 0 0 -0.001 -0.0001 -0.221 0 0 0 0.002 0 0.027
0 0 0 0 0 0 0 0 -0.004 1.064 0 0 0 0 0.061
0 0 0.97 0 0 0 -0.002 0 0 0.036 0 0 0 0 0.004
0 0 0 0 0 0 0 0 0 0 1.043 0 0 0 0.043
0 0 0 0 0 0 0 0 -0.007 -0.028 1.117 0 0 0 0.082
0 0 0 0 0 0 0 0 0 0 0 1.06b 0 0 0.06b
0 0 0 0 0 0 0 0 0 0 0 0 1.06b 0 0.06b
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
c
c
c
c
c
c
c
c
c
c
a El. refers to electrolysis; dist. to distilled; and source to both primary source, such as concentrate, as well as secondary sources, such as scrap. b Hypothetical values. c No entry for this study.
is no process that produces them as primary outputs. Following the framework of WIO (7), the generation of byproducts and the use of secondary inputs occur as negative entries, while the generation of residues occurs as positive entries. For ease of notation, we denote the six primary products referring to copper, lead, and zinc by M; silver and gold by P; and the five metal sources (and the production processes of concentrate) by C. The submatrix consisting of the 6 × 6 elements in the northwest corner can then be denoted by AMM. In the primary production process of silver and gold, silver and gold concentrate represent the only input of metal source: none of the eight metals occurs as input. No entry of input occurs in the columns referring to the production of concentrate either because they use as input mineral ores that do not occur in Table 1. Accordingly, the submatrices AMP, APP, AMC, and APC are zero matrices. For a hybrid IOA, the matrix in Table 1 needs to be integrated into a full framework of WIO that involves the remaining sectors of the economy, such as manufacturing, services, waste management, and final demand. Denoted by R are the remaining production sectors (of goods and services), by Z the waste management sectors, and by W the waste and residues that include slag and loss. The quantity of production and final demand are represented by the columns x and f with subscripts referring to particular groups of sectors (henceforth, a lowercase letter in boldface refers to a vector). For instance, xp refers to the quantity of production of silver and gold, xz to the quantity of waste processed by waste management sectors, and fw to the quantity of waste generated in the final demand sector. The quantity of different types of waste to be treated is denoted by w. Using the notations of the matrix partition as stated previously, the following expression can be obtained for the balance between the supply of and the demand for goods, services, and waste:
()(
xM AMM 0 0 APM 0 xP 0 xC ) ACM ACP 0 ARM ARP ARC xR AWM AWP AWC w
AMR APR ACR ARR AWR
AMZ APZ ACZ ARZ AZZ
)( ) ( ) xM fM fP xP xC + fC fR xR fW xZ
(1)
where the coefficients referring to the generation of slag and loss are subsumed in AWM and AWP. Using obvious matrix
notations, this expression can be simplified to
() (
A· Z x ) A AW · AZZ w
)( ) ( )
x + f . xZ fW
(2)
Note that, in general, this matrix equation cannot be solved for x (consisting of xj and xz) because it is not the output of waste management sectors, xz, but the quantity of different types of waste, w, that occurs on its left-hand side. In WIO, this problem of nonsquareness is coped for by use of the allocation matrix S ) (sij), with sij referring to the share of waste j to be treated by waste management process i, and the following solution for x is obtained (see ref 7 for details):
( )
x ) xZ
(
I-A - S AW ·
- A· Z I - S AZZ
)( ) -1
f S fW
(3)
where I refers to the identity matrix of an appropriate order.
Case Study Scenarios. For illustration, a hypothetical case study of the introduction of lead-free solders involving the production of silver as a byproduct of copper and lead smelting processes was developed and implemented using Japanese data. Of the several types of Pb-free solders that are available (ref 9, Table 1.1), we chose to consider only SAC (99.5Sn/3.9Ag/ 0.6Cu) because of its wide use. Of world silver production, only about 25% has been from silver ore, with the rest being obtained as a byproduct of other metals (8). In Japan, more than 50% of silver comes from domestic copper and lead smelters with the share of the former about 80% and the rest mostly import (10). Henceforth, it is assumed that the copper and lead smelters are the single domestic source of silver supply and that the rest is met through the import of silver concentrate from silver mines abroad. Two scenarios were considered, a default scenario and a Pb-free scenario, the details of which are as follows: (i) Both PbSn and SAC solders were domestically supplied, and none was imported from abroad. (ii) In the Pb-free scenario, the PbSn solder was completely replaced by the SAC solder, while under the default scenario, only the PbSn solder was used. In reality, the use of a Pb-free solder was limited to electronics, and even among electronics, there were many cases where VOL. 42, NO. 10, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 2. Effects on the demand for selected output of the introduction of SAC solder. Rate of change in percentage relative to the default where only SnPb solder is used. it was not used. This simple scenario thus represents an extreme case. (iii) Except for the difference in the composition of materials, the manufacturing process of the two solder types was assumed to be identical. It also was assumed that there was no difference in the soldering process. The latter can be justified on the grounds that the smaller density of SAC compensates for the need for a higher temperature in the soldering process that results from the higher melting point of the SAC solder (11). Data and Methods. A mixed unit IOT (input-output table) with 427 endogenous sectors including a solder sector was compiled by the combined use of Japanese IOT for the year 2000 (12–15) and information on the operations of major Japanese smelters. In the language of ISO-LCA, the Japanese final demand as of the year 2000 stood for the functional unit. Except for the row and column elements that refer to solder, the input coefficients matrix was adjusted for domestic inputs by excluding the intermediate use of imports. Our evaluation thus is limited to the effects on Japanese domestic sectors: International IOTs describing the international flow of goods and services will be needed for considering the effects at a global level. In the Japanese IOT, the domestic mining processes for metal ores (except gold) are not available because of the absence of major mining operations (except for gold) in Japan. Accordingly, the mining processes of metal ores are not considered in the following analysis. The composition of different solder types (ref 9, Table 1.1) is reflected in the elements of AMR and APR in eq 1 that refer to the production of solder. The lower density of the SAC solder implies that a smaller mass (by a factor 183/218 ) 0.84) of the SAC solder is necessary for a given application. Under the SAC scenario, this point is taken into account by multiplying the row elements of ARR in eq 1 that refer to the use of solder by this factor. Through the use of the scenariospecific matrices of input coefficients thus obtained, the effects on x of the alternative solder scenarios are obtained by eq 3. The effects on resource consumption of the introduction of lead-free solders have been the subject of quite a few studies (2, 9, 11, 16–18). None, however, is based on a hybrid approach.
Results Figure 2shows the effects on the demand for relevant metals and solder of the replacement of PbSn solder by SAC solder. The demand for silver and tin increases by 50 and 24%, while the demand for lead and solder decreases by 7 and 11%. The decrease in the demand for solder (weight) is due to the smaller density of the SAC solder than the PbSn solder (ref 9, Table 1.1). As long as silver remains a byproduct of copper and lead smelters, there would be no incentive for the smelters to increase their production to meet the increased demand for silver. In fact, there would be a slight reduction in domestic supply due to the reduction in the production of lead. The 3846
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FIGURE 3. Demand for and supply source of silver under alternative solder types.
TABLE 2. Direct Use of Solders by Producta products electrical equipment for internal combustion engines other electronic components electric bulbs wiring devices and supplies other special industrial machinery semiconductor-making equipment relay switches and switchboards household electrical appliances (except air conditioners) household air conditioners electron tubes semiconductor devices others a
share (1.0 ) 100%) 0.19 0.16 0.14 0.07 0.07 0.07 0.06 0.05 0.02 0.02 0.02 0.13
Source: own calculation.
increasing demand for silver would then have to be met with an increase in import from silver mines abroad (Figure 3): the increase in the price of silver caused by the increased demand for it would encourage silver mines to increase their production.
Discussion Given the increase in the demand for silver, and the rather inelastic nature of the silver supply (8, p 38), previous studies on the resource consumption of lead-free solders pointed to the need for an increase in the recovery and recycling of silver from end-of-life (EoL) products (11, 16, 17). To meet this need, proper information about the flow in the economy of products with major silver content will be necessary. The replacement of solder changes the flow of silver in the economy. Table 2 shows the direct use of solder per unit (1 million Japanese yen) of products. The replacement would result in a significant increase in the silver content of products such as electrical parts, components, and equipment. Some of these products are final products such as home electrical appliances. Most of them, however, are intermediate products (or semis) such as parts and components that are further assembled into final products. Parts and components are usually not discarded separately but are in the form of an entire EoL final product. This implies the need for information concerning the indirect use of solder in final products, that is, the final destination of solder by product and “demand category”. Under “demand category”, we mean the category of final demand in IOT such as household consumption, private and public capital accumulation, and export. Consideration of the “demand category” is important because it refers to the locations where
FIGURE 4. Final destination of silver under alternative solders (top 10 users). Calculated by use of WIO-MFA (19).
FIGURE 5. Final destination of solder (SAC) by products and use categories: products listed represent 70% of the total use in Japan. Calculated by use of WIO-MFA (19). products become EoL products, which in turn have significant implications for the possibility of recovery and the resource value of recovered EoL products. For a given EoL product, its recovery is easier when it is concentrated in a few public sectors than when it is scattered over a large number of private households. The same would apply to the resource value of recovered EoL products as well, due to the likelihood of a lesser degree of contamination with other elements when they are generated from a few concentrated locations. MFA is concerned with the compilation and analysis of the flow of materials and substances (see 8). While many different types of MFA methodologies exist, the WIO-MFA methodology (6, 19) is the one that is best suited to the current framework. WIO-MFA is based on an extended form of IOA and allows for a simultaneous consideration of an arbitrary number of materials contained in a product, whereas the usual MFA is concerned with the flow of one material at a time. Because of this distinguishing feature, WIO-MFA enables one to estimate the material composition of a product, which is not the case for the usual MFA. WIO-MFA can thus be used, among other methods, to estimate the destination of material by product and by the use category and also to identify the input origin of materials of a given product by tracing the fabrication stage backward (see refs 6 and 19 for further details). Owing to these features, WIOMFA turns out to be the MFA methodology best suited to the current framework. In the following, our analysis is based on results obtained from the application of this methodology. Figure 4 shows the final destination of silver by products under alternative scenarios. Note that because of the inclusion of export as a final-use category, intermediate
products such as chemicals, parts, and components also occur as the final destination: they represent the final destination in the sense of crossing the Japanese border and, hence, leaving the system boundary. The introduction of SAC solder makes passenger motor cars the largest single user of metallic silver in Japan (“other industrial inorganic chemicals” refers to ionic compounds of silver such as Ag2NO3). A passenger car is estimated to contain about 33 g of silver per 1 million Japanese yen (or 48 g for an average price of 1.45 million Japanese yen per unit (ref 19, p 2551)). Because a passenger car consists of a huge number of parts and components, it is of interest to search for the input origin of silver. For instance, one may be interested in knowing the portion of this 33 g that originates from electrical components. Tracing the fabrication stage backward (6), it is estimated that of the 33 g of silver, 20 g occurs in “motor vehicle parts and accessories” and “internal combustion engines for motor vehicles and parts”. In other words, these are the components in which silver occurs with the highest concentration in the car. Effective disassembling of these parts would be required if silver resources are to be recovered from an EoL vehicle, the largest single source of silver among EoL products. We now turn to quantitative aspects of the possibility of silver recovery from EoL products at a macro level. Figure 5 shows the final destination of solder under the SAC scenario for the largest 17 products that consumed about 70% of the solder supplied in Japan in the year 2000 (see ref 19 for details of calculation). As we have already seen, solders are mostly embodied in passenger motor cars and electronics. These products are characterized by a high percentage of exports: VOL. 42, NO. 10, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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more than 40% of passenger motor cars is exported. For the 17 major products listed in Figure 5, the share of domestic use amounts to 51% on average. This value can be regarded as the theoretical maximum of the rate of solder recovery from EoL vehicles and appliances in Japan. It is known that about 80% of solder can be technically recovered from PCBs by intensive use of solder recovery and separation equipment (20). It follows that as a whole, only 40% of solder can be recycled even under extremely optimistic and hence unrealistic conditions (all EoL appliances and vehicles are collected for recycling, all the components and parts containing solder are disassembled for solder recovery, and the recovered solder is recycled to its alloy components). It is apparent that the increased demand for silver cannot be met by domestic recycling alone. While international recycling may mitigate this situation, spatial extension of the loop of recycling is likely to increase the generation of loss. It is hoped that significant reduction in solder consumption be achieved through technological developments such as miniaturization and integration (16). There are some limitations of this study, a relaxation of which will be an important future direction for research. First, the system boundary was limited to the Japanese economy. An extension of this boundary by use of an international IOT would be a challenging future task of research. Closely related to the limited nature of the system under consideration is the absence of mining processes in our analysis, which are attributed to the absence of major domestic mining operations (except for a limited amount of gold). From a global perspective, mining activities are known to be of significant environmental importance (21). The proper consideration of mining processes will be another important topic of future research.
Acknowledgments This research was partially supported by the Ministry of Education, Science, Sports and Culture, a Grant-in-Aid for Scientific Research (C-19510050), and by the Shinsei Foundation.
Supporting Information Available Data on flow of metals that underlie Figure 1. This material is available free of charge via the Internet at http://pubs. acs.org.
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(3) Suh, S.; Lenzen, M.; Treloar, G.; Hondo, H.; Horvath, A.; Huppes, G.; Jolliet, O.; Klann, U.; Krewitt, W.; Moriguchi, Y.; Munksgaard, J.; Norris, G. System boundary selection in life-cycle inventories using hybrid approaches. Environ. Sci. Technol. 2004, 38, 657– 664. (4) Hawkins, T.; Hendrickson, C.; Higgins, C.; Mathews, S.; Suh, S. A mixed-unit input-output model for environmental life-cycle assessment and material flow analysis. Environ. Sci. Technol. 2007, 41, 1024–31. (5) Murakami, S.; Yamanoi, M.; Adachi, T.; Mogi, G.; Yamatomi, J. Material flow accounting for metals in Japan. Mater. Transact. 2004, 45, 3184–3193. (6) Nakamura, S.; Nakajima, K.; Kondo, Y.; Nagasaka, T. The waste input-output approach to material flow analysis: Concepts and application to base metals. J. Ind. Ecol. 2007, 11, 50–63. (7) Nakamura, S.; Kondo, Y. Input-output analysis of waste management. J. Ind. Ecol. 2002, 6, 39–63. (8) Johnson, J.; Gordon, R.; Graedel, T. Silver cycles: The stocks and flows project, Part 3. JOM 2006, 58, 34–38. (9) Geibig, J.; Socolof, M. Solders in Electronics: A Life-Cycle Assessment, EPA744-R-05-001, August 2005. http://www.epa.gov/dfe/pubs/solder/lca/index.htm. (10) Metal Mining Data Book 2006; Japan Oil, Gas, and Metals National Corporation: Tokyo, 2006. (11) Deubtzer, O.; Griese, H.; Suga, T. Lead free solderingsFuture aspects of toxicity, energy, and resource consumption. In Proceedings of EcoDesign 2001; IEEE: Los Alamitos, CA, 2001; pp 952–957. (12) 2000 Input-Output Tables for Japan; Ministry of Internal Affairs and Communications: Tokyo, 2005. (13) Year Book of Minerals and Non-Ferrous Metals Statistics;Research and Statistics Department; Ministry of Economy, Trade, and Industry: Tokyo, 2004. (14) Review of non-ferrous production metallurgy in Japan. The Mining and Materials Processing Institute of Japan: 1993; pp 109–12 (in Japanese with English summary). (15) Estimation of CO2 emission and energy consumption in extraction of metals. NIMS-EMC Materials Data for the Environment 1; Tsukuba, Japan, 2004; (in Japanese). (16) Deubtzer, O.; Meysel, F.; Munoz, J. Modelling the solder and resource consumption in lead-free soldering. In Proceedings of EcoDesign 2003; IEEE: Los Alamitos, CA, 2003; pp 714–720. (17) Hamano, H.; Suga, T.; Okamoto, M.; Deubtzer, O. Environmental impact evaluation for the full life cycle of products using Pbfree solders. In Proceedings of EcoDesign 2001; IEEE: Los Alamitos, CA, 2001; pp 1079–1083. (18) Ekvall, T.; Andrae, A. Attributional and consequential environmental assessment of the shift to lead-free solders. Int. J. LCA 2006, 11, 344–353. (19) Nakamura, S.; Nakajima, K. Waste input-output material flow analysis of metals in the Japanese economy. Mater. Transact. 2005, 46, 2550–2553. (20) Development of the Integrated Recycling System of Waste Electric Home Appliances: Progress Report; Association for Electric Home Appliances: Tokyo, 1998; (in Japanese with English summary). (21) Hester, R. Mining and Its Environmental Impact; The Bath Press: Bath, U.K., 1994.
ES702647B
