THE APPLICATION OF MATERIAL FLOW ANALYSIS FOR THE EVALUATION OF THE RECOVERY POTENTIAL OF SECONDARY METALS IN AUSTRALIA

Transcription

1 THE APPLICATION OF MATERIAL FLOW ANALYSIS FOR THE EVALUATION OF THE RECOVERY POTENTIAL OF SECONDARY METALS IN AUSTRALIA D. van Beers 1, R. van Berkel 2, T.E. Graedel 3 1 Previously with Yale University, now with Centre for Sustainable Resource Processing 2 Curtin University of Technology Centre of Excellence in Cleaner Production 3 Yale University Centre for Industrial Ecology Contact Details of Corresponding Author: Collaborative Research Centre for Sustainable Resource Processing (CSRP) C/o Centre of Excellence in Cleaner Production, Curtin University of Technology GPO Box U 1987, Perth WA 6845, Australia. Tel. +61 (0) , Fax +61 (0) , d.vanbeers@curtin.edu.au SUMMARY The rate of metal use has risen rapidly in recent decades resulting in increasing amounts of landfilled mining wastes and produced metals being stockpiled as in-use products. These two reservoirs will become important for their metal content recovery over the next decades as a result of population growth, increasing per capita resource use, and anticipated metal price increases due to supply limitations. This paper discusses the potential and availability of secondary metals for recovery in Australia, illustrated by research results and case-study examples for copper and zinc. Barriers and enabling mechanisms for enhanced utilisation of secondary (non-virgin) resources are evaluated against the mining of virgin resources with the aim to present decision support guidelines to industry and government for resource policies and practices, and technology innovations. Keywords: Material Flow Accounting, resource management, decision support, secondary metals, Australia. 1 INTRODUCTION Historically, material use by our technological society has been largely based on virgin stocks (mineral deposits). For a number of reasons, these stocks may in the future become inadequate or unavailable at various times and locations. However, other reservoirs do exist: these are products stored or discarded over the years by corporations and individuals. These reservoirs may become important over the next few decades as a result of population growth and resource use. As yet, however, we have very little quantitative information on their total abundance and distribution, as well as the chemical and physical forms in which they may exist [1]. Material flow accounting (MFA) is the technique used for estimating and analysing flows of material within a geographic boundary [2]. The characterisation of material flows, within and between countries and continents, has the potential to inform analyses of resource availability, energy consumption, environmental degradation, and governmental policy. Regularising these approaches, directing them to specific industrial metals, and applying them to all the world s continents is the goal of the Stocks and Flows (STAF) project at the Centre for Industrial Ecology, School of Forestry and Environmental Studies, Yale University, USA. 1

2 This paper discusses the application and the potential value of material flow accounting for the evaluation of the recovery potential of secondary metals in Australia, illustrated by a selection of Australian results from the Yale STAF project focusing on copper and zinc. The Australian component of the STAF work presents qualitative and quantitative assessments of the stocks and flows of copper and zinc going through and residing in the Australian economy in order to provide directions for industry and government policies and strategies. At the end of the paper, barriers and enabling mechanism for enhanced utilisation of secondary metals are evaluated against the mining of virgin resources in order to produce further directions for sustainable metal use. Copper and zinc are examples of materials that are of interest to both resource economists and environmental scientists. They have been widely used for millennia, and are stored in several different chemical and physical forms. Figure 1 illustrates that the growth of use of copper and zinc use has by far exceeded population growth in recent decades, showing a growing dependency on these metals. It is obvious that this usage trend cannot be sustained indefinitely, especially since copper and zinc are materials that may eventually be supply-limited, at least at the low contemporary prices [3, 4] A 8 B 12 7 Usage (Tg Cu/year) Usage (Tg Zn/yr) Year Year Figure 1. The global rate of use of copper (a) and zinc (b) during the 18th - 20th centuries. Data taken from [5] and [6]. 2 MATERIAL FLOW ACCOUNTING, RECYCLING AND SUSTAINABILITY It is generally believed that a sustainable society cannot be achieved without major changes in the way goods and services are produced and how our material needs are satisfied. Tremendous innovations in the supply chain and life cycles seem to be required to move towards a more sustainable direction [7]. Goods and services need to be delivered with a fraction of the current ecological impacts, meaning that technical obstacles for elimination of wastes and emissions in the metal cycles need to be removed. To address sustainable development successfully we cannot view one process, product or effect of the supply chain in isolation. It is essential that processes and production chains are drawn together in a generic framework that gives a holistic view of its performance and progress [8]. A rigorous mass and energy balance with a clear understanding of inputs and outputs is recommended to start moving towards a more sustainable society. It will be very difficult to manage material flows in a society if there is no information available on the quantity and quality of the materials leaving and entering the society at all stages of the supply chain in different chemical properties. Material flow accounting provides a framework from which to address resource management and estimate gross environmental impacts, both spatially and temporally. If mass and energy balances are conducted over an extended time period, economic and environmental indicators can be attached to input and output streams for performance monitoring or scenario planning, such as the impact of a future carbon tax, increased waste management costs, new water access rates [7]. Metals recycling will be a critical feature of sustainable development. Metals seem to have the highest potential for recycling of all the materials used by society. The creation of a recycling-based society will not lead to specific action unless it is clarified what should be circulated and to what extent. Currently, we are at the stage where reviews are being done on what kind of circulating society should be created and what the stance of industry should be in order to achieve it [9]. We hope that the case-studies discussed in this paper contribute to the knowledge required to move Australia to a more sustainable direction. 2

3 3 PRIMARY (VIRGIN) VERSUS SECONDARY RESOURCES Primary and secondary metals have many different characteristics. These differences need to be taken into account when making decisions on the way forward in establishing a sustainable or recycle-based society. Figure 2 shows the involved processes for the production of primary metals versus the production (read: recycling) of secondary metals. Primary metal production covers the whole supply chain from mining, milling, smelting/refining, fabrication of semiproducts, and the manufacturing of finished products ready for use. Obviously, if a metal is recycled it does not have to go through the whole metal production chain in order to be transformed into a new product. Depending on the quality of the secondary metal, it is recycled in the smelting/refining process (generally alloys and low purity metals) or in the fabrication or manufacturing process (mostly high purity metals). Production of virgin metals Mining Ore Milling Concentrate Smelting / Refining Metal Fabrication of semiproducts Semi-products Manufacturing of finished products Finished products Processing of secondary metals Figure 2. Involved processes for processing of virgin resources versus secondary resources. The mining, milling, and smelting/refining processes represent particularly critical stages for the potential release of liquid or solid wastes and gaseous emissions because of the chemical transformation steps that are necessary to smelt and refine the metals from the extracted ores. The intensive use of reagents, water and fuels in primary metal production contributes to the generation of wastes [7]. For example, each kilogram of produced primary copper and zinc consumes a total energy in the range of MJ, and produces 3 to 7 kg carbon dioxide, about 10 kg solid waste, and 15 to 19 kg of liquid wastes [10-12]. The energy consumption and emissions quantities obviously depend upon the ore quality and processing methods. It has been reported that 84% [13, 14] and 75% [15] respectively of energy savings can be achieved when copper and zinc are recycled rather than produced from virgin ore. Recycling has therefore a significant positive impact on energy consumption, greenhouse gas emissions, and solid and liquid wastes per tonne of produced metal than primary metal production. Table 1 summarises some typical differences in characteristics between virgin (primary) and secondary resources. The table shows that the typical grade of a virgin resource ranges from % to 30%. The lower end of the scale is gold ore and the higher end of this scale includes alumina and iron ores. Secondary resources have generally much higher metal concentrations in the range of 0.05% (e.g. paints, chemicals) to 100% (e.g. rolled zinc roofing and copper plumbing tube) depending on the type of end product. As outlined in previous paragraph, the energy, water consumption and waste generation is much higher for the production of virgin resources than for secondary resources. Another interesting contrast is the location of the reservoirs (or deposits). Virgin resources are generally located in comparatively large deposits far from fabrication and use whereas secondary materials are mostly generated close to end-use and fabrication meaning that the re-processing of secondary metals might be possible with lower transportation costs in smaller and disperse quantities and associated environmental impacts, but will generally have to take place on a much smaller scale. Characteristics Virgin Resources Secondary resources Typical grade to 30% % Separability Difficult Difficult to easy, depending on residue form and repository Value of surrounding material Low Moderate to high 3

4 Characteristics Virgin Resources Secondary resources Wastes from metal production Very high Low Energy for metal production Very high Low to very low Water for metal production High to very high Low Location of reservoir Far from fabrication and use Close to end use and fabrication Table 1. Characteristics of virgin versus secondary resources. 4 ESTIMATING IN-USE COPPER AND ZINC STOCKS IN AUSTRALIA In the early 1940s, in his classic economic geography text, Bernard Ostrolensk [16] wrote: The time is not far distant when New York will be as important a source of raw materials for metal industries as is the Mesabi Range or Anaconda. Nearly three decades later, Jane Jacobs [17], one of the great urban planners of the 20 th century, made a similar statement: The largest, most prosperous cities will be the richest, the most easily worked, and the most inexhaustible mines. These visionary ideas have not yet come to pass, in part because the resources available for mining in cities have never been adequately quantified so that one could consider the potential for transforming that vision to action. This section of the paper reports on a methodology that has been developed and applied to the whole of Australia to characterise the in-use copper and zinc stocks as part of the global Stocks and Flows Project executed by Yale University [18, 19]. This research was conducted with the aim to address the following hypothesis: is it useful and feasible, from a resource perspective, to regard large urban conurbations as major future sources of materials, bearing in mind that the increasing occurrence of large urban areas has led to higher concentrations of in-use resources in constrained geographical areas? Three pieces of information are required to consider mining a resource from any reservoir, natural or otherwise: how much (1) of the resource is present, in what form (2), and at which locations (3)? Once this quantitative and qualitative information is known, the costs of recovery and processing can be examined. These costs can be compared to the anticipated market price, and a decision on whether or not to proceed can thus be made. In this way, we are following the common practice in resource geology of locating and quantifying virgin resources, but applying the approach to the secondary resources, i.e. the metals contained in products (e.g. buildings, infrastructure) currently being stockpiled in the in use reservoir. 4.1 Introduction to in-use reservoirs of copper and zinc Copper is used mainly for its electrical conductivity and heat transference properties, its corrosion resistance, and its aesthetic qualities. According to CRU International [20], there are six major copper consuming reservoirs which together account for virtually all the copper put into service: building & construction (e.g., plumbing & electrical wiring), infrastructure (e.g., electrical power distribution and telecommunications), transportation (e.g., motor vehicles and railway transport), consumer durables (e.g., household appliances), business durables (e.g., electrical & electronic products), and industrial durables (e.g., industrial machinery & equipment). Because zinc is mainly used as an anti-corrosion coating (in a technical sense as a sacrificial anode), the majority of its applications involve zinc plating (i.e., electro-deposition and hot dip galvanising). Zinc is also used in brass, precision components (die-castings), pharmaceuticals, cosmetics, and zinc-rich paints. Zinc products can be in the form of finished products (e.g., rolled zinc roofing) or they can be embedded within assembled products (e.g., motor vehicles). According to the International Zinc Association [21], there are five major reservoirs which together account for virtually all the zinc put into service: building & construction (e.g., galvanised steel), infrastructure (e.g., light poles, crash barriers), transportation (e.g., motor vehicles, tires), consumer durables (e.g., household appliances, digestible products, cosmetics, pharmaceutical products), and business durables (e.g., paints, fittings, business electronics, rubber goods). 4.2 Methodology for estimating in-use copper and zinc stocks Stocks of in-use materials result from an excess of material entering a reservoir over time compared with that leaving the reservoir. There are two ways to determine in-use stocks. One is to measure or estimate the input and output flows over time and compute the difference. The second way, which is the approach of this section, is to measure or estimate the reservoir contents directly. The determination of in-use reservoir stocks is straightforward when reservoir contents are relatively uniform from location to location and a convenient measurement technique is available. However, reservoirs of in-use metals are distributed unevenly over a host of rather poorly-quantified products. We therefore need 4

5 to identify proxy indicators, count them, and estimate their metal contents. By doing this, the in use reservoirs of products are assessed in detail. The developed approach employs representative concentrations of copper and zinc in the in-use reservoirs together with Geographic Information System (GIS) data sets of the spatial locations and densities of these reservoirs. For building & construction, transportation, and infrastructure the available information permitted a detailed assessment of in-use stocks by employing representative concentrations of copper and zinc in the proxy indicators. The end-use fractions for copper and zinc [21, 22] (i.e., the fractional flows into various in-use reservoirs) were used as a basis for estimating the stocks in consumer, business, and industrial durables. In summary, the analytical approach for the developed methodology is as follows: 1. Determination of the major copper and zinc reservoirs within Australia. 2. Application of proxy indicators for material uses (e.g., buildings, automobiles). 3. Processing and analysis of the proxy data on a spatial basis using geographic information system (GIS) data and software. A more detailed description of the methodology is given in [18, 19]. 4.3 Quantitative results Our estimates on the in-use copper and zinc stocks are provided in Table 2. The total stock of in-use copper in Australia is estimated at about 5,000 Gg. Building & construction and infrastructure (mainly power distribution) are the two largest reservoirs of in-use copper. We estimate the total in-use zinc stock at about 3,800 Gg with the building & construction reservoir accounting for about three-fourths of the total in-use stock. Overall, therefore, we regard estimates for the in-use copper stock to be accurate to about ± 40%, the uncertainty range for the in-use zinc stocks is 40% / +50%. The uncertainty ranges in Table 2 are estimates made for the purpose of a sensitivity analysis and are not empirical estimates derived from literature. In-use reservoirs In-use copper stocks [Gg] Estimated uncertainty [%] In-use zinc stocks [Gg] Estimated uncertainty [%] Building & construction 2,190 ± 40% 2,645 ± 40% Infrastructure 1,295 ± 30% 240 ± 50% Transportation 340 ± 40% % / +200% Consumer durables 250 ± 50% 375 ± 50% Business durables 495 ± 50% 375 ± 50% Industrial durables 395 ± 50% - - Total 4,965 ± 40% 3,765-40% / +50% Table 2. Estimated in-use copper and zinc stocks in Australia [18, 19]. Australia s total economic reserve of virgin copper and zinc consists of approximately 24,100 Gg Cu and 33,000 Gg Zn [23], equivalent to about 6% [24] and 12% [25] of the world s copper and zinc reserves. The total contemporary stocks of in-use copper and zinc in Australia thus account to about 21% and 12% respectively of Australia s mineral reserves of copper and zinc. At the end of the 1990s, the copper concentrate production in Australia was on average 600 Gg Cu/year [26]. The total contemporary in-use copper stock in Australia thus accounts for almost 8½ years of Australian s copper concentrate production. Australia s zinc concentrate production was about 1,000 Gg Zn/yr at the end of the 1990s [27], so the total contemporary in-use zinc stock represents almost 4 years of Australia s zinc concentrate production. 4.4 Spatial distribution of virgin and in-use copper and zinc stocks The GIS data sets Local Governmental Areas (LGAs) from the Population Census Report [28] were used as a template for the spatial distribution and analysis of in-use copper and zinc stocks in Australia. The Population Census report provides data on residential distribution factors (e.g., population and residential dwellings). Data on the location and size (in terms of employees) of businesses, and the industry in which they are active, was available from the Australian Bureau of Statistics Business Register [29]. 5

6 Figure 3 shows the spatial distribution of the virgin and in-use (non-virgin) copper and zinc stocks for Australia at the Local Governmental Area (LGA) level. This figure demonstrates that a small percentage of the total area of the Australia contains most of the in-use metal stocks. Figure 3 confirms an earlier statement in this paper about the difference in location of the virgin metal reservoirs (deposits) versus reservoirs of in-use products. The virgin deposits are generally located far from fabrication and use while the high spatial density areas of in-use copper and zinc are clearly concentrated in and around the urban regions (e.g., Sydney, Melbourne, Perth, Brisbane). Outside these urban regions are areas with much lower spatial densities of in-use copper and zinc stocks. This uneven distribution is potentially important when developing plans for metal recovery and re-use, or when evaluating copper and zinc losses to the environment during use. The policy implications of this work are discussed in the next subsection. The GIS model that is developed here enables an assessment of contemporary stocks of in-use copper and zinc in selected uses in Australia, and on smaller spatial levels. The results are potentially useful for consideration of policy options related to the magnitude of metal stocks in Australia, and to their principal locations, and the method can readily be applied to other resources and to other geographical areas. A B Figure 3. Spatial distribution of virgin versus in-use copper (a) and zinc (b) stocks in Australia. Data on spatial distribution of virgin copper and zinc stocks is taken from [30]. 6

7 4.5 Implications for industry and government A quantitative assessment and spatial characterisation of in-use copper and zinc stocks in Australia are presented in this section. Attributes of importance for optimising the collection and recycling of end-of-life copper and zinc include the following: Building & construction and infrastructure (mainly power distribution) are the two largest reservoirs of in-use copper. About three-fourths of the total in-use zinc stocks are stored in the building & construction reservoir. These in-use stocks are the principal reservoirs of secondary metals becoming available over the next decades as products become obsolete. Programs to recover and reuse copper will be most economical and productive if concentrated in the high spatial density areas. These high-density areas of in-use metal stocks are clearly located in and around the urban regions, and can have spatial in-use densities more than two orders of magnitude higher than in rural areas. This presents a quite dramatic perspective on the ability of modern cities to attract and concentrate the industrial metals. In this connection, we note that 50% of all in-use copper and zinc stock resides in just 10% of Australia s Local Government Areas, and about 75% of the total copper and zinc in-use stocks in Australia reside in three states: New South Wales, Victoria, and Queensland. Recycling collection centres are mostly located in the urban areas where the bulk of the discards occurs. The further a material has to be transported for recycling, the higher the transportation costs will be and the less economically viable and environmental beneficial recycling becomes (as has been assessed for kerbside recycling of packaging materials [31]. If we define urban areas as Local Governmental Areas with a population density over 50 persons/km 2 and rural areas with less than this value, then we can estimate that about 75% of the Australia s inuse copper and zinc is residing in urban areas, and the remaining 25% in rural areas where the transportation costs will obviously be higher. It is also valuable for recycling programs to know where the copper and zinc resides: in residential or commercial & industrial reservoirs. Residential reservoirs contain the material that is used for domestic or non-commercial applications, such as residential dwellings and consumer durables. Commercial & industrial reservoirs include the copper and zinc being used for commercial and industrial purposes such as stocks in industrial and business durables. It is estimated that about 50% and 65% respectively of the total copper and zinc stocks resides in residential reservoirs. Commercial & industrial reservoirs account for the remaining 50% and 35%. Information can be extracted from the GIS plots on the quantity and density of copper and zinc stocks in each LGA allocated to residential and commercial & industrial reservoirs. Recycling programs can use this information to select priority areas, and to refine approaches for the collection of end-of-life copper and zinc. 5 CONTEMPORARY AUSTRALIAN COPPER AND ZINC CYCLES: ONE YEAR STOCKS AND FLOWS In this section, we report on one-year copper and zinc cycles for Australia that were constructed within the framework of the Yale STAF project [32, 33]. In these studies, the major flows of copper and zinc in Australia over the entire lifecycle are examined; these include production (mining, milling and refining), fabrication and manufacturing of semi- and finished products, use, and the waste management system. The goals of the development of these contemporary metal cycles are fourfold: assessment of the magnitude of copper and zinc uses in Australia during the mid-90s, the estimation of the amount of copper and zinc leaving the Australian economy in various waste streams, the determination of the amount of metal recovered, and the estimation of the amounts of copper and zinc accumulating in specific reservoirs. 5.1 Methodology for constructing contemporary metal cycles The methodology used to characterize the cycles of copper and zinc has been described in detail in earlier publications [1, 34, 35]. We summarise the approach briefly here for the convenience of the reader. It is based on the framework shown in Figure 4, which consists of the four life stages in which an anthropogenically - utilised material participates: processing, fabrication and manufacturing, use, and waste management. Earth s lithosphere serves as the initial source of the material, and the environment as the eventual sink (though discarded materials are commonly retained for long periods of time in tailings ponds or landfills). Import and export is possible at any of the four stages. We refer to these stages as reservoirs, because they are storage locations for metals. In practice, only the in-use stage engages in longterm storage. An alternative designation for the other three stages could be processes. A cycle is considered characterised when the flows that connect the reservoirs and the changes in stock that enhance or deplete the reservoirs are quantified for a particular time or temporal interval. 7

8 A realistic metal cycle is much more complex than it appears in Figure 4, as has been shown previously [35]. Assembling the data for such a cycle requires the use of numerous sources of varying quality, mostly available at country level. In general, the reliability of the information decreases as one moves from left to right on Figure 4. This occurs because global metal markets provide detailed information so long as a metal is being sold as a unique material (metal ore, refined copper or zinc, etc.). Once it is utilised in manufacturing, usually in combination with other materials, data tend to be available only in the form of products or groups of products (e.g., machine tools), for which the copper and zinc contents must be estimated. Flows of copper and zinc from use into waste management are even less well characterised; we have combined data on waste stream magnitudes (often available) with information on the copper and zinc contents in the several waste streams (sparse, and not readily generalisable). Import / Export Cross-boundary Exchange Cross-boundary Exchange Cross-boundary Exchange Cross-boundary Exchange Production Fabrication & Manufacturing Use Waste Management Ore Tailings Slag Mine/Mill Concentrate Smelter Refinery Refined Metal Semi Fabrication New Scrap Semi Alloy Fabrication New Scrap Finished Products Manufacturing Finished Alloy Products Manufacturing Finished Products Finished Alloy Products Domestic Uses Industrial Uses Exchange with Stock Stock MSW C&D WEEE ELV SS C&I HW Collection & Separation Comb. Wastes Incineration Old Scrap New Scrap Old Scrap Landfilled Wastes Ashes Overburden Lithosphere Landfill & Environment System Boundary Australia Legend: MSW C&D WEEE ELV SS C&I HW Municipal Solid Waste Construction & Demolition Waste Waste from Electrical and Electronic Equipment End-of-Life Vehicles Sewage Sludge Commercial and Industrial Waste Hazardous Waste Figure 4. One-year metal cycle model for Australia. The waste management acronyms are: MSW = municipal solid waste; C&D = construction and demolition waste; WEEE = waste from electrical and electronic products; ELV = end-of-life vehicle; SS = sewage sludge; C&I = commercial and industrial waste; HW = hazardous waste. Because of low or negligible rates of metal extraction, processing, and/or use, frequently in combination with an absence of archival data, it is not possible nor important to characterise all metal flow magnitudes. A pragmatic goal is to capture at least 80% of the flow magnitude to and from the following reservoirs: virgin ore bodies (extraction), the mining and processing industries, the fabrication industries, the in-use reservoir, and the waste management industries. A time-period of one year was chosen as the temporal interval since most statistics are given on an annual basis was selected as the year of investigation in the mid-90s as this corresponds with the base year of contemporary metal cycles of other continents constructed by the STAF project. 8

9 Australia Copper Cycle A Net Import (-) or Export (+) +291 Concentrate Blister 6 Cathode Copper 164 Alloy Semis Copper Semis Finished Products Old Scrap Ore 482 Production Mill, Smelter, Refinery 18 Stock Cathode Copper 172 Fabrication & Manufacturing Prod.Cu 95 Prod.Alloy 25 Use 134 Stock Discards 40 Waste Mangement 7 29 New Scrap 36 Landfilled Waste Tailings 17 7 Old Scrap Slag Lithosphere -482 Landfill & Environment +74 Australia Zinc Cycle System Boundary Australia Net Import (-) or Export (+) +848 B Concentrate Refined Zinc 138 Semi Products Finished Products Old Scrap Ore 1119 Production Mill, Smelter, Refinery 9 Stock Refined Zinc 193 Fabrication & Manufacturing Prod.Zn 161 Use 152 Stock Discards 24 Waste Mangement Tailings Slag 49 Wastes Old Scrap 53 Landfilled Waste 17 Lithosphere Landfill & Environment +181 Scale < System Boundary Australia > 999 Figure 5. Mid-90s total copper (a) and zinc (b) flow diagrams for Australia. All units are in Gg/yr (1,000 metric tonnes/yr). 9

10 5.2 Quantitative results The application of the methodology and the one-year metal cycle model to Australia, as discussed in previous subsection, results in the copper and zinc flow diagrams presented in Figure 5. A number of features of interest in the copper and zinc cycles can readily be identified: In the mid-1990s, the extraction of copper and zinc from the Australia lithosphere accounted for approximately 482 Gg Cu/yr and 1,119 Gg Zn/yr, while a relatively small proportion (18 Gg Cu, 9 Gg Zn) became available from production stocks. About 24 Gg Cu and 33 Gg Zn entered the production stage as secondary material. An estimated 55% and 75% respectively of the extracted copper and zinc was exported from Australia. About 172 Gg Cu and 194 Gg Zn were sent on to Australian fabricators, and about 68 Gg Cu and 164 Gg Zn were discarded in tailings and slag. The largest export flow in the Australian copper cycle is the export of copper cathode (164 Gg Cu/yr). The export of zinc concentrate (711 Gg Zn/yr) is by far the largest export flow in the Australia zinc cycle. Australia has a net import of copper semis (6 Gg Zn/yr) and finished products (54 Gg Cu/yr). The zinc flow in imported finished products (15 Gg Zn/yr) accounts for the only net import flow in the zinc cycle. Overall, the production, fabrication and manufacturing, and waste management process are characterised by net exports, while the use process shows a net import. The difference between the input and output flows to the use phase is estimated at 134 Gg Cu/yr and 152 Gg Zn/yr; this flow represents a net addition to the in-use stock. The net-addition to stocks goes for a large part into building & construction and infrastructure. In Australia, the apparent separation rate for copper and zinc entering the waste management system is estimated at about 80% and 60% respectively. These fractions are likely to be lower due to uncertainties in the metal content of post-consumer wastes. Also, the entire zinc flow in the net export of old zinc scrap will probably not be recycled, however, since this flow includes galvanised zinc on steel (7 Gg Zn/yr) for which the recovery costs are high. An estimated and 68 Gg Cu and 164 Gg Zn is deposited on the ground near milling, smelting, and refining operations while approximately 6 Gg Cu and 17 Gg Zn is landfilled as fabrication & manufacturing wastes and post-consumer wastes each year in Australia. Undetermined amounts are dissipated in various ways. Overall, the movement of about 482 Gg Cu/yr and 1,119 Gg Zn/yr from natural reserves is to a limited extent balanced by a return flow of at least 74 Gg Cu/yr and 181 Gg Zn/yr. 5.3 Implications for industry and government The contemporary Australian copper and zinc cycles presented here may provide the directions for industry and government policies and strategies. The main policy implications can be summarised as follows: The reservoir of landfilled production wastes is a fast-growing reservoir for both copper and zinc. An estimated 15% of the copper and zinc mined is landfilled as tailings and slag in the near vicinity of the mine. Firstly, it is important to improve the operation of existing mines and minerals processing plants through cleaner production and eco-efficiency technologies and practices [36]. Examples such as the Golden Grove zinc/copper mine in Western Australia, show that remarkable improvements in metal recovery in primary production are often quite possible through comparatively simple methods such a containment of ore storage, hydrocarbon management in the mine and improved feed water quality control for a hydrometallurgical plant [37]. Secondly, it is important to manage these reservoirs of landfilled copper and zinc mining wastes in such a way that they may serve as a possible supply of secondary resources in the future, alongside with the lower grade ore currently considered as overburden. Improvements in extraction technologies will most likely see the economic grade of ores drop over time, making currently discarded low grade ores a resource for the future. This process is already happening in the gold industry, where old underground mining areas and rock and tailings deposits are now being re-mined as open pit mines (for example Super Pit in Kalgoorlie, Western Australia). The rate of use of copper and zinc has risen rapidly in the recent decades, as world usage of new metal continues a long established upward trend. We anticipate increasing end-of-life flows over the next few decades, since significant amounts of copper and zinc have been put into use during the past half-century. This is confirmed in the Australia copper and zinc cycles, where about 75-85% of the copper and zinc entering use can be considered a netaddition to the in-use stock. Waste management practitioners should be prepared to collect, separate, and recycle the increasing end-of-life waste flows in the most effective and efficient manner in the future. In some cases there will be challenges or limitations in the recovery of the accumulated in-use stocks. For example, it will be difficult to dismantle and remove underground piping systems (e.g. Amsterdam still has most of its lead plumbing tubes sitting in the ground). 10

11 The separation rates of all copper and zinc entering the waste management system are less than 80% and 60% respectively, including both post-consumer waste and fabrication and manufacturing waste. The most important waste stream, in terms of total copper content, is waste from electrical and electronic equipment. End-of-life vehicles (including tyres), fabrication and manufacturing waste, and municipal solid waste seem to be the waste streams with the highest total zinc content. The metal content in construction & demolition waste is expected to increase over the next decades due to the large amounts of metal that has been put into use in building & construction over the years. If one wishes to increases the recycling rates of copper and zinc in Australia, primary attention should be given to these waste streams. Since copper is often used in pure form and the recycling of end-of-life copper is not as complex as other metals, the recycling rate of copper is rather high overall. The basic (and obvious) rule is that the easier it is to separate the copper from its obsolete application, the higher the recycling rate. Since copper is used in a wide range of applications with different physical and chemical properties, the recovery and recycling rate will vary per application. Copper-containing products with a lower copper content (and therefore likely lower recycling rate) are generally consumer durables. End-of-life zinc being recycled is mainly pure zinc (e.g., zinc roofing and gutter), alloys (e.g., die-castings and brass), and residues from the hot dip galvanising process (zinc oxide, dust, dross). The costs for the recovery of zinc from galvanised steel are high. Most galvanised steel that is recycled goes directly to electric arc furnaces (EAF), where the zinc coating is vaporised and landfilled as electric arc furnace dust (EAFD). Galvanising is a growing application of zinc, especially in the automotive industry. Depending on the life-times of galvanised products, this zinc will become available as an end-of-life flow over the next few decades. An additional example of a zinc application with a low recycling rate is in waste tyres. Although efforts are made to recycle or reuse waste tyres (predominately for energy recovery or road surfaces), most zinc in waste tyres is not being recycled. The end-of-life flows quantified in the presented cycles may assist a feasibility analysis on the recycling of copper and zinc from the more challenging products (in terms of recovery) in Australia. 6 BARRIERS AND POSSIBLE ENABLING MECHANISMS FOR ENHANCED UTILISATION OF SECONDARY METALS As outlined earlier in the paper one of the ways to move towards a more sustainable society is to enhance the recovery and recycling rate of the metal contents generated and landfilled during the production phase (mainly tailings and slag) and the metals embedded in end-of-life products. From the case-study results discussed in this paper it is apparent that there will be a significantly larger proportion of end-of-life products as a potentially utilisable resource over the next few decades (in the range of 100% and 150% increase in end-of-life copper and zinc respectively over the next 30 years [38]). In order to achieve this challenging task, one needs to know more about the associated barriers for enhanced utilisation of secondary metals and possible enabling mechanisms to overcome these barriers. We have listed a selection of barriers and suggestions for enabling mechanisms in Table 3. As shown in this table, the economic barriers deal with the costs of the collection (retrieval, dismantling and transportation), recovery and recycling processes of the secondary metals and the competition from countries with low labour costs. Technical barriers seem to evolve around the segmentation and the relatively small scale of metal recycling operations (in comparison with primary metal plants), the dilution of primary with secondary metals to produce high-grade metals, and the difference in anthropogenic alloys with naturally occurring metal ore compositions. Social barriers for recycling mainly deal with the occupational health and safety issues from contaminated scrap and the need for processing industries to work more closely together. Economic issues: Barriers Australian scrap is processed overseas where labour costs are cheaper (and environmental standards are likely lower) resulting in potential shortages in the supply of scrap to local re-processing and manufacturing plants [39]. The further a metal has to be transported for recycling, the higher the transportation costs will be and the less economical recycling becomes. Recycling collection centres are mostly located in the urban areas where the bulk of the discards are generated. There are economic limits to the efficient collection, transportation, and recovery of metals for recycling [39]. Possible enabling mechanisms Innovative, more efficient and less-labour intensive process technologies will reduce the costs for reprocessing of secondary metals in Australia. Quantitative and qualitative information on the magnitude and spatial location of secondary metals have the potential to assist industry and government in optimising the collection and recovery system of metals in urban and rural areas. Given that metal recycling rates tend to decrease when metal prices fall, it may be necessary to devise economic drivers that encourage metal recycling when prices fall. 11

12 Technical issues: Barriers Metal recycling operations are typically a lot smaller in scale than primary smelter operations. Although furnace fumes and dusts are collected at secondary smelters, the operations are typically too small to justify the capital costs to treat the fumes and they are also sent to primary smelters capable of handling a wide range of feed materials [39]. The current practice of dilution of secondary metals to produce high-grade metals is regarded as a major problem. Dilution will eventually undermine the continued (re)use of stocks of metals in the economy. The current practice of metal use and metal recovery already results in a steady decline of the quality of metal stocks [40]. Anthropogenic alloys quite differ from naturally occurring metal ore compositions. Therefore current metallurgical processes might not be suitable for all secondary metal recycling. If you close one metal cycle, another metal cycle is opened. Some metals are by-products of other metals [40]. Additionally, the composition of consuming products is becoming increasingly diverse these days due the market demands, making it more challenging to recycle the metals contents. Social issues: Metal recovery from complex end-of-life products (motor vehicles, electrical equipment, etc) still highly depends on manual work. Occupational health and safety standards have lowered permissible levels of repetitious manual tasks. Contamination of the scrap with other waste material and metals is a possible problem for recyclers [39]. Processing industries need to work together in order to reduce the quantity of waste discharged without restraining production activity. The metal production industry can treat by-products and waste discharged from other manufacturing industries [9]. Social issues limiting the cooperation between companies are trust, company competition, and reluctance to cultural change, and increased dependency and complexity of the supply chain. [39]. Possible enabling mechanisms Efficiency improvements could be gained by improving feed quality by better separation of metals, reducing manual handling, rapid and cheap on-line analysis, through to improved safety in transport and handling of molten products [39]. Current metallurgic knowledge and industrial infrastructure have the capacity to address this challenge, but only if the metallurgic constraints of metal recovery are taken into account in waste management, policy development, and product design (and visa versa). [40]. A combined effort of product designers, waste managers, and metallurgist would enable the design of products, separation of the resultant wastes, and blending of separated fractions at the metallurgical plant to produce suitable feedstock for metals with the desired characteristics for new products. In order to design or separate for recovery, an understanding of operation of the metallurgical system is necessary [40]. Greater use of design for disassembly / material recovery, the further development of disassembling technologies, and the use of robotics in the recovery of metals from endof-life products will reduce the health and safety risks associated with scrap recycling. There is a need for methodological and industry-focused approaches to identify and eliminate the social barriers related to networking of companies. There is lack of such methodologies at present time, but this area is getting increasing attention from various research institutions and industries. Table 3. Barriers and possible enabling mechanism for enhanced utilisation of secondary metals. 7 FINAL DISCUSSION AND CONCLUSIONS This paper discussed the application of material flow analysis for the evaluation of the recovery potential of secondary metals in Australia, illustrated by a selection of the Australian results from the Stocks and Flows project at Yale University. It presents qualitative and quantitative assessments of the stocks and flows of copper and zinc going through and residing in the Australian economy in order to provide directions for industry and government policies and strategies. The implications for industry and government deriving from the copper and zinc case-studies on the in-use stocks and the metal cycles were discussed separately in previous sections. Bearing in mind the limitations and uncertainties in available data and estimations, potentially valuable information can be extracted from these studies to assist in the establishing and/or refining of metal recycling programs in Australia. 12

13 An assessment of the economic, technical, and social barriers and possible enabling mechanisms associated showed that the further enhancement of the utilisation of secondary metals is not as simple as it may seem. Many challenges still need to be addressed to move towards a recycled based society, and on-going collaborative efforts are required for the future bearing in mind that the end-of-life metal flows are expected to more than double over the next three decades. The GIS model that is described in this paper (Section 4) enables an assessment of contemporary stocks of in-use copper and zinc in Australia, and on smaller spatial levels. The results are potentially useful for consideration of policy options related to the magnitude of copper and zinc stocks in Australia, and to their principal locations, and the method can readily be applied to other resources and to other geographical areas. Additional attributes such as input and output flows of copper and zinc, and the locations of landfills, manufacturing, and recycling facilities can be added to the GIS model. These enhancements would identify opportunities for the spatial linking of facilities with one another, and provide additional information for the optimisation of metal recycling in Australia. Additional research and data sets will be required to refine the results presented in this paper. Significant limitations exist in the paucity and uncertain reliability of data for certain parts of the copper and zinc models, particularly the waste management process. Improvements in data availability, consistency, and detail will be required if a more accurate stocks and flows models for Australia are to be constructed. Although the studies presented in this paper do not focus on dissipative copper and zinc losses and their environmental impacts, the study can serve as a first step in addressing these issues. 8 ACKNOWLEDGEMENTS The case-studies presented in this paper were conducted within the framework of the Stocks and Flows (STAF) project at Yale University. The STAF project was funded by the U.S. National Science Foundation under grant BES Professor van Berkel s Chair in Cleaner Production is cosponsored by CSBP Ltd, Alcoa World Alumina Australia, and Curtin University of Technology. The Centre for Sustainable Resource Processing is established under the Australian Commonwealth Collaborative Research Centres Program. 9 REFERENCES 1. Graedel, T.E., M. Bertram, K. Fuse, R. Gordon, R. Lifset, H. Rechberger, and S. Spatari., The characterisation of technological copper cycles, Ecological Economics, 42, p. 9-26, Baccini, P. and P.H. Brunner, Metabolism of the anthroposphere, Springer, New York, USA, Kesler, S.E., Mineral resources, economics, and the environment, Macmillan, New York, USA, Tilton, J., On borrowed time? Civilization and the Threat of Mineral Depletion, Resources for the Future, Washington DC, USA, WBMS, Metal Statistics , 82nd Edition, World Bureau of Metal Statistics, Ware, U.K., Craig, J., in Workshop on Material Flows, National Academy of Engineering, Washington, DC, USA, Herbertson, J. and P. Sutton, Foundations of sustainable resource processing, in Green Processing Conference, Cairns, QLD, Australia, Hancock, P.M., Application of lifecycle assessment to mineral sector sustainable development - developing sustainability indicators, in Green Processing Conference, Cairns, QLD, Australia, Nakamura, T., The role of the metallurgical industry in the recycling-based society, in Green Processing Conference, Cairns, QLD, Australia, Norgate, T.E. and W.J. Rankin, The role of metals in sustainable development, in Green Processing Conference, Cairns, QLD, Australia, Norgate, T.E. and W.J. Rankin, An environmental assessment of lead and zinc production processes, in Green Processing Conference, Cairns, QLD, Australia, Lunt, D., Y. Zhuang, and S. La Brooy, Life cycle assessment of process options for copper production, in Green Processing Conference, Cairns, QLD, Australia, Bureau of International Recycling website, Kellog, H.H., Sizing up the energy requirements for producing primary metals, Eng and Min J, 178(4), p ,