Introduction

Minimizing the losses of nonrenewable resources requires creating the closest possible approach to a truly circular use of resources, a goal emphasized by Moriguchi (this volume) as crucial to sustainability. Achieving this goal will require harmonious interaction among all actors in the resource cycle: the mining industry, metallurgical processors, original equipment manufacturers (OEMs), nongovernmental organizations, ecologists/environmentalists, legislators, and consumers (to name a few). First principles based on physics and chemistry link many of these actors in the product system. Therefore, models for assessing the "sustainability" of nonrenewable resource usage in products should integrate fundamental natural laws to model and predict change at all levels. In this chapter, we illustrate how product design interacts with fundamental engineering and principles of recycling and metal processing to address this challenge.

Implementing progress in the use of nonrenewable resources on this fundamental basis has been embraced by some of the largest and most visionary companies. For example, the largest steel companies of the world operate in mining and extractive metallurgy, steel production, and recycling, while maintaining close ties to large OEMs, such as the automotive and consumer electronics industries; throughout, they strive for high recycling rates of steel. Although the large nonferrous and precious metal-producing companies of the world are not as resource-comprehensive, they do have close links to the large OEMs in the consumer electronic and goods fields to move toward material cycles that are increasingly closed (Reuter and van Schaik 2008a, b). These companies understand the geology and the fundamental properties of the elements, and have developed and perfected postconsumer extraction technologies as far as possible to maximize recovery of metals. However, because material combinations defined by product design often do not consider the natural limitations of metal extraction, these designs compromise the actual recovery of materials and force detailed shredding and sorting in an attempt to achieve "acceptable" recyclate quality. In this chapter, we demonstrate how product designs that incorporate concepts of disassembly and resource recovery from the start can address many of these concerns.

Fundamental Principles of Recycling

The recycling/recovery rate of products can be considered one of the metrics that expresses the performance of the recycling system and the recyclability and recoverability of a product. The performance of the recycling system is a function of the separation efficiency of the individual processes, ranging from dismantling, shredding, and physical separation to metallurgical and thermal treatment, and is determined by the quality of the recycling streams. Recycling stream quality is not only defined by the different materials and alloys used in the product design, but also by the particle size and multi-material particle composition that exists after shredding and liberation (Reuter and van Schaik 2008a, b). Figure 9.1 illustrates the components that characterize the materials cycle:

• Product design: The functional and aesthetic specifications of a product determine the combination of materials chosen, how these are joined, which coatings are used, etc. These constantly change, however, thereby affecting material supply and demand, how much and how long resources are locked up in the material chain, and what technology is required now and in the future to recycle these materials. These changes are driven by consumer demand versus the marketing campaigns of

Primary metal/ material = p(t)

Product m(t)Car inflow

'Car outflow manufacture

Market

Losses (e.g. export)

Losses Secondary metal/ :

Physical separation material = s(t-t)

Losses

Stoc

Losses Secondary metal/ :

Stoc

Losses

Losses

(flue dusts/slags)

Figure 9.1 Summary of aspects that affect recycling rate and material flows of end-of-life consumer products (from left clockwise): time and property distributions, product design, degree of liberation, separation physics, solution thermodynamics in metallurgical furnaces, recycling technology, recyclate quality, and quality of final output streams.

Losses

Losses

(flue dusts/slags)

Optimization model

Figure 9.1 Summary of aspects that affect recycling rate and material flows of end-of-life consumer products (from left clockwise): time and property distributions, product design, degree of liberation, separation physics, solution thermodynamics in metallurgical furnaces, recycling technology, recyclate quality, and quality of final output streams.

OEMs, both being important drivers for design changes and requirements and technological development.

• Physical separation: The ease of separating materials from each other is determined by product design and the physical properties of the constituents. The physics of separation defines what can be recovered from this mixture of materials and to which level of purity. Any impurity affects the carbon footprint of metal recovery from primary resources. In the end, the grade (or purity) of the primary resources and recyclates determine whether these are economic to exploit—one of the key drivers in closing the material cycle.

• Metallurgical processing: In the final instance, recovering metals and materials from primary resources and recyclates is determined by thermodynamics, kinetics, and technology, all of which affect the economics of the system. If these factors are favorable, metals and/or energy can be recovered and the material cycles can be closed. Being able to quantify the economic potential of resources and recyclates in this manner creates a first-principles basis by which the material cycle can be optimized, adjusted, and predicted into the future, as well as feeding back to design and suggesting more sustainable designs.

• Dynamic feedback control loop: The actual closure of the material and/ or energy cycle of products is determined by final treatment processes, such as metallurgical and thermal processing, which in turn must be defi ned in terms of thermodynamics. This fundamental information, dynamically fed back to the designer, is a key to closing the cycle in a sustainable manner.

These physical and chemical approaches are implemented through several key operational concepts:

• Systemic analysis: Evaluation of the use of nonrenewable resources can only be conducted ifthe interconnectivity of material/metal cycles, technology, and design considerations are accounted for in a fundamental manner, through the physics and chemistry of the system. This links recycling rates and the prediction of the recyclate quality to metallurgical and thermal process efficiency, as well as to primary metal production in the complete web of materials and metals. Because thermodynamics determines what can and cannot be recovered, those recyclates that do not have the correct properties, and hence economic value, will be lost from the resources cycles. In the past few years, models have proven capable of capturing quality decreases, system effi ciency, and the intensity of primary resource usage in recycling (Ayres 1998; Szargut 2005). This is possible if process models predict recyclate quality as a function of product design and, therefore, of a product's economic value and sustainability.

• Recycling and simulation system models: The fundamentals of thermodynamics, physics, chemistry, and technology are combined in systems models that capture the dynamics of progress which static models (e.g., material flow analysis, MFA, and life cycle assessment, LCA) cannot. The design models of the OEMs are based on the technological and economical rigor of engineering design; hence recycling system models must be linked to computer-aided design.

• Design for recycling (DfR): A first-principles basis is required to simulate and predict the recycling/recovery behavior of products, thus facilitating the closure of resource cycles and the minimization of environmental impacts from resource usage. This basis links recycling technology and the environmental consequences of recycling directly to product design (Braham 1993; Deutsch 1998; Tullo 2000; Rose 2000; Ishii 2001). Ultimately, the leakage from the material and metals system is determined by impure (and hence uneconomic) recyclates, which are created by poor recycling systems, unsustainable product design, and poor linkage of design and recycling.

It is crucial in discussions of resource sustainability that product analyses predict and suggest change at the technological level, as this is where nonrenew-able resources are employed, and where they are recovered and recycled.

Material Liberation during Material Processing

The design of the product determines the selection of materials and the diversity and complexity of the material combinations (e.g., welded, glued, alloyed, layered, inserts). The liberation (separation) of the different materials, which have been integrated as a consequence of the product design, determines the quality of recycling streams (Reuter et al. 2005). For simple products,

Table 9.1 Connection types and liberation behavior upon shredding.

Connection type

Before shredding

After shredding

Bolting, riveting t

High degree of liberation (if materials are brittle)

Glueing

Moderate degree of liberation

Painting, coating

Low degree of liberation disassembly may be as easy as removal of a single screw (Braham 1993). For more complex products that undergo shredding and/or dismantling, particles or components are created that consist of one material (pure particle) or more materials (impure particles) (Table 9.1).

Prediction of Liberation Behavior

Understanding and predicting the effect of design on liberation and recyclate quality requires gathering a large body of industrial information from shredding and recycling experiments or actual field data (van Schaik and Reuter 2004a, b). Careful dismantling and separation of the product into its various component materials provides the required information to set up a material mass balance of the product. The material analysis can then be used to predict the amount of the different materials in the connected and unconnected particles as well as the mass flows through the recycling system.

Careful and accurate analyses of the connections between the different materials reveal various connected materials, connections types (e.g., bolted, shape connection, glue), and characteristics of the connection (e.g., connected surface, size of connection) before and after shredding. This information can then be used to derive heuristic rules to predict the degree of liberation and the material connections and combinations that will result after shredding or size reduction (van Schaik and Reuter 2007).

Physical Separation Efficiency

Sorting processes are governed by the physics of separation and hence by the physical properties of the different materials present in the shredded product and the (intermediate) recycling streams. Inevitably, the separation and sorting steps are imperfect, resulting in different grades of recyclates, as shown in Figure 9.2. The separation efficiency of the individual mono- and multimaterial particles is determined in practice by the actual composition of the

* ^li'sJlaïà Physical separation sorting Physical separation sorting

/ Imperfecta f ImperfecA \separationy V liberation J

/ Imperfecta f ImperfecA \separationy V liberation J

Various grades/qualities of recyclates

Figure 9.2 Grades (qualities) of recyclâtes following imperfect shredding and sorting processes.

Various grades/qualities of recyclates

Figure 9.2 Grades (qualities) of recyclâtes following imperfect shredding and sorting processes.

particle and the ratio of the different materials, as these affect the properties (e.g., magnetic, density, electric) that govern their physical separation. Thus, separation effi ciency needs to be accounted for as a function of the particle composition, rather than assuming that only pure particles are present.

Metallurgical, Thermal, and Inorganic Processing

Whereas nonliberated materials cannot be further separated during physical processing, there is potential for the separation and recovery in subsequent metallurgical and thermal processes. During the latter, the separation into different phases (metal, slag, flue dust, off gas) is determined by thermodynamics as a function of temperature, the chemical content of the particles, and interactions among different elements/phases/compounds present in the recyclates. Table 9.2 provides some insight into the complexity of consumer products and hence suggests the detailed processing that would be required to recover all of these materials, so that they do not end as waste. Ultimately, the designs and the models that describe them must address this complexity to estimate where major elements go as well as, more importantly, to know what happens to minor elements. Hence, any predictive model for minor elements should incorporate this knowledge to be of any use in estimating recovery and depletion.

It is important to note that a fundamental link is created between the physical (i.e., the material combinations created by the designer and by physical separation) and chemical description of postconsumer goods (i.e., pure metal, alloys, composite materials), and this link must be intact to bridge the gap between design, physical separation, metal and material recycling, and energy recovery. For each material in postconsumer products, a corresponding chemical composition must be defined to describe and control the final treatment

Table 9.2 General description of materials within a recycling system: dismantling groups, their material grouping, and their respective chemical composition. PVC: polyvinyl chloride; PWB: printed wire boards; PM: precious metal; W: Wolfram (tungsten).

Coils

Copper, ceramics, plastics,

Cu, Fe3Ö4, [-C3H6-]n,

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