502 INDUSTRIAL ECOLOGY INTRODUCTION Industrial ecology is an emerging field of study that deals with sustainability. The essence of industrial ecology was defined in the first textbook of the field in this way: Industrial ecology is the means by which humanity can deliberately and rationally approach and maintain sustain- ability, given continued economic, cultural, and technologi- cal evolution. The concept requires that an industrial system be viewed not in isolation from its surrounding systems, but in concert with them. It is a systems view in which one seeks to optimize the total materials cycle from virgin material, to finished material, to component, to product, to obsolete product, and to ultimate disposal. Factors to be optimized include resources, energy, and capital. (Graedel and Allenby, 2003, 18) Industrial ecology is industrial and technological in the sense that it focuses on industrial processes and related issues, including the supply and use of materials and energy, adoption of technologies, and study of technological envi- ronmental impacts. Although social, cultural, political, and psychological topics arise in an industrial-ecology context, they are often regarded as ancillary fields, not central to industrial ecology itself (Allenby, 1999). Industrial ecology’s emphasis on industries and technolo- gies can be explained with the “master equation” of industrial ecology. Originating from the IPAT equation (impact, popu- lation, affluence, and technology; Ehrlich and Holdren, 1971; Commoner, 1972), the master equation expresses the relation- ship between technology, humanity, and the environment in the following form: EnvironmentalimpactPopulation GDP Person Environmentalimpa ϭϫ ϫ cct UnitofGDP (1) where GDP is a countrys or region’s gross domestic product, the measure of industrial and economic activity (Graedel and Allenby, 2003, pp. 5–7; Chertow, 2000a). In this equation, the population term, a social and demo- graphic one, has shown a rapid increase in the past several decades, and continues to increase. The second term, per- capita GDP, is an economic indicator of the present popula- tion’s wealth and living standards. Its general trend is rising as well, although there are wide variations among countries and over time. These trends make it clear that the only hope of maintaining environmental interactions in the next few decades at an acceptable level is to reduce the third term, envi- ronmental impacts per unit of GDP, to a greater degree than is the product of the increases in the first two terms—a substan- tial challenge! This third term is mainly technological and is a central focus of industrial ecology. The name “industrial ecology,” combining two normally divergent words, relates to a radical hypothesis—the “biologi- cal analogy.” This vision holds that an industrial system is a part of the natural system and may ideally mimic it. Because biological ecology is defined as the study of the distribu- tion and abundance of living organisms and the interactions between those organisms and their environment, industrial ecology may be regarded as the study of metabolisms of tech- nological organisms, their use of resources, their potential environmental impacts, and their interactions with the natural world. The typology of ecosystems has been characterized as three patterns (Figure 1a–c). A Type I system is a linear and open system that relies totally on external energy and materials. In biology, this mode of action is represented by Earth’s earliest life forms. A Type II system is quasi-cyclic, with much greater efficiency than Type I. However, it is not sustainable on a planetary scale, because resource flows retain a partially linear character. Only a Type III system possesses a real cyclic pattern, with optimum resource loops and external reliance only on solar energy. This is how the natural biosphere behaves from a very long-term perspective. The evolutionary path from Type I to Type III taken by nature (from open to cyclic, from unsustainable) provides per- spective on the evolution of industrial ecosystems. Historically, the industrial system has mimicked the Type I pattern, with little concern about resource constraints. The best of today’s industries come close to Type II (Figure 1d), and a Type III industrial system is a vision of a possible sustainable future for industrial ecosystems. The biological analogy has been explored in other ways as well. From a metaphysical perspective, industrial ecology’s philosophy might be labeled as: “nature as model,” “learning from nature,” and “orientation by nature” (Isenmann, 2002). © 2006 by Taylor & Francis Group, LLC INDUSTRIAL ECOLOGY 503 In this context, industrial firm-to-firm interactions have been examined by ecological food-web theory (Hardy and Graedel, 2002), and the theoretical approaches of thermody- namics and self-organization have also been applied to these systems (Ayres, 1988). The interaction between the worlds of industry and ecology emphasizes that industrial ecology is a systems science that places emphasis on the interactions among the components of the systems being studied. This sys- tems orientation is manifested in several of the research topics of the field, including life-cycle analysis, industrial metabolism, system models and scenarios, and sustainabil- ity assessment (Lifset and Graedel, 2002), topics that are discussed below. THE ORIGINS OF INDUSTRIAL ECOLOGY For many thousands of years, nature dominated the human-nature relationship. This dominance was reversed by the growth of agriculture and especially by the industrial revolution of the 1800s. The implications for nature of this ECOSYSTEM Component ECOSYSTEM Component ECOSYSTEM Component ECOSYSTEM Component ECOSYSTEM Component ECOSYSTEM Component ECOSYSTEM Component Unlimited waste Unlimited resources Limited waste Energy & Limited resources (a) Type I: linear material flows (b) Type II: quasi-cyclic material flows (c) Type III: cyclic material flows FIGURE 1 Typology of ecosystems. From Graedel and Allenby, 2003; Lifset and Graedel, 2002. (a) Type I: linear material flows; (b) Type II: quasi-cyclic material flows; (c) Type III: cyclic material flows; (d) Type II industrial ecosystem. © 2006 by Taylor & Francis Group, LLC 504 INDUSTRIAL ECOLOGY transformation were called out in the third quarter of the twentieth century by several seminal environmental thinkers (Carson, 1962; Lovelock, 1988; Ward et al., 1972). The pub- lication of the Club of Rome’s report The Limits to Growth also received considerable public attention (Meadows et al., 1972). That report predicted that economic growth could not continue indefinitely because of Earth’s limited availability of natural resources, as well as its limited capacity to assimi- late pollution of various types. Most of the Club of Rome’s dire projections about resource exhaustion have not thus far come to pass. Nonetheless, the issue of the sustainability of human civilization has become a concern of global scope and reach. The concept of industrial ecology, in which the technology–environmental linkage is explicitly recognized and addressed, can be traced to the early 1920s (Erkman, 1997, 2002). However, 1989 is generally viewed as the formal year of birth of the field (Figure 2). In that year, R. Frosch, then vice president of the General Motors Research Laboratories, and his colleague N. Gallopoulos developed the concept of industrial ecosystems in their seminal article “Strategies for Manufacturing” (Frosch and Gallopoulos, 1989). Their view was that an ideal industrial system would function in a way analogous to its biological counterparts. In such an industrial ecosystem, the waste produced by one process would be used as a resource for another process. No waste would therefore be emitted from the system, and the negative impacts to the natural environment would be mini- mized or eliminated. This analogy between biological and industrial systems was the conceptual contribution that led ultimately to the new field of industrial ecology. Industrial ecology’s growth since the early 1990s has been marked by a series of institutional milestones, including the first textbook ( Industrial Ecology; Graedel and Allenby, 1995), the first university degree program (created by the Norwegian University of Science and Technology [NTNU] in 1996), T. E. Graedel’s appointment as the first professor of industrial ecology in 1997, the birth of the Journal of Industrial Ecology in 1997, and the founda- tion of the International Society for Industrial Ecology (ISIE) in 2001. As a consequence of these activities, an academic community of industrial ecologists has been formed, research methodologies are being developed and refined, and industrial ecology is being practiced all over the world. INDUSTRIAL ECOLOGY’S TOOLBOX Given an evolving field with a wide and evolving scope, industrial ecology’s toolbox has become equipped with a variety of methods of approaching the concepts and practices of interest. Three of the most common tools, material-flow analysis (MFA), life-cycle assessment (LCA), and input- output analysis (IOA), are discussed below from a method- ological point of view. Material-Flow Analysis MFA is “the systematic assessment of the flows and stocks of materials within a system defined in space and time. It connects the sources, the pathways, and the intermediate and final sinks of a material” (Brunner and Rechberger, 2004, p. 3), thus providing information on the systemic utilization of the material within the given boundaries. (d) T y pe II industrial ecos y stem Limited waste Energy & Limited resources Materials Extractor RecyclerCustomer Manu- facturer FIGURE 1 (continued) © 2006 by Taylor & Francis Group, LLC INDUSTRIAL ECOLOGY 505 The principal terminology used in MFA studies is as fol- lows (Graedel and Allenby, 2003, pp. 284–289; Brunner and Rechberger, 2004, pp. 34–40): Substance: Any (chemical) element or compound composed of uniform units Material: Substances and combinations thereof, both uniform and nonuniform Goods: Entities of matter with a positive or negative economic value, comprised of one or more sub- stances Process: The operation of transforming or transporting materials Flux: The rate at which an entity enters or leaves a process Budget: An accounting of the receipts, disbursements, and reserves of a substance or material Cycle: A system of connected processes that transfer and conserve substances or materials The central principle upon which MFA is based is that of mass balance, which states that the mass of all inputs into a process equals the sum of the mass of all outputs and any mass accumulation (or depletion) that occurs within. This renders the results of MFA useful for studies of resource availability, recycling potential, environmental loss, energy analysis, and policy studies. MFA may be per- formed on a local scale and from a technical engineering perspective (as in Type A in Table 1), or, on a broader scale, associated with a geopolitical or socioeconomic dimension (as in Type B in Table 1; Bringezu and Moriguchi, 2002). In each case there is the potential for achieving a better understanding of the materials aspects of the process or entity under study, as well as identifying opportunities for achieving improvements. Life-Cycle Assessment LCA is a tool broadly used by industrial ecologists to identify and quantify the environmental impacts associated with a product, progress, service, or system across its “cradle- to-grave” life stages. Unlike the more targeted examination of a product or process in order to understand and quantify its direct environmental impacts, the use of a life-cycle perspec- tive enables one to examine the direct and indirect environ- mental effects of an object through the stages of extraction of raw materials; various manufacturing, fabrication, and trans- portation steps; use; and disposal or recycling. LCA began in the United States in 1969, in an effort to compare several types of beverage containers and deter- mine which of them produced the lesser effect on natural resources and the environment (Levy, 1994; U.S. EPA, 2004). Since the 1990s, the Society for Environmental Toxicology and Chemistry in North America and Europe and the U.S. Environmental Protection Agency (EPA) have worked to promote consensus on a framework for conduct- ing life-cycle inventory analysis and impact assessment. In 1993, the International Organization for Standardization 1960 1970 1980 1990 2000 R. Carson, SILENT SPRING, 1962 B. Ward et al., ONLY ONE EARTH, 1972 United Nations Conference on Human Environment, 1972 D.H. Meadows et al., LIMITS TO GROWTH, 1972 WCED, OUR COMMON FUTURE, 1987 Foundation of UNEP, 1972 United Nations Conference on Environment and Development (1st Earth Summit), 1992 2nd Earth Summit, 2002 Founding of ISIE, 2000 T.E. Graedel, Professor of industrial ecology, 1997 Yale & MIT. JOURNAL OF INDUSTRIAL ECOLOGY, 1997 T.E. Graedel and B.R. Allenby, INDUSTRIAL ECOLOGY, 1995 NTNU, Industrial ecology degree, 1996 R. Frosch and N. Gallopoulos, STRATEGIES FOR MANUFACTURING, 1989 R.U. Ayres, Industrial metabolism, 1980s National Academy of Science’s Colloquium on Industrial Ecology, USA, 1991 Industrial ecology’s appearance in the literature, 1970s Beginning of industrial symbiosis in Kalundborg, 1970s FIGURE 2 Industrial ecology and sustainable development: time line of events. © 2006 by Taylor & Francis Group, LLC 506 INDUSTRIAL ECOLOGY (ISO) included LCA in its ISO 14000 environmental certi- fication process. As a result of these efforts, an overall LCA framework and a well-defined inventory methodology have been created. LCA consists of three phases (Udo de Haes, 2002): Goal and scope definition: A phase to set the pur- poses and boundaries of a study, such as geographic scope, impact categories, chemicals of concern, and data-availability issues Life-cycle inventory analysis: The most objective and time-consuming process, in which the energy, water, and natural resources used to extract, produce, and distribute the product, and the resulting air emissions, water effluents, and solid wastes, are quantified Life-cycle impact assessment: An evaluation of the ecological, human-health, and other effects of the environmental loadings identified in the inventory These three phases are usually being followed by an inter- pretation phase in which the results from the above pro- cesses are tracked and possibilities for improvement are discussed. Data availability and uncertainty are continuing concerns of LCA, as are the time and expense required. As a result, there have been efforts to streamline, or simplify, LCA to make it more feasible while retaining its key features (e.g., Curran, 1996). Input-Output Analysis IOA is a technique of quantitative economics intro- duced by Leontief in 1936 (Leontief et al., 1983, p. 20; Polenske, 2004). In this approach, an input-output table is constructed to provide a systematic picture of the flow of goods and services among all producing and consum- ing sectors of an economy. IOA also registers the flow of goods and services into and out of a given region. The mathematical structure of the basic input-output models is simple: x Ϫ Ax ϭ y (2) where x is a vector of outputs of industrial sectors and y is a vector of deliveries by the industries to final demand. A is a square matrix of input-output coefficients; each element a ij represents the amount of sector i ’s output purchased by sector j per unit of j ’s output (Leontief et al., 1983, p. 23). IOA approaches material cycles by replacing the mon- etary flows with material ones. Its initial demonstration was a projection of U.S. nonfuel-minerals scenarios, completed by the creator of the input-output method in the early 1980s (Leontief et al., 1983, pp. 33–205). The analogous approach for physical flows is termed a “physical input-output table” (PIOT). It is the product of the efforts of scholars from vari- ous disciplines between the 1970s and 1990s, and has been applied to establish the material accounting system of several TABLE 1 Types of material-flow-related analysis Type of analysis A ab c Objects of primary interests Specific environmental problems related to certain impacts per unit flow of: substances materials products e.g., Cd, Cl, Pb, Zn, Hg, N, P, C, CO 2 , CFC e.g., wooden products, energy carriers, excavation, biomass, plastics e.g., diapers, batteries, cars Within certain firms, sectors, regions B ab c Problems of environmental concern related to the throughput of: firms sectors regions e.g., single plants, medium and large companies e.g., production sectors, chemical industry, construction e.g., total or main throughput, mass flow balance, total material requirement associated with substances, materials, products Source: Bringezu and Moriguchi, 2002. (With permission) © 2006 by Taylor & Francis Group, LLC INDUSTRIAL ECOLOGY 507 countries (Strassert, 2001, 2002). Duchin did the pioneer work to bring the IOA approach to industrial ecology (Duchin, 1992). More recently, the IOA approach has been linked with LCA to produce a new method: economic input-output LCA (EIO-LCA; Matthews and Mitchell, 2000). INDUSTRIAL ECOLOGY IN PRACTICE Micro-Level Practice Micro industrial ecology’s practices are mostly centered on firms and their products and processes. Firms are the most important agents for technological innovation in market economies. The persistent supply of greener products from greener processes in facilities constitutes the microfoun- dations of world environmental improvement. In addi- tion, a present firm is not a sole “policy taker” any more. To overcome the low efficiency of command-and-control environmental regulation, many firms have become “policy makers,” so far as the relationship between technology and the environment is concerned. Pollution prevention (P2), also termed “cleaner produc- tion,” is industry’s primary attempt to improve upon passive compliance with environmental regulations. In P2, attention is turned to reducing the generation of pollution at its source, by minimizing the use of, and optimizing the reuse or recycling of, all materials, especially hazardous ones. The pioneer of this approach is 3M’s Pollution Prevention Pays (3P) program in 1975. It succeeded in avoiding 1 billion pounds of pollutant emissions and saved over $500 million for the company from 1975 to 1992. Many companies were spurred to learn 3M’s approach, and according to a recent survey, pollution preven- tion has become an importance operational element for more than 85% of manufacturing companies (Graedel and Howard- Grenville, 2005). While pollution prevention addresses a manufacturing facility as it finds it, design for environment (DfE) is trans- formational: it attempts to redesign products and processes so as to optimize environmentally related characteristics. Often used in concert with LCA, DfE enables design teams to consider issues related to the entire life cycle of products or processes, including materials selection, process design, energy efficiency, product delivery, use, and reincarnation. DfE practices are currently being implemented by many firms, large and small. DfE is mainly a technological approach. It can address a wide range of environmental issues throughout a prod- uct’s life cycle. However, its capability to address some environmental impacts, especially in disposal of end-of-life products, is limited: it can facilitate, but cannot ensure, recycling. However, the approach designated “extended producer responsibility” (EPR) complements the firm-level practice from the perspective of policy. In this regard, most Organization of Economic Cooperation and Development countries encourage manufacturers to take greater respon- sibility for their products in use, especially in postconsumer stages. EPR follows the “polluter pays principle,” transfer- ring the costs of waste management from local authorities to those producers with greater influence on the characteristics of products (Gertsakis et al., 2002). It is foreseeable that the acceptance of EPR will, in turn, intensify DfE activities in many firms. We thus begin to see a sequence of environmentally related steps by responsible industrial firms. The first is pollution prevention, which is centered within a facility. The invention and adoption of LCA next expands a company’s perspective to include the upstream and downstream life stages of its products. Later on, a core issue—sustainability—is brought to the table. Some assessment methods have been developed to quantify a facility’s sustainability, although this remains a work in progress as of this writing. Meso-Level Practice Most interfirm practices of industrial ecology relate to the concept of industrial symbiosis and its realization in the form of eco-industrial parks (EIPs). As Chertow (2000b) puts it: “Industrial symbiosis engages traditionally separate industries in a collective approach to competitive advantage involving physical exchange of materials, energy, water, and/ or by-products. The keys to industrial symbiosis are collabo- ration and the synergistic possibilities offered by geographic proximity” (314). The classic example of industrial symbiosis is Kalundborg, a small Danish industrial area located about 100 km west of Copenhagen. Its industrial symbiosis began in the 1970s as several core partners (a power station, a refinery, and a phar- maceutical firm) sought innovative ways of managing waste materials (Cohen-Rosenthal et al., 2000). Over time, many other industries and organizations have become involved; the result is a very substantial sharing of resources and a larger reduction in waste (Figure 3). Industrial symbiosis thinking is implemented by but not confined to EIPs. Chertow (2000b) has proposed a taxon- omy of five different material-exchange types of industrial symbiosis: 1. Through waste exchanges (e.g., businesses that recycle or sell recovered materials through a third party) 2. Within a facility, firm, or organization 3. Among firms co-located in a defined EIP 4. Among local firms that are not co-located 5. Among firms organized “virtually” across a broader region Only Type 3 can be viewed as a traditional EIP. No matter which type, or on what scale, industrial symbiosis has proven to be beneficial both to industries and to the environment. Macro-Level Practice At macro scales (e.g., a city, a country, or even the planet), MFA has proven to be an important tool for considering the relationships between the use of materials and energy use, © 2006 by Taylor & Francis Group, LLC 508 INDUSTRIAL ECOLOGY Liquid Fertilizer Production Lake Tissθ Fish Farming Farms Yeast slurry Sludge (treated) Novo Nordisky/ Novozymes A/S Pharmaceuticals Recovered nickel and yanadium Cement roads A-S Soilrem Fly ash Water Water Water Sulfur Heat Steam Hot Water Sludge Steam Boiler water Waste water Cooling water Heat Scrubber Sludge Gas (back up) Organic residues District Heating Wastewater Treatment Plant Municipality of Kalundborg Gyproc Nordic East Wall-board Plant Statoil Refinery Energy E2 Power Station FIGURE 3 Industrial symbiosis at Kalundborg, Denmark. From Chertow, 2000b; updated by M. Chertow. <100 100–279 280–794 795–2239 2240–6499 >6500 System Boundary (Closed System): “STAF World” Environment Old Scrap 2,084 Landfilled Waste, Dissipated 1,775 Waste Management Discards 3,859 Stock Stock Use 7,718 11,577 11,585 688 Products New Scrap 579 1,396 Production: Milk, Smelter Refinery 250 200 Reworked Tailings Tailings, Slag 1,550 10,710 Ore Base Year: 1994 Unit: Gg = 1,000,000 kg Cu/yr Fabrication & Manufacturing Cathode –10,710 Lith. +2,925 FIGURE 4 Global anthropogenic copper cycle in 1994. From Graedel et al., 2004. © 2006 by Taylor & Francis Group, LLC INDUSTRIAL ECOLOGY 509 Towards Sustainability millennium century decade year month day TIME 10 11 sec 10 10 sec 10 9 sec 10 8 sec 10 7 sec 10 4 sec 10 0 sec 10 –9 sec 10 –9 m 10 –8 m10 0 m 10 3 m 10 4 m 10 5 m 10 6 m 10 7 m SPACE Earthregion country city inter-firm firm product creature moleculeatom Regulatory como Pollution prevention Design for environment Green accounting Industrial symbiosis Product life cycle industrial sector initiatives Models and scenarios Budgets & cycles industrial metabolism Dematerialization Decarbonization Earth systems engineering Towards Sustainability (a) (b) Applied Industrial Ecology Experimental Industrial Ecology Theoretical Industrial Ecology Further development of DTE and manufacturing for environment Relation between industrial ecology and land use Policy incentives of industrial ecology Promotion of industrial ecology in developing countries Budgets for the materials of technology Design and development of eco-industrial parks Industrial food webs Metabolism of cities Theory of industrial ecosystem Multiscale energy budget for technology Model of interaction between human and natural systems Theory of quantitative sustainability Green chemistry FIGURE 5 A graphical framework of industrial ecology. (a) The spacetime of industrial-ecology tools and methods; (b) An industrial-ecology roadmap. © 2006 by Taylor & Francis Group, LLC 510 INDUSTRIAL ECOLOGY environmental impact, and public policy. An example, the global copper cycle in 1994, is shown in Figure 4. During 1994, global copper inputs to production were about 83% ore, 11% old scrap, 4% new scrap, and 2% reworked tail- ings. About 12 Tg of copper entered into use, while nearly 4 Tg were discarded, giving a net addition to in-use copper stock of 7–8 Tg. Some 53% of the copper that was discarded in various forms was recovered and reused or recycled through waste management. The total environmental loss, including tailings, slag, and landfills, was more than 3 Tg and equaled one third the rate of natural extraction. All of this information provides perspectives impossible to achieve from a less comprehensive analysis. Material-flow studies can address another macro issue of industrial ecology—dematerialization, which is the reduction in material use per unit of service output. Dematerialization can contribute to environmental sustain- ability in two ways: by ameliorating material-scarcity con- straints to economic development, and by reducing waste and pollution. Dematerialization may occur naturally as a consequence of new technologies (e.g., the transistor replac- ing the vacuum tube), but can also result from a more effi- cient provisioning of services, thus minimizing the number of identical products needed to provide a given service to a large population. SUMMARY It is difficult to provide a holistic and systematic picture of a young field with its evolving metaphors, concepts, methods, and applications. We attempt to do so graphically, however, in the “spacetime” display of Figure 5a. In this figure, the tools and methods of industrial ecology are located dimen- sionally, with time and space increasing from the bottom left to the upper right, as does complexity. The figure demon- strates that industrial ecology operates over very large ranges of space and time, and that its tools and methods provide a conceptual roadmap to sustainability. As an emerging field, industrial ecology has a long list of areas where research and development are needed (Figure 5b). The urgent theoretical needs are to develop general theories for industrial-ecosystem organization and function, and to relate technology more rigorously to sustainability. Experimental industrial ecology needs to complete a set of analytical tools for the design of EIPs, the dynamics of industrial food webs, and the metabo- lism of cities. 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Industrial Ecology Theoretical Industrial Ecology Further development of DTE and manufacturing for environment Relation between industrial ecology and land use Policy incentives of industrial ecology Promotion. ecology Promotion of industrial ecology in developing countries Budgets for the materials of technology Design and development of eco -industrial parks Industrial food webs Metabolism of cities Theory of industrial