In order to illustrate the sensitivity of the issue, the remainder of this chapter attempts to analyze the real meaning, and some more or less commonly accepted implicit extensions, of three rather well-established and closely related concepts: ecosystem management, industrial metabolism and industrial ecology.
Ecosystem management expresses the notion of including the natural surroundings into our planning, as most human activities have an impact on the surrounding ecosystem (see, for example, Christensen et al. 1996). Thus ecosystem management can be seen as a neutral, simple and straightforward extension of a rational resource management effort. But there is also a larger, partially concealed, implicit message. When we speak of ecosystem management, we not only convey the need for proper attention to the ecosystem. The word 'management' also implies the need for a businesslike, utilitarian management approach putting human needs in the center. The ecosystem is thus presented as something to be managed - and hence utilized - without ever bringing the issue explicitly to the table. An important element of today's debate around sustainability is consequently neglected altogether.
Industrial metabolism conveys the descriptive idea of the industrial system as a living complex organism, 'feeding' on natural resources, material and energy, 'digesting' them into useful products and 'excreting' waste. This is a rather value-neutral description helping us to see the need for a broader view, focusing on interactions of material and energy flows, rather than on single issues as previously was the case. In passing, it is interesting to note that, while industrial metabolism metaphorically suggests that machines behave like living cells, an early metaphor used by Descartes (one of the architects of the Enlightenment) used the same metaphor 'nature is a machine' to increase his understanding of nature.5
Industrial metabolism traces material and energy flows from initial extraction of resources through industrial and consumer systems to the final disposal of wastes. It makes explicit use of the mass balance principle. First developed by Ayres and collaborators in a series of papers and books (Ayres et al. 1989; Ayres 1989a, 1989b, 1993b, 1994b; Ayres and Simonis 1994) industrial metabolism has become an important foundation of industrial ecology. Industrial metabolism can usefully be applied at many different levels: globally, nationally, regionally, by industry, by company and by site. By invoking the parallel to biological metabolism, industrial metabolism analysis highlights the dramatic difference between natural and industrial metabolic processes, in particular the large difference in energy and material densities and fluxes and the lack of a primary producer (analogous to photosynthetic organisms) in the industrial world. Also, in natural systems, some nutrients flow in closed loops with near universal recycling, whereas industrial systems are mostly dissipative, leading to materials concentrations too low to be worth recovering but high enough to pollute.
So far industrial metabolism studies have tended to focus on flows of chemicals and metals, but the approach is also useful in analysis of energy and water flows. Some companies have conducted environmental audits based on this method and regional application gives valuable insight into the sustainability of industry in natural units such as watersheds or atmospheric basins. Mapping sources, processes and transformations, and sinks in a region, offer a systemic basis for public and corporate action. In an early application, Ayres et al. (Ayres and Rod 1986; Ayres et al. 1988) studied the historical development of pollutant levels in the Hudson-Raritan basin over the period 1880-1980. A similar study has also been made for tracing chromium and lead poisoning in Sweden over the period 1880-1980 (Lohm et al. 1994). The International Institute for Applied System Analysis (Stigliani, Jaffe and Anderberg 1993) has completed an industrial metabolism study of the Rhine basin, the most ambitious application so far. The study examined for the whole basin sources of pollution and pathways by which pollutants end up in the river. Materials studied include cadmium, lead, zinc, lindane, PCBs, nitrogen and phosphorus. The results suggest that, in the Rhine basin, industry has made major progress on reducing emissions. However, there are increasing flows of pollution from 'non-point' or diffuse sources, including farms, consumers, runoff from roads and highways, and disposal sites. The findings are of great value in design of policy, industrial practice and public education. Experience seems to suggest that industrial metabolism, in spite of its suggestive biological symbolism, can be used as a practical tool for further understanding of the complex relations of material and energy fluxes in the industrial context.
Industrial ecology is a concept whose origins are not so easy to trace (but see Erkman 1998; Chapter 9). The concept existed in the 1970s, well before the name became popular (Watanabe 1972; Odum 1955; Hall 1975). In those times it was often used almost synonymously with industrial metabolism. However, as now understood, industrial ecology goes further than industrial metabolism: it attempts to understand how the industrial system works as an interactive system, how it can be regulated and how it interacts with the biosphere and other industrial systems. The latter is an important extension. But the crucial question arises: is industrial ecology only a descriptive name: is it a tempting vision? Or can it be used as an actual guide for industrial planning in an effort to mimic ecological dependencies in nature? If the latter holds true, important implications could be developed to provide guidance to restructure the industry to make it more compatible with its natural environment.
Industrial ecology is claimed to be 'ecological' in that it places human activity 'industry' in the very broadest sense in a larger context of the biophysical environment from which resources are extracted and which is negatively affected by the emissions of effluents and wastes (Lifset 1997). It is also claimed that the natural systems can function as models for the man-made system in terms of efficient use of resources, energy and wastes. In this context, the famous Kalundborg example is often cited (for example, Ehrenfeld 1997). (Kalundborg is an industrial city in Denmark, where wastes from petroleum refineries and a power plant are profitably utilized in other industries.) On the critical side, voices have been raised that what has been achieved in Kalundborg is in fact standard engineering practice realized in many other places as well (Johansson 1997).
Thus, when we speak of industrial ecology, we want to further broaden the picture to include the possible interaction of different industrial systems with each other, and their future development in relation to each other, drawing upon our knowledge from natural systems (Ayres, Rod and McMichael 1987; Ayres et al. 1989; Ausubel and Sladovich 1989; Patel 1992; Allenby and Richards 1994; Richards and Frosch 1994; Schultze 1996). In some applications the borderline between science and wishful thinking becomes very thin. Further, in the author's view, it remains yet to be proved that this particular metaphor actually can be helpful in defining new strategies for industrial development. Natural processes can only evolve by reacting to changes. However, anthropogenic systems should be able to foresee both risks and opportunities, and actively plan ahead.
In conclusion, one could say that successful metaphors in science are often victims of their own success. The imaginative strength of a successful metaphor takes over, migrates to other domains in science, and carries the message further than was intended, frequently conveying feelings and values that are not justified by the scientific content. This can have particularly far-reaching consequences in the formulation of environmental policies, an area where important social and economic decisions are made by non-scientists. But we must keep in mind that this indeterminacy is organically linked to the use of metaphors: the extension of the imagination beyond what is known as truth is their very reason for existence, it is a tool for bringing creative intuition into science, and occasionally also to a greater public.
Reverting to Carnot's case, mentioned earlier, there was no such substance as 'caloric'. In fact, it is the incoherent thermal motion of atoms or molecules that is partly converted to directed motion in a heat engine. Nevertheless, the metaphor worked and laid the foundation of a new branch of physics-thermodynamics. It also contributed to a wonderful step forward in engineering and, indirectly, to the 'age of steam' and the 'industrial revolution' (a metaphor, of course).
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