An early application within industrial ecology of ecological concepts to industrial systems is the design and implementation of so-called industrial ecosystems, or eco-industrial parks. Industrial ecosystems are characterized by the prevalence of what has been named industrial symbiosis, a relationship between two or more firms that involves the exchange of materials, energy, or information in a manner that is mutually beneficial. The most famous
The industrial ecosystem of Kalundborg, Denmark
of these is located in Kalundborg, Denmark; its structure is illustrated in Figure 4. By utilizing what would otherwise be waste products from one firm as input resources for others, the adverse environmental impact of this system of firms can be greatly reduced.
Industrial ecologists undertake to design industrial ecosystems either from scratch or around an existing plant. Kalundborg, however, emerged in the absence of advance planning and represents a sequence of accommodations and agreements between pairs of firms. Like any ecosystem, this eco-industrial park is continually evolving. New firms may be introduced. Some existing firms increase in size or modify their product lines and input requirements, while other firms decrease in size or disappear altogether.
Some industrial ecologists have turned their attention to larger systems, namely entire economies, using the concepts and methods of IO economics, a systems approach to describing and analyzing an entire economy in terms of the inputs and outputs of dozens or even hundreds of individual industries, products, and resources. The use of IO models in industrial ecology has grown substantially in recent years as their ability to describe both physical stocks and flows and the associated money costs and prices has been emphasized and expanded. IO models require a database, a large portion of which for past years is provided on a periodic basis by national statistical offices around the world. When evaluating scenarios about the future, the framework is reliant on technical data about resources and products, and it increasingly makes use for this purpose of the kinds of information originating in MFA and LCA studies.
IO studies have investigated such environmentally significant challenges as water scarcity and water management in different parts of the world including China, Spain, and Southern Africa; emissions of carbon dioxide and other greenhouse gases; and the management of a variety of wastes. Emissions of carbon, sulfur, and nitrogen under alternative scenarios about future technological attributes have been estimated for the world economy described in terms of the production and trade in the outputs of a few dozen industrial sectors in over a dozen geographic regions. As concern builds that the industrialized countries are appropriating disproportionately large shares of the Earth's resources via resource-intensive imports from developing countries, IO models of the world economy that incorporate data from MFA and LCA studies are becoming more prevalent.
An IO model can represent the complex interplay of ecological and industrial system concepts. Since being introduced in a modified form into ecology, IO models have been valued by ecologists for their ability to track the paths of flows, thus accounting for indirect as well as direct interactions and allowing for a more accurate estimate of the total (direct plus indirect) energy and biomass requirements. IO techniques have also been the basis for developing measures of ecosystem structure, such as throughput and cycling, which have been applied to the analysis of numerous ecosystems. The direct relevance of these ecological system measures to industrial systems is evident, especially when recycling of resources is of major interest. As a result these ecological measures have recently been introduced into industrial ecology in, for example, analyzing material flow in the nylon tufted carpet industry.
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