The objective of industrial ecology is to provide actionable input to those taking decisions about the industrial system. These decision makers include not only corporate managers, responsible for the extraction of resources and fabrication and distribution of products, and the policy makers who oversee them, but also consumers, acting both individually and as members of households or of the growing number of social institutions that operate in the public interest. The decisions may pertain to an individual resource or product or to an entire industrial system.
Even when studying an individual resource or product, industrial ecologists are concerned with its role in an industrial system. They gather data on system behavior and develop concepts and methods for analysis at the system level. Among industrial ecology's most fundamental activities is gathering data for describing the flow of energy and materials throughout an economic system. The scale of the economic system can range from a single factory to a regional economy to the global economy.
Many industrial ecologists are engaged in compiling information to describe the flow of a specific material from sources to sinks within the global industrial system or some geographically delimited portion of it. Conventions and procedures have been developed for material flow analysis (MFA, and its variants such as substance flow analysis), which is in certain ways similar to the study of nutrient cycling in ecology. The depiction of the global copper cycle, shown in Figure 3, is reminiscent of illustrations of the carbon cycle in ecological systems, but closer inspection indicates that the copper cycle is nowhere near as efficient as the carbon cycle. A significant fraction of the copper is not recycled but instead ends up being lost to the system. Identifying and quantifying these major flows provides grounding for interventions that aim to modify the existing system to reduce its impact on the environment by making it more efficient in its use of resources. Similar approaches are applied not only to individual elements such as copper but also to compound materials. By pinpointing the
Production Mill, smelter, refinery 200
Production Mill, smelter, refinery 200
Landfilled waste, dissipated
Landfilled waste, dissipated
System boundary (closed system): "STAF World"
© STAF project, Yale university
Figure 3 The global copper cycle in the 1990s. Reprinted with permission from (Graedel TE, van Beers D, Bertram M, et al. (2004) Multilevel cycle of anthropogenic copper. Environmental Science and Technology 38:1242-1252). Copyright (2004) American Chemical Society.
presence of wastes that go unnoticed in conventional economic monitoring systems, MFA can direct efforts to improve system performance. MFA has also been applied to the aggregate of all materials (measured in tons per person) in attempts to quantify a society's industrial metabolism.
The wide range of MFA studies underscores the increasingly great variety of distinctly different materials in use in the contemporary industrial system, each with unique properties, to support the great number of products required by consumers. The literature includes MFA studies of metals such as copper and zinc, forest products such as pulp and paper, and industrial chemicals such as bisphenol A and nonylphenol. This expansive range of materials contrasts industrial with ecological systems which, relying on the breakdown of complex biochemical compounds by digestion, is typically characterized by a few major cycles - carbon, nitrogen, phosphorous, hydrogen, oxygen - the principal, elemental constituents of biomass. Moreover, since the resources required by industrial systems often are found in specific locations distant from the site of production, which may also be distant from where consumption takes place, considerable amounts of transportation may be required, involving even more energy and material inputs. The material flow analyses of broadest conceptual scope trace simultaneously the physical movements associated with a variety of interrelated human activities. While the objective of most MFA studies is to quantify material flows, such flows can in an additional step provide inputs to a model of the industrial system that explicitly distinguishes their use in specific industrial sectors and modes of transportation to satisfy the product demand of different categories of consumers.
Moving up from resources to products, two additional research areas within industrial ecology are concerned with the individual product, situated in the context of its entire life cycle from resource extraction through resource processing and fabrication of the product to its utilization, reuse, recycling, and disposal. These are design for the environment (DfE) and life-cycle assessment (LCA) (see Life-Cycle Assessment). Both address the system-wide environmental impacts associated with products.
DfE involves the design of industrial products and processes to minimize their adverse environmental impacts over their lifetimes. Often it is a redesign of an existing product or process that is undertaken. The focus can be on different phases of a product's life cycle, such as design for product retirement. Actual applications are varied and have included the design of chemical processes, electronic products, mechanical components, and freezer insulation, as well as the increasingly important area of packaging design.
LCA involves the evaluation of the environmental impact of a product during its entire life history on the basis of detailed technical information. Each stage from extraction of resources through disposal of residuals is associated with distinct resource requirements and emissions or other forms of damage, and their impacts, which are experienced at specific times and places. LCA is often used to compare the environmental impacts of alternative products or production processes and has been applied to substances such as chlorine and aluminum, the entire mining industry, industrial materials like PVCs, and to alternative uses of agricultural land.
LCA studies quantify emissions and resource use per units of output or service delivered. The modeling of the production network, including the quantification of the amounts of inputs required from different production processes, is traditionally based on direct measurement or engineering analysis. This process inventory modeling has generally ignored the contribution of nonphysical inputs, such as legal and accounting services or wholesale and retail trade, and left out minor inputs to make the analysis tractable. Empirical studies have established that such an approach overlooks a significant portion of the total impact. As a result, increasing numbers of LCA researchers are integrating their analyses with the use of input-output (IO) models of the economy to capture indirect as well as direct requirements associated with a single process or product. The integrated, hybrid approach has made it possible to go beyond examining individual products to examining the impacts of one entire bundle of consumption goods as compared to another.
LCA also includes an impact assessment step, in which different types of emissions are aggregated to a manageable number of indicators reflecting specific problem areas such as global warming or human toxicity. Alternatively, impact assessment can be based on the modeling of damages, for example, human health effects measured in years of life lost from both toxicity and climate change. The development of these impact assessment methods build on the knowledge and models of environmental scientists, including eco-toxicologists and ecologists.
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