Concepts of environmental management have shifted, perhaps only during the last decade or so, towards the idea of acting preventively to reduce environmental emissions from human activities. Various names have been used to describe the emerging conceptual approach. These names include waste reduction, waste minimisation, pollution prevention and source reduction.12 Later, phrases such as clean technology13 and clean (or cleaner) production14 were introduced to try and capture the idea of technologies and production processes which were inherently cleaner, emitted less waste and were less environmentally damaging than their predecessors. The principal characteristic of all these approaches was the emphasis on taking measures to reduce environmental emissions, and consequently reduce the need for expensive clean-up technologies, disposal sites, environmental remediation, and blind faith in nature's assimilative capacity.
The emerging environmental strategy has two main avenues to it. The first is to reduce the material intensity of economic activities. That is: for each activity carried out, fewer materials are used, fewer materials flow through the industrial process, and consequently fewer materials end up in the environment. If this reduction is to occur without losing the value of the service which those material flows provide, then what we are talking about is improving the material efficiency of providing different services.
Given the broad range of materials over which environmental concern exists, these efficiency improvements need to be applied quite generally to all the material flows in the industrial economy. On the other hand, there are certain kinds of materials which represent particular priority hazards in the environment. And this fact suggests that we might sometimes wish to substitute for one kind of material—a priority hazard material— another material, considered less hazardous. Substitution is therefore the second main avenue for a preventive approach to environmental management. It is important, however, that we should recognise that substitution does not only mean substituting one particular input material for another. Sometimes we may want to substitute one product for another. At other times we may need to substitute one whole industrial process for another. And occasionally, it may be legitimate to ask whether we can substitute one whole set of industrial activities for another.
We can see that, in a way, both these avenues are aiming at the same thing: to make the economic system look more like a natural ecosystem. The pathway of improving material efficiency appears to be one of the evolutionary progressions within natural ecosystems. At any rate, improvements in material efficiency can reduce the burden placed by the industrial ecosystem on the global ecosystem. Fewer materials flow out of the system. The burden of human intervention in the natural material cycles is reduced.
Substitution also has a role to play in developing a new industrial ecology. Some hazardous materials do belong to natural material cycles. Toxicity is certainly not restricted to the industrial economy. The toxic heavy metals, for example (such as mercury, lead and cadmium), have quite specific cycling patterns associated with the weathering of rocks, evaporative processes and patterns of sedimentation in rivers and oceans. But these cycles are relatively limited, and now subject to distortion by human activities.
In general terms, therefore, we should regard substitution away from particular kinds of hazardous materials as the prudent course of action. In particular, substitution away from dissipative uses of synthetic chemicals or materials which are toxic, persistent and liable to accumulate is a key strategy for a new approach to environmental management.
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