Material flow along a food chain Material flow in recycling
Figure 1.7. Comparison of materials flow in natural and industrial ecological systems.
is determined by the market demand for its products. Natural ecosystems are guaranteed their diurnal solar energy ration in the foreseeable future, whereas the energy-intensive industrial systems could easily face a fossil fuel energy crisis in the coming centuries. These differences are illustrated in Figure 1.7
2. Ecosystems are built upon a hierarchy of species that constitutes a food web. The solar energy initially fixed by photosynthetic primary producers is transferred in steps along the biosphere to grazing herbivores and finally to meat-eating higher animals including humans. Energy trapped in food is essentially passed along the food chain. No net energy input is needed by the herbivores to extract the energy from plants or by the carnivores to survive on herbivores or the microbial communities deriving to derive energy from dead plant or animal tissue.
The polyester bottles manufactured by industry A and disposed of as postconsumer waste by its customer can be regarded as a valuable raw material for business B. Business B recycles the shredded bottles into fiberfill for jackets or plastic tape. The recycler (business B), however, does not derive any energy from the waste polyester; it rather uses additional thermal energy again derived from fossil fuel to convert the waste plastic into fiberfill. Generally, however, energy savings do accrue in recycling because it takes less energy to reprocess already synthesized polymer compared to making new resin and processing it. It is the material resources that are passed along between the industries at different "trophic" levels. There is no flow of energy from level to level as is typical of natural food chains.
The exceptional recycling effectiveness of nature's bio-geo-chemical cycles to conserve and reuse material resources has no parallel even in the best integrated industrial systems. In industry, the waste is generally either poorly recycled or not recycled at all, leading to a slow but certain depletion of the reserves of nonrenewable resources in the long term. Industrial production proceeds at variable rates in response to market demand for its products. This variability in the rates of production of the associated material waste often makes it difficult for businesses at a "lower level" in the system to utilize the waste and by-products in a planned and consistent environment. Stimulating the development of an environmentally integrated industrial economy requires planning for resource availability and waste reuse at the very inception of broad business concepts.
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