Summary and conclusions

In the "industrial metabolism" metaphor, industrial organizations are likened to biological organisms that consume food and discard waste products. This chapter builds on and extends this metaphor beyond the biological organisms to an entire ecosystem. The human analogue of the ecosystem is the anthroposystem, consisting of producers, consumers, and recyclers.

Using these components, both ecosystem and anthroposystem are described by a conceptual material flow model that is also a suitable framework for an economic model. It is noted that the current anthroposystems differ from ecosystems mainly in that they lack efficient material recyclers that allow sustainable development. In this sense, the anthroposystem is an open system and the analogy with the ecosystem is incomplete.

The environmental spheres analogy extends the ecosystem analogy further by considering the flow of matter in all environmental compartments or conceptual "spheres" - air, land, water, and biota. This extension allows a closing of the system by following the flow and fate of matter regardless of the location and medium of transfer. It is concluded that human activities most closely resemble the role of the biosphere in the mobilization of matter.

The current work could be extended in several ways, in particular by combining the ecosystem and the environmental metaphors into a single "model." In principle, the multimedia "spheres" approach to material flows lends itself to rigorous mathematical formulation using basic conservation laws. In fact, it could incorporate all the features of the ecosystem approach. The resulting model could encompass the complete, end-to-end flow analysis, from the point of "production" i.e. removal of the matter from one geochemical reservoir - to its fate in the receiving reservoir. Such a multimedia physical model would also be a suitable framework for environmental economic analysis.