A book written by Robert U. Ayres and Udo E. Simonis

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The term "metabolism," applied to a plant or animal, is a notion so familiar and comprehensive that it resists formal definition. Webster, nevertheless, defines it as "the sum total of the build-up and destruction of cell tissue; the chemical cellular changes providing the energies for the life process and the elimination of waste materials." It is, in other words, the totality of internal processes - both physical and chemical - that supply the energy and nutrients required by an organism as the conditions of life itself. These processes can be described, in the aggregate, in terms of the transformations of inputs (sunlight, chemical energy, nutrients, water, air) into biomass - the substance of the organism itself - and waste products.

Industrial metabolism, by analogy, is the set of physico-chemical transformations that convert raw materials (biomass, fuels, minerals, metals) into manufactured products and structures (i.e. "goods") and wastes. To an economist these processes, in the aggregate, are called "production." A further transformation of economic goods into services (and wastes) is also implied by the economic term "consumption." Thus industrial metabolism comprehends all the materials/ energy transformations that enable the economic system to function, i.e. to produce and consume.

Seen from this perspective, the human economic system takes its proper place within the larger natural system of the earth (and sun). The anthroposphere is only a part of the biosphere,' which itself can only exist in a continuing dynamic equilibrium with the sun, the air (atmosphere), the oceans (hydrosphere) and the earth's crust (lithosphere).

In the pre-industrial era, the anthroposphere was in a more or less uneasy balance with the biosphere and the other elements of the earth system. Humans were a part of the natural ecosystem; and animals were harvested for food, clothing and even structural materials. Wastes were recycled by natural decay processes. Mineral and metal items from building blocks to weapons, tools or coins - were used and reused for centuries or even millenia.

The Industrial Revolution of the eighteenth century changed this situation radically. In pre-industrial times the only truly unsustainable consequence of human economic activity was irreversible loss of forest cover and topsoil in some regions (mainly North Africa and the Middle East). Since the Industrial Revolution, and the large-scale exploitation of fossil fuels, the list of unsustainable environmental trends has grown much larger:

- The build-up of "greenhouse gases" in the atmosphere.
- The destruction of the ozone layer in the stratosphere.
- The acidification of the soil and surface waters.
- The build-up of toxic metals in sediments and soil.
- The build-up of radioactive wastes.
- The accumulation of long-lived non-biodegradable chemicals in the environment.
- The contamination and exhaustion of groundwater.
- The loss of tropical forests, wetlands, biodiversity, etc.

Continuing with the biological metaphor, the spread of industrial activity in the last two centuries can best be described as a cancer: industrialization, in its present form, is a process of uncontrolled, unsustainable "growth" that eventually destroys its host - the biosphere.

The death of the biosphere is not necessarily unavoidable. But with every year and decade that passes without a radical change in direction and quality, the death of the biosphere becomes more likely. However, the long-range prognosis of the state of planet Earth is not the main subject of this book. Our purpose here is to elucidate and exemplify- a new kind of analysis.

Our intellectual tradition is essentially reductionist: we try to explain complex large-scale systems by subdivision into ever smaller subsystems, components, and subcomponents. We explain the forest as a collection of trees; we explain the tree in terms of roots, trunk, branches, bark, and leaves. The infinite regression continues as the power of the microscope increases. Then, at last, when we see the forest in terms of biochemical reactions, we think we have understood it. But in so doing we have missed the essence of the forest.

Yet, there are other perspectives and other modes of analysis. The earth system can be viewed as a whole. The anthroposphere can be viewed as part of the planetary system. Industry can be examined within this larger context, not as a collection of individual firms, plants, and processes. Further, some powerful analytical tools remain at our disposal. The law of conservation of mass and energy (the "first law" of thermodynamics) is one of them. In our context this law of physics gives rise to the materials balance principle. One implication of this principle is that materials extracted from the natural environment for the production of goods and services must eventually be returned to the environment in degraded form.² So simple a principle, and yet with such profound implications.

The present book consists of 14 chapters which are grouped into three parts. Part 1 provides an overview of the various aspects and implications of the "industrial metabolism" paradigm. In chapter 1, Robert U. Ayres elaborates the concept in theoretical terms, and discusses some of its policy implications - not all of which are immediately obvious.

Chapter 2, by Rudolf B. Husar, presents useful metaphors to bridge biosphere and ecosphere. The question of how strong the impact of industrialization has been on the environment and whether or not a de-linking of economic activity from environmentally sensitive inputs has taken place in the industrial nations is addressed by Udo E. Simonis in chapter 3. As regards the developing countries, this question is asked by Rajendra K. Pachauri, Mala Damodaran, and Himraj Dang in chapter 4. Evolution, sustainability, and industrial metabolism are looked at in a more general, theoretical manner by Peter M. Allen in chapter 5.

In part 2, from chapters 6 to 11, a number of case-studies of industrial metabolism are presented, at various levels of aggregation. Ulrik Lohm, Stefan Anderberg, and Bo Bergback start with a study on chromium and lead pollution at the national level, taking Sweden as an example (chapter 6). Next are William M. Stigliani and Stefan Anderberg with a study on cadmium pollution in the Rhine basin (chapter 7). Paul H. Brunner, Hans Daxbeck, and Peter Baccini studied industrial metabolism in a Swiss region (chapter 8). Casestudies on carbon moNoxide and methane emissions and sulphur and nitrogen emissions in the United States are presented by Robert U. Ayres, Leslie W. Ayres, and Joel A. Tarr (chapter 9), and Rudolf B. Husar (chapter 10) respectively. Finally, the consumptive uses and losses of toxic metals in the United States are addressed by Robert U. Ayres and Leslie W. Ayres (chapter 11).

Part 3 of the book provides some future perspectives. Timothy O'Riordan, on the basis of the industrial metabolism concept, asks, in chapter 12, how far the precautionary principle could lead in environmental management. In chapter 13, Sergio C. Trindade looks at the conditions under which a more efficient industrial metabolism could be reached in developing countries by transfer of clean(er) technologies. The physical exchanges between the industrial economy and the natural environment need improved - i.e. rather different accounting and information systems; Marina Fischer-Kowalski, Helmut Haberl, and Harald Payer present their concept in chapter 14.

Finally, a select bibliography on industrial metabolism and industrial restructuring is presented by Rudiger Olbrich and Udo E. Simonis.