Industrial Ecology: Towards Closing the Materials Cycle

Robert U. Ayres is one of the inventors of the field of industrial ecology, through his decades of work on materials flows and most notably through his essay “Industrial Metabolism” (Ausubel and Sladovich 1989). In that essay, Ayres vividly portrayed the wastefulness of industry and consumers, pointing out that most of the materials we use become waste almost immediately. He made an analogy between today’s industrial systems and the earth‘s earliest primitive life-forms. Just as life on earth evolved to form complex ecosystems that produce little or no waste and whose components are highly interdependent, Ayres suggested that our industrial systems might also evolve into complex industrial ecosystems, with wastes from one industry becoming the feedstock for another. This has become the central analogy of industrial ecology. True to form, Ayres and Ayres’s Industrial Ecology is a significant addition to the field, full of new and provocative ideas. While most works on industrial ecology can manage only a handful of case studies, the list of chapters in itself shows that this is a tour de force: aluminum, alumina, and galium; cobalt, copper, silver, and arsenic; chromium; zinc and cadmium; sulfur and sulfuric acid; phosphorus, fluorine, and gypsum; nitrogen-based chemicals; the chlor-alkali sector; electronic-grade silicon for semiconductors; postconsumer packaging wastes; scrap tires; and coal ash. The focus is on the reduction of waste in processes used to produce the metal or compound. With the exception of the chapters on scrap tires and postconsumer packaging wastes, the main topic of the book is the industrial ecology of the production of raw materials, with much less discussion of the use or disposal of products. This emphasis on materials flows and the technology of production is just one part of the industrial ecology field. Other aspects of the field include the redesign of products to reduce their environmental impacts and increase recyclability; the growing postsale responsibility of manufacturers for the products they have produced; and efforts to relate environmental impacts to the industrial activities and processes. An underlying issue of this book, and of the entire field of industrial ecology, is the question of what will drive the transition to the Ayres’ vision of industrial ecosystems. To encourage more efficient use of mined materials, the authors propose taxation of resources and pollution. Although they do not go into much detail, the authors refer to European studies of a shift from the taxation of labor to the taxation of energy, pollution, and resource use. If the development of efficient industrial ecosystems is to be taken seriously, this topic will require much more attention. The major contribution of this book is that it identifies numerous viable technological options for revolutionizing the processing of minerals. Many of these examples could provide a basis for focused efforts to implement change in these industries. Although this review will not delve into details in the book such as alternative smelting technologies, a few examples of the general analysis can provide a sense of the issues involved in increasing the efficiency of materials production. Recent progress in closing the materials cycle for zinc shows the potential for government intervention to promote recycling. About half of slab zinc is used for galvanizing, that is, for coating sheet iron and steel to enhance corrosion resistance. One might think that this zinc would be difficult to recover. But because of its volatility, the zinc is easily captured in the baghouse dust from electric arc furnaces (EAFs) that process iron and steel scrap. However, the actual recov-