Making metals count: Applications of material flow analysis

Industrial ecology is frequently regarded as the organizing framework for studying interactions of technological societies with the environment. A theme central to industrial ecology is the way that materials are used which, in turn, relates to environmental and resource availability concerns. The material fluxes seen between the production of raw materials, the manufacture and use of products, and their fate at their end of life are quantified using material flow analysis, the record keeping of atoms mobilized by humans within a bounded system. The Stocks and Flows project at Yale University examines the full life cycle of anthropogenically mobilized material on a variety of spatial levels, including city-, country-, regional-, and global-level cycles. Different temporal levels are also examined, with research conducted on historical studies, contemporary studies, and scenario development. Material cycles have been completed for copper, zinc, and silver, with current work including iron and steel, chromium, nickel, tungsten, tin, and lead cycles. Such results illuminate the numerous and diverse drivers for constructing technological material cycles: global and local material scarcity, human health and ecosystem effects, energy and water consumption, high unit value of the material, pertinent regulations, waste management strategies, and economic considerations. The goal of this paper is to provide an overview of selected topics in the field of industrial ecology, to gather from diverse literature key results from the Stocks and Flows project, and to introduce novel analyses related to environmental losses and waste streams that result from anthropogenic use of materials. This is done with the intent to emphasize to the environmental engineering and science audience what may be termed "forward-looking" environmental engineering.