Wastes as raw materials

Post consumer waste, industrial scrap and unwanted by-products from manufacturing operations should not be viewed as wastes. Rather, they are raw materials, but these raw materials are often significantly underutilized. One of the challenges of the emerging discipline of Industrial Ecology will be to identify productive uses for materials that are currently regarded as wastes, and one of the first steps in meeting this challenge will be to understand the nature of industrial and post consumer wastes. More than 12 billion tons of industrial waste (wet basis) are generated annually in the United States (EPA, 1988a,b; Allen and Jain, 1992). Municipal solid waste, which includes post-consumer wastes, is generated at a rate of 0.2 billion tons per year (EPA, 1990). When these material flows are compared to the annual output of the top 50 commodity chemicals (0.3 billion tons per year; Chemical and Engineering News, 1991), it is apparent that wastes should not be ignored as a potential resource. While these comparisons between waste mass and the mass of commodity products make apparent the magnitude of industrial wastes, just considering mass flows can be somewhat misleading. The extent to which industrial wastes could serve as raw materials is dependent not only on the mass of the waste stream, but also on the concentration of resources in the wastes. As shown in Figure 1, the value of a resource scales with the level of dilution at which it is present in the raw material. Resources that are present at very low concentration can only be recovered at high cost, while resources present at high concentration can be recovered economically. Thus, to understand the extent to which wastes can be used as raw materials, both waste stream flow rates and waste stream composition must be determined. The primary goal of this paper will be to evaluate the flow rates and concentrations of valuable resources in waste streams and determine the extent to which materials currently regarded as wastes might be used as raw materials. The results of this examination of waste stream compositions and flow rates will demonstrate that 0 many materials currently discarded in waste streams may be economically recoverable based on current market prices 0 deficiencies in waste stream data limit the range of materials and waste streams that can be included in industrial ecology studies. Mapping the flows of more than 12 billion tons of industrial and post-consumer waste …