9. Efficient Resource UseLower-density and newer communities require more natural resources and produce more of the growth in pollutants than do older and denser ones. The compact nature of urban living makes recycling of consumer wastes easier than in sparsely populated areas. Compact areas also allow for easier exchange of industrial wastes between firms (one firm's waste is often another firm's gold, this is the theory behind the design and siting of "eco-industrial" parks).47 Increasingly, materials are being moved out of the earth's crust and stored in man-made structures. Most of these structures are in urban centers. Buildings, infrastructure or scrap piles in metropolitan areas contain most of the materials ever mined out which are still in reusable condition. 48Analysts and activists look at these material deposits as the "mines" of the future. 49Interestingly, all structures age and require maintenance, if not eventual replacement. Each metropolitan area has the resources necessary to develop recycling industries, regardless of whether or not an area is close to natural resource deposits or currently has industrial materials processing capacity. From where does the demand for these "used" or secondary materials originate? The good news is, everywhere. Over the past forty years the portions of major commodities, which came from secondary or used materials increased significantly. Today 8% of construction minerals, 25% of paper and fiberboard, 30% of aluminum, 33% of copper, 40% of tin, 51% of steel and 78% of lead are derived from recycling. Scrap or secondary materials are the source of over half of all metals used in the United States.50 The differences between 100% and each of these respective figures are the prospective market sizes for increased secondary materials use. The locations of human settlements and the locations of industry are, for the most part, the locations of materials demands. This is why metropolitan regions are the logical locus of materials markets. There are at least three benefits associated with finding new uses for used materials First, such use replaces depleted domestic raw materials sources with new domestic sources, rather than with distant foreign sources or deeply located natural resources in environmentally sensitive areas. Second, recycling reduces the demand for energy needed to process raw materials into finished products by up to 95%. Third, these activities reduce the spatial mismatch between materials sources and destinations. Seventy percent of mineral materials used in the US economy are for construction.51 Since urban communities use fewer roads, sewers and power line on a per capita basis, materials use is more efficient than in sprawl development. For example, the Bureau of Mines found that per capita use of construction minerals in densely populated Cook County was 4½ tons per year. In sparsely populated nearby Lake County the annual rate was 11 tons. 52Urban centers also provide specialized opportunities to extend the life of major industrial equipment such as engines and motors. 53Researchers at Boston University have just compiled a first-time census of these re-manufacturing industries, and find total direct employment to be at least 468,000, more than the entire domestic steel industry. 54Finally, there is some evidence that compact urban areas may use less energy per capita for heating, cooling and transportation. Centralization tends to reduce reliance on transportation because of the closer proximity of producers and consumers. The use of higher-density and multi-story buildings (both office and apartment housing) reduces materials used due to shared infrastructure, and energy resources due to shared heat. 55
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