Go to page: 17  18  19  20  21  I n 1900, the average U.S. citizen’s average life span was 47 years.  He traveled about 1,900 km (1,200 miles) in a lifetime and resided in a home with an ice- box for food storage and oil or gas for lighting.  He com- municated by mail, telegraph and crude telephones with limited availability and range. By 2000, the average citizen’s life span was 77 years. He traveled an average of 19,000 km/a (12,000 miles/ year) by automobile alone.  He resided in a home with many electrical appliances, including refrigerators and electric lights.  And he communicated almost instanta- neously with any other part of the globe by several widely available means, including portable phones and e- mail. Technology, the application of knowledge about the Earth’s materials, their extraction and fabrication into products, helped create this change.  Throughout the 20th century, the United States was a leader in technology. Automobiles, refrigerators, electric lighting, telephones and personal computers are only a few examples of the products invented and improved or further developed by American technology (National Academy of Engineer- ing, 2000). The United States is endowed with natural re- sources, a diverse, rapidly growing population, a dynamic economy and a location with ports on the world’s two major oceans.  So technology flourished in the United States as new and improved products were manufac- tured and made available to a growing population. The interaction of technology and increasing mate- rial demand induced manufacturers to use materials ef- ficiently to increase profit.  As metals use increased, more scrap metals became available for recycling at the end of metal products’ lifetimes. Source reductions enabled the manufacturing of products that perform the same function with smaller material inputs.  And materials substituted for one an- other as the functions of products were improved and product costs were decreased. Materials Mountain Changes in raw materials use in the United States between 1900 and 2000 illustrate the nature of materials demand and growth in the efficiency of materials use. Figure 1 is the “Materials Mountain.”  It shows the amount, by weight, of six categories of non-food, non- fuel materials demanded by U.S. industry throughout the 20th century.  Nine classes of materials are shown graphi- cally.  Paper and recycled paper are split from wood and recycled metals are separately rep- resented from primary metals.  The upward trends in demand are evi- dence of growth and prosperity.  The occasional downward trends reflect economic recessions and depres- sions. New raw materials, new prod- ucts, population growth and efficient materials use explain the shape of the areas for the nine raw material classes (from six material catego- ries), which form the mountain. The stone and sand and gravel category represents the largest ton- Raw materials and technology fuel U.S. economic growth Thomas D. Kelly Thomas D. Kelly is a minerals and materials specialist with the U.S. Geological Survey, Box 25046, MS 750, Denver Federal Center, Denver, CO 80225-0046. Construction materials, including aggregates, currently make up the greatest portion, by weight, of U.S. materials use.  Photo shows Lafarge’s Specification Aggregates Quarry in Golden, CO.  (Photo courtesy of Lafarge.)
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