384 18.Economic and Environmental Considerations and tin (cans,alloys).Some technocrats see this,however,in a different light.They claim that there will always be enough re- sources available through price-driven explorations.Moreover, optimists believe that human ingenuity will eventually provide new avenues which have not yet been imagined that may satisfy our needs.However,recycling is also an obligation for protect- ing the environment,by reducing landfills(which emit methane, a powerful greenhouse gas)and removing toxic and other dele- terious elements (mercury,lead,selenium,heavy metals)from soil and water.Additionally,recycling can have economic bene- fits by saving the energy and other costs for extracting valuable materials from minerals and agricultural sources. Table 18.7 displays the amount of secondary materials which were recovered in the United States from scrap during 1990.It TABLE 18.7.Recycling of metals in the United States in 1990 Value of Percent Percent secondary of value Secondary of total metal of total metal secondary (million secondary Metal (metric tons) metal dollars) metal Iron (incl.steel) 55,500,000 91 25,000 68 Aluminum 2,400,000 4 3,900 11 Copper 1,300.,000 3,600 10 Lead 920,000 2 930 2 Zinc 340.000 1 560 2 Manganese 60,000 3 Magnesium 54,000 170 Nickel 25,000 220 Antimony 20,400 Titanium 15,000 Tin 7,800 Molybdenum 3.,000 Tungsten 2,200 Silver 5950 1,700 Cobalt 1.600 Cadmium 700 05 Selenium 100 Vanadium 100 12 Chromium 90 580 1 Mercury 90 <1 Platinum Group 71 660 2 Tantalum 50 18 Gold 49 600 2 Totals (rounded) 60,600,000 100 36,800 100 Source:U.S.Department of the Interior,Bureau of Mines.and tin (cans, alloys). Some technocrats see this, however, in a different light. They claim that there will always be enough re￾sources available through price-driven explorations. Moreover, optimists believe that human ingenuity will eventually provide new avenues which have not yet been imagined that may satisfy our needs. However, recycling is also an obligation for protect￾ing the environment, by reducing landfills (which emit methane, a powerful greenhouse gas) and removing toxic and other dele￾terious elements (mercury, lead, selenium, heavy metals) from soil and water. Additionally, recycling can have economic bene￾fits by saving the energy and other costs for extracting valuable materials from minerals and agricultural sources. Table 18.7 displays the amount of secondary materials which were recovered in the United States from scrap during 1990. It 384 18 • Economic and Environmental Considerations TABLE 18.7. Recycling of metals in the United States in 1990 Value of Percent Percent secondary of value Secondary of total metal of total metal secondary (million secondary Metal (metric tons) metal dollars) metal Iron (incl. steel) 55,500,000 91 25,000 68 Aluminum 2,400,000 4 3,900 11 Copper 1,300,000 2 3,600 10 Lead 920,000 2 930 2 Zinc 340,000 1 560 2 Manganese 60,000 — 3 — Magnesium 54,000 — 170 — Nickel 25,000 — 220 — Antimony 20,400 — 35 — Titanium 15,000 — 140 — Tin 7,800 — 65 — Molybdenum 3,000 — 17 — Tungsten 2,200 — 9 — Silver 1,700 — 260 1 Cobalt 1,600 — 30 — Cadmium 700 — 5 — Selenium 100 — 1 — Vanadium 100 — 2 — Chromium 90 — 580 1 Mercury 90 — 1 — Platinum Group 71 — 660 2 Tantalum 50 — 18 — Gold 49 — 600 2 Totals (rounded) 60,600,000 100 36,800 100 Source: U.S. Department of the Interior, Bureau of Mines