18 Economic and Environmental Considerations Materials scientists often need to advise other engineers who work in different and more specialized areas as to the best suit- ability of certain materials for specific applications.An airplane for example,requires light-weight and high-strength materials such as aluminum or titanium alloys,whereas rotor blades for turbine engines,which have to withstand extremely high tem- peratures,are better served by certain nickel alloys.However, cost,availability,safety,aesthetic appearance,and recyclability of materials likewise need substantial consideration.The latter issues shall be discussed in the present chapter. 18.1。Price Figure 18.1 depicts the price per unit weight of some typical in- dustrial materials between 1900 and 2000.It is observed in this graph that the expense for aluminum decreased in the first half of this century,mostly due to more efficient production tech- niques but also because domestic producers held the price for aluminum at a low steady level to improve their competitive edge against copper in the electrical industry.It can be further seen that,among the materials displayed in Figure 18.1,steel is still the least expensive one if one considers the price on a weight ba- sis.The relative price increases during the past 50 years are es- sentially alike for all depicted substances.Long-term changes in price are caused by increases in cost of labor,energy,trans-
18 Materials scientists often need to advise other engineers who work in different and more specialized areas as to the best suitability of certain materials for specific applications. An airplane, for example, requires light-weight and high-strength materials such as aluminum or titanium alloys, whereas rotor blades for turbine engines, which have to withstand extremely high temperatures, are better served by certain nickel alloys. However, cost, availability, safety, aesthetic appearance, and recyclability of materials likewise need substantial consideration. The latter issues shall be discussed in the present chapter. Figure 18.1 depicts the price per unit weight of some typical industrial materials between 1900 and 2000. It is observed in this graph that the expense for aluminum decreased in the first half of this century, mostly due to more efficient production techniques but also because domestic producers held the price for aluminum at a low steady level to improve their competitive edge against copper in the electrical industry. It can be further seen that, among the materials displayed in Figure 18.1, steel is still the least expensive one if one considers the price on a weight basis. The relative price increases during the past 50 years are essentially alike for all depicted substances. Long-term changes in price are caused by increases in cost of labor, energy, transEconomic and Environmental Considerations 18.1 • Price
374 18.Economic and Environmental Considerations 1.4 10 1.2 8 6 Sn 1.0 2 (punod/s) 0.8 60*70'80902000 0.6 0.4 0.2 Steel 0 1 1900*102030'40506070'80902000 Year FiGURE 18.1.The price per pound of some commonly used industrial materials from 1900 to 2000 in the United States.Prices are not cor- rected for inflation.For plastics,see Table 18.1.[Source:U.S.Bureau of Mines,U.S.Department of the Interior.] portation,and by the usage of leaner ores.Short-term fluctua- tions depend on speculators,supply and demand,and political factors such as strikes and wars.For example,the steep price in- creases in the late 1970s were caused by the OPEC oil embargo and by the removal of government price controls. It is interesting in this context to compare the prices of met- als with those of plastics.The prices of polymeric materials vary, however,with types and properties,and can therefore not be readily included in Figure 18.1.For this reason Table 18.1 lists the cost of plastics as published on August 4,2003.It is noticed that the cost of steel based on weight is essentially still lower than that for plastics.This is,however,not always true if the price is based on volume. 18.2.Production Volumes Figure 18.2 displays the production volumes of various materi- als over the past 16 years.It can be learned from this graph that timber and concrete are essentially the most widely used ma- terials in the United States.(It needs to be kept in mind that
portation, and by the usage of leaner ores. Short-term fluctuations depend on speculators, supply and demand, and political factors such as strikes and wars. For example, the steep price increases in the late 1970s were caused by the OPEC oil embargo and by the removal of government price controls. It is interesting in this context to compare the prices of metals with those of plastics. The prices of polymeric materials vary, however, with types and properties, and can therefore not be readily included in Figure 18.1. For this reason Table 18.1 lists the cost of plastics as published on August 4, 2003. It is noticed that the cost of steel based on weight is essentially still lower than that for plastics. This is, however, not always true if the price is based on volume. Figure 18.2 displays the production volumes of various materials over the past 16 years. It can be learned from this graph that timber and concrete are essentially the most widely used materials in the United States. (It needs to be kept in mind that FIGURE 18.1. The price per pound of some commonly used industrial materials from 1900 to 2000 in the United States. Prices are not corrected for inflation. For plastics, see Table 18.1. [Source: U.S. Bureau of Mines, U.S. Department of the Interior.] 374 18 • Economic and Environmental Considerations 1.4 1.2 1.0 0.8 0.6 Price ($/pound) 0.4 0.2 0 1900 ’10 ’60 2 4 6 8 Sn 10 ’70 ’80 ’90 2000 ’20 ’30 ’40 ’50 Year Steel Cu Sn Zn Al Pb Zn Al Cu ’60 ’70 ’80 ’90 2000 18.2 • Production Volumes
18.2 Production Volumes 375 TABLE 18.1.Average price of plastics (virgin and recycled)in dollars per pound as of 8-4-03 when bought at volumes between 2 and 5×10 pounds Material $1b. PVC resin (pipe grade) 0.48 Recycled PVC(clean,regrind,or flaked) 0.29 Polystyrene (high impact) 0.71 PET(PETE)packaging resin(for bottles,etc.) 0.73 ABS (high impact,for telephones,suitcases,etc.) 1.27 High-density polyethylene(HDPE)(for milk bottles) 0.54 Recycled HDPE (pellets) 0.36 LDPE (low density polyethylene)for grocery bags,wrappings 0.65 PP(polypropylene)yogurt containers,medicine bottles 0.50 Recycled PET(PETE)(clear,post-consumer,pellets) 0.61 Source:Plastics News,August 2003 the consumption of concrete is almost one order of magnitude larger than that of cement due to the addition of gravel and sand.This raises the output figures for concrete above the lev- els of timber and steel.)Also interesting to observe is the steady increase of polymer production over the past 16 years.It should be noted that,on a volume basis,light-weight aluminum and Timber 100 Crude Steel Cement suo] Plastics 10 Kaolin Al Wood pulp FIGURE 18.2.U.S.annual produc- Flat glass tion figures on a weight basis for various materials from 1984 Synthetic rubber Cu until 2000.[Source:Industrial Cotton Commodities Statistics Yearbook (2002),United Nations and US 848688 90929496 982000 Census Bureau(Flatglass).] Year
the consumption of concrete is almost one order of magnitude larger than that of cement due to the addition of gravel and sand. This raises the output figures for concrete above the levels of timber and steel.) Also interesting to observe is the steady increase of polymer production over the past 16 years. It should be noted that, on a volume basis, light-weight aluminum and 18.2 • Production Volumes 375 TABLE 18.1. Average price of plastics (virgin and recycled) in dollars per pound as of 8-4-03 when bought at volumes between 2 and 5 106 pounds Material $/lb. PVC resin (pipe grade) 0.48 Recycled PVC (clean, regrind, or flaked) 0.29 Polystyrene (high impact) 0.71 PET (PETE) packaging resin (for bottles, etc.) 0.73 ABS (high impact, for telephones, suitcases, etc.) 1.27 High-density polyethylene (HDPE) (for milk bottles) 0.54 Recycled HDPE (pellets) 0.36 LDPE (low density polyethylene) for grocery bags, wrappings 0.65 PP (polypropylene) yogurt containers, medicine bottles 0.50 Recycled PET (PETE) (clear, post-consumer, pellets) 0.61 Source: Plastics News, August 2003 100 10 1 84 86 Year U.S. Production in million tons 88 90 92 94 96 98 2000 Timber Cement Crude Steel Plastics Kaolin Al Wood pulp Cu Cotton Synthetic rubber Flat glass FIGURE 18.2. U.S. annual production figures on a weight basis for various materials from 1984 until 2000. [Source: Industrial Commodities Statistics Yearbook (2002), United Nations and US Census Bureau (Flatglass).]
376 18.Economic and Environmental Considerations plastics are even more utilized than Figure 18.2 might suggest because the presented data are based on weight rather than on volume.Figure 7.2 depicts the world steel production. 18.3●World Reserves Next,the future availability and the remaining world's supply of raw materials need to be taken into consideration when design- ing an industrial product.Table 18.2 lists some data concerning current world productions and known world reserves for some minerals.Table 18.2 also reveals the number of years these sup- plies are projected to last if usage proceeds at the present rate and no new sources are discovered.As probably expected,iron, oil,and coal top the list by far with respect to world production. Some forecasters predict an exponential growth of usage for some materials.This would deplete the resources much faster than the above-assumed constant level of consumption.A spe- cific time interval,tp,may be defined,during which future con- sumption is predicted to have doubled,that is,tp=69/r,where TABLE 18.2.Annual world production and estimated world reserves of materials(data in 106 metric tons except for crude oil,which is given in 109 barrels (bbl),whereas 1 bbl of oil is 0.159 m3 or 0.18 tons).The production data are for 2000 and the world reserves from 2001/02 World World Years' Materials production reserve base supply Iron ore 620 160,000 258 Copper 13.0 650 50 Aluminum 30.1 6,600- 219 Lead 6.0 130 22 Zinc 8.8 450 51 Tin 0.3 11 37 Nickel 0.9 140 155 Silicon 4.5 Essentially unlimited Potash 25.0 17.000 680 Phosphate 41.4 37,000 894 Crude oil 27.9 1,047.5 38 Coal 4,343 984,453 227 World iron ore reserve base:330,000 X 106 tons.Two tons of iron ore yield approximately one ton of iron.Note:Scrap iron is not included. bBauxite world reserve:33,000 X 106 tons;Bauxite yields 1 ton of Al from 4 to 6 tons of ore. Sources:USBM,Mineral Commodity Summaries 2002,"World Oil,"Au- gust 2002,for crude oil,and "1999 Survey of Energy Resources,"World Energy Council for coal
plastics are even more utilized than Figure 18.2 might suggest because the presented data are based on weight rather than on volume. Figure 7.2 depicts the world steel production. Next, the future availability and the remaining world’s supply of raw materials need to be taken into consideration when designing an industrial product. Table 18.2 lists some data concerning current world productions and known world reserves for some minerals. Table 18.2 also reveals the number of years these supplies are projected to last if usage proceeds at the present rate and no new sources are discovered. As probably expected, iron, oil, and coal top the list by far with respect to world production. Some forecasters predict an exponential growth of usage for some materials. This would deplete the resources much faster than the above-assumed constant level of consumption. A specific time interval, tD, may be defined, during which future consumption is predicted to have doubled, that is, tD 69/r, where 376 18 • Economic and Environmental Considerations 18.3 • World Reserves TABLE 18.2. Annual world production and estimated world reserves of materials (data in 106 metric tons except for crude oil, which is given in 109 barrels (bbl), whereas 1 bbl of oil is 0.159 m3 or 0.18 tons). The production data are for 2000 and the world reserves from 2001/02. World World Years’ Materials production reserve base supply Iron ore 620 160,000a 258 Copper 13.0 650 50 Aluminum 30.1 6,600b 219 Lead 6.0 130 22 Zinc 8.8 450 51 Tin 0.3 11 37 Nickel 0.9 140 155 Silicon 4.5 Essentially unlimited Potash 25.0 17,000 680 Phosphate 41.4 37,000 894 Crude oil 27.9 1,047.5 38 Coal 4,343 984,453 227 aWorld iron ore reserve base: 330,000 106 tons. Two tons of iron ore yield approximately one ton of iron. Note: Scrap iron is not included. bBauxite world reserve: 33,000 106 tons; Bauxite yields 1 ton of Al from 4 to 6 tons of ore. Sources: USBM, Mineral Commodity Summaries 2002, “World Oil,” August 2002, for crude oil, and “1999 Survey of Energy Resources,” World Energy Council for coal
18.3·World Reserves 377 r is the current rise in consumption per year in %(assuming ex- ponential growth).For example,if copper use increases by 8% per year,the consumption would double in 9 years.However,an increase in price and recycling may eventually slow down a too- rapid rise in consumption so that an exponential growth rate may not be encountered. Table 18.2 does not contain timber (a renewable material), which currently grows worldwide on about 3.4 x 109 hectares (27%of the land area)and whose 1995 world harvest was 1.4 X 109 m3.If used responsibly,and if substantial amounts of pulp are recycled(see below),the same amount of wood which has been harvested can probably be regrown.This would preserve the forests on all continents.However,between 1980 and 1990, the world lost an average of 9.95 X 106 hectares of net forest area annually,i.e.,roughly the size of South Korea.Most of the de- cline in forest area has occurred since 1950 and has been con- centrated in the tropical areas of developing countries to expand crop land,build cattle ranges,and extract timber.The temper- ate forests in industrial countries have essentially remained con- stant but consist largely of even-aged monoculture tree farms that do not support a high level of biodiversity as an ecologically com- plex natural forest does.Further,air pollution destroys large amounts of forests,particularly in Europe;specifically,26%of this continent's trees have moderate to severe defoliation.The world production of various forest products in different geo- graphic regions is listed in Table 18.3. The potential for fabricating polymeric materials depends largely on the availability of petroleum and coal.To illustrate Table 18.3 World wood production in 2000.Unit:106 m3,except wood pulp,which is given in 103 tons.Note:1 ton of sawn wood coniferous=1.82 m3;1 ton sawn wood broadleaved =1.43 m3;1 ton veneer sheets =1.33 m3;I ton plywood 1.54 m3;1 ton particle board 1.54m3. Sawn wood Sawn wood Veneer Particle Wood Country coniferous Broad-leaved sheets Plywood board pulp Africa 2.4 5.3 0.7 0.7 0.5 0.3 N.America 156.0 37.1 0.6 19.6 31.6 17.5 S.America 14.1 15.5 3.6 3.1 2.8 1.2 Asia 29.7 24.6 2.7 27.5 8.7 2.4 Europe 109.6 17.2 7.2 5.6 37.0 15.0 Oceania 6.5 1.7 0.4 0.7 1.2 1.2 Total 318.9 101.3 15.3 60.0 81.8 37.6 Source:2000 Industrial Commodities Statistics Yearbook,United Nations (2002). 1100n2
r is the current rise in consumption per year in % (assuming exponential growth).1 For example, if copper use increases by 8% per year, the consumption would double in 9 years. However, an increase in price and recycling may eventually slow down a toorapid rise in consumption so that an exponential growth rate may not be encountered. Table 18.2 does not contain timber (a renewable material), which currently grows worldwide on about 3.4 109 hectares (27% of the land area) and whose 1995 world harvest was 1.4 109 m3. If used responsibly, and if substantial amounts of pulp are recycled (see below), the same amount of wood which has been harvested can probably be regrown. This would preserve the forests on all continents. However, between 1980 and 1990, the world lost an average of 9.95 106 hectares of net forest area annually, i.e., roughly the size of South Korea. Most of the decline in forest area has occurred since 1950 and has been concentrated in the tropical areas of developing countries to expand crop land, build cattle ranges, and extract timber. The temperate forests in industrial countries have essentially remained constant but consist largely of even-aged monoculture tree farms that do not support a high level of biodiversity as an ecologically complex natural forest does. Further, air pollution destroys large amounts of forests, particularly in Europe; specifically, 26% of this continent’s trees have moderate to severe defoliation. The world production of various forest products in different geographic regions is listed in Table 18.3. The potential for fabricating polymeric materials depends largely on the availability of petroleum and coal. To illustrate 18.3 • World Reserves 377 1100 ln 2. Table 18.3 World wood production in 2000. Unit: 106 m3, except wood pulp, which is given in 103 tons. Note: 1 ton of sawn wood coniferous= 1.82 m3; 1 ton sawn wood broadleaved 1.43 m3; 1 ton veneer sheets = 1.33 m3; 1 ton plywood = 1.54 m3; 1 ton particle board 1.54 m3. Sawn wood Sawn wood Veneer Particle Wood Country coniferous Broad-leaved sheets Plywood board pulp Africa 2.4 5.3 0.7 0.7 0.5 0.3 N. America 156.0 37.1 0.6 19.6 31.6 17.5 S. America 14.1 15.5 3.6 3.1 2.8 1.2 Asia 29.7 24.6 2.7 27.5 8.7 2.4 Europe 109.6 17.2 7.2 5.6 37.0 15.0 Oceania 6.5 1.7 0.4 0.7 1.2 1.2 Total 318.9 101.3 15.3 60.0 81.8 37.6 Source: 2000 Industrial Commodities Statistics Yearbook, United Nations (2002)