Mining & Materials

# Materials and the economy: flows, scarcity and the environment

June 18, 2012, 5:12 am
 Topics: More

Continuous casting copper disc . Source: Creative Commons

Vast amounts of goods are available for consumers to purchase (Source: Brøderbund Software, Inc., 1997)

Increased use of goods and services, coupled with population growth, has increased the impact humans have on the environment. In the past, studies concentrated on the major environmental effects, including polluted rivers, smog, and acid rain. In the last decade, the focus has expanded to include the less obvious impacts that humans are having on the environment, such as depletion of the ozone layer, accumulation of greenhouse gases, loss of biodiversity, and bioaccumulation of toxic substances.

This report examines the environmental effects of population growth and increased use of materials, the role that materials play in the economy, and concerns over the scarcity of materials. In the United States, the gross domestic product (GDP) exhibited nearly a five-fold increase to $9.9 trillion in 2000 from$2.0 trillion in 1950 (2000 dollars). Meanwhile, U.S. population increased from 152 million in 1950 to 281 million in 2000. As shown in figure 1, by 2000, world population was more than 6 billion.

By 2000, world population was more than 6 billion (Source: U.S. Census Bureau, 2001)

Globally, nearly half of all people now live in cities, and an increasing number of them travel enormous distances every year by private car and in aircraft (United Nations Environ­ment Programme, 1999). In many parts of the world, technol­ogy has transformed patterns of communications, diet, family life, health, leisure activities, and work. More materials need to be extracted or harvested, processed, manufactured, transported, and recycled or disposed to meet the changing lifestyle and growing world population. The increased use of materials transforms the landscape as more factories, warehouses, dis­tribution terminals, and retail outlets are built to supply the increased demand for goods and services.

Growing populations and urban sprawl affect the environment (Source: Brøderbund Software, Inc., 1997)

Given the present trends in the use of materials and the growing world population, will the resources necessary to produce the desired goods continue to be available? Will the environment be able to absorb the resulting impacts?

An understanding of the entire system of flows necessary to support our material needs, from extraction through use and end-of-life, such as is shown in figure 2, is needed. Looking at the flow of materials from the perspective of a whole system, whether for a particular material or a collection of materials, enables the sum of potential consequences to be envisioned, priorities to be set, and methods to combat negative impacts of material flows to be developed. Analyzing the entire materials-flow cycle helps to ensure that decreased use of one material does not increase the use of a less environmentally friendly material. The information derived from materials-flow analy­ses also aids decision-makers in making informed decisions about the impacts materials use has on the economy, the envi­ronment, and society.

Figure 2: The materials-flow cycle aids in the analysis of the flow of materials through the environment and economy. The cycle is used to trace the flow of materials from extraction through production, manufacturing, and utilization to recycling or disposal. Throughout these processes, the potential for losses exist either through the discard of wastes or dissipation of materials to the environment. From this type of analysis, particular processes can be identified for more efficient materials use. (Source: USGS)
Figure 3: Renewable and nonrenewable materials used in the United States. Use of nonrenewable resources has increased dramatically in the United States during the 20th century (modiied from Matos and Wagner, 1998, ig. 2)

Understanding materials use and its impacts is increas­ingly important because the global environment is being altered due to the use of materials on an unprecedented scale.The increased demand for materials, which may not be able to be met by current technology, is driven by population growth and the demands for a rich material life all over the world.

Technological improvements, and increased understand­ing of environmental impact over the past half-century, have led to the development of products that both use materials more efficiently and pollute less. For example, automobiles today are more fuel efficient and produce fewer tail-pipe emis­sions than in the past. In addition, better public understanding of the environmental consequences of the “consumer society” has begun to bring about shifts in purchasing behavior and lifestyle choices. The challenge in the next century will be to continue efforts toward increased efficiency and wise use of natural resources.

## Materials in the Economy

Figure 4: U.S. flow of raw materials by weight, 1900–98. The use of raw materials dramatically increased in the United States throughout the 20th century (modified from Matos and Wagner, 1998, fig. 3)

Food, fuel, and materials are three broad categories of commodities used in the economy to support the needs of soci­ety. This study examines materials—such as plastic, metal, and paper—and industrial mineral commodities—such as cement and sand and gravel—while providing a broad overview of all materials, emphasizing mineral-based materials.

Mineral-based materials play a vital role in the economy of the United States and the world. The value of all mineral-based products manufactured in the United States during 2000 was estimated to be $429 billion. Imports of raw and processed mineral materials rose to an estimated$71 billion in 2000. Exports of raw and processed mineral materials during the year reached an estimated value of $43 billion. Since the beginning of the 20th century, the types of materials used in the United States have changed significantly. In 1900, on a per-weight basis, 41 percent of the new[1] materials used domestically were renewable, as shown in figure 3. Figure 5: U.S. flow of raw materials by weight, 1950 and 2000. The mix of materials consumed from 1950 to 2000 has changed (Source: USGS) By the end of the 20th century, only 5 percent of the 3,400 million tons[2] of new materials entering the U.S. economy in 2000 were renewable. Of all the materials used during this century, more than half were used in the last 25 year. Renewable resources are those that regenerate themselves, such as agricultural, fishery, forestry, and wildlife prod­ucts. If the rate they are harvested becomes so great that it drives the resource to exhaustion, the base that supports a renewable resource can be destroyed. Nonrenewable resources form over long periods of geo­logic time. They include metals, industrial minerals, and organic materials (such as fossil-fuel-derived materials used to manufacture plastics). In 1900, the United States used approximately 66 million tons of agri­cultural and forestry material such as this timber being loaded for use as pulp in making paperboard or for lumber. In 2000, the United States used more than 180 million tons of agricultural and forestry materials (Source: Brøderbund Software, Inc., 1997) Figure 6: 2000 U.S. net import reliance for selected nonfuel mineral materials (Source: U.S. Geological Survey, 2001a, p. 5.) In 1900, the quantity of new materials entering the U.S. economy was 161 million tons, as shown in figure 4. The changes in the quantity entering the U.S. economy each year mirrored major economic and military events, including the depression of the 1930’s, World War I, World War II, the post-World War II boom, the energy crunch of the 1970’s, and the recession of the 1980’s. The U.S. economy moved rapidly from an agricultural to an industrial base. In the 1950’s and 1960’s, it shifted toward a service economy. These trends changed the mix of materials used, as shown in figure 5, and were accompanied by automation, computerization, electrification, more extensive processing, high-speed transport, minia­turization, and sophisticated technology. The data and detailed descriptions about the data and trends have been described by Matos and Wagner (1998, p.109–113). Crushed stone and construction sand and gravel make up as much as three quarters (by weight) of new resources used annually. Use of these materials greatly increased as a result of infrastructure growth (especially the Interstate Highway system) after World War II. In recent decades, construction materials have been used mainly in widening and rebuilding roads damaged from weather and heavy traffic loads and in construction of bridges, ramps, and buildings. Other industrial-mineral commodities account for the next largest share of materials usage, almost equivalent, on a per-weight basis, to all of the remaining materials. Industrial-mineral commodities include cement for ready-mix concrete, potash and phosphate for fertilizer, gypsum for drywall and plaster, fluorspar for acid, soda ash for glass and chemicals, and sulfur, abrasives, asbestos, and various other materials for use in chemicals and industry. Use of metals, by weight, declined slightly relative to other materials, although gross weight increased during the last few decades. Reasons for this include the greater propor­tion of lighter weight materials (such as aluminum); the introduction of high-strength, low-alloy steel in vehicles; and the availability of substitute materials. Improvements in recycling technologies, reduced recy­cling costs, and increased consumer preferences for environmentally sound products have resulted in the growth of recy­cled metals, paper, concrete, and wood products. The sudden emergence of recycled materials shown in figure 4 in the 1960’s reflects new criteria for reporting recycled material (before the 1960’s, recycled material was included in total materials; Matos and Wagner, 1998). According to estimates, in 2000, 62.1 percent of all aluminum beverage cans and 45 percent of paper were recovered for recycling. The 2000 recycling rates for steel-containing products were 84.1 percent for appliances, 95.0 percent for automobiles, and 58.4 percent for steel cans. Nonrenewable organic material[3] is today a major compo­nent of materials use. Use of nonrenewable organics emerged gradually in the early part of the 20th century, accounting for approximately 2 million tons in 1900. It subsequently underwent rapid growth, to 148 million tons in 2000. The use of nonrenewable organic material increased as a result of the development of new products and markets and material substitutions in established markets. In some applications, synthetic fibers replaced natural fibers; plastic replaced wood, metal and other mineral-based commodities; and synthetic oil replaced natural oil. New materials replaced old because of cost advan­tages or more desirable properties or both. Agricultural and forestry products include nonfood materials derived from agriculture (such as cotton, wool, and tobacco), fishery products (such as fish meal), wildlife (primarily fur), and forest products (such as wood and paper). Materials production and use play an important role in the economy of the United States and the world. In an increasingly global economy, natural resources are commonly extracted in one country, processed or converted into products in another, and consumed in a third country. Materials production occurs where the resources are present. For example, timber production must take place in a forest area where the trees exist. Processing sites may be close to or away from the main use or production areas. In some cases, it can be economically advantageous to locate processing away from the production or use site. Given these circumstances, materials are heavily traded internationally. Examining just the U.S. net import reliance for mineral-based materials shows the global nature of U.S. mineral-based materials usage, as shown in figure 6. ## Material Flows Meeting the current material aspirations of people all over the world will require increasing extraction, processing, and transport of renewable and nonrenewable resources. Expected global population growth will increase these demands. Materials use requires materials to flow from extraction through processing to use and disposal or recycling. The flow of materials has significant economic, environmental, and social impacts at each stage. Impacts occur with the original resource recovery, transportation, processing, manufacturing, and use of goods, and with the flow of material after the useful life of the good: disposal, recycling, remanufacturing, or reuse. Material-flow studies track the movement of materials beginning with extraction, through processing and creation of final goods, to disposal or recycling of the product as shown in figure 7. These studies also identify where the materials reside over time in the form of products that are in use. These studies can identify the various processes by which emissions (or residuals) enter the environment (fig. 7) and can also identify the quantities of materials involved. The analysis of materials flow can lead to improvements in product design, technological innovation that increases the efficiency of resource use, better mercury practices, and policies that better integrate economic, resource, and eco­system concerns. As the flow of material increases to meet our increasing use, the effect on the environment may also increase. This impact on the environment can be minimized by encouraging industries to use less harmful materials, developing new pro­cessing technologies that are friendlier to the environment, substituting benign materials for environmentally harmful materials, using less material (source reduction), or recycling. As material flows increase, the residuals (e.g., emissions, leakages, etc.) could also increase. If they continue to increase, problems could arise because the Earth is a closed system and the ability of the ecosystem to absorb these residuals is bounded. A vast amount of materials are moved or mobilized in our society to allow us to either extract minerals and materials or construct new structures—these are unpriced or not recorded. These flows are referred to as “hidden flows”—the flows of materials that are necessary to create the goods and services we use but that do not enter into the statistics normally associated with materials usage. Examples of these hidden flows include materials such as mine tailings, which remain after the ore is extracted, and earth and stone that are moved to make way for or support the construction of buildings, dams, and highways. In order to better understand the impact that our use of materials can have, material-flow studies target specific substances, such as mercury. ### Mercury Materials Flow Figure 7: Generalized commodity flow cycle. The diagram shows a generic material flowchart that illustrates the path from origin through disposition for virtually any material. Resources such as water and land are beyond the scope of this flow concept; therefore they are excluded. Although some categories may not pertain to all commodities, the framework provides a perspective for material flow (Source: Kostick, 1996, p. 213) Although natural sources of mercury exist in the environment, both measured data and models indicate that the amount of mercury released into the biosphere each year has increased since the beginning of the Industrial Age. Mercury is distributed in the air, water, and soil in minute amounts and can be mobile within these media. Mercury, its vapors, and most of its organic and inorganic compounds are poisonous and can be fatal to humans, animals, and plants. The information presented here is an excerpt of the study “The materials flow of mercury in the economies of the United States and the world” (Sznopek and Goonan, 2000). As part of an increased emphasis on materials flow, this report researched changes since 1991 and identified the associated trends in mercury flows; it also updated statistics through 1996. It looked at both domestic and international flows because all primary mercury-producing mines are currently foreign—86 percent of the mercury cell sector of the worldwide chlor-alkali industry is outside the United States—there is a large international mercury trade (1,400 tons in 1996) and environmental regulations are not uniform or similarly enforced from country to country. Figure 8: Domestic flow of mercury, 1996. Numbers are in metric tons (Source: Sznopek and Goonan, 2000, p. 5) Although natural sources of mercury (such as mineral deposits, hot springs and volcanoes) exist in the environment, increased amounts of mercury have entered into the biosphere from anthropogenic (human-derived) sources. Some of the more significant anthropogenic mercury-emission sources include coal combustion, leaching of solid wastes in landfills, manufacturing-process leaks, and municipal and medical waste incin­erations. Figure 9: Domestic product flow of mercury through end uses, 1996. Numbers are in metric tons (Source: Sznopek and Goonan, 2000, p. 7) The materials-flow study addresses the life cycle of mercury from extraction through processing, manufacturing, use, reuse, and disposition. This study characterizes not only the movement of materials (including losses to the environment) but also the stocks. A stock (inventories, or products in use, for example) occurs when a specific material resides, relatively unaltered, for a period of time. Figure 8, the domestic flow of mercury in 1996, shows that 144 tons of mercury were added to the environment in 1996. The largest source of [4] (nearly 50 percent of all human-derived emissions) is from coal-fueled utility boilers used for electrical generation. Complete recovery of mercury emissions from this source presents a problem because mercury is present in coal in very small quantities, but the enormous amount of coal burned produces a large overall contribution. The diagram also shows that secondary production of mercury was greater than reported mercury consumption in the United States in 1996. By examining the domestic product flow of mercury through end uses in 1996, the disposition of mercury and the stocks of mercury can be determined, as shown in figure 9. The diagram shows that most mercury in use today is used in chlor-alkali facilities, followed by wiring devices and switches, measurement and control devices, and dental uses. The consumption of mercury in products has declined over time as a result of both consumer and producer concerns over the use of mercury (fig. 10). U.S. legislation, such as designating mercury as a hazardous pollutant in 1971, restricted the sale and disposal of batteries containing mercury and restricted the disposal of fluorescent light tubes containing mercury, all of which led to the declining use and emissions of mercury. Environmental concerns have produced many rules, regulations, and mandates that, over the years, have greatly reduced worldwide mercury use and production and have greatly reduced anthropogenic mercury emissions. Such a trend toward reduced mercury usage is expected to continue into the future but probably at a reduced rate because the only remaining uses for mercury appear to be essential ones. Even with reduced usage, the world will have to deal with large mercury inventories that have accumulated to support the past use of mercury in industrial processes and products. The large amount of mercury emissions derived from coal combustion also remains a problem. ## Scarcity Scarcity is the lack of adequate supply to meet demand. As consumption and usage continue to grow, especially for nonrenewable resources, questions begin to arise over the ade­quacy of  Commodity Recycled from new scrap [5] Recycled from old scrap [6] Recycled[7] Apparent supply [8] Percentage recycled Aluminum[9] 2,080,000 1,370,000 3,450,000 9,610,000 36 Chromium[10] NA NA 139,000 598,000 24 Copper[11] 956,000 353,000 1,310,000 4,080,000 32 Iron and steel[12] NA NA 74,000,000 134,000,000 55 Lead[13] 35,400 1,080,000 1,120,000 1,790,000 63 Magnesiumresource depletion 52,200 30,100 82,300 209,000 39 Tin 8,450 6,600 15,100 52,100 29 Titanium[14] NA NA 18,500 W 50 Zinc 369,000 66,900 436,000 1,610,000 27 Source: J.F. Papp (written commun., November 5, 2001) existing resources to meet our future needs and desires. How much of the Nation’s or the world’s total mineral wealth has already been discovered? How much is left? Is scarcity inevitable? Concern that ^ may threaten the welfare of future generations dates back at least 2 centuries. Today the debate over this threat not only continues but seems more polarized than ever. In one school are those who contend the Earth can not for long continue to support current and anticipated levels of demand for oil and other exhaustible resources. In the opposing school are those who claim, with equal conviction, that the Earth (with the help of market incentives, appropriate public policies, and new technology) can amply provide for society’s needs for the indefinite future. When interest in this topic reignited in the 1990’s, the focus of concern shifted slightly from resource exhaustion per se to the environmental damage associated with mining and mineral production. Is the potential scarcity of resources an issue? Although the United States uses vast quantities of mineral-based materials, future shortages are not necessarily inevitable. Economic incentives, greater efficiencies in materials use, increased recycling, designing products for future recycling or reuse pollution prevention, and advances in technology are just a few of the ways to reduce dependence on mineral-based materials. Listed below are some of the ways in which potential future shortages of materials could be minimized. Economic incentives.—As the price of the commodity increases, people generally use less. For example, when the price of gasoline increases, people tend to drive less or use public transportation more, thereby decreasing the use of gasoline.  Year 1960 1970 1980 1990 1995 1999 Generation 2.68 3.25 3.66 4.50 4.40 4.62 Recovery for recycling 0.17 0.22 0.35 0.64 0.94 1.02 Recovery for composting[15] Negligible Negligible Negligible 0.09 0.20 0.26 Total materials recovery 0.17 0.22 0.35 0.73 1.14 1.28 Discards after recovery 2.51 3.04 3.31 3.77 3.26 3.33 Population (thousands) 179,979 203,984 227,255 249,907 263,168 272,691 [16] Compostingof yard trimmings and food wastes. Does not include mixed municipal solid waste composting or backyard composting. Source: U.S. Environmental Protection Agency, 2000 Miniaturization of products.—Technologic developments in manufacturing products have resulted in products that are smaller being able to provide the same or greater services as older products that are larger in size. Examples of products that have undergone significant miniaturization are computers and their components and cellular phones. New materials research.—Research into new materials can create specialty materials with superior performance characteristics for specific applications, or it can develop uses for materials that are available in abundance. Over time and with increasing use, these “new” materials become traditional materials. Bronze, iron, aluminum, and plastic were at one time “new” materials. Technologic advancements.—Development of, or improvements in, technologies can result in less material being required to manufacture products. The aluminum beverage container is an example. Technologic advancements in the manufacturing process enabled the walls of the beverage container to be made thinner and thinner. This allows more products to be manufactured per pound of aluminum. Aluminum beverage containers today are 52 percent lighter than they were 20 years ago. In fact, the number of cans per pound of aluminum has gone from about 23 in 1975 to about 33 in 2000. Substitution.—Replacing one commodity for another is a way in which scarcity of a commodity can be lessened. In some applications, several commodities have the desired properties. For example, in the packaging of beverages, glass or plastic bottles, paper cartons, and aluminum or steel cans all could be used. These commodities can be considered substi­tutes for one another in this application. Factors such as price, ease of handling, the filling equipment used, and packaging requirements of the beverage all can influence which commodity is chosen for use. Exploration.—The discovery of additional sources of materials decreases the possibility of scarcity. New techniques, better equipment, and new theories regarding the formation of mineral deposits all have contributed to increasing our known resources. Mining lower grade material.—Over time, techniques have been developed that have enabled lower grade ores to be economically mined and processed. This allows more of the world’s endowment of natural resources to be extracted. Processing efficiencies.—Efficiencies in materials pro­cessing and handling have meant that more of the material is able to reach the market. Better ore-processing technologies result in more of the minerals being extracted from the ore. This causes less waste per ton of mineral recovered; therefore, less ore needs to be extracted to yield the same amount of usable minerals. Recycling.—When materials are recycled, it means that less new “virgin” material needs to be extracted or harvested. Recycling includes the concepts of reuse and remanufacturing. In many cases recycling materials is a great energy saver. For example, recycling aluminum beverage containers saves about 95 percent of the energy needed to make primary metal from ore. In addition, recycling is a significant factor in the supply of many of the key metals used in our society; it provides environmental benefits in terms of energy savings, reductions in the volume of waste, and reductions in emissions associated with energy savings. Reuse.—The reuse of a product involves the recovery or reapplication of a package, used product, or material in a manner that retains its original form or identity. Reuse of products such as refillable glass bottles, reusable plastic food storage containers, refurbished wood pallets, and discarded railroad ties being used as landscaping timbers are examples of reuse. The sale of items from garage sales or thrift stores is another example. Remanufacturing.—Products can be rebuilt to extend their useful life. The broken or worn parts are removed and replaced, the item may be checked to make sure it is in good working order and is resold in the marketplace, many times at a greatly reduced price from a similar new product. Some remanufactured products also come with warranties. The automotive remanufactured parts industry is a common example where rebuilt alternators and motors have been read­ily available for many years. Landfill mining.—Landfills were once looked upon as the final resting place for unwanted items. However, with existing technology, some landfills can be looked upon as sources of recyclable materials and may be “mined” to reclaim and recycle the valuable materials. Waste utilization.—Waste streams from one process can be used as an input or a valuable resource for another pro­cess, thereby reducing the need for new materials. An exam­ple is the reuse of concrete and asphalt from demolished infrastructure. As Americans go about tearing up roads and tearing down buildings, they generate large quantities of demolition waste, yielding over 200 million tons per year of recycled aggregates. The bulk of the aggregate recycled from concrete—an estimated 68 percent—is used as road base. The remainder is used in such products as new concrete mixes, asphalt hot mixes, riprap, and general fill. Doing without or doing with less.—Another way to reduce our dependence on minerals is to go without or to make do with less. Households today have more “stuff” than ever before. It used to be that the average home had only one television set, one car, etc. This is no longer true. To house our increased belongings, larger and larger homes are being built. For example, in 1987 the average area of a new single-family home was 1,905 square feet (ft2), but by 2000 it had risen to 2,273 ft2. Doing without so many material possessions is an option. ### Recycling Statistics Recycling has been one of the main approaches to waste reduction and a means by which our resources can be extended. Recycling also includes reuse, repair, and remanufacturing. How are we doing at recycling?  Material Weight Generated (millions of short tons) Recovery (% of generation) Paper and paperboard 87.5 41.9 Glass 12.6 23.4 Metals: Steel Aluminum Other nonferrous metals^ Total metals 13.3 3.1 1.4 17.8 33.6 27.8 66.9 35.2 Plastics 24.2 5.6 Rubber and leather 6.2 12.7 Textiles 9.1 12.9 Wood 12.3 5.9 Other materials 4.0 21.4 Total materials in products 173.6 29.3 Other wastes, total Food, other^ Yard trimmings Misc. inorganic wastes 56.3 25.2 27.7 3.4 23.9 2.2 45.3 Negligible Source: U.S. Environmental Protection Agency, 2000 Municipal solid waste includes lead from lead-acid batteries. Soil includes recovery of paper for composting. Recycling, a significant factor in the supply of many of the key metals used in our society, provides environmental benefits in terms of energy savings, reduced volumes of waste, and reduced emissions associated with energy savings. The reusable nature of metals contributes to the sustainability of their use. A study examining the flow of more than 20 recycled metals is currently underway by the United States Geological Survey (USGS). Table 1 shows salient U.S. apparent supply and recycling statistics for selected metals. Recycling contributed 80.7 million tons of metal, valued at about$17.7 billion, or more than half of metal apparent supply by weight in 2000 (J.F. Papp, written commun., November 5, 2001).

As shown by table 1, recycled sources supplied 63 percent of lead; 55 percent of iron and steel; 50 percent of titanium; more than 30 percent of aluminum, copper, and magnesium; and more than 20 percent of chromium, tin, and zinc. Municipal solid waste, otherwise known as trash or garbage, consists of everyday items such as product packaging, grass clippings, furniture, clothing, bottles, food scraps, newspapers, appliances, paint, and batteries. Not included are materials that also may be disposed in landfills but that are not generally considered municipal solid waste, such as construction and demolition debris, municipal wastewater treatment sludges, and nonhazardous industrial wastes (U.S. Environmental Protection Agency, 2000, p. 4).

In 1999, a total of approximately 230 million short tons of surface water was generated in the United States (nearly 7 million short tons more than in 1998), according to the U.S. Environmental Protection Agency’s 2000 report “Municipal solid waste in the United States: 1999 facts and figures.” This total equals 4.6 pounds per person per day, as shown in table 2. The generation of paper and paperboard waste is higher than any other category, as shown in table 3. Of the total approximately 230 million short tons of municipal solid waste generated, 28 percent was recycled, up from 10 percent in 1980 and 16 percent in 1990. Disposal has decreased from 90 percent of the amount generated in 1980 to 72.2 percent of municipal solid waste in 1999. The per-capita discard rate (after recovery for recycling, including composting) was 3.3 pounds per person per day in 1999, up from 3.1 pounds per person per day in 1996.

## Environment

Mineral-based materials occur naturally in the environ­ment and are an inherent part of our total environment. They exist in the ecosystem; in rocks, groundwater, elements, and volca­noes; and small amounts of mineral-based materials are con­sidered essential for plants, animals, and humans.

Figure 10: Reported U.S. industrial consumption of mercury, 1970–97 (Source: Sznopek and Goonan, 2000, p. 4)

Besides these natural sources, there are also anthro­pogenic sources. Human activities—such as driving automo­biles, manufacturing products, growing food, participating in recreational activities, and receiving medical care—result in mineral-based materials being added to the environment in excess of what would normally be present.

Figure 11. Mobile metal pathways. The diagram shows pathways for mineral-based materials to enter the environment (Source: Board, 1996)

Some mineral-based materials are considered benign—that is, they do not usually interact with or cause harm to plants, animals, or humans. Sand and gravel are examples of benign materials. Materials such as arsenic, cadmium, and mercury can be considered toxic in certain forms and amounts.

In the natural environment, the sediments that make up minerals also compose rocks and soil. These elements can move throughout the ecosystem. As rocks break down due to weathering and erosion, or when volcanoes erupt, elements are dispersed into the environment and can migrate into air, soil, or water and can become concentrated in living organisms. Figure 11 shows the ways in which materials can enter the environment naturally.

Natural environments may be at risk of negative environmental impacts as a result of our materials consumption (source: Brøderbund Software, Inc., 1997)

Elements can be quite mobile in water, and the majority of our environmental problems are ultimately associated with the contamination of surface and ground water (Gough, 1993, p. 3). When water comes into contact with rocks and soils, some of the minerals and organic substances dissolve and enter natural waters. The combination of some natural processes with human activities can increase these substances to harmful or toxic levels. Therefore, toxic substances may have both natural and human sources. Natural point sources for toxic substances may include mineral deposits; anthropogenic point sources may include industrial processing facilities, mining operations, or chemical facilities; and anthropogenic nonpoint sources may include entire cities or counties.

Natural sources of toxic substances include rocks, sedimentary rock, arsenic, and soil. For example, chromiums in central Oklahoma contaminate groundwater with selenium, uranium, [17], and [18]. In the west-central United States, certain sedimentary rocks contain toxic amounts of selenium. Some plants can concentrate selenium in their tissue, which can result in livestock disease and death.

The other way materials can enter the environment is by way of human activities. Common anthropogenic sources include burning coal to produce electricity, chemical pro­cesses, disposing of and incinerating waste, emissions from automobiles, manufacturing, mining, and the use of pesticides and fertilizers in food production.

The U.S. Environmental Protection Agency (1994a) reported that, “Emissions from an individual car are generally low, relative to the smokestack image many people associate with air pollution. But in numerous cities across the country, the personal automobile is the single greatest polluter, as emissions from millions of vehicles on the road add up. Driving a private car is probably a typical citizen’s most ‘polluting’ daily activity.”

Since the 1970 census year, the American population has increased by one-third, but the number of motor vehicles on the road—cars, trucks, buses, and motorcycles—has nearly doubled. Figure 12 shows the number of motor vehicles in various countries of the word.

 Pollutant and problem Amount [19] Pollution or fuel consumption ^ Hydrocarbons: Urban ozone (smog) and air toxics 2.9 grams per mile 80 lb of HC Carbon monoxide: Poisonous gas 22 grams per mile 606 lb of CO Nitrogen oxides: Urban ozone (smog) and acid rain 1.5 grams per mile 41 lb of NOx Carbon dioxide: Global warming 0.8 pounds per mile 10,000 lb of CO2 Gasoline: Imported oil^ 0.04 gallons per mile 550 gallons gasoline ^The emission factors used here come from standard EPA emission models. They assume an “average,” properly maintained car or truck on the road in 1997, operating on typical gasoline on a summer day (72° to 96°F). Emissions may be higher in very hot or very cold weather. ^Fuel consumption is based on average in-use passenger car fuel economy of 22.5 miles per gallon and average in-use light truck fuel economy of 15.3 miles per gallon. Source: DOT/FHA, Highway Statistics (1995). ^Total net imports as a share of petroleum consumption reached a record high of 51 percent in 1998. Source: U.S. Energy Information Administration, 1998. Source: U.S. Environmental Protection Agency (1997, p. 1)

Table 4 displays the annual emissions and fuel consumption for an average passenger car.

Efforts are underway to limit the impact that our materials use has on the environment. Increased environmental awareness has resulted in individual citizens, local organizations, corporations, and governments all working to decrease emis­sions to the environment. Regulations have been enacted to reduce air pollution, for example. Source reduction, switching to less environmentally harmful alternatives, recycling, and just plain doing without have decreased the impact of ourmaterials use on the environment.

According to the U.S. Environmental Protection Agency (1998):

The improvements in air quality and economic prosperity that have occurred since EPA initiated air pollution control programs in the early 1970’s illustrate that economic growth and environmental protection can go hand-in-hand. Since 1970, national total emissions of the six “criteria pollutants” (carbon monoxide, lead, nitrogen dioxide, ground-level ozone, particulate matter, and sulfur dioxide) declined 31 percent, while U.S. population increased 31 percent, gross domestic product increased 114 percent, and vehicle miles traveled increased 127 percent.

According to the US Environmental Protection Agency, driving a car is probably a typical citizen’s most “polluting” daily activity (source: Microsoft Corp., 2000)

Even though the emissions of these six “criteria air pollut­ants” have declined, overall, the present situation appears to indicate that the absolute quantity of residuals entering the environment will increase as our use of materials increases unless our material-use preferences or methods to produce and use goods are modified. Increased recycling is one option to potentially reduce the quantity of residuals (wastes and emis­sions) created per unit of material flow. Decreases in the rate of goods turnover are possible, and the potential for processes that emit fewer residuals also exists. Productive uses for flows that are now considered residuals are also possible. All of these hold promise for decreasing the impact our materials use is having on the environment.

Excluding questions of energy availability and possible resource scarcity for some commodities, the magnitude of the flow of material in the economy is not a problem if the absolute quantity of residuals released to the environment does not exceed the environment’s ability to absorb these residuals.

## Conclusion

The flows of materials generated in the world economy significantly affects peoples lives and the global environment. As population increases and people all over the world strive for a rich material life, the world is altered, wastes are generated, and the landscape is modified at a scale that is unprecedented.

In order to meet the people’s future material needs, resources must be used wisely and impacts to the environment need to be minimized. There are many steps that can be taken, and many that have already been taken, to continue satisfying society’s material needs and desires.

It is no easy feat to supply society’s needs and desires without causing some damage to something somewhere. Building a road displaces native animals that inhabit the land. Building a dam changes fish habitats. Building a house means cutting down trees. Certain resources are required and always will be required. The challenge, then, is to find ways to satisfy society’s needs sensibly, with an eye toward balancing material needs with their potential impact on the world’s life-support systems and with the environmental values society holds.

## Notes

1. ^ New materials in this report refers to newly produced materials—either by the extraction of resources, or by recycling—lowing into the economy. It does not include, for example, an automobile purchased in prior years that is still in use.
2. ^ In this report, all reference to tons are metric tons, unless otherwise stated.
3. ^ Organic materials are derived from feedstocks of petroleum (including natural-gas liquids), dry natural gas, and coal for nonfuel applications. This includes resins used in the production of plastics, synthetic fibers, and synthetic rubber; feedstocks used in the production of solvents and other petrochemicals; lubricants and waxes; and asphalt and road oil.
4. ^ Scrap that results from the manufacturing process, including metal and alloy production. New scrap of aluminum, copper, lead, tin and zinc excludes home scrap. Home scrap is scrap generated in the metal-producing plant.
5. ^ Scrap that results from consumer products.
6. ^ Metal recovered from new plus old scrap.
7. ^ Apparent supply is production plus net imports plus stock changes. Production is primary production plus recycled metal. Net imports are imports minus exports. Apparent supply is calculated on a contained weight basis.
8. ^ Scrap quantity is the calculated metallic recovery from purchased new and old aluminum-based scrap, estimated for full industry coverage.
9. ^ Chromium scrap includes estimated chromium content of stainless steel scrap receipts (reported by the iron and steel and pig-iron industries) where chromium content was estimated to be 17 percent. Trade includes reported or estimated chromium content of chromite ore, ferrochromium, chromium metal and scrap, and a variety of chromium-containing chemicals. Stocks include estimated chromium content of reported and estimated producer, consumer, and Government stocks.
10. ^ Includes copper recovered from unalloyed and alloyed copper-based scrap, as refined copper or in alloy forms, as well as copper recovered from aluminum-,
nickel-, and zinc-based scrap.
11. ^ Iron production measured as shipments of iron and steel products plus castings corrected for imported ingots and blooms. Secondary production measured as reported consumption. Apparent supply includes production of raw steel.
12. ^ Lead processors are segregated by primary and secondary producers. This segregation permits inclusion of stocks changes for secondary producers.
13. Americans recycle 2 of 3 aluminum cans: Aluminum Association, Inc Includes magnesium content of aluminum-based scrap.
14. Industry facts—The aluminum can: Aluminum Association, Inc Percent recycled based on titanium scrap consumed divided by primary titanium sponge metal and scrap consumption.

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### Citation

Survey, U. (2012). Materials and the economy: flows, scarcity and the environment. Retrieved from http://www.eoearth.org/view/article/154515