Materials in the Economy 

Material Flows, Scarcity, and the Environment 

U.S. Department of the Interior 

U.S. Geological Survey 

U.S. Geological Survey Circular 1221 
Materials in the Economy—
 

Material Flows, Scarcity, and the Environment
 

By Lorie A. Wagner

U.S. Geological Survey Circular 1221

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

First printing February 2002
 

Free on application to U.S. Geological Survey, 
 

Information Services
 

Box 25286, Denver Federal Center
 

Denver, CO 80225
 

For more information about the USGS and its products:
 

Telephone: 1-888-ASK-USGS
 

World Wide Web: http://www.usgs.gov/
 

This publication is also available online at:

http://geology.cr.usgs.gov/pub/circulars/c1221/

Any use of trade, product, or firm names in this publication

is for descriptive purposes only and does not

imply endorsement by the U.S. Government
III
 

Contents

Introduction ................................................................................................................................................... 1
 

Materials in the Economy............................................................................................................................ 2
 

Sidebar: Consumption and Use of Materials .................................................................................. 5
 

Material Flows............................................................................................................................................... 9
 

Sidebar: The Need for Data ............................................................................................................. 10
 

Sidebar: Mercury Materials Flow .................................................................................................. 11
 

Scarcity ........................................................................................................................................................ 14
 

Sidebar: Recycling Statistics........................................................................................................... 16
 

Environment................................................................................................................................................. 18
 

Sidebar: Point and Nonpoint Sources of Contamination—Industrial and Natural................. 21
 

Sidebar: Are Electric Vehicles the Answer? ................................................................................. 23
 

Sidebar: Sulfur—A Materials-Flow Analysis................................................................................ 24
 

Conclusions ................................................................................................................................................. 28
 

References Cited ........................................................................................................................................ 28
 

Figures

1. Graph showing world population growth from 1950 to 2000 ................................................. 2
 

2. Flowchart showing materials flow cycle.................................................................................. 3
 

3–4. Graphs showing:
 

3.	 Percentage, by weight, of renewable and nonrenewable materials 
 

used in the United States from 1900 to 2000.................................................................. 3
 

4. U.S. flow of raw materials by weight, 1900–2000 ......................................................... 4
 

5. Pie chart showing U.S. flow of raw materials by weight, 1950 and 2000 ............................ 7
 

6.	 Graph showing U.S. net import reliance for selected nonfuel mineral 
 

materials in 2000 ........................................................................................................................... 8
 

7–9. Flowcharts showing:

7. Generalized commodity flow cycle................................................................................. 9
 

8. Domestic flow of mercury, 1996 .................................................................................... 12
 

9. Domestic product flow of mercury through end uses, 1996..................................... 13
 

10. Graph showing reported U.S. industrial consumption of mercury, 1970–97..................... 14
 

11.	 Diagram showing pathways for mineral-based materials to enter 
 

the environment.......................................................................................................................... 19
 

12.	 Bar graph showing number of motor vehicles, by world region, in 1980, 
 

1990, and 1996.............................................................................................................................. 20
 

13. Graph showing trends in sulfur production in the United States, 1978–2000................... 25
 

14. Flowchart showing sulfur cycle in the environment ............................................................ 27
 
IV
 

Tables

1. Salient U.S. recycling statistics for selected metals, 2000.................................................. 17
 

2.	 Generation, materials recovery, composting, and discards of 
 

municipal solid waste, 1960–99................................................................................................ 17
 

3. Generation and recovery of materials in municipal solid waste, 1999.............................. 18
 

4. Annual emissions and fuel consumption for an average U.S. passenger car................. 21
 

Conversion Factors

Conversion factors for SI (metric) and inch/pound (U.S. customary) units of measurement. 

 Multiply By To obtain 

 mile 1.609 kilometer 

 gallon 3.785 cubic decimeter 

 pound avoirdupois 0.4536 kilogram 

 ton, short (2,000 pounds) 0.9072 metric ton 
Materials in the Economy—
 

Material Flows, Scarcity, and the Environment
 

By Lorie A. Wagner 

Introduction 

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) (U.S. Bureau of Labor 

Statistics, 2000; International Monetary Fund, 1980, 2001). 

Meanwhile, U.S. population increased from 152 million in 

1950 to 281 million in 2000 (International Monetary Fund, 

1980, 2001). As shown in figure 1, by 2000, world population 

was more than 6 billion (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. 

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 materialsflow 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. 

Understanding materials use and its impacts is increasingly important because the global environment is being 

Vast amounts of goods are available for consumers to purchase 

(source: Brøderbund Software, Inc., 1997). 

1 
2 Materials in the Economy—Material Flows, Scarcity, and the Environment 

7000 

6000 

5000 

4000 

3000 

2000 

1000 

0
 

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
 

YEAR 

Figure 1. By 2000, world population was more than 6 billion (U.S. Census Bureau, 2001). WORLD POPULATION, IN MILLIONS 

Europe 

Asia and Oceania 

Africa 

North America 

South America 

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. 

Growing populations and urban sprawl affect the environment 

(source: Brøderbund Software, Inc., 1997). 

Technological improvements, and increased understanding of environmental impacts 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 

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 mineralbased products manufactured in the United States during 2000 

was estimated to be $429 billion. Imports of raw and processed 
Materials in the Economy 3 

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. 

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 (U.S. Geologi• 

cal Survey, 2001a, p. 6). 

Since the beginning of the 20th century, the types of 

materials used in the United States have changed signiÞcantly. 

In 1900, on a per-weight basis, 41 percent of the new1 materi• 

als used domestically were renewable, as shown in Þgure 3 

(Matos and Wagner, 1998, Þg. 2). 

By the end of the 20th century, only 5 percent of the 

3,400 million tons2 of new materials entering the U.S. econ• 

omy in 2000 were renewable. Of all the materials used during 

1

New materials in this report refers to newly produced materials—either 

by the extraction of resources, or by recycling—flowing 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. 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 

Renewable materials 

Nonrenewable materials 

YEAR 

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 (modified from Matos and 

Wagner, 1998, fig. 2). PERCENTAGE OF TOTAL MATERIALS USED, ON A PER-WEIGHT BASIS 
4 Materials in the Economy—Material Flows, Scarcity, and the Environment 

selves, 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 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 

The production of metals and minerals play a vital role in the econo- and 1960’s, it shifted toward a service economy. These trends 

mies of the United States and the world (source: Brøderbund Soft- changed the mix of materials used, as shown in figure 5, and 

ware, Inc., 1997). were accompanied by automation, computerization, electrification, more extensive processing, high-speed transport, miniathis century, more than half were used in the last 25 years turization, and sophisticated technology. The data and detailed 

(Matos and Wagner, 1998, p. 107). descriptions about the data and trends have been described by 

Renewable resources are those that regenerate them- Matos and Wagner (1998, p.109–113). 

4000 

3500 

3000 

2500 

2000 

1500 

1000 

500 

0 

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 

YEAR 

World 

War I 

World 

War II 

Agricultural and 

forest products 

Nonrenewable 

organics 

Crushed stone, 

sand, and gravel 

Oil 

crisis 

Recession 

Industrial 

minerals 

Primary 

metals 

Recycled 

metals 

Great 

Depression 

U.S. RAW MATERIALS FLOW, IN MILLIONS OF METRIC TONS 

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). 
Materials in the Economy 5 

Consumption and Use of Materials 

“Consumption” refers to the use of the services that goods, made from materials, 

provide. It means the destruction of the economic value added to a product, through 

design for example, not necessarily the destruction of the materials of which the product 

is composed. For example, consumers purchase items such as automobiles, clothing, 

electricity, housing, and refrigerators. When a new automobile is purchased, both the 

materials of which the automobile is physically composed and the assembly of these 

materials into a working automobile is purchased, but, more important, the services of 

transportation that the automobile provides is acquired. When the automobile reaches the 

end of its useful life and is no longer able to provide reliable transportation, the materials 

of which the automobile is composed are available to be transformed or recycled into 

other useable products. Therefore, although the use of materials is generally referred to as 

consumption, in many cases, the materials remain after the end of the useful life of the 

product to be reused or recycled into new products. 

In 2000, 95 percent of all automobiles that had reached the end of their useful 

life were recycled (Steel Recycling Institute, 2001, photo source: Brøderbund 

Software, Inc., 1997). 

Through use, some products are dissipated. That is, the materials of which they are 

made are not available for recycling at the end of the product’s useful life. An example of 

a dissipative use in an automobile is a brake lining. Over time much of the brake lining 

wears away, with the resulting small particles being dropped along roadsides. Whereas 

the remnant of the worn down brake lining is available for recycling, the worn away 

portion is not. 
6 Materials in the Economy—Material Flows, Scarcity, and the Environment 

A new automobile, for statistical purposes, is considered “consumed” in the year it is 

purchased by a consumer and driven off the showroom floor, even though it will provide 

many years of service. This statistical accounting is used for other commodities as well. 

For example, large quantities of cement, sand and gravel, and stone were “consumed” in 

the construction of the Hoover Dam (built from 1931 to 1936). The Hoover Dam is still 

providing its intended services today. The same can be said of such American icons as 

the Golden Gate Bridge (constructed 1933–37), the Statue of Liberty (erected 1885–86), 

and the Empire State Building (constructed 1930–31). Infrastructure (bridges, buildings, 

highways, etc.) may last 35, 50, or 100 years or more. In such cases, the use of materials 

today is an investment for tomorrow. 

The Golden Gate Bridge, constructed in the 1930’s, still serves the needs of 

society (source: Microsoft Corp., 2000). 

Consumption and Use of Materials—Continued

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 (Tepordei, 1999). 

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. Industrialmineral 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 (Aluminum Association, Inc., 2001a) and 45 percent of paper were 

recovered for recycling (American Forest & Paper Association, 

2001). The 2000 recycling rates for steel-containing products 
Materials in the Economy 7 

1950 

Crushed stone, 

sand, and gravel 

62% 

minerals 3% 

Nonrenewable 

organics 

8% 

Metals 

10% 

Agricultural 

and forest 

products 

17% 

Industrial 

2000 

Crushed stone, 

sand, and gravel 

75% 

4% 12% 5% 

Industrial 4% Nonrenewable Agricultural 

minerals Metals organics and forest 

products 

Figure 5. U.S. flow of raw materials by weight, 1950 and 2000. The mix 

of materials consumed from 1950 to 2000 has changed. 

were 84.1 percent for appliances, 95.0 percent for automobiles, 

and 58.4 percent for steel cans (Steel Recycling Institute, 

2001). 

Nonrenewable organic material3 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 

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. 

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. 

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). 
8 Materials in the Economy—Material Flows, Scarcity, and the Environment 

2000 U.S. NET IMPORT RELIANCE FOR SELECTED 

Trinidad and Tobago, Canada, Mexico, Venezuela
 21 

Canada, China, Spain, Venezuela
 20 

Canada, Brazil, Venezuela, Australia
 19 

European Union, Canada, Japan, Mexico
 17 

Canada, India, Finland, Japan
 17 

Greece
 15 

Canada, Chile, Mexico, The Bahamas
 15 

China, Canada, France, Japan
 12 

Canada, Belgium, Australia
 6 

Morocco
 1 

1

In descending order of import share 

Additional mineral commodities for which there is some import dependency include: 

Gallium France, Russia, Kazakhstan, Canada Rhenium Chile, Germany, Kazakhstan, Russia
 

Germanium Russia, Belgium, China, United Kingdom Selenium Philippines, Canada, Belgium, Japan
 

Indium Canada, China, Russia, France Vanadium South Africa, China
 

Mercury Canada, United Kingdom, Kyrgyzstan, Spain 	 Vermiculite South Africa, China
 

Zirconium South Africa, Australia 

Figure 6. 2000 U.S. net import reliance for selected nonfuel mineral materials (U.S. 

Geological Survey, 2001a, p. 5.) 

ARSENIC TRIOXIDE 

ASBESTOS 

BAUXITE and ALUMINA 

COLUMBIUM (niobium) 

FLUORSPAR 

GRAPHITE (natural) 

MANGANESE 

MICA, sheet (natural) 

QUARTZ CRYSTAL 

STRONTIUM 

THALLIUM 

THORIUM 

YTTRIUM 

GEMSTONES 

BISMUTH 

ANTIMONY 

TIN 

PLATINUM 

STONE (dimension) 

TANTALUM 

CHROMIUM 

TITANIUM CONCENTRATES 

COBALT 

RARE EARTHS 

BARITE 

POTASH 

IODINE 

TUNGSTEN 

TITANIUM (sponge) 

ZINC 

NICKEL 

PEAT 

SILVER 

SILICON 

DIAMOND (dust, grit, and powder) 

MAGNESIUM COMPOUNDS 

MAGNESIUM METAL 

COPPER 

BERYLLIUM 

ALUMINUM 

PUMICE 

LEAD 

GYPSUM 

SULFUR 

NITROGEN (fixed), AMMONIA 

CEMENT 

IRON ORE 

IRON and STEEL 

MICA, scrap and flake (natural) 

PERLITE 

SALT 

TALC 

CADMIUM 

PHOSPHATE ROCK 

NONFUEL MINERAL MATERIALS 

Commodity1 Major Import Trade Sources (1996–99) Percent 

China, Chile, Mexico
 100 

Canada
 100 

Australia, Guinea, Jamaica, Brazil
 100 

Brazil, Canada, Germany, Russia
 100 

China, South Africa, Mexico
 100 

China, Mexico, Canada
 100 

South Africa, Gabon, Australia, France
 100 

India, Belgium, Germany, China
 100 

Brazil, Germany, Madagascar
 100 

Mexico, Germany
 100 

Belgium, Canada, Germany, United Kingdom
 100 

France
 100 

China, Hong Kong, France, United Kingdom
 100 

Israel, India, Belgium
 99 

Belgium, Mexico, United Kingdom, China
 95 

China, Mexico, South Africa, Bolivia
 94 

China, Brazil, Peru, Bolivia 
 86 

South Africa, United Kingdom, Russia, Germany
 

Italy, Canada, Spain, India
 

Australia, China, Thailand, Japan
 

South Africa, Kazakhstan, Russia, Zimbabwe
 

South Africa, Australia, Canada, India
 

Norway, Finland, Zambia, Canada
 

China, France, Japan, United Kingdom
 

China, India, Mexico, Morocco
 

Canada, Russia, Belarus
 

Chile, Japan, Russia
 

China, Russia, Bolivia
 

Russia, Japan, Kazakhstan, China
 

Canada, Mexico, Peru
 

Canada, Norway, Russia, Australia
 

Canada
 

Canada, Mexico, Peru
 

Norway, South Africa, Russia, Canada
 

Ireland, China, Russia
 

China, Canada, Austria, Australia
 

Canada, Russia, China, Israel
 

Canada, Chile, Mexico
 

Russia, Canada, Kazakhstan, Germany
 

Canada, Russia, Venezuela, Mexico
 

Greece, Turkey, Ecuador, Italy
 

Canada, Mexico, Peru, Australia
 

Canada, Mexico, Spain
 

Canada, Mexico, Venezuela
 

83 

80 

80 

78 

76 

74 

72 

71 

70 

69 

68 

62 

60 

58 

52 

52 

48 

47 

45 

40 

37 

35 

33 

33 

24 

22 

22 
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. 

Ore and finished product Semi-manufactured 

Material Flows 9 

The analysis of materials flow can lead to improvements 

in product design, technological innovation that increases the 

efficiency of resource use, better waste-management 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 (Rogich, 1996, p. 208). 

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 

POST CONSUMPTION 

Concentrates 

Animal 

Vegetable 

Mineral 

Gases 

Primary 

Coproduct 

Byproduct 

products 

ENVIRONMENT 

INCINERATION 

Quaternary 

recycling 

DISPOSAL 

RECYCLE 

Secondary 

recycling 

RECYCLE 

Tertiary 

recycling 

LANDFILL 

COMPOST 

EXPORTS 

EXPORTS 

IMPORTS 

IMPORTS 

CONSUMPTION 

INVENTORY 

CHANGES 

SUPPLY 

SOURCES PRODUCTION PROCESSING FABRICATION

SCRAP 

Primary recycling 

Atmospheric emissions generated 

Solid waste discharge 

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 (Kostick, 1996, p. 213). 
10 Materials in the Economy—Material Flows, Scarcity, and the Environment 

Ships, such as the one shown here unloading containers, transport goods to and from the United 

States (source: Brøderbund Software, Inc., 1997). 

The Need for Data 

Inherent in materials-flow analyses is the need for reliable, consistent data. As stated 

by the U.S. Interagency Working Group on Industrial Ecology, Material and Energy Flow 

(2000, p. 78–79): 

Data collected by Federal Agencies on consumption of commodities, use of energy resources, 

and industrial and municipal waste generation provide an essential base for analyzing the flow 

of physical materials through the U.S. economy. Data on environmental emissions (urban air 

quality, toxic releases, etc.) reveal trends in the environmental performance of U.S. industry, as 

well as the efficacy of policies to reduce air and water pollution. Federal Agencies also provide 

geological data on the U.S. land mass and scientific information on the geographic extent and 

impact of human activities on the landscape. 

National-level information is useful for an overview and a sense of the trends, problems and 

opportunities in materials and energy flows. Information needed to support decision-making 

is most useful when disaggregated to a regional, local, industry sector or enterprise level. 

This level of detail in the gathering and analysis of data can be expensive but is necessary 

to support informed decisions and more efficient use of energy and materials with less 

environmental degradation. 
Material Flows 11 

use but that do not enter into the statistics normally associated support the construction of buildings, dams, and highways. 

with materials usage. Examples of these hidden flows include In order to better understand the impact that our use 

materials such as mine tailings, which remain after the ore is of materials can have, material-flow studies target specific 

extracted, and earth and stone that are moved to make way for or substances, such as mercury. 

Trucks, such as the one shown here, transport vast quantities of the materials used within the United 

States. In 1997, in terms of value of shipments and tons, trucks transported approximately 70 percent 

of all goods transported (U.S. Census Bureau, 1999, p. 9) (photo source: Lorie Wagner). 

Mercury Materials Flow 

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 (Carrico, 1985, p. 506). 

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. 
12 Materials in the Economy—Material Flows, Scarcity, and the Environment 

Mercury Materials Flow—Continued

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. 

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 anthropogenic mercury 

emissions (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. 

Figure 8. Domestic flow of mercury, 1996. Numbers are in metric tons (Sznopek and Goonan, 

2000, p. 5). 
Material Flows 13
 

Mercury Materials Flow—Continued

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. 

Figure 9. Domestic product flow of mercury through end uses, 1996. Numbers are in metric tons 

(Sznopek and Goonan, 2000, p. 7). 

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. 
14 Materials in the Economy—Material Flows, Scarcity, and the Environment 

YEAR 

U.S. INDUSTRIAL CONSUMPTION OF MERCURY, 

IN METRIC TONS 

1970 

0 

500 

1000 

1500 

2000 

2500 

1975 1980 1975 1990 1995 

Other 

Dental 

Instruments 

Batteries 

Switches 

Lighting 

Laboratory 

Paint 

Chlor-alkali 

EXPLANATION 

Figure 10. Reported U.S. industrial consumption of mercury, 1970–97 (Sznopek and Goonan, 2000, 

p. 4). 

Mercury Materials Flow—Continued

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 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 resource depletion 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 (Tilton, 1996). 

Is the potential scarcity of resources an issue? Although 

As populations continue to expand, more pressures are placed on 

natural resources (source: Brøderbund Software, Inc., 1997). 

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, 
Scarcity 15 

One of the concerns over our increasing usage of materials is 

whether adequate resources will be available for future generations 

(source: Cheryl Bloomquist, Duluth, Minn.). 

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. 

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 (U.S. Bureau of Mines, 1990). 

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 

(Aluminum Association, Inc., 2001b). 

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 (Wilburn and Wagner, 1993). 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 (U.S. 

Geological Survey, 2001b, p. 62.1). 

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 (U.S. Environmental Protection Agency, 1999, p. 7). 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 warrantees. 

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. 
16 Materials in the Economy—Material Flows, Scarcity, and the Environment 

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 (Goonan, 

1999). 

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 singlefamily home was 1,905 ft2, but by 2000 it had risen to 2,273 ft2 

(National Association of Home Builders, 2001). 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? 

Recycling rates can be measured at various points, for example at the industrial 

phase where the product is being produced, after the product is used, or at different 

collection points—residential, commercial, and institutional. Below are two examples of 

recycling rates in the United States. 

Metals 

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 U.S. 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 

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 municipal solid waste 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 
Scarcity 17 

Table 1. Salient U.S. recycling statistics for selected metals, 2000. 

[In metric tons and percent recycled for each material. Data are rounded to three significant digits; may not add to totals shown. NA, not available; W, data 

withheld to avoid disclosing company proprietary data. Source: J.F. Papp (written commun., November 5, 2001)] 

Commodity Recycled from Recycled from Recycled3 Apparent Percentage 

new scrap1 old scrap2 supply4 recycled 

Aluminum5 2,080,000 1,370,000 3,450,000 9,610,000 36 

Chromium6 NA NA 139,000 589,000 24 

Copper7 956,000 353,000 1,310,000 4,080,000 32 

Iron and steel8 NA NA 74,000,000 134,000,000 55 

Lead9 35,400 1,080,000 1,120,000 1,790,000 63 

Magnesium10 52,200 30,100 82,300 209,000 39 

Tin 8,450 6,600 15,100 52,100 29 

Titanium11 NA NA 18,500 W 50 

Zinc 369,000 66,900 436,000 1,610,000 27 

1Scrap 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. 

2Scrap that results from consumer products. 

3Metal recovered from new plus old scrap. 4Apparent 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. 

5Scrap quantity is the calculated metallic recovery from purchased new and old aluminum-based scrap, estimated for full industry coverage. 

6Chromium 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. 7Includes 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. 

8Iron 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. 

9Lead processors are segregated by primary and secondary producers. This segregation permits inclusion of stocks changes for secondary producers. 10Includes magnesium content of aluminum-based scrap. 11Percent recycled based on titanium scrap consumed divided by primary titanium sponge metal and scrap consumption. 

Table 2. Generation, materials recovery, composting, and discards of municipal solid waste, 

1960–99. 

[In pounds per person per day; population in thousands. From U.S. Environmental Protection Agency (2000, 

p. 2)] 

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 

composting1 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 

1Composting of yard trimmings and food wastes. Does not include mixed municipal solid waste composting 

or backyard composting. 
18 Materials in the Economy—Material Flows, Scarcity, and the Environment 

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. 

Recycling Statistics—Continued

Table 3. Generation and recovery of materials in municipal solid 

waste, 1999. 

[Includes wastes from residential, commercial, and institutional sources. 

Negligible, less than 50,000 short tons or 0.05 percent. From U.S. 

Environmental Protection Agency (2000, p. 6)] 

Weight Recovery 

Material generated (% of generation) 

(millions of short tons) 

Paper and paperboard 87.5 41.9 

Glass 12.6 23.4 

Metals 

Steel 13.3 33.6 

Aluminum 3.1 27.8 

Other nonferrous metals1 1.4 66.9 

Total metals 17.8 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 56.3 23.3 

Food, other2 25.2 2.2 

Yard trimmings 27.7 45.3 

Misc. inorganic wastes 3.4 Negligible 

1Includes lead from lead-acid batteries. 2Includes recovery of paper for composting. 

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, soil, surface water, and ground 

water; and small amounts of mineral-based materials are considered essential for plants, animals, and humans. 

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. 

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 elements 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 
Environment 19 

According to the US Environmental Protection Agency, driving a car 

is probably a typical citizen’s most “polluting” daily activity (source: 

Microsoft Corp., 2000). 

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. 

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 (Gough, 1993, p. 3). 

Natural sources of toxic substances include rocks, volcanoes, sediments, and soil. For example, sedimentary rocks 

in central Oklahoma contaminate ground water with arsenic, 

chromium, selenium, and uranium. 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 (Gough, 1993, 

p. 3). 

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 

Inhalation

Absorption

Ingestion

Decay 

Evaporation

Decay 

Condensation Chemical/ 

Sedimentation 

biological 

reactions 

Solution

Precipitation

Evaporation 

Sedimentation

Weathering 

Decay 

Chemical/biological reactions SOIL SEDIMENT 

ROCKS 

ATMOSPHERE 

BIOSPHERE HYDROSPHERE

Figure 11. Mobile metal pathways. The diagram shows pathways for 

mineral-based materials to enter the environment (Board, 1996). 

Natural. environments may be at risk of negative environmental 

impacts as a result of our materials consumption (source: Brøderbund 

Software, Inc., 1997). 
20 Materials in the Economy—Material Flows, Scarcity, and the Environment 

with air pollution. But in numerous cities across the country, ness has resulted in individual citizens, local organizations, 

the personal automobile is the single greatest polluter, as emis- corporations, and governments all working to decrease emissions from millions of vehicles on the road add up. Driving sions to the environment. Regulations have been enacted to 

a private car is probably a typical citizen’s most ‘polluting’ reduce air pollution, for example. Source reduction, switching 

daily activity.” to less environmentally harmful alternatives, recycling, and 

Since the 1970 census year, the American population has just plain doing without have decreased the impact of our 

increased by one-third, but the number of motor vehicles on materials use on the environment. 

the road—cars, trucks, buses, and motorcycles—has nearly According to the U.S. Environmental Protection Agency 

doubled (Anderson, 1999). Figure 12 shows the number of (1998): 

motor vehicles in various countries of the word. The improvements in air quality and economic prosperity that Table 4 displays the annual emissions and fuel consump- have occurred since EPA initiated air pollution control programs tion for an average passenger car. in the early 1970’s illustrate that economic growth and environEfforts are underway to limit the impact that our materials mental protection can go hand-in-hand. Since 1970, national 

use has on the environment. Increased environmental aware- total emissions of the six “criteria pollutants” [carbon monoxide, 

EXPLANATION 

West Asia 

North America Total = 676.2 

6.4 

Latin America and the Caribbean 

Europe and Central Asia 

Asia and the Pacific 

223.2 

Africa Total = 541.7 

5.5 

208.6 

44.2 

Total = 391.1 

2.3 

32.3 

184.7 

256.5 

191.0 

17.4 

129.1 

127.3 

93.2 

52.3 

5.3 11.1 18.6 

1980 1990 1996 

NUMBER OF MOTOR VEHICLES, BY REGION, IN MILLIONS 

Figure 12. The number of motor vehicles in the world has nearly doubled in the last 16 years, 

from 391.1 million in 1980 to 676.2 million in 1996. Transportation now accounts for one-quarter of 

world energy use and about one-half of the world’s oil production (United Nations Environment 

Programme, 1999). 
Environment 21 

Table 4. Annual emissions and fuel consumption for an average U.S. passenger car. 

[Values are averages. Estimated mileage is 12,500 miles per year. Individual vehicles may travel more or less 

miles and may emit more or less pollution per mile than indicated here. Emission factors and pollution/fuel 

consumption totals may differ slightly from original sources due to rounding. From U.S. Environmental 

Protection Agency (1997, p. 1)] 

Pollutant and problem Amount

1 Pollution or 

fuel consumption2 

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 3 .....................0.04 gallons per mile...............550 gallons gasoline 

1The 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. 2Fuel 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). 3Total net imports as a share of petroleum consumption reached a record high of 51 percent in 1998. Source: 

U.S. Energy Information Administration, 1998. 

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. 

Even though the emissions of these six “criteria 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. 

Point and Nonpoint Sources of Contamination— 

Industrial and Natural 

—From Gough (1993, p. 27–29): 

Point-source pollution 

Point-source pollution comes from a single source located in a small area such as a factory, 

power plant, or natural spring. There are many types of point-source pollution that degrade 

the quality of water, air, and soils. Examples include emissions of particulates and acidic 

gases into the atmosphere from active volcanoes, metalliferous springs whose waters have 
22 Materials in the Economy—Material Flows, Scarcity, and the Environment 

interacted with unmined mineral deposits, natural oil seeps, and acid-mine drainage from mine 

and mill tailings. If pollutants are released underground, then they can contaminate the ground 

water and the rock aquifers through which the ground water flows. 

Air pollution can arise from activities such as power generation, mineral smelting, or industrial 

processing. Solid particles (particulates) generated by these sources can degrade air quality 

and visibility, and gases released from these sources (such as sulfur dioxide and various 

nitrogen gases) can react with atmospheric water to generate rain that is acidic or that has 

other chemically hazardous qualities. 

Soil pollution can result from both air- and water-based pollution. For example, high concentrations of heavy metals can be found in soils near smelters and in soils through which metalbearing surface waters or ground waters have flowed. 

To effectively clean up sites that have been affected by point-source pollution, it is necessary 

to understand the geochemical processes that control how the pollutants interact with the 

environment. 

The following two USGS activities involving both general research and specific site studies 

help address the geochemical behavior of natural and human (anthropogenic) point-source 

contaminants. 

In Hawaii, USGS scientists are examining the origin of natural, volcano-related, acidic aerosols 

in the atmosphere, which can cause respiratory problems among island inhabitants. Chemical 

and isotopic data on the aerosols show whether they resulted from the interactions of molten 

lava from the Kilauea Volcano with sea water or from the reaction of sulfur dioxide of volcanic 

origin with moisture in the atmosphere. By understanding the origin of the aerosols, health 

officials can recommend measures to help humans avoid contact with the aerosols. 

Another study showed that springs in areas of uranium-rich bedrock can be local point 

sources of dissolved uranium. The uranium is dissolved during normal weathering of uraniumrich rocks and can be reconcentrated onto organic matter as the springs emerge in organicrich soils or wetlands. The following is an example of one such uranium-bearing spring that 

enters a wetland in the Colorado Rocky Mountains. The natural spring waters that help 

sustain this wetland contain 30 to 80 parts per billion (ppb) uranium compared to a regional 

background value of less than 5 ppb. The concentration of dissolved uranium by peat is very 

efficient and produces haloes (peat regions that are high in uranium) in the immediate vicinity 

of the emergent source springs. Dried samples of peat collected near the spring pools contain 

as much as 3,000 parts per million uranium, which represents up to a 100,000-fold concentration. This direct observation of the extraction of uranium by peat provides another example of 

how wetlands can improve water quality through their metal-sorption capabilities. 

Nonpoint-Source Pollution 

Nonpoint-source contamination has no single, clearly defined source area and can result from 

both natural and human-induced processes. The most commonly studied are those either 

introduced or exacerbated by human activities. Agriculture is an important nonpoint source 

of contamination. This is a result of two generalized activities—leaching of contaminants that 

man has added to the soil or the crops, such as organic herbicides or pesticides and nitrates 

or phosphates from fertilizers, and leaching of naturally occurring pollutants in the soil, chiefly 

as the result of irrigation, which are then concentrated to abundances incompatible with plant 

or animal life. 

Point and Nonpoint Sources of Contamination— 

Industrial and Natural—Continued
Environment 23
 

The role of the USGS in the study of nonpoint-source pollution studies is focused on its 

ability to understand the chemical and physical processes controlling the pollutants in the 

environment. The definition of base-lines in agricultural and native soils and parent material 

has helped define what the pollution source is, how large the source is, the associated 

elements, and what the controlling processes are. With the knowledge of source and controls, 

remediation steps can be effectively planned and implemented with minimal impact on human 

health. 

[One such example is uranium from marine deposits.] Marine shales and sandstones underlie 

large parts of the Western United States. Much of the uranium in these rocks is loosely bound 

and the rocks can weather under conditions typical of the semiarid West, [releasing uranium 

to the environment]. Irrigation can increase the natural loss of the uranium. 

Runoff from irrigation may directly reenter irrigation ditches for reuse. Local ponding of 

runoff waters or creation of waterlogged soils can also bring uranium and other elements to 

the surface, where they are concentrated by evaporation. Soils thus contaminated may be 

rendered unfit for cultivation. Additionally, uranium and other elements concentrated at the 

surface may be removed by rainfall runoff and carried downstream, thus contaminating waters 

far beyond the irrigated fields. 

Irrigation-return waters, regardless of the paths they have followed, may drain into their 

originating rivers via natural or artificial flow paths. Further downstream they may be taken out 

again and again for irrigation. When these waters become unfit for use on fields, they may be 

stored in permanent reservoirs and become more saline through further evaporation. These 

reservoirs may reach high levels of toxicity for animal or plant life. Towns and individuals may 

get their drinking water from aquifers that have been recharged, in part, by irrigation-return 

waters. 

Point and Nonpoint Sources of Contamination— 

Industrial and Natural—Continued

Are Electric Vehicles the Answer? 

—From U.S. Environmental Protection Agency (1994b): 

Electric vehicles are gaining attention as an option for improving air quality and lessening 

United States dependence on imported oil. Research and development is under way on 

advanced battery and fuel cell technology and automakers are stepping up efforts to design 

electric vehicles for fleets and personal use. Even though today’s technology is new, batterypowered vehicles have been around for a long time. Electrics flourished before the rise of 

the gasoline automobile and some 50,000 electric vehicles were in use in the United States 

by 1912. 

Electric vehicles are sometimes referred to as “zero-emission vehicles” because they produce 

essentially no pollution from the tailpipe or through fuel evaporation. This is important, for it 

means that the use of electric vehicles could greatly reduce emissions of carbon monoxide 

and smog-forming pollutants in cities with dirty air. 

While electric cars themselves are clean, generating the electricity to charge vehicle batteries 

produces air pollution and solid waste. If electric powerplants produce electricity using clean 

energy sources such as solar or hydropower, then emissions are negligible. But power plants 

which combust conventional fuels like coal (used for more than half of the electricity generated in the United States today) produce emissions such as particulate matter, sulfur oxides, 

nitrogen oxides, hydrocarbons, and carbon monoxide. These same plants also create carbon 

dioxide, a combustion product of all fossil fuels, which contributes to global warming. 
24 Materials in the Economy—Material Flows, Scarcity, and the Environment 

There are several factors that affect this pollution tradeoff. It may be easier to control pollution 

at a power plant than from individual vehicles. Power plants often are located outside major 

centers of urban air pollution, and finally, while only a fraction of today’s power plants use 

renewable resources (biomass, wind, geothermal, or solar power), electricity can be produced 

from these clean sources of energy. 

Potential health or safety risks associated with widespread electric vehicle use have not 

yet been fully evaluated. Many vehicle batteries contain toxic elements or produce toxic 

emissions, which could make battery production, transport, use, and disposal a significant 

solid waste issue. The United States must consider how to safely dispose of or recycle these 

batteries. 

What about hybrid electric vehicles? Hybrid electric vehicles have batteries to provide electric 

power but are also equipped with a small internal combustion engine (usually powered by 

gasoline). The engine provides a power boost and/or can be used to recharge the batteries, 

as pure electrics today simply cannot achieve the range, performance, or convenience of a 

modern gasoline car. Unfortunately, the extra engine substantially increases pollution from the 

vehicle, erasing many of the air quality benefits of pure electric vehicles. 

Are Electric Vehicles the Answer?—Continued

Sulfur—A Materials-Flow Analysis 

—From J.A. Ober (written commun., May 22, 2000): 

Through its major derivative, sulfuric acid, sulfur ranks as one of the more important 

elements used as an industrial raw material. In fact, consumption of sulfuric acid has 

been regarded as one of the best indexes of a nation’s industrial development. More 

sulfuric acid is produced in the United States every year than any other chemical (Ober, 

2000). The USGS collects, analyzes, and disseminates information on the domestic and 

international supply of and demand for sulfur. 

The sulfur industry is different from many other important modern mineral industries in that the disposal of excess supplies of sulfur is becoming a more important 

consideration than the question of how to sustain production. Unlike other industries 

that are searching for economical methods to produce a usable product from decreasing 

reserves and poorer grades of ore, sulfur producers must strive to find innovative uses 

for continually growing sulfur supplies. As environmental concerns increase, the trend 

is to minimize the effects of mining by recycling mineral materials or substituting with 

more environmentally friendly materials. For the sulfur industry, however, increased 

environmental awareness results in further increases in the sulfur supply and smaller 

increases in the demand for sulfur in many industrial processes. 

The unusual sulfur situation is a result of the changes of sulfur supply sources 

throughout the past 70 years. Whereas many mineral commodities are produced as a 

primary product from the mining of discreet ore bodies, or as desirable byproducts 

from mineral processing, the majority of sulfur produced is the result of environmental 

measures implemented to reduce emissions of sulfur dioxide into the atmosphere at 

petroleum refineries and nonferrous metal smelters and to remove poisonous hydrogen 

sulfide gas from natural gas deposits. Voluntary sulfur production, whether in the form 

of mined elemental sulfur or pyrites that are produced and burned to recover their sulfur 

content as sulfuric acid, has become continually less important in the global sulfur supply 

equation as shown in figure 13. 
Environment 25
 

The long-term prospect is that 90 percent or more of the world sulfur supply will 

come from environmentally regulated sources and that output from these sources will be 

produced regardless of world sulfur demand. As a result, new operations that produce 

sulfur as the primary product will probably not be developed, and more voluntary 

operations will be curtailed. In 2000, voluntary sources of production—Frasch-process 

sulfur, 

4 native sulfur, and pyrites—accounted for only 14 percent of the world output of 

about 57.2 million tons; in 1980, these same sources supplied 50 percent of the world 

production of 55.0 million tons. 

Voluntary production of sulfur should continue to decline, and recovered sulfur 

supply will continue to expand at a faster pace than demand. As more countries enact 

and enforce environmental legislation on a par with European and North American 

laws, tremendous new quantities of sulfur could be recovered. More stringent regulation 

and compliance will be long-term developments and cannot be quantified at this time, 

but changes are inevitable. In fact, the impact of projects to improve sulfur recovery, 

especially at copper smelters, is already being felt. 

Demand for sulfur has not kept up with production, creating a growing inventory of 

elemental sulfur globally. This situation is not expected to change significantly as long as 

most energy is produced from fossil fuels. Disposal of excess sulfur may become difficult 

if new high-volume uses for elemental sulfur are not implemented. 

Figure 13. Trends in sulfur production in the United States, 

1978–2000 (Ober, 2000, 2002). The Frasch process, used to mine native 

sulfur, is one in which superheated water is forced into the sulfur 

deposit for the purpose of melting the sulfur. Molten sulfur is then 

pumped to the surface. 

4

The Frasch process, used to mine native sulfur, is one in which superheated water is forced into the sulfur 

deposit for the purpose of melting the sulfur. Molten sulfur is then pumped to the surface. 

Sulfur—A Materials-Flow Analysis—Continued U.S. SULFUR PRODUCTION, IN MILLIONS OF METRIC TONS 

0 

2 

4 

6 

8 

10 

12 

14 

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 

YEAR 

* Includes 10 months of Frasch-process data for 1993; the other 2 months are 

included with recovered sulfur data to conform with proprietary data requirements. Data are estimates for 1994 through 2000. 

Total 

Recovered 

Frasch-process production*

Byproduct 
26 Materials in the Economy—Material Flows, Scarcity, and the Environment 

Global Sulfur Cycle 

When considering the materials flow of any mineral, the global cycle must be 

considered; the scope of the global sulfur cycle dwarfs those of most others. More than 50 

million tons of sulfur in all forms is produced annually worldwide for industrial consumption. The natural sulfur cycle is much harder to quantify but may be comparable in size. 

In addition, the burning of fossil fuels, especially coal, liberates tremendous quantities of 

sulfur dioxide, only some of which is recovered as byproduct sulfur compounds or waste 

material through gas-cleaning processes; the rest is released into the atmosphere. 

Although most chemical elements have a global cycle, the global sulfur cycle is 

unusually active and pervasive with inputs from natural and man-made sources. Much of 

the cycle is difficult to quantify. The amount of sulfur that is produced through mining 

or as environmental byproducts at oil refineries, natural gas processing plants, and nonferrous metal smelters is reasonably well defined, but the quantity of sulfur dioxide released 

from electric power plants and industrial facilities in developing countries is harder to 

measure. Estimates of sulfur emissions from natural sources are even more difficult to 

measure because of the variety of sources, variability of emissions over time, the wide 

range of compounds involved, and the difficulties in measuring in remote locations. 

The Natural Sulfur Cycle 

The natural sulfur cycle is extremely complex and difficult to measure. Sulfur is 

pervasive in nature; it is a component of many forms of rock; and it is found in most fossil 

fuels (in varying quantities in coal, crude oil, and natural gas). Sulfur is essential in all 

living things, both plants and animals (Moss, 1978, p. 23). 

Natural sources of sulfur include volcanoes, sea spray, organisms, and the weathering of sulfide minerals to sulfates, as shown in figure 14. Sulfates from the weathering 

of sulfide minerals can eventually reach the oceans through river runoff and erosion and 

become components of marine sediment. Other weathered sulfates react with bacteria to 

form compounds that are incorporated into the soil and plant systems. Animals may then 

ingest the plants and the sulfur compounds and are ultimately returned to the environment 

as sulfates (Moss, 1978, p. 27–29). 

Volcanoes are the most dramatic natural source of sulfur, emitting sulfur during 

eruptions and also during noneruptive periods of volcanic activity. Most volcanic emissions enter the atmosphere, but some—especially elemental sulfur deposits—are found 

surrounding the volcano. 

Seawater contains about 2.65 mg of sulfate per gram of water, and, as bubbles of 

seawater break, particles of sea salt are formed and emitted into the atmosphere. This sea 

spray is one of the largest sources of sulfur in the atmosphere, especially over open oceans. 

About 90 percent of this material is believed to cycle back into the oceans, with the remainder 

passing over the continents (Kellogg and others, 1972). The sulfate in seawater may come 

from weathered minerals discussed previously or through the decay of ocean organisms. 

One of the more recent estimates of natural sulfur sources in the atmosphere places 

the input for open-ocean biogenic production (derived from the physiological activities 

of organisms) at 46 percent of total natural sulfur in the atmosphere, volcanoes at 18 

percent; eolian (wind-raised) dust at 16 percent, terrestrial plants and soils at 13 percent, 

biomass burning at 4 percent, and coastal zone and wetland biogenic sources at 3 percent 

(Whelpdale, 1992, p. 6). 

Sulfur—A Materials-Flow Analysis—Continued
Environment 27
 

The Anthropogenic Sulfur Cycle 

The amount of sulfur entering the atmosphere through human activityÑthe anthro• 

pogenic sulfur cycleÑis easier to deÞne than the natural sulfur c ycle, but there remain 

signiÞcant uncertainties to its size in less developed areas of the world. The majority 

of anthropogenic sulfur emissions are in the form of sulfur dioxide resulting from the 

burning of fossil fuels (coal, petroleum, and natural gas) and the smelting of nonferrous 

metal ores and other industrial processes and burning (Whelpdale, 1992, p. 6). 

Globally, man-made sulfur inputs to the atmosphere began to increase signiÞcantly 

early in the 20th century and continued the trend until about the mid-1970Õs when 

environmental regulations in North America and Western Europe began to limit allowable 

sulfur emissions. 

Figure 14. Contributors of sulfur to the environment are many and diverse. Natural sources of sulfur 

include volcanoes, oceans, plants, and animals. The burning of fossil fuels provides most of the 

sulfur from industrial sources. 

Sulfur—A Materials-Flow Analysis—Continued
28 Materials in the Economy—Material Flows, Scarcity, and the Environment 

Conclusions 

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. 

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