Mass Balance Technique
Material Cycles
Water Cycle
Carbon Cycle
Nitrogen Cycle
Sulfur Cycle
Oxygen Cycle
Industrial Use of Materials
Industrial Ecology
Industry as an Ecological System
Industry as an Economic System
Decision Making Techniques of Industrial Ecology
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Industrial Use of Materials

"If man began with speech, and civilization with agriculture, industry began with fire. Man did not invent it, probably nature produced the marvel for him...He put the wonder to a thousand uses. First, perhaps... to conquer his fearsome enemy, the dark; then...for warmth,...then he applied it to metals, tempering them, and combining them into stronger and suppler than those in which they had come to his hand..."

Beginning with fire, "industry" or, in these early days, humans learned to use energy to manipulate materials, transforming them to suit our purposes. These rearrangements, while bringing great progress, has also left us with large prices to pay because of our disregard or ignorance of evolving the material use on a scale of time and space that learned its lessons from natural material cycles.

The natural material cycles described in the previous sections are a part of our ecosystem. Over billions of years, materials, energy and life have all evolved with mutual interactions to become part of a natural ecology. Most materials that form part of the biosphere occur in cycles, especially those that play central roles in biological systems.

The use of materials by humans has changed over time in quantity and quality, and especially over the last century. The early use of materials for food, shelter and energy required small amounts of materials for each person and were conserved to large extent because it was hard to get, shape and work with materials. Often, materials remained as part of a product such as a tool or a plough for decades and were reused or recycled.

The trends of material use in products have changed significantly with the technological age - particularly in the 20th century. Plastics are perhaps the most radical material invention, in the way that material permeated society. In 1900, 75% of products used renewable materials (that is, agricultural and forest materials, such as wood and natural fibers). By 1980, 70% of materials used were from non-renewable sources such as ores, minerals, and petroleum. In 1955, 8% of materials in products were petroleum-based (plastics). By 1980, 32% of materials in products were petroleum-based.

Wood and stone were the earliest "materials" to be shaped and used by humans. In the course of time, natural materials such as clay and mud were used for cooking and building. With the advance of technology, discoveries of ways to extract metals from ores, methods to shape and transform materials, and eventually with the knowledge afforded by synthetic, organic, and nuclear chemistry, we have made numerous combinations of materials that have never existed in nature. The age of "synthetic" materials started with forming alloys of metals. Bronze (an alloy of tin and copper), brass (an alloy of zinc and copper), and gold alloys (14 carat gold is 14 parts of gold and 10 parts of copper; 24 carat gold is pure gold metal) have all been used since ancient civilization.

The first transformations of materials gave humans the ability to shape materials into forms they wanted. As pure gold is too soft and pliable, the addition of copper was an early invention to make gold stronger. Metallic elements were alloyed to increase strength to make strong and lasting tools, structures and weapons. Iron, copper, sulfur and phosphorus were probably the materials that received the greatest attention for these uses as "industry" emerged. Of course, stones of various kinds, including marble (CaCO3), granite, gypsum (MgSO4), sand (SiO2) were all used since early times for building. There were also fuel materials such as wood, coal, and oil, - hydrocarbons - that were used first to build fires, then for controlled extraction of energy.

With increasing technological capabilities, the human ingenuity and art (techne in Greek means art or "cunning" as in Charles Dickens' Artful Dodger) combined with scientific understanding led to unprecedented arrangements and transformations of materials. In pressing to get the functionality of various desirable properties and technological progress in designing and producing new materials, we did not know or think of these materials as part of our natural environmental system. In extracting them from the natural system, and combining them into new forms, we began concentrating materials, producing materials that did not exist in nature, and extracting or "purifying" into elemental form large quantities of elements that existed in nature only in chemical combinations with others.

In these processes, there was no awareness of how much "useless" material - wastes - was produced as we extracted the "useful" material, or of the role that "indestructible" synthetic or even natural materials may play when released into the environment after their use in unprecedented quantities over relatively short periods of time. The greatest ignorance we exhibit as an industrialized "civilization" is perhaps a lack of respect or even a total ignorance - of the role of time and of cycles in providing system balance. In pressing on with our economy, we lost sight of our ecology!

Robert Ayres, one of the originators of the idea of industrial ecology summarizes the crux of our material use in the beginning paragraph of his book Industrial Ecology, co-authored with Leslie Ayres.

"...every substance extracted from the earth's crust, or harvested from a forest, a fishery or from agriculture, is a potential waste, it soon becomes an actual waste in almost all cases, with a delay of a few weeks to a few years at most. The only exception worth mentioning are long-lived construction materials. In other words, materials consumed by the industrial economic system do not physically disappear. They are merely transformed to less useful forms. In some cases (as with fuels) they are considerably transformed by combination with atmospheric oxygen. In other cases (such as solvents and packaging materials) they are discarded in more or less the same form as they are used. It follows from this simple relationship between inputs and outputs - a consequence of the law of conservation of mass - that economic growth tends to be accompanied by equivalent growth in waste generation and pollution." (Ayres 1)

Though this realization has not fully hit most parts of our society even today, the 1960's environmental consciousness articulated three features/problems of the industrial rearrangement of material: resource depletion, increasing waste materials, and the presence of toxic materials in the environment. The first idea - resource depletion which came from industry - was the realization that the earth does not have an infinite bank of materials. The second of increasing waste came from people noticing the ugliness of waste - as garbage on highways, junked cars, the "blooms" of algae in lakes from over-nitrificiation from detergents and pesticides, or mounds of mining overburden. The presence of toxic materials in the environment was a slower realization, spurred most notably by Rachel Carsons' Silent Spring which has a chapter titled "And the Birds Sing No More" to signify the impact of the pesticide DDT which weakened the eggshells of birds.

Prior to this century, industrial countries did not consider pollution or resource shortage a serious problem. When resources in the home countries were hard to access, trade or conquests were used to procure material. Historians Will and Ariel Durant make the point that the Industrial Revolution came to England first because of the long history of British command of the seas, because science in England was mainly "directed by men of practical bent", and because England had a constitutional government sensitive to business interests.

The reaction to resource depletion in this century was a foray into ideas of conservation and resource management, finding out how the economies of recycling would compare with the economies of resource extraction from nature. Thus early in this century, the aluminum industry began its quest for recycling. Aluminum recycling is one of the most advanced processes of recycling because of decades of learning. Conservation ideas also developed through the desire to conserve the natural beauty of forests and other landscapes.

In the 1970's, economic and political pressures such as the oil cartel and depletion of coal led to ideas of energy conservation in the United States. Energy-intensive, material-producing industries such as aluminum, and paper started serious looks into recycling. Energy conservation measures in the U.S. also led to down-sizing of cars, which had hitherto gone on with the philosophy of "bigger the better" - station wagons for family uses and recreational vehicles for vacations were a common sight during the economic upsurge of the 1950's and early 1960's. Automobile recycling became big and achieved 90% material recovery in the 1980's.

In 1994, the National Environmental Technology Act was passed to encourage the government to work with industry to promote technologies that will have positive environmental impact. Particularly, the government was interested in and more efficient and non-polluting technologies so that we can maintain our current standard of living in light of population growth. In the Senate, those supporting the measure contended that "coming up with new, nonpolluting technologies will ultimately help efficiency and the economy."1

All of these conservation measures were, of course, totally anthropocentric, with an objective of preserving our conveniences, and meeting our wants and desires. It was not the ethos of conservation practiced by older civilizations with a respect for value and an eye to the future - to the "seventh generation" as described in the unit on Ethical Systems. (link)

Faced with resource depletion, we began defining materials as renewable and nonrenewable resources. Materials like coal that can only be replaced over long periods of time compared to the time periods of human activities involving their use, are called nonrenewable resources. Materials such as wood which can be replenished in reasonable periods of time are called renewable resources. Note that these are renewable only if we replant trees at a rate that keeps up with use. Thus the Redwoods or old-growths forest trees should not be looked on as "renewable" resources because of the time it would take to replace.

The increasing waste and its disposal was the second mounting problem. Europe with its older industrial base and limited land area felt the waste problem sooner and more acutely than the United States. The concentration of people - and hence of quantities of waste is higher in the urban areas. In his book, (link to anobib) The Search for the Ultimate Sink, historian Joel Tarr writes that urban pollution is the "product of the interaction among technology, scientific knowledge, human culture and values and the environment", reduced or exacerbated at times with environmental policy and control technology. Sinking of waste and recycling of usable items have been a part of all cultures. But an economy that valued overproduction and marketed convenience items as necessary to the quality of life and the accompanying perception we have of an inexhaustible resource supply has led to a throwaway society, especially in the U.S.

Often, in analyzing environmental problems, we focus on industrial generation of waste, without a full realization that industry generates waste to meet consumer demands. In 1976, an average consumer spent 15% of his/her income on "durable goods" - automobiles and parts, furniture and other appliances, 18.5% on food, and 22% on "nondurable goods" such as clothing and shoes, gasoline, and alcoholic beverages! (U.S. Bureau of Economic Analysis-link?)


Often, in analyzing environmental problems, we focus on industrial generation of waste, without a full realization that industry generates waste to meet consumer demands. In 1976, an average consumer spent 15% of his/her income on "durable goods" - automobiles and parts, furniture and other appliances, 18.5% on food, and 22% on "nondurable goods" such as clothing and shoes, gasoline, and alcoholic beverages! (U.S. Bureau of Economic Analysis) Calculate the percentages of income spent by a consumer on durable goods, food, and non durable goods for 1996 and the current year.

This situation found the U.S. in ridiculous scenarios such as: a boat of garbage from New York City floating in the Hudson River and mountains of Uranium mill tailings blowing radioactive material around some of the western United States. In addition to garbage and sewage, industrial wastes in air, water, and land have also posed formidable problems. The philosophy of waste management has been evolving slowly, spurred by regulation, but making slow progress in the U.S. because of various types of social perceptions.

Toxic materials in the environment is a much subtler problem. Basically, the problem arises when we produce new compounds or isolate elements in configurations not found in nature with properties such as a resistance to degradation. Many of these materials do not decompose on exposure to the usual agents that nature uses to decompose — air, light, water, or bacteria. Persistent substances, such as plastics and chlorofluorocarbons, produce cumulative, long-term and long-range effects on plant, animal and human health.

In many cases the effects were not predictable because of our lack of knowledge and the absence of consideration of systemic, long-term impacts. Joe Thornton writes in (anobib link) Pandora's Poison, a book on the impacts of chlorine compounds, "the chemistry of the chlorine atom gives chlorine gas and organochlorines useful properties, but these same qualities (high reactivity and chemical stability) create enormous environmental problems...Organochlorines that are stable in their intended use, however, are also persistent in the environment." [Thornton]. Organochlorines, other organic compounds and metals give rise to health hazards such as cancer and endocrine disruptions discussed in the unit on Heath and Risk.

The U.S. Bureau of Mines maintains an account of the world production and flows of metals and other primary materials such as coal and other fossil fuels. Table 4 shows the amount of some metal ores extracted in 1988.


Weight of Ore KMT

Weight of Metal KMT Mine & Mill Waste
Table 4. World Production of some Metals and mine waste in 1000 metric tonnes (KMT) (adapted from Ayres 1996)

Table 4 shows that each pound of aluminum extracted produces 1-7 pounds of waste at the mine, and almost all of the uranium ore is waste! The main intent of the table is to show the amounts of waste at the very first stage — mining and milling — in the production of a metal. Note that in all cases, we produce much more waste than metal. This is only the beginning. Each stage of production of a consumer good such as an automobile or a toaster, requires many more stages of manufacturing, each with its own wastes discarded to air, land, and water.

The Flows of Copper and Aluminum

Figures _ and _ are flowcharts showing the stages in the use of two metals — copper and aluminum. The flow of copper is shown only from the mine to the point of input into an industrial process. The figure for Aluminum is drawn to represent the whole sequence of use, including recycling. These flow charts are the beginning stages of doing a life cycle analysis which we describe in the next section on Industrial Ecology. In the unit on Energy Systems, we have shown similar diagrams for the production of energy from different sources.



Figure IU4. Scheme of copper metal flow from mine to entry into manufacturing process.

Over nine million metric tons (18,000 million lbs.) of copper is mined annually. The two main countries producing copper are Chile and the U.S., each producing about 2 million MT annually. Canada, the former USSR, Zaire, Zambia and Poland are the other countries. Copper is usually mined via open pits.

After a large amount of processing, each process with its other inputs and wastes, copper metal is delivered to the various industries that use it. Because copper is used in alloys such as brass and wires, it is difficult to extract and reuse the metal economically. Separation is one of the major obstacles in the attempt to recycle copper.

Copper is the oldest known metal to be extracted and used by humans. There are signs of copper use as early as 6000 B.C. toward the end of the Neolithic Age, considered by historians as the beginning of the Age of Metals. Alloying copper with tin or zinc to form bronze and brass seems to have happened by 3000 B.C. and other metallurgical heat-treatment processes like casting seems to have started by 1500 B.C. (Durant, Vol. I, p. 103).


Figure IU5. Aluminum flowchart

Aluminum plays a very crucial role in modern society. It is the basis of aircraft and large mirrors used in telescopes! It is a versatile metal. The extraction and processing of aluminum from its ore - bauxite, Al2O3 — is environmentally destructive. Aluminum is not abundant in the earth's crust (14.3 atomic % or 8% by mass compared to 27.7% for Si (Silicon) and 5% for Fe (Iron), but it is in combination with oxygen. This strong combination requires a lot of energy to break!

The main producers of aluminum are Australia, Guinea, Jamaica and Brazil with much smaller amounts from Greece, France and Hungary. To separate aluminum (pure Al2O3) from the bauxite ore which also contains Fe2O3, SiO2, TiO2 and other minerals, a significant amount of electricity, water and chemicals such as limestone (CaCO3) and Caustic Soda (NaOH) are needed. Separation of the metal Al from Al2O3 is done by means of an electrolytic process that consumes large amounts of electricity. Because of this, the companies producing aluminum had, in the early days, also developed hydroelectric power plants close to the mines. Thus the Tacurai Dam in Brazil sends one-third of its output electricity to aluminum smelters!

Because the extraction of Aluminum from the Alumina (Al2O3) ore requires an enormous amount of electrical energy, the aluminum industry initiated processes to recycle the used aluminum and was one of the first industries to do so. For many other materials, the sequence is not closed, that is, the used product is not processed to get the original material back.

Exercise: List the materials in a familiar consumer product such as toaster, clothes, soap, cleaners. Find the source of the material and where it ends up finally.


Flows in the Case of a Consumer "Material" : Packaging

In the previous two cases, and in the material cycles earlier in the unit, we looked at the flows and cycles of materials that occur in nature. A large and diverse group of materials central to the consumer economy of today is all the material that could be categorized as packaging. The amounts and flows of packaging materials is an important aspect to consider because of their large effect on the environment.

Packaging including cartons, cans, and bottles used for consumer items are individually small but contribute to resource use and waste because of the sheer number of units we use. Packaging also has an often overlooked aspect; their centralized production and large distribution systems mean that we transport a large amount of consumer items over long distances, each with its own packaging. Thus transportation involves large expenditures of energy.

Packaging includes containers (made of glass, metals, or plastics), one-use containers (paper, plastic bags, cartons, and toothpaste tubes) and wrapping materials (paper, plastic, Aluminum foil). Recycling of packaging materials is very limited in the U.S. In 1993, we used about 310 kg (or 700 lbs.) per person of paper and paperboard for packaging, leading to a total of 80 million metric tons. Europe uses more plastics than paper because of the relative scarcity of land to grow wood.

As two examples of packaging materials, we now briefly describe the schemes of flow of paper and plastic. Paper and paperboard products are made mostly from wood pulp, and some paper from plant fibers such as cotton, linen and grasses.

Figure __ outlines the scheme of material flow of paper.

insert image

Five thousand tons of paper are made per day in the U.S. to satisfy the 700 lbs per person per day demand. In 1996, 45% of post consumer waste paper was recycled, and the industry has set a 50% paper recovery goal. ("Industrial Environmental Performance Metrics," NAE Press, 1999.)

Increasingly, the industry in the U.S. is attempting to obtain wood grown on plantations or intensively managed forests rather than use wood from natural forests. Still, some of the tropical forests in South America and South East Asia are being harvested at alarming rates to provide wood for paper.

Paper pulping process uses high amounts of electricity and water — 2000 Kwh and 8000 gallons of water per ton of pulp produced. Large amounts of energy is also used when "pulp mats" are dried over hot rolls to become paper. The processing of paper, and especially the bleaching, consumes large amounts of chemicals. In particular, several million tons of chlorine are used which combines with the organic material in the process waste to produce over 1,000 types of organochlorine by-products. About 50 tons of organochlorines are released into water and air by an average size paper mill. Organochlorine byproducts are also concentrated in the sludge, 80% of which are buried in landfill. Environmental damage to plants, aquatic life and health risks to workers are well documented effects of paper mill effluents. The byproducts include dioxins which are both hazardous and bioaccumulative. Health and water pollution concerns have led the paper industry to look into chlorine free bleaching processes such as using ozone. A new family of bleaching compounds that decompose into water and oxygen has been developed by Professor Terry Collins of Carnegie Mellon University.

Plastics TBD

Chlorine TBD

Pollution of the different media - air, water, and land - are discussed in the unit on the Atmospheric System, in the section on water cycle in this unit, and in the following section on solid and hazardous waste. Rethinking the use of materials using principles of ecology and "closing the circle" (a term used first by Barry Commoner) is the topic of the next section on Industrial Ecology.

Exercise: Quantitative LCA:
  • 1. Choose an appliance you use daily.
  • 2. List as accurately as possible, the materials in the appliance (excluding energy source). Consider how long you would keep it and what happens to it after you no longer use it. Draw a flow chart of the system of production, use, and the after-use of the appliance. Consider barriers and incentives to recycling the materials.
  • 3. Add to the flow chart arrows to indicate energy inputs and water inputs.
  • 4. Try to describe as closely as possible the "final" fate of each material. What are the differences from the way they existed originally and their final form?





  ©Copyright 2003 Carnegie Mellon University
This material is based upon work supported by the National Science Foundation under Grant Number 9653194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.