Materials and the Environment

Eco-informed Material Choice

Michael F. Ashby

• Publisher: Butterworth-Heinemann
• Year: 2012
• eBook ISBN: 9780123859723
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Materials and the Environment: Eco-Informed Material Choice, Second Edition, is the first book devoted solely to the environmental aspects of materials and their selection, production, use and disposal, by one of the world's foremost materials authorities. It explores human dependence on materials and its environmental consequences and provides perspective, background, methods, and data for thinking about and designing with materials to minimize their environmental impact.Organized into 15 chapters, this new edition looks at the history of our increasing dependence on materials and energy. It explains where materials come from and how they are used in a variety of industries, along with their life cycle and their relationship to energy and carbon. It also examines controls and economic instruments that hinder the use of engineering materials, considers sustainability from a materials perspective, and highlights the importance of low-carbon power and material efficiency. Furthermore, it discusses the mechanical, thermal, and electrical properties of engineering metals, polymers, ceramics, composites, and natural materials in relation to environmental issues. The volume includes new chapters on Materials for Low Carbon Power & and Material Efficiency, all illustrated by in-text examples and expanded exercises. There are also new case studies showing how the methods discussed in the book can be applied to real-world situations.This book is intended for instructors and students of Engineering, Materials Science and Industrial/Product Design, as well as for materials engineers and product designers who need to consider the environmental implications of materials in their designs. - Introduces methods and tools for thinking about and designing with materials within the context of their role in products and the environmental consequences - Contains numerous case studies showing how the methods discussed in the book can be applied to real-world situations - Includes full-color data sheets for 40 of the most widely used materials, featuring such environmentally relevant information as their annual production and reserves, embodied energy and process energies, carbon footprints, and recycling data New to this edition: - New chapter of Case Studies of Eco-audits illustrating the rapid audit method - New chapter on Materials for Low Carbon Power examines the consequences for materials supply of a major shift from fossil-fuel based power to power from renewables - New chapter exploring Material Efficiency, or design and management for manufacture to provide the services we need with the least production of materials - Recent news-clips from the world press that help place materials issues into a broader context.are incorporated into all chapters - End-of-chapter exercises have been greatly expanded - The datasheets of Chapter 15 have been updated and expanded to include natural and man-made fibers

Chapter 1

Introduction: Material dependence

Contents

1.1 Introduction and synopsis

1.2 Materials: a brief history

1.3 Learned dependency: the reliance on nonrenewable materials

1.4 Materials and the environment

1.5 Summary and conclusions

1.6 Further reading

1.7 Exercises

Renewable and non-renewable construction.Above: Indian village reconstruction. (Image courtesy of Kevin Hampton http://www.wm.edu/niahd/journals). Below: Tokyo at night. (Image courtesy of http://www.photoeverywhere.co.uk index).

1.1 Introduction and synopsis

This book is about materials and the environment: the eco-aspects of their production, their use, and their disposal at end of life. It is also about ways to choose and design with them in ways that minimize the impact they have on the environment. Environmental harm caused by industrialization is not new. The manufacturing midlands of 18th century England acquired the name “Black Country” with good reason; and to evoke the atmosphere of 19th century London, Sherlock Holmes movies show scenes of fog—known as “pea-soupers”—swirling round the gas lamps of Baker Street. These were localized problems that have, today, largely been corrected. The change now is that some aspects of industrialization have begun to influence the environment on a global scale. Materials are implicated in this. As responsible materials engineers and scientists, we should try to understand the nature of the problem—it is not simple—and to explore what, constructively, can be done about it.

This chapter introduces the key role materials have played in advancing technology and the dependence—addiction might be a better word—that this has bred. Addictions demand to be fed, and this demand, coupled with the world’s continued population growth, consumes resources at an ever-increasing rate. This has not, in the past, limited growth; the earth’s resources are, after all, very great. But there is increasing awareness that the limits do exist, that we are approaching some of them, and that adapting to them will not be easy.

1.2 Materials: a brief history

Materials have enabled the advance of mankind from its earliest beginnings—indeed the ages of man are named after the dominant material of the day: the Stone Age, the Copper Age, the Bronze Age, the Iron Age (Figure 1.1). The tools and weapons of prehistory, 300,000 or more years ago, were bone and stone. Stones could be shaped into tools, particularly flint and quartz, which could be flaked to produce a cutting edge that was harder, sharper, and more durable than any other naturally occurring materials. Simple but remarkably durable structures could be built from the materials of nature: stone and mud bricks for walls; wood for beams; bark, rush, and animal skins for roofing.

Figure 1.1 The materials timeline. The scale is nonlinear, with big steps at the bottom, small ones at the top. A star (*) indicates the date at which an element was first identified. Unstarred labels give the date at which the material became of practical importance.

Gold, silver, and copper, the only metals that occur in native form, must have been known about from the earliest time, but the realization that they were ductile, that is, that they could be beaten into a complex shape, and, once beaten, become hard, seems to have occurred around 5500 BC. By 4000 BC, there is evidence that technology to melt and cast these metals had developed, allowing for more intricate shapes. Native copper, however, is not abundant. Copper occurs in far greater quantities as the minerals azurite and malachite. By 3500 BC, kiln furnaces, developed for pottery, could reach the temperature and create the atmosphere needed to reduce these minerals, enabling the tools, weapons, and ornaments that we associate with the Copper Age to develop.

But even in the worked state, copper is not all that hard. Poor hardness means poor wear resistance; copper weapons and tools were easily blunted. Sometime around 3000 BC the probably accidental inclusion of a tin-based mineral, cassiterite, in the copper ores provided the next step in technology—the production of the copper-tin alloy bronze. Tin gives bronze a hardness that pure copper cannot match, allowing superior tools and weapons to be produced. This discovery of alloying—the hardening of one metal by adding another—stimulated such significant technological advances that it, too, became the name of an era: the Bronze Age.

“Obsolescence” sounds like 20th century vocabulary, but the phenomenon is as old as technology itself. The discovery, around 1450 BC, of ways to reduce ferrous oxides to make iron, a metal with greater stiffness, strength, and hardness than any other then available, rendered bronze obsolete. Metallic iron was not entirely new: tiny quantities existed as the cores of meteorites that had impacted the earth. The oxides of iron, by contrast, are widely available, particularly hematite, Fe₂O₃. Hematite is easily reduced by carbon, although it takes temperatures close to 1,100°C to do it. This temperature is insufficient to melt iron, so the material produced is a spongy mass of solid iron intermixed with slag; this mixture is then reheated and hammered to expel the slag, then forged to the desired shape. Iron revolutionized warfare and agriculture; indeed, it was so desirable that at one time it was worth more than gold. The casting of iron, however, presented a more difficult challenge, requiring temperatures around 1,600°C. There is evidence that Chinese craftsmen were able to do this as early as 500 BC, but two millennia passed before, in 1500 AD, the blast furnace was developed, enabling the widespread use of cast iron. Cast iron allowed structures of a new type: the great bridges, railway terminals, and civil buildings of the early 19th century are testimony to it. But it was steel, made possible in industrial quantities by the Bessemer process of 1856, that gave iron the dominant role in structural design that it still holds today. For the next 150 years metals dominated manufacturing. It wasn’t until the demands of the expanding aircraft industry in the 1950s that the emphasis shifted to the light alloys (those based on aluminium, magnesium, and titanium) and to materials that could withstand the extreme temperatures of the gas turbine combustion chamber (super alloys—heavily alloyed iron- and nickel-based materials). The range of application of metals expanded into other fields, particularly those of chemical, petroleum, and nuclear engineering.

The history of polymers is rather different. Wood, of course, is a polymeric composite, one used in construction from the earliest times. The beauty of amber—petrified resin—and of horn and tortoise shell—made up of the polymer keratin—attracted designers as early as 80 BC and continued to do so into the 19th century (in London, there is still a Horners’ Guild, the trade association of those who work horn and shell). Rubber, which wasn’t brought to Europe until 1550, was already known of and used in Mexico. Its use grew in importance in the 19th century, partly because of the wide spectrum of properties made possible by vulcanization—cross-linking by sulfur—to create materials as elastic as latex and others as rigid as ebonite.

The real polymer revolution, however, had its beginnings in the early 20th century with the development of Bakelite, a phenolic, in 1909, and of the synthetic butyl rubber in 1922. This was followed mid-century by a period of rapid development of polymer science, visible as the dense group at the upper left of Figure 1.1. Almost all the polymers we use so widely today were developed in a 20-year span from 1940 to 1960; among them were the bulk commodity polymers polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), and polyurethane (PU), the combined annual tonnage of which now approaches that of steel. Designers seized on these new materials—they were cheap, brightly colored, and easily molded to complex shapes—to produce a spectrum of cheerfully ephemeral products. Design with polymers has since matured: they are now as important as metals in household products and automobile engineering.

The use of polymers in high-performance products requires a further step. “Pure” polymers do not have the stiffness and strength these applications demand; to provide it, they must be reinforced with ceramic or glass fillers and fibers, making them composites. Composite technology is not new. Straw-reinforced mud brick (adobe) is one of the earliest materials of architecture, one still used today in parts of Africa and Asia. Steel-reinforced concrete—the material of shopping centers, road bridges, and apartment blocks—appeared just before 1850. Reinforcing concrete with steel gave it tensile strength where previously it had none, thus revolutionizing architectural design; it is now used in greater volume than any other man-made material. Reinforcing metals, already strong, took much longer, and even today metal matrix composites are few.

The period in which we now live might have been named the Polymer Age had it not coincided with yet another technical revolution, that based on silicon. Silicon was first identified as an element in 1823, but found few uses until the realization, in 1947, ...

Table of contents

• Cover Image
• Table of Contents
• Title
• Copyright
• Preface and acknowledgments
• Chapter 1. Introduction: Material dependence
• Chapter 2. Resource consumption and its drivers
• Chapter 3. The material life cycle
• Chapter 4. End of first life: A problem or a resource?
• Chapter 5. The long reach of legislation
• Chapter 6. Eco-data: Values, sources, precision
• Chapter 7. Eco-audits and eco-audit tools
• Chapter 8. Case studies: Eco-audits
• Chapter 9. Material selection strategies
• Chapter 10. Eco-informed materials selection
• Chapter 11. Sustainability: Living within our means
• Chapter 12. Materials for low-carbon power
• Chapter 13. Material efficiency
• Chapter 14. The bigger picture: Future options
• Chapter 15. Material profiles
• APPENDIX. Useful numbers and conversions
• Index