Constructing a Material Century<br > he intensive use of materials in this century has deep<br > historical roots. Since the Industrial Revolution，<br > advances in technology and changes in society and in busi-<br > ness practices have interacted to build economies that could<br > extract， process， consume， and dispose of tremendous quan-<br > tities of materials. Although the roots of these trends extend<br > back centuries， most have matured only in the last 100<br > years.~~<br > The case of iron， the emblematic material of the Indus-<br > trial Revolution， illustrates how technological advances fed<br > materials use. In 1879， a British clerk and his chemist cousin<br > invented a process for making high-quality steel--a harder<br > and more durable alloy of iron--from any grade of iron ore，<br > eliminating the need for phosphorus-free ore. This innova-<br > tion cut steelmaking costs by some 80-90 percent which in<br > turn drove demand skyward: between 1870 and 1913， iron<br > ore production in Britain， Germany， and France multiplied<br > 83-fold. Further innovations and robust demand led to a six-<br > fold increase in world production between 1913 and 1995.<br > Today， iron and steel account for 85 percent of world metals，<br > and a tenth， by weight， of world materials production."<br > As richer ores were depleted， new extractive technolo-<br > gies made it possible to mine metal from relatively poor<br > lodes， a practice known as "low-grading." In 1900， it was not<br > feasible to extract copper， for example， from ore that con-<br > tained less than 3 percent of the metal. But technological<br > advances have since lowered the extraction threshold to less<br > than 0.S percent， increasing the number of sites where min-<br > ing is viable， and greatly expanding the quantity of ore<br > needed to extract the same amount of copper. As world cop-<br > per ploduction grew 22-fold over the century， in step with<br > rising demand for automotive and electrical uses， waste pro-<br > dLtction grew 73-fold. Likewise， modern logging and mining<br > equipment have made it possible to reduce tracts of forest<br > into sawn lumber in a matter of hours， or to shear off entire<br >