Earlier in this century, tin was a critical metal for can-making and packaging industries; since then, other materials have been substituted for tin, including plastic, glass, and aluminum. The amounts of lead and steel used in telecommunica­tion:- cables have decreased dramatically during the past 5 years, while the amount of plastics has had a corresponding increase. In addition, glass fibers have replaced copper wiring in telephone cables.

Although substitution can extend our mineral supplies, it is not a cure-all for dwindling resources. Certain minerals have no known substitutes. Plati­num, for example, catalyzes many chemical reac­tions that are important in industry. So far, no other substance has been found that possesses the catalyzing abilities of platinum.

Mineral Conservation

Our mineral supplies can be extended by conserva­tion. In recycling, used items such as beverage cans and scrap iron are collected, remelted, and repro­cessed into new products. The reuse of items such as beverage bottles (which can be collected, washed, and refilled) is another way to extend min­eral resources. In addition to the introduction of specific conservation techniques such as recycling and reuse, public awareness and attitudes about re­source conservation can be modified to encourage low waste.

.Recycling: A large percentage of the products m.ioV¹ from minerals—including cans, bottles, chemical products, electronic devices, and batteries are typically discarded after use. The minerals in some of these products—batteries and elec­trons devices, for instance—are difficult to recycle. Minerals in other products, such as paints containing lead, zinc, or chromium, are lost through normal use.

However, there is no question that we have the technology to recycle many other mineral products. Recycling of certain minerals is already a common practice. Significant amounts of gold, lead, nickel, steel, cooper, silver, zinc, and aluminum are now being recycled.

Recycling has several advantages in addition to mending mineral resources. It saves unspoiled land from the disruption of mining, reduces the amount of solid waste that must be disposed, and reduces energy consumption and pollution. For example, recycling an aluminum beverage can saves the energy equivalent of about 180 ml (6 in) of gasoline. Recycling aluminum also reduces the emission of aluminum fluoride, a toxic air pollutant produced during aluminum process­ing.

More than half the aluminum cans in the United States are currently being recycled. The aluminum industry, local governments, and private groups have established more than 5,000 recycling centers across the country. People who turn in alu­minum cans receive a small refund (usually a penny or a nickel) for each can. It takes approximately six weeks for a can that has been returned to be melted, reformed, filled, and put back on a super­market shelf. Clearly, however, more recycling is possible. It may be that today's sanitary landfills will become tomorrow's mines, as valuable minerals and other materials are extracted from them.

Reuse: When the same product is used over and over again, as when beverage containers are col­lected, washed, and refilled, both mineral con­sumption and pollution are reduced. The benefits of reuse are even greater than those of recycling. For example, to recycle a glass bottle requires crushing it, melting the glass, and forming a new bottle. Reuse of a glass bottle simply requires wash­ing it, which obviously expends less energy than recycling. Reuse is a national policy in Denmark, where nonruseable beverage containers are prohib­ited.

A number of countries and states have adopted beverage- container deposit laws, which require consumers to pay a deposit, usually a nickel, for each beverage bottle or can they purchase. The nickel is refunded when the container is returned to the retailer or to special redemption centers. In addition to encouraging recycling and reuse, thereby reducing mineral resource consumption, beverage container laws save tax money by reduc­ing litter and solid waste. Countries that have adopted beverage container deposit laws include the Netherlands, Norway, and Sweden. Parts of Canada and the United States also have deposit

Changing Our Mineral Requirements We can re­duce our mineral consumption by becoming a low-waste society. Americans have developed a "throw-away" mentality in which damaged or unneeded articles are discarded. This attitude has been encouraged by industries looking for short-term economic profits, even though the long-term economic and environmental costs of such an attitude are high. Products that are durable and repairable enable us to consume fewer resources. Laws such as those requiring a deposit on beverage containers also reduce consumption by encouraging recycling and reuse.

The throw-away mentality has also been evi­dent in manufacturing industries. Traditionally, industries consumed raw materials and produced not only goods but a large amount of waste that was simply discarded. Increasingly, however, manufacturers are finding that the waste products from one manufacturing process can be used as raw materials in another industry. By selling these "wastes," industries gain additional profits and lessen the amounts of materials that must he thrown away. For example, ARCO's oil refinery in Los Angeles now sells its used alumina catalysts to Allied Chemical. Until this market was found, used alumina catalysts were classified as a hazardous waste that required special disposal procedures. Such minimization of waste by industry is known as sustainable manufacturing.

Dematerialization: As products evolve; they tend to become lighter in weight and often smaller. Washing machines manufactured in the 1960s were much heavier than comparable machines manufactured in 1990s, for example. The same is true of other household appliances, automobiles, and elec­tronic items. This decrease in the weight of products over time is called dematerialization.

Although dematerialization gives the appear­ance of reducing consumption of minerals and other materials, if may have the opposite effect. Often products are, that are smaller and lighter Late of lower quality. Because repairing broken lightweight items is difficult and may cost more than the origi­nal products, consumers are encouraged by retailers and manufacturers to replace rather than repair the items. Thus, although the weight of materials being used to make each item has decreased, the number of such items being used in a given period of time may have actually increased.