Materials Crisis

Even with energy expenditures stringently controlled, or an abundant clean source of energy developed, the prospects of achieving sustainability in the long term is seriously threatened by the rapid depletion of essential material and mineral resources. The manufacturing of goods invariably involve using concentrated pools of naturally occurring raw material resources leading to their eventual dissipation in the environment. For instance, the manufacture of plastics uses up a fraction of the crude oil reserves or natural gas that is invariably dissipated as postconsumer plastic waste in the municipal solid waste (MSW) stream or as gaseous incineration products in the atmosphere. Clearly, this unidirectional materials flow is viable only as long as the intact reserves are available. All estimates published for the global "reserves" of these nonfuel resources, of course, are increased frequently as new discoveries of reserves are made (as with the oil). The quantitative information is therefore easily outdated.

The estimated value of domestic (nonfuel) mineral raw materials mined in the United States is $40 billion (net imports into the United States amount to $29 billion)! Nine of these minerals have an annual production value of over $1 billion at the present time. These are mainly commodity construction materials such as sand and gravel but also include key metals such as gold, copper, iron, as well as phosphate rock. For some important minerals the United States depends entirely21 on exports and conscientious exploitation of the ore resources in foreign countries will be crucial to domestic economic development. Ores of precious and rare-earth metals, for instance, cannot be replenished in a practical time scale and their applications typically do not allow these to be recycled effectively. An energy-rich material-poor world is as bleak a prospect as one with no future energy options.

A reasonable, albeit incomplete, measure of future availability of critical raw materials is the ratio of known world resources for a given material to the present annual consumption of that material worldwide [13]. Adequacy of global reserves has been studied using this ratio (which is an estimate of the number of years for which the reserves will last) and the findings divide the mineral reserves into several broad classes. The following longevity of the supplies was estimated assuming the consumption rates in 1997 and the reserves known in 1998 (according to the U.S. Geological Survey database):

< 100-year supply Copper, gold, silver, zinc, sulfur, tin, molybdenum

100- to 200-year supply Nickel, boron, asbestos >200-year supply Aluminum, iron, cobalt, chromium

These estimates should not, of course, be taken to mean absolute depletions in the time scale indicated (i.e., for instance, that there will be no more copper

21 These include alumina, natural graphite, manganese, fluorspar, quartz crystal, strontium, thallium, thorium, and yttrium. These come from places such as Canada, China, Mexico, Germany, and South Africa.

1900 1920 1940 1960 1980 2000

Figure 1.4. Global materials use intensities for selected classes of materials in the recent past showing increased reliance on plastics. [Source: I. K. Wernick and J. H. Ausbel, Dardalus, 125(3), 171 (1996).]

1900 1920 1940 1960 1980 2000

Figure 1.4. Global materials use intensities for selected classes of materials in the recent past showing increased reliance on plastics. [Source: I. K. Wernick and J. H. Ausbel, Dardalus, 125(3), 171 (1996).]

ore after 2100!). It is more a guide on the relative scarcity of the materials. Exploring substitute materials that might be used in place of the more rapidly depleting critical materials needs to be an integral component of any plan toward sustainable growth.

Beginning with the post-World War II construction boom the U.S. consumption of all materials including plastics has significantly grown in volume. Data from the U.S. Geological Survey indicates an increasing trend for materials in the United States (and in the world as a whole) during 1970-1995. The oil crisis in mid-1970s and the economic recession in early 1980s had little effect on the patterns of consumption. Intensity of material use in the United States in the past decade shows that plastics use grew at a relatively faster rate compared to that of conventional materials. Figure 1.4 shows the trends in the annual U.S. consumption of key materials divided by the gross domestic product (GDP) in constant 1987 dollars (and normalized for the base year 1940). While conventional materials used in infrastructure improvement, such as steel, copper, lead, and lumber, gradually became relatively less important to the economy, the use of light-weight materials such as aluminum and plastics gained ground vigorously since World War II.

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