A "Worst-Case" Approach to Mineral Availability

Many people are deeply concerned with what appears to be the rapid depletion of the world's essential resources. While there is reason for this concern, it is often based on a misunderstanding of the nature of the problem, resulting from confusion over meanings of words and assumptions of forecasters.

A few years ago, the Institute of Ecology made the dismal prediction that "known potential supplies of phosphorus, a nonrenewable resource essential to life, will be exhausted before the end of the 21st century." An analysis of the report in which this statement appears shows that by "known potential supplies," the Institute of Ecology was referring to supplies of a specific ore content, mineable at roughly current costs, with current technology. This kind of definition is common in resource availability studies. As a result, words like "reserves," "known deposits," and so forth, have a meaning for the authors of such studies that differs markedly from that usually understood by the lay reader.

An alternative to this "current conditions" approach is to estimate resource exhaustion times and costs on a "worst-case" basis. That is, to determine what our choices would be if we indeed "used up" currently mined or proven reserves. This is the kind of approach taken by Frederick Wells in the study on which this report is based. Because run-out or exhaustion times are as much a function of demand as of supply, Wells considers both, using as a starting point the assumptions usually made in predictions like that of the Institute of Ecology.

The Institute assumed that only ores with 8 percent phosphorus content were "usable." There seems to be no factual basis for this assumption, since ores with a lower percentage of phosphorus content are even now being mined. Wells points out that the size of the deposit and its distance from transport modes are as important economically as the phosphorus content. He also shows that additional subeconomic ore is not unusable—it will simply cost more to mine. Finally he discusses the possibility of mining the most uneconomic ore of all—that found in common rock. On a per capita basis, assuming that the population would have to be many times its present size to make such a step at all necessary, the cost would probably not be prohibitive. However, Wells is careful to point out that before common rock is mined, many other solutions to the problem would be more feasible. To give an idea of the range of exhaustion times, if supply and the current ratio of phosphorus to yield alone were considered, Wells estimates on the basis of the institute's own formula that, with a constant population of 20 billion people (five times the current population) phosphorus supplies from ore with an 8 percent or higher phosphorus content would run out in 17 years; it would take 509,000 years to run out of the supplies in common rock.

But there may be better solutions to the problem. For instance, the first, and probably the cheapest, is to determine whether the amount of phosphorus fertilizer now applied to the land in modern farming is indeed the minimum amount possible to produce the desired yield. Wells indicates that in many areas of the world, yields have been substantially increased without increasing the amount of phosphorus. Indeed, since phosphorus fertilizer use is usually accompanied by the use of other modern and efficient farming methods, it is difficult to find evidence that shows the effects on yields of fertilizer alone.

The Institute of Ecology's prediction was based on the crop yield obtainable on the current amount of arable land, although only a small fraction of the land surface of the planet has been put under cultivation. Wells considers the effect on crop yield of a doubling of the arable land area and calculates the resulting phosphorus exhaustion times projected. Using the two extreme supply conditions mentioned above, the 17-year exhaustion time would be extended to 56 years, and the 509,000 common rock run-out time would be extended to 11/2 million years—by doubling the amount of land under cultivation.

It was assumed in the Institute of Ecology's report that all the phosphorus used in fertilizers would be unavailable for reuse—it would be drained away through runoff or sewage. Wells estimates that the costs of recycling a goodly portion of it might be quite modest. He considers the effect of an 80 percent recycle, and estimates that, under the same supply and usage extremes mentioned above, an 80 percent recycle would extend the 17-year exhaustion time to 86 years, and the common-rock exhaustion time to 2.5 million years. A combination of an 80 percent recycle and a doubling of the arable land would even more dramatically delay exhaustion time-280 years in the first case and 8.25 million years at the other extreme.

Finally, the institute's report assumes that large quantities of phosphorus are essential because large quantities of fertilizer are essential to obtain sufficient crop yields to feed present and future (much larger) populations. Wells, on the other hand, estimates the amount of phosphorus that would be needed if human nutrition were supplied, not by crop cultivation, but by laboratory synthesis. Combining the minute amounts of phosphorus needed in that event, with an 80 percent recycle, it becomes clear that the supplies of phosphorus will not run out before the sun grows cold. Obviously, when one talks about the costs of mining common rock or of synthesizing proteins thousands of years in the future, not to mention a population of 20 billion, one is not making a serious projection. The value of such an exercise lies only in giving perspective and in outlining alternatives to complete disaster.

The human race has not proved especially capable of achieving its highest aims, but it has excelled in one thing—adaptability. And because we are so highly adaptable, it is much too soon to write ourselves off merely because of our profligacy. There is nothing wrong with sounding warnings. Indeed, we need them. But before we panic, we should view our choices in a broader framework. In the long run, we might bear in mind the following:

• In our search for new deposits of valuable minerals, we have barely scratched the surface of our planet. Digging deeper and over a wider area may reveal many new deposits. And indeed, as shown in Wells' case study, as a last resort the mining of common rock might not be as uneconomic as is usually assumed.
• In the case of nonfuel minerals, very little is actually "used up." Much of it is simply returned to the earth and sea in exceedingly dilute form. To gather it together again may be costly, but perhaps not as costly as some think.
• A resource has little value in itself. It is the purpose it serves that matters. If a resource becomes scarce, it may be less costly to turn to substitutes for it than to try to find more.
• In the last analysis, it is theoretically possible through transmutation, to create any mineral, or indeed any element, from the atoms of air around us. To develop the technology to do this would be extremely costly—and indeed this solution to our resource problems has not yet been seriously considered. But, if it should ever become necessary, this "breakthrough" could, and probably would occur.

It should be clear that the primary question is that of cost. It should be clear, also, that the question of how much we will have to pay may depend on many factors other than the currently available supply of the resource in question.