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M. King Hubbert (*)
The energy resources of the world consist of contemporary solar radiation; the fossil fuels: coal, oil and gas, tar sands and oil shales; and nuclear energy from the fissionable elements uranium and thorium, and from the fusion of the light element deuterium. The fossil fuels represent stored solar energy accumulated during the post 500 million years. According to current geological estimates, the initial supplies of the various kinds of fossil fuels, prior to human exploitation, which are producible by present methods, were approximately the quantities shown in Table 1.
From this it will be seen that nearly three-quarters of the fossil fuels is represented by coal and the remaining one-quarter by petroleum and natural gas, and tar sands and oil shales. About 4 percent of the coal and 10 percent of the oil and gas have been consumed already.
The curve of production rate versus time for any fossil fuel must start at zero and ultimately, when the fuel is exhausted, must return to zero. The area under this curve is proportional to the cumulative production, which cannot exceed the amount of the fuel present initially. From the data in Table 1, and the production curves up to the present, it is possible to set limits within which future production must lie. Curves plotted subject to these restrictions indicate that world production of coal would probably not reach a peak sooner than about 200 years hence, but world production of crude oil and natural gas should reach their peaks about 40 years from now. Similar curves plotted for the United States indicate likewise that coal production should not peak before about 200 years, but that the peak for natural gas production should occur in about 15 years and that for crude oil within the next 6 to 8 years.
From these considerations it is clear that although it has taken some 500 million years to produce the fossil fuels, their period of exploitation will be but a few centuries, which is brief even by the standard of human history. As a replacement for the fossil fuels we have the contemporary solar radiation, which is very large in magnitude but diffuse and difficult to accumulate, and the newly developed means of obtaining energy from nuclear sources. The exploitation of energy on an industrial scale from the fissioning of uranium is already an accomplished fact, and energy from the fusion of deuterium is obtainable in the uncontrolled form by the explosion of thermonuclear bombs. Controlled release of deuterium energy for power purposes appears to be a probable development in the comparatively near future. The energy obtainable from the known uranium and thorium deposits is several hundred times as large as that from all the fossil fuels; and, when controlled fusion of deuterium is accomplished, energy equivalent to that of all the fossil fuels can be obtained from only 7.6 cubic kilometers of sea water.
Thus, if humanity could solve its other problems, the outlook for a continuing energy supply would be very bright indeed. Offsetting this, however, is the report just released by the United Nations that the present world population of nearly 3 billion people is due to double in about 40 years, and would, at this rate of increase, reach a density of one man per square meter in 600 years. How or whether we shall ever escape from this predicament nobody knows.
Averitt, Paul, Berryhill, Louise R., and Taylor, Dorothy A. (1953), "Coal Resources of the United States (A progress report, October 1, 1953)," U. S. Geol. Surv. Circ. 293.
Hubbert, M. King (1958), "The Mineral Resources of Texas," Shell EPR Pub. 167; to be published in The Texas Quarterly.
United Nations (1958), "The Future Growth of World Population," Population Studies No. 28, Department of Economic and Social Affairs, New York.
Table 1. INITIAL WORLD SUPPLY OF FOSSIL FUELS EXTRACTABLE BY PRESENT METHODS
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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES
(*) Shell Development Company, Houston, Texas
Copyright © 1999 by The Gulf Coast Association of Geological Societies