OPENING REMARKS

One of the most important developments in contemporary scientific and technical thought is the growing awareness of the significance of energy in human affairs. The universality of energy in terrestrial activities can be appreciated when we consider that the earth is a nearly closed material system through whose surface environment occurs a continuous influx, degradation, and efflux of energy. As a consequence, the mobile materials of the earth’s surface undergo either continuous or intermittent circulation. These statements encompass just about everything that happens on the earth, including our being here today at this Conference.

This flux of energy is a continuing process that, with only minor variations, has persisted throughout the span of geologic time. The principal sources of energy influx are but three: the solar radiation intercepted by the earth, geothermal energy from the earth’s interior, and tidal energy from the potential and kinetic energy of the earth-moon-sun system.

Measured in units of 1012 thermal watts (Wth), the rates of influx from these sources are solar, 174,000; geothermal, 32; tidal, 3. It is thus seen that the solar influx is about 5000 times the sum of the other two.

Of the solar influx, about 30%, or 52 ˙ 1012 Wth, is reflected and scattered into outer space as visible short-wavelength radiation. This fraction is ineffective with respect to terrestrial processes. The remaining 70%, or 122,000 ˙ 1012 Wth, warms the earth, drives the circulation of air and water, and a small fraction, stored chemically by the process of photosynthesis, becomes the basic energy source for the physiological requirements of the plant and animal kingdoms of the earth’s biological system. With one small exception, this energy undergoes a series of degradations until it reaches an end state of heat at the lowest ambient temperature of the earth’s surface. This is then re-radiated to colder outer space as long-wavelength thermal radiation.

The minor exception pertains to the minute fraction of plant and animal materials that become deposited in peat bogs and other oxygen-deficient localities where they cannot completely decay. When these became buried under great thicknesses of sedimentary sands and muds during the geologic past, they were preserved and converted into the earth’s present supply of fossil fuels.

These processes are occurring now, and they also have been occurring during at least 600 million years of geological history. The oldest gas field of which I am aware has been found in Australia in late Pre-Cambrian rocks–perhaps 600 to 700 million years ago. In the USA and other parts of the world, oil and gas accumulations have been found in rocks of all geological ages from the Cambrian, nearly 600 million years ago, to the last million years in the Mississippi delta of coastal Louisiana.

The oldest major coal deposits are the bituminous and anthracite coals of the Carboniferous Period, about 280 to 350 million years ago. Then there are younger subbituminous coals of Mesozoic age (65 to 200 million years ago), Tertiary lignites, and finally peat which is accumulating at present.

The energy stored in the initial supply (before human exploitation) of recoverable fossil fuels is estimated to amount to 2.3 ˙ 1023 thermal joules (Jth). Other static stores of energy within mineable or drillable depths beneath the earth’s surface are represented by earth heat, and by the nuclear energy obtainable from the heavy elements uranium and thorium by fissioning, or from the lightest element, hydrogen, by fusion.

An informative comparison can be made between the magnitude of the stored energy of the fossil fuels and the rate at which energy impinges upon the earth from sunshine. The energy obtainable from the fossil fuels, as we have noted, amounts to about 2.3 ˙ 1023 Jth. The effective solar energy influx is at a rate of about 1.22 ˙ 1017 Wth, or joules per second. This amounts to 1.05 ˙ 1022 joules per day, and the time required for the energy accrual from the solar influx to equal the stored energy of fossil fuels is only 22 days.

Considering that the solar influx is continuous and has been at about the same rate for hundreds of millions of years, it becomes obvious that the largest source of energy available to the earth, past, present, or future, is that from the sun.

Let us now consider the human historical evolution which I think is pertinent to this Conference. We have noted that the time required for the accumulation of the fossil fuels was about 600 million years. It has been only within the last 2 or 3 million years that man has emerged as the world’s dominant animal species. During this period man began to do things with the environmental energy flux that no other animal in geological history had ever done before. Initially, this consisted of the manipulation of the ecological-biological system in such a manner as to increase the food supply. Then, about a million years ago, he did a momentous thing: he learned to build a fire, thus tapping the energy of wood–still a biological source of energy, but one not previously utilized for human purposes. By the time of the ancient Egyptians, he tapped a nonbiological energy channel, namely windpower, and by Roman times, waterpower. The net effect of all such activities was to increase the human population, both in density and in geographical extent, with corresponding adjustments in the populations of all other plant and animal species of the ecological system. However, the energy per capita increased but slightly because these changes occurred so slowly that the growth of the human population was fully able to keep pace with the increase of the energy supply. In fact, it was not until continuous exploitation of the fossil fuels was begun–coal about nine centuries ago and petroleum in 1859–that a supply of energy became available whose rate of increase of exploitation was capable of being greater than the rate of growth of the population.

There is a great contrast between the recent past and the present. Despite the fact that coal has been mined continuously since the eleventh century, the amount of coal mined since 1940 exceeds somewhat the amount mined during the preceding nine centuries. Similarly, the amount of oil produced since 1965 is slightly more than all the oil produced before 1965.

Finally, the fossil fuels are absolutely exhaustible. When coal or oil is burned the material constituents remain on the earth, but the energy content, after a series of degradations, eventually leaves the earth by outward radiation. According to the best present estimates of the world’s ultimate crude oil supply–which I think are reasonably accurate–the world will probably reach the peak in its rate of oil production before the end of the present century. Disregarding the first and last 10-percentiles of the ultimate production each of which will require a longer period of time, the time required to consume the middle 80% of the world’s ultimate oil supply will probably be close to the 60-year period from about 1970 to 2030. Thus, a child born within the last decade, if he lives a normal life expectancy, will see the world consume most of its oil during his lifetime. In the case of coal, the time span for the middle 80% is somewhat longer, but, according to one of the papers to be given at this Conference, it is possible that recent estimates of the world’s coal resources may have been too large. In that case the peak in the rate of coal production may be reached within about a century from now. The time required to produce the middle 80% of coal may be as short as 200 years.

Hence, if we regard the period of exploitation of the world’s supply of fossil fuels in the context of a period of human history extending from about 5000 years in the past to 5000 years in the future, the curve of the rate of production of energy from the fossil fuels would appear as...