114 PRESENTATIONOF FRANKLIN MEDAL. [J. F. I. THE PROBLEM OF THE WORLD'S SUPPLY OF ENERGY. BY SVANTE AUGUST ARRHENIUS, Ph.D., M.D., D.Sc., LL.D. SINCE the days of Watt the physical well-being of mankind has become more and more dependent on fossil fuels. The life of to-day would be impossible without the enormous supply of coal necessary to industrial establishments, for railways and steamships, in the metallurgical arts and for the heating and lighting of our houses. The demand for fossil coal has increased very rapidly, about doubling every ten years during the last .cen- tury, and is now some 12oo millions of metric tons per year. It is clear to those who have studied the matter that our coal fields will be exhausted after a certain, time. When this calamity will happen, and the probability of the discovery of substitute sources of energy, are questions of vital importance. One of these questions was answered by the Geological Con- gress in Canada in I913. The quantity of fossil coal down to a depth of IgOO metres would suffice for 6ooo years, at the present rate of consumption, if it were all recoverable, but a very great deal of this coal occurs in beds too thin for profitable working, a considerable part is lost as dust, or !eft in the mines as pillars, and further, the use of coal will probably increase in the future just as it has done in the past. It is, therefore, necessary to reduce the indicated time considerably, probably to one-fourth, or about I5OO years. Of the different countries the United States, in the matter of coal, has the best position, as it has in the matter of other natural resources. The coal treasures there will probably suffice for about two thousand years. The worst situation among the great coal- producing countries is that of England, where the coals will be exhausted within a little less than two hundred years. Germany will be able to meet its demands during a little more than a thousand years. This time of some few hundreds or thousands of years is very short compared with the time e~timate made at the Geo- logical Congress referred to, and only about one per cent. of the period of man's existence, which probably lies between the thou- sandth and ten-thousandth part of the time during which life July, 192o.] PRESENTATION OF FRANKLIN MEDAL. I 1.5 has existed on our earth. It is quite clear that we must soon ration our coal, and substitute as far as possible for fossil fuel other sources of energy. It is often suggested that we might use mineral oils as fuel instead of coals. This advice rather reminds one of the words of Marie Antoinette: " If the people complain that they have no bread to eat, why do they not ,eat cakes ?" Petroleum is a far more valuable fuel than coal, because it is much easier to trans- port and to use effectively. The world's yearly production of mineral oils represents not quite three per cent. o.f the energy contained in the yearly production of coal. Petroleum ought, therefore, to be reserved for better purposes, e.g., production c,f light and lubricants. Further, the recent failure of many oil fields indicates that we must economize this valuable material. ~'\ccording to David T. Day, U. S. Geological Survey, the produc- tion per well in the Appalachian oil field decreased from 2o 7 barrels in I86~ to 1.73 barrels in 19o 7 . The production of West Virginia had, in I9IO, declined 56 per cent. from its maximum output. The oil obtained from the New York and Pennsylvania oil fields fell to 5o per cent. from the year 1891 to 1898. If we suppose the present fields o,f the United States and the present rate of exploitation should continue, petroleum would be ex- hausted by about 1935, and if the present production goes on with no increase, the product would be exhausted in about ninety years, said Charles R. van Hise in I91O, who has done so much to warn against waste in the expenditure of our natural resources. The output of mineral oil has been kept up through an enormous increase in the number of oil wells in each field, and by opening ~lp new fields, e.g., in Oklahoma and California. There are ve D" rich new oil fields in the world which are still not used, or only in a small degree, e.g., in Mexico and Mesopotamia and Turkes- tan, but certainly they will not last as long as the coal fields, even if the production of this fuel is restrained to but three per cent. of the simultaneous production of the latter. Still much less is the hope that sources of natural gas may deliver more than a small fraction of the fuel value of the oil fields. Even peat, although an important fuel, can by no means compete with coal. Thus, for instance, in the United States the available peat is less than one-half of one per cent. of the esti- mated coal. Probably the relative value of the European peat i i6 PRESENTATION OF FRANKLIN MEDAL. [j'. F. I. bogs is about the same as compared with the European coal fields. For heating purposes petroleum and peat cannot play an important r61e as compared with fossil coal. It is very often said that for coal should be substituted the water power of our rivers, often called the " white coal." Ac- cording to an estimate of Engler, the energy which might be economically taken out from these waterfalls amounts to about 6o per cent. of the energy of the present output of coal. But even this figure seems too high, for many o.f the waterfalls are located in rather inaccessible parts of the world, where no indus- try is likely to be developed for a long time. So it seems wise to reduce the figure of Engler about 5 ° per cent. If this is done, it is evident that there is little hope that white coal will be able to substitute for black, except in a small degree. For heating purposes, water power will probably not be used in a noteworthy degree, because used directly for the production of mechanical or electrical energy it is at least three times as valuable as the equivalent quantity of heat. Further, the well-situated water- falls are already developed in greatest part, at least, in Europe. Thus, for instance, in Switzerland nearly all the waterfalls which have a commercial value are developed, and in a little less degree the same is true in all the other industrial countries of Europe. During the unhappy situation created by the world war, when there was a great scarcity of fuel, and even now, when fuel is extremely expensive, waterfalls were and rapidly are being put to use. Within a short time, therefore, this source of energy will be taken into the service of man, not sensibly diminishing the demand for coal. An estimate of the power of the waterfalls has been made by Koehn and by Keplan, and is of much interest. Although the figures are only approximate, I give them below, with some later corrections. The power is given in millions of horsepower and horsepower per inhabitant: Horsepower Horsepower Country in Millions per Inhabitant Asia ................................... 236 0.27 Africa ................................. i6o 1.14 North America ......................... 16o I.I7 South America ......................... 94 5.25 Europe ................................ 65 o.13 Australia ............................... 30 3.75 Total ............................... 745 Average 0.45 July, I92O-] })RESENTATION OF FRANKLIN ~,'IEDAL. II 7 Horsepower Horsepower Country in Millions per Inhabitant Canada ................................. 26 4 United States ........................... ioo I Iceland ................................. 2 22 Norway ................................ 13 5.2 Sweden ................................ 6. 7 1.2 Finland ................................ 2.6 0.8 Balkan Countries ....................... IO 0.6 Switzerland ............................ 1.5 0.4 Spain .................................. 5.2 0.26 Italy ................................... 5.5 o.15 France ................................. 6.0 o.15 Austria-Hungary ........................ 6.2 o.12 Germany ............................... 1.43 0.02 Great Britain .......................... 1.0 0.02 Russia ................................. 3.0 0.02 These figures are not altogether reliable. Thus, for instance, Leighton gives for the United States 2oo millions, and van Hise says: " Others regard this estimate as too high, and say Ioo million horsepower is nearer to truth." I think this latter figure is more to be depended on. Van Hise is of the opinion that even it will meet the needs of a population of 25o,ooo,ooo. Since his estimate made in 19IO the demands for power have greatly increased, and probably only about one-half of the energy given in the table above is available at present without excessive initial expenditures. We may, therefore, assume o. 5 horsepower per inhabitant as adequate to present needs. We find then that Europe and Asia are the only parts of the world where water power is really scanty--in Asia the demand is still so small that even this power per inhabitant is more than sufficient. Especially fortunate are those countries, such as South American Republics, and Australia, where water power per unit of population is well beyond this figure, and may be developed at a moderate cost. The United States is among the great powers very well endowed in this regard, as in most other natural sources of wealth, such as metal, ores and coal. In Europe, Iceland ranks first, because of its small population, and the old Saga Island may yet know a new and flourishing era. Then come the Scandinavian countries, the first being Norway, which has already greatly profited through its cheap power, and is destined to be one of the leading industrial countries of the future.