Edward A. Walters University of New Mexico Albuquerque, 87131 and Eugene M. Wewerka Universitv of New Mexico Northern Branch Los Alamos, 87544
I I I
An Overview of the Energy Crisis
The events of the past year or two have convinced almost everyone that we are in the midst of an energy crisis of potentially disastrous proportions. The import of this crisis has created almost instant turmoil in the developed nations throughout the world. The economic and social implications of the energy crisis now dominate world politics, and energy has become a means of exerting intemational leverage. Unfortunately, a look to the future tells us that we can anticipate many more yeam-possibly even decades-of limited energy supplies, and that things are likely to get much worse before they get hetter. Certainly, the energy crisis represents one of the most serious technological problems ever to face mankind. In this article, we show how the energy crisis inevitably arose as a consequence of man's growing numbers and increasing standard of living. After these factors, we consider our current energy predicament, particularly the implications of our dwindling fossil-fuel resources. Finally, with a look into the future, we attempt to examine the altemative sources of man's energy needs as we approach the 2lst century. Long Term Trends in Energy Consumption The problem we call the energy crisis is the necessary culmination of two very long-term trends: the exponential increase in world population and the drive to higher per capita energy cons&$ion through social advancement. Energy is absolutely crucial for all we do. In fact, how much of it we consume may be used as a measure of our cultural development as illustrated by Figure 1. T o sustain his basic bodily functions man requires in the vicinity of 8000 Btu of energy per day. This is the daily energy requirement of today's most primitive people and probably is very close to the requirements of our anceston as civilization began to emerge thousands of years ago. With improvements in his ways of gathering food man found his life to be a little easier hut his energy requirements were increasing as well. For instance, when he learned to use oxen to do the work of plowing fields and drawing carts,
,.,-
".*
............ ... ...,..,........ ".................. ".. ".. ".r.1-,,1..
1..1~
......%...I
. . . . . . . . .a
Figure 1. The correlation between cultural development of man and per capita energy consumption is apparent in this comparison.
282 / Journal of Chemical Education
...............................
c.,,..,
Figure 2. The correlation between commercial energy consumption and gross national product (1972 data) is a general one that extends over the entire range of countries and their various stages of development.
he had to supply extra energy (food) for the oxen, but they more than paid him hack by allowing him to farm more land and raise more crops. The net result is an increase in standard of livine: it bmueht with it a corresponding increase in the eo&y cost of providing for each individual. Each maior cultural advance in man's history has been accompanied by a pronounced increase in capita energy consumption so that in today's post-industrial era each person is responsible for the consumption of about 900,000 Btu of energy per day. Of this only 1%is necessary to maintain our bodily functions; the rest is associated with the culture in which we live. This phenomenon reaches an extreme in the technologically advanced societv of the United States in which 6% of the earth's population consumes almost 35% of its energy. This concent can he illustrated for the world of todav in another manner. In Figure 2 we see what appears to 6e a good correlation between standard of livina as measured i y the gross national product (GNP) and capita energy consumption. The developing countries with their low GNP'S also have low per capita energy consumption and the more highly developed countries (high GNP) have high energy consumption rates. Perhaps the most striking feature of this graph is the very lofty position of the US. It is apparent that the crude, but direct, relationship between standard of living and per capita energy consumption is one of fundamental and long-term significance. By itself this relationship implies forbidding prohlems in assisting the developing countries into post-industrial society, hut these difficulties are amplified by a second, highly nonlinear, influence. This additional problem is known as the population explosion. Consider the earth's population growth illustrated in Figure 3. For about the last one-half million years world population has been increasing, initially at a fairly linear
Figure 3. When agriculture was introduced about 10.000 years ago human population was about 0.1 billion people. The population increased very gradually until about 1500 A.D. when it was approximately 0.7 bill i o n Since that time the population increased sharply to the current value of 3.9 billion (72).
rate but more recently a t an exponentially increasing rate. This rate has been nearly constant a t about 2% per year for a number of centuries. A 2% growth rate corresponds to a population douhling time of a.bout 36 years. One immediate rmsequence of this growth rate is that the 1976 world .oonulation of 3.9 x lo9 oeoole will increase to 6.0-6.5 X 109 by the year 2000. 0;e can also note that the wars, plagues, natural disasters, and epidemics of the last couple of millenia have not been of sufficient magnitude to cause even inflection points or slope changes on the population growth curve ( I ) . The energy crisis and the vast array of social, economic, and technological prohlems that this phrase engenders are then the inevitable result of both increasing standard of living and increasing population, each operating on a finite resource base. It is quite likely that earth will let man enjoy one or the other but not both.
.
Energy Consumption in the United States
Let us now turn our attention to the U S . as the c o d t r y perhaps most typical of the direction towards which much of the rest of the world is moving and for which a large amount of energy resource and consumption data is available (2). The energy source and consumption curves for the U.S. for the past 125 years are shown in Figure 4. In 1850 virtually all of our energy came from wood. This was followed by a period in which coal was the dominant energy source. Eventually petroleum and natural gas began to gain prominence, so that now about 95% of our energy comes from three fossil fuels: coal (20%), petroleum (45%), and natural gas (30%). Note that the last two by themselves account for about 75% of our energy. The current energy
,
j.,,
1.0.
I..,
l l J 0
1.11
ze..
Figure 4. Historical energy production curve for the U.S. from 1850 to the present (2).
consumption rate for the U S . is about 85 quadrillion (85 x 10'5) Btu per year. With a doubling time for energy consumption of about 20 years, the current rate will increase to almost 200 quadrillion Btu/yr by the year 2000. This extrapolation ignores the influence of any external forces to restrict growth in energy consumption in spite of the fact that it appears very unlikely that unrestricted gmwth will continue for long. In the U S . approximately one-third of the total energy goes into each of three end-use sectors; industry, household and commerce, and transportation. At the present time only about 10% of our total energy is used as electricity. Although this is a relatively small fraction, i t is gradually increasing with more and more electricity golng into the household-commercial and transportation sectors. Much of this increase can he attributed to increased use of air conditioning in homes and commercial buildings. Electricitv is expensive to produce; almost 25% of the nation's total energy output is now used to generate electricity. This is because the conversion of other forms of energy to electricity is seldom more than about 35% efficient. By the year 2000 it is anticipated that about 25% of our total work will be done by electricity; this will require a commitment of over one-half of the national energy budget. The Current Predicament
The current energy prohlem can now he defined: The two factors of exponential population growth and an ever increasing standard of living have combined to result in a doubling time for energy consumption in the U S . of about 20 years; yet we still depend almost exclusively on fossil fuels to meet these ever increasing demands for energy. The U.S. is but a familiar example of this worldwide problem and not a unique illustration. The pressing nature of the problem is clarified when the current reserves of the fossil fuels-coal, oil, and gas-are examined. For example, the area under the curve in Figure 5 is a composite of recent estimates (3) of the total amount of recoverable crude oil in the world. The bellshaped envelope measures the annual rate of utilization of cmde oil. The slow rise of the curve is attributed to the early difficulties of exploring for and extracting the oil; as methods are perfected the production rate increases rapidly until the limited supply forces a decrease in the production rate. Eventually the only known deposits will he in old fields which will be worked again until the reserves are finally depleted. The most significant time period for characterizing this curve is that in which the central 80% of the petroleum is produced. This ignores the initial ex-
Figure 5. Total oil production history of the world. If the ultimate quantity of oil produced were double that in this estimate. the useful lifetime of the world's petroleum reserves would be extended by only one or two decades. The year of maximum production in the United States is variously estimated to lie between 1970and 1985.
Volume 52. Number 5, May 1975 / 283
............. ......
................ ............ .... ...... ..... .,.."
I . . .
"1I.I.
"-3..
Figure 6. Location and quantity of petroleum reserves around the world. The shaded area indicates the total amount of oil produced in the period 7859-1971 and the height of each bar indicates total original reserves.
ploratory period as well as the terminal one. In this particular estimate the characteristic time is the 64-year period from 1967 to 2031. Maximum world production is estimated to he close to the year 2000. It has become apparent that not only is the quantity of crude oil an important parameter, hut so is its location. This geographical information is given in Figure 6. The height of each bar on the graph indicates the total original reserves in that part of the world, and the shaded area indicates the amount removed by 1973. I t is evident that about 75% of the reserves in North America have already been consumed, and that by far the greatest fraction of the world's remaining reserves is located in the Middle East. Since industrial nations typically derive about 45% of their energy from petroleum, it appears that the Middle East will play a pivotal role in world politics, economics, and finance at least as long as it owns a large fraction of the world's petroleum reserves. Data for U S . petroleum reserves and consumption rates are summarized in Table 1. The total probable reserves of crude oil are 882 x 10'5 Btu assuming a recovery efficiency in new fields of 42%. Presently employed primary and secondary extraction techniques recover only about 28% of the petroleum in a field. At the current consumption rate U S . petroleum reserves will last about 30 years. It is quite widely appreciated that the reserves of natural gas are relatively limited. On the basis of projections analogous to the one illustrated for petroleum, i t has been estimated that 80% of the nation's initial supply of natural gas will he extracted between 1950 and 2015. The year of maximum production was around 1970 (4). The pmhahle U S . reserves amount to approximately 945 X ~
~1. Us. b Energy l ~ Reserves and Consumption Rates, loLSm u (.I I .) consumption
Rate
Yea's
Probable reservea Oil Gaa
Coal Urhnium'-235 Plutonium-239
882 (@ 42% recovery) 945 (@ 82% recover^) 30,200 (@ 5070 recovery) 0""
ited Probable reserves consist of those known to exist plus those reasonably aeaured eiven oresent data and technology. ~
~
~
~
At 1970 mkxnption ram. "Traditional uses only,not including gasification, d A t estimated 1985 consumption rate. than $30/lb of ore concentrate. or uIOscostimg no in 10" ~ t u / y rby the year 2000. I P-ible generating
&.
284 / Journal of ChemicalEducation
10'"tu based in part on a presumed recovery efficiency of 82%. This would he sufficient to last more than 45 yean a t current production rates. These figures contain contributions from unorthodox techniques such as the use of underground explosions (nuclear or conventional) to stimulate gas flow. The fossil fuel, coal, is one for which t h e e are large known reserves. It is believed that all major coal deposits have been located and at least crudely mapped. According to an estimate made several years ago 8090 of the world's coal would he removed over a 350-year period beginning about 2030 (4). Very recent events have encouraged a dramatic increase in the rate of coal production which, if continued for a significant period of time, could shorten the anticipated lifetime of this fossil fuel. Coal is as unevenly distributed over the earth as is oil. By far the richest countries in coal are the U S . and U.S.S.R. In addition to having virtually no coal deposits, South America, Africa, India, and Oceania are generally deficient in all types of fossil fuel. Since fossil fuels have historically provided the energy to run the industries of the developed countries, it is clear that the future industrial growth of these countries depends upon ensuring their access to the world's p w l of fossil fuels. Within the U S . , the coals have a variety of grades depending upon the extent of carbonization of the plant matter from which they came. The harder and more carboniferous coals, anthracite and bituminous, are generally located in the eastern U S . Although there are large quantities of these high energy fuels available, they are somewhat unsatisfactory because their high sulfur content tends to produce undesirable sulfur oxide levels in the atmosphere. On the other hand, the sub-bituminous coals of the western U S . are low in sulfur and quite adequate for electrical generation purposes. (Sub-bituminous coals often contain a large fraction of inorganic material which is converted to oxide and silicate particulate matter. If not removed, particulates can cause environmental prohlems as serious as those of the high-sulfur coals.) The western coal reserves are in many cases accessible only by strip mining methods. If 50% of the known U S . coal deposits are recoverable, then reserves amount to 30,200 X 1015 Btu, which is enough to last more than 2000 years a t the current consumption rate. Unquestionably, coal will he our major source of energy in the relatively near future. From this discussion it is evident that the United States presently derives about 9590 of its energy from fossil fuels, the majority of it from gas and oil, and only about 20% from coal. There are tremendous problems associated with dramatically increased coal consumption-strip mining, the volume of material to he processed, water, environmental distress, low use efficiency, etc.-which, as we shall see later, will probably encourage the development of new and more efficient methods of conversion of coal to energy in more usable forms. Energy Alternatives for the Future
For convenience the foreseeable future can he divided into short-term and long-term components. Oddly enough, it is easier to anticipate our long-range possibilities than it is to detail what is in store during the intermediate transition period. Consequently, we review first the longterm possibilities and then the near-term alternatives. Neglecting the fossil fuels, the four long-term potential energy sources are nuclear fission reactors (including the different versions of the breeder reactor), geothermal sources, solar energy, and nuclear fusion. Let us consider each of these in more detail. Nuclear fission takes advantage of the fact that the nucleus of the uranium isotope with a mass of 235 amu can he cleaved when it is struck by slow moving thermal neutrons
"TI +
n
fission products
+ 2n + energy + radiation
The fission products consist of a large variety of species such as 83Rh, 141Cs, 1311, 90Sr, and s5Kr whose masses cluster around 85 and 135 amu. In nuclear reactors the ene -, m released hv fission is converted to heat, which in turn is used to generate electricity. Ideally, the fission products remain trarmed .. within the fuel rods inside the reactor. Nuclear fission is an attractive energy source because of the compactness of the fuel and the concentration of the are capable of energy. For example, about 3 kg of 23" generating as much electricity a t 2000 railmad cars of coal. One problem with uranium is, however. that i t is not a very abundant element on earth. The current price of minine uranium is about $8/lh of the oxide, U308. Until recenGy only the most condentrated nranium ores could compete economically with petroleum as a source of enersince the very dramatic increases in the cost gy. of oil during late 1973, it has become possible to consider mining lower grade uranium ores; therefore exploration and mining activities are once again beginning. There are approximately 900 x 1015 Btu of known and prohab!e reserves of U3OS (Table 1) available a t $30/lh, wh~ch1s close to the current equivalent cost of petroleum energy. Although the 1970 consumption rate of nuclear energy was very small, rapid development of this energy source is anticipated so that by 1985 the consumption rate will be such that U S . reserves of 235U will last only 30-40 years. The advantages and disadvantages of fission reactors are summarized in Tahle 2. Unlike all the other long-term energy options, we currently have the necessary knowledge and technology for using it. In addition, nuclear energy is known to be inherently less damaging to the environment than the fossil fuels because problems of sulfur oxides, hydrocarbons, nitrogen oxides, and fly-ash do not exist for nuclear installations. On the other hand there are clear and definite disadvantages of almost crippling proportions associated with this method. The thermal efficiencv of eeneratine electricity from nuclear reactions is significantry below ihe ahead; low value for coal powered ~ l a n t s Also. . the known reserves of uranium are quite limited. There is much concern-and rightly s-about possible spills and accidental release of radioactive contaminants. An additional set of prohlems that will continue to grow as the number of nuclear installations increases are those associated with the transportation and handling of highly radioactive and fissionahle material by untrained personnel. This also raises the possibility of fissionahle isotopes falling into the hands of irresponsible people
ow ever,
Table 2. Advantages and Disadvantages of Future Energy Sources Advantaees
Disadvantaaae
" ' U fission
Present technology exists Leas pouutiing than fossil fuels
Breeder reactors
Technology almost ready Les ~ U u t i n gthan fossil f,,da -.-Relstivdy large reserves Relatively clean Few hazards Relatively simple tech-
Small resewRadioactive wastes Hazards involving radioactive species Radioactive wastea Radioactive and fi=iionable materials hazards
.%..."o
Geothermal
" " I" ." . . . a >
Reserves uncertain Parsibla teetonic &ecta Air wllution Some noise muution L&
Solar
Fueion
Unlimited reserves very clehn Reduction o; thermal poU"ti0" Conceptually simple Adaptable to individual Cksn
(?I
Unlimited -vae
"= etli2i"w
vary diffuse, diffioult to collect Technolow not ready for large Gale uae Distribution and storage problems Geographical limitation and restrictions Technology will not be available for many (50) years .Others (?I
through hijack or sabotage. Finally, the spent fuel is contaminated with many radioactive fission products, some of which must he stored for thousands of years before they can he safely released into the environment. For us this is a complex problem, and for our children's children it will he a most interesting legacy (5). The auestion arises: With the vew limited reserves of 6 , wkY do we press so vigorously tb enlarge our nuclear eeneratine- capability? The answer lies in the fact that an. other class of nuclear reactors, hreeder reactors, can pmduce more fuel than they consume. The isotope 235U is the only naturally occurring fissionahle isotope present in sufficient quantity to consider employing it. Even a t that 235U makes up only 0.7% of native uranium; the remaining 99.3% is almost entirely the nonfissionahle isotope 23W. I t has been known since the early 1940's that 238U can he transformed into a fissionahle isotope of plutonium, Z39Pu, if it is bomharded by high energy neutrons
-
In addition, 232Th, which makes up virtually all of natural thorium, can he bred into the fissionahle isotope 233U
With proper design, reactors in which hreeding reactions occur can he made to generate electricity from the excess heat from the nuclear reactions which produce the fast neutrons. The net result is that more fuel is produced than is consumed while electricity is generated. These new fissionahle materials can now be used in exactly the same way as 235U ='PU
+n +n
+
+ n + beat + radiation fission products + n + heat + radiation fission products
The reason for the excitement and research in hreeder reactors becomes evident when we examine the effect breeding has on the potential reserves. At $30/lh of U3O8 the uranium (only) reserves are about 130 times greater with hreeding than without. This means that the 35-year reserve of naturally fissionahle material can he extended to something in the vicinity of a 4500-year reserve, at 1985 consumption rates, with breeding. The significant advantage of this fuel source (Table 2) is the potential reserve. Breeding is also a proven process; hreeder reactors have been operational since the 1950's. Many of the same disadvantages that apply to simple fission reactors are important here, too. There are additional drawbacks, however; one of these is associated with t h e , engineering, materials, safety, and reliability prohlems arising from trying to move too quickly from small-scale breeders to very large-scale power generating facilities. Another major drawback is that it is widely believed that the hazards associated with plutonium are very severe because this element is one of the most toxic materials known to man. Although no humans are known to have died from plutonium poisoning it is believed, on the hasis of animal tests. that on the order of 6 ME .inhaled into the lungs are capable of inducing cancer: Consider now geothermal energy (6). In the conventional method heat 'from the earth's molten core collects in ground water by 'converting it to steam which is then tapped and used to do work. There are fundamentally two different kinds of steam encountered below the earth's surface. In places where underground water is superheated by hot rock to produce a mixture of hot water and steam the product is referred to as "wet steam." The water in wet steam generally contains a high concentration of dissolved salts and is therefore very corrosive to the machinery it contacts. On the other hand, "dry steam" conVolume 52, Number 5. May 1975 / 285
sists almost entirely of steam that comes from the water of hydration of the heated rocks. A newer and undeveloped technique is also being explored which produces "dry rock steam." In this method a hole is drilled into a site of unusually hot rock near the earth's surface and the wellknown oil field technique of hydrofracturing is used to shatter the hot rock so that many pores and crevices are created. Then, water is pumped into the fractured region where it is converted to steam which in turn is removed through a second hole drilled into the top of the fractured region. The steam is used in the conventional way to produce electricity. The reserves of geothermal energy are very difficult to estimate because of the lack of knowledge of locations of wet and d w steam reserves and of thermal anomalies near the surface. In Tahle 1 are some conservative estimates of the amount of Dower available in the year 2000 from all three sources. Recall, by comparison, that the total U S . energy consumption in that year is projected to be in the vicinity of 200 x 10'5 Btu, so that although geothermal energy may make a significant contribution to our energy requirements, it cannot he expected to assume the role that any of the fossil fuels play atpresent on the energy market. The advantages (Tahle 2) of geothermal energy are related to the conceptual simplicity and cleanliness of the method. Geothermal energy does have its drawbacks as well, most of which are related to its unknowns. In the first place, the reserves are uncertain; different authorities give widely varying estimates. Additionally, it is thought possible that shifts in the earth's crust (tectonic effects) may he induced by pumping large quantities of water into geologically sensitive areas. There will probably be relatively small amounts of localized air pollution from the sulfur compounds brought to surface. Finally, more effort must he put into the design of turbines operating a t low temperatures in order to improve their efficiency. All in all, it appears that geothermal energy has some significant possibilities, hut many questions remain to he answered. One of the most attractive, and glamorous, of our potential energy sources is the sun. The plans for generating large quantities of power by this method generally involve collecting the solar energy over arid, nonpopulous locations and transmitting it to urban areas for use. The advantages ofsolar energy, seen in Tahle 2, are numerous: unrestricted reserves, probable compatibility with a high quality environment, conceptual simplicity, and adaptability to individual use. There are a variety of reasons why this resource is not extensively used today. The fact that the energy is so dilute has discouraged commercial exploitation and caused the efforts for utilizing solar energy to he oriented not towards large scale devices, but towards individual household collecting units. There still remain many uncertainties related to alternate power facilities for nights and cloudy days. Finally, it is true that most population centers are not located where the sun shines most, so that geographical considerations become significant. The fourth long-term energy source is nuclear fusion. The principle behind this concept is that when nuclei of atoms are fused together the binding energy must be released. The magnitude of this energy is very great and when properly contained it could he used to perform large amounts of work. The nucleus which undergoes fusion at the lowest temperature is deuterium; the important fusion steps are D + D 3 ~ e n energy D + D T H + energy
-- ++ + + - + + + + T
5D
D
'He
' ~ e n
+
%e
H
286 / Journal of Chemical Education
The net result is a fusion of five deuterium atoms to produce neutrons, hydrogen, two isotopes of helium, and energy. On a weight basis, deuterium fusion produces approximately three times as much energy as fission of Z35U. Ideally there is no net production of radioactive products. Even though neutrons are generated in large quantity a t the reaction site, they have short lifetimes and pose no hazard beyond the immediate vicinity of a reactor. There are other fusion reactions that occur a t somewhat higher temperature with even more abundant fuel sources than deuterium. For example, a hydrogen and deuterium atom or two hydrogen atoms may he fused provided the requisite ignition temperatures can be attained. Reaching these very high temperatures (-109'C) has been a problem that is not yet solved. Currently one of the most active areas of fusion research is centered on attempts to achieve fusion temperatures by concentrating the output of high intensity laser radiation on a pellet of fusible fuel. The likelihood of success of this approach is highly questionable, however. The potential reserves of deuterium for fusion fuel are reasonably easy to estimate. Most of the world's hydrogen is hound up in the water of the oceans. If all the deuterium in seawater were used in nuclear fusion, the energy generated would he about 1028 Btu (Tahle 1). This quantity of energy is about 101' times the current annual energy consumption of the U.S. This number would he orders of magnitude larger if hydrogen could he used as a fuel. Thus, nuclear fusion is potentially an undepletahle energy process for all of mankind. The prospective reserve is one of the chief advantages of nuclear fusion (Tahle 2) and another is the likelihood that it would he a clean energy source as well. How true this will he when full-scale plants become possible is not clear yet, because the process is not developed to the extent that the problems coming from the high neutron flux can be accurately predicted. There will doubtless be severe materials problems to he surmounted before commercial reactors are used. The most serious disadvantage that currently looms is that the technology for carrying out controlled fusion is not now available so the commercial scale installations will not he possible for perhaps another 50 years. As the shape, design, and performance of the eventual reactors become known, we may come to recognize additional drawhacks to fusion. T o summarize, it appears that there are several longterm energy options open to us: breeder reactors, nuclear fusion, geothermal sources, and the sun. It is not likely, however, that any of them will contribute in a substantial
energy
2n f energy
Figure 7. A projection of future energy sources. This projection reflects the discussion oresented in the text.
manner to our energy demands prior to the year 2000, but during the next century they should achieve maturity. One plausible way in which the development of these sources may proceed is shown in Figure 7. The projection has the total energy consumption leveling at a rate of 250 x 10'5 Btu/yr towards the end of the next century. This is a rather optimistic projection in light of the very serious proposal to develop a national economy that requires no more than 100 X 1015Btu/yr (7). Short Term Problem The question now arises: How can we bridge the gap between our present fossil-fuel economy and the long-term energy-based society that will become ever more prevalent during the next several decades? Somehow the currently available sources are the ones that must be used. The other options have been reviewed and they are not comforting. There are three categories of short t e r n alternatives: unlikely1 (solar, hydroelectric, tidal, wastes, wood, wind, and water-including thermal gradients and ocean currents); ~ossible(geothermal and fission reactors); likely (fossil fuels, but especially coal). Coal is the only immediately available energy resource for which the use technology is well developed. Compared to either natural gas or oil, the U.S. reserves oC coal are immense (Table 1 ) . This is its prime advantage (Table 2). The disadvantages of coal are numerous. Were it not for the fact that coal is our nation's only convenient large-scale energy resource, i t would probably not be used extensively. Regardless of our distaste for its drawbacks, coal will be used in very large quantities in the near future. Much of it will be used in the conventional process of combustion to produce electricity, hut there are other ways in which coal can be used which may be both more efficient and less damaging to the environment. Let us now examine some of the possible future nonconventional uses of the coal. Two of these are coal gasification (8) and magnetohydrodynamics (9). The development of either of these methods into commercially acceptable processes could provide a substantial boost in the nation's efforts to make the transition from the fossil fuel economy to the longterm economy a comfortable one. The chief reactions in the gasification of coal are coal
-
CO
+ H*O
CO
+
3H,
CH,
+
+C CO,
+ H,
CH4
+ H20
In the initial steps coal is heated to a high temperature a under high pressures and reacted with steam to mixture of carbon monoxide and hydrogen. This gas has a low energy content, but it may he burned on-site t o generate electricity. If a high energy gas is desired, some of the carbon monoxide is reacted further with water to generate more hydrogen, which is eventually used in the catalytic reduction of carbon monoxide to methane. The resulting gas (high Btu gas) is virtually equivalent to natural gas, so it can be used as a substitute pipelines gas. One of the chief advantages to this route of-coal consknption is the relative ease of removal of sulfur contaminants from the gas. There still remain serious technological, social, and
environmental problems which must he surmounted hefore coal gasification will be ready for commercial use in this country, but several companies have announced their intention to construct huge gasification plants in Western states in the near future. In the magnetohydrodynamic method of burning or consuming coal an effort is made to improve the thermodynamic efficiencies which characterize conventional electrical generating plants. The technique consists of heating coal to a high enough temperature (> 2000°C) to partially ionize it. The ions are then drawn through a magnetic field by charged plates; the flow of ions induces an electric current in windings about the magnets. The current may then be removed and distributed in customary ways. The high operating temperature is expected to make possible efficiencies on the order of 65%. Unfortunately, this method has not yet been developed to the point where it can be used on a large scale. Parenthetical to what we have already said about fossilfuel reserves, there is yet another potential source of hydrocarbon feedstock worth considering. This is the massive deposit of oil shale located in the inter-mountain region of Colorado, Wyoming, and Utah. In spite of its name, oil shale is neither shale nor does it contain oil, rather it is a marlstone that has interspersed within its structure about 20% of a difficult-to-~rocesshydrocarbon polymer called kerogen. Products resembling crude oils can be obtained from oil shale by crushing the shale and pyrolvzine it to degrade the keroeen. Serious doubts exist. " however, as to whether the technical and environmental problems of ~rocessinaoil shale can be worked out in an &onomically'feasible manner. In any case, i t is doubtful that oil shale would have any significant impact on our energy economy before 1990 or so. Nevertheless, there is an impressively large return in store if it is possible to come up with suitable solutions to the oil-shale-processing problems. The potential reserves of shale oil in Colorado alone may be as much as ten times as large as our total original reserves of conventional crude oil. We must conclude, however, that of all the alternatives available for the production of the energy there is only one-coal-for which the resources and technology are ready to meet increased energy requirements during the next few decades.
-
Conclusion The current energy problems and hence many of the worldwide economic difficulties are a consequence of the long-term factors of population growth and rising standards of living. Although possibilities exist for obtaining almost undepletable energy resources, they appear to be several decades removed from the large scale production stage. In the meantime, we may anticipate recurrent energy shortages coupled with rising prices for energy. It is also quite likely that international tension will remain high as oil supplies dwindle. These considerations emphasize the need for this nation to embark on a serious program of energy conservation. If the national energy consumption-and, therefore, the standard (but not necessarily the quality) of living-can be restrained, then perhaps the next few decades will not be quite so unsettling as we have just implied (10). Literature Cited
'These are regarded as unlikely because the sources are so widely and thinly. distributed (solar and wastes) that large scale energy production is now economically unfeasible, because the quantities are so limited (hydroelectric, tidal, winds, and wood), and because we lack the technology to use the resources effectively (ocean currents and thermal gradients).
(11 The Sept,tembor, 1974 issue of Scientific Amencan is devoted to an analysis of tho sfatusof the human population. (2) US. E n e r ~ yOutlaoh. National Petmleum Council. Washington, D.C.. IOecember
,"*", 'z,z,,
(31 Hubben. M . K., in ''Resource$ and Man," Fleernsn. San Fmneinco. 1969. g. 157; Berg, R.R.. Calhoun..lr., J.C.. and Whitinp.R.L..Scienrr, 184,331 (19741. (41 Hubhert. M.K., SeeRef(3J.
Volume 52, Number 5, May 1975 /
287
(5) BulleLin of the Atomic Scientists, October and November. 119741. Thew h e 8 mntain avcryreecnt analyrisof nuelcar d e f y pmhlemsand the"status. 161 R0bnon.G.R.. Sclpnee. 184,371 119741. y APreliminaryRepon."TheFordFoundation, 1974. (71 "ExploRng E n e ~ Choiiii, 181 Hemmond. A.. Motz. W., and Mauah II. T., "Eneqy and the Future." M S . 197% S w i m . A.M..Scloner. 184,NOI19741. 191 Hsmmond.A., Metz, W.. andMauphII.T.. SeeRef. (8).
288 / Journal of Chemical Education
