Air University Review, November-December 1980

Coal A Long-Term Energy Alternative

OVER the ages man's energy problem has consistently been to develop the means to convert available energy sources from their native state to a form usable to perform a specific task. Worldwide energy resources are virtually limitless. However, as the more economically recoverable sources are depleted, there can be lags in developing the technology to exploit the less available energy resources. For example, it is estimated that the lead time for conversion of electricity production plants from liquid to solid fuel is five years.¹

The ultimate source of all energy is the sun. The vast amounts of radiant energy received by the earth energize the photosynthetic processes of green plants. Plants provide the basic material from which coal, natural gas, and oil have evolved. By heating the land and oceans, the sun sets in motion the processes that create rain and wind, making it possible for man to capture energy through windmills and waterwheels. (The only significant sources of energy not derived from the sun are nuclear power and the as yet untapped energy of tides.) Scientists describe energy with a common term heat, and the standard of measurement is the British thermal unit (Btu). Each Btu represents the amount of heat required to raise the temperature of one pound of pure water one degree Fahrenheit at sea level.

Man's first experience with combustibles is obscure. Perhaps volcanic action or lightning ignited savanna or forest, and fire became a tool rather than a transient phenomenon. Wood was the first of man's fuels. He was surrounded by seemingly endless tracts of forest, and it must have appeared that there was no limit to this energy supply. By the time of Babylonian, Greek, and Roman civilizations, man had learned to produce light from animal fats and vegetable oils and from pitch, a black, oily substance from the earth. With fire, man could operate on his own schedule; the day could be used for outdoor labor while the evening, now lighted, allowed time for tool repair and social activity.

Lost in the mists of antiquity is man's first encounter with a black, rocklike substance that could burn with a hot flame. There is archaeological evidence that coal was used by the inhabitants of Glamorgan, Wales, during the Bronze Age, 3000 to 4000 years ago. As early as the fourth century of the Christian era, Roman garrison troops in Britain burned coal to heat their baths and quarters. However, coal, the first-used fossil fuel, was not extensively used until the seventeenth century.² In the middle of the eighteenth century, wood was still the major source of fuel, but its limitations were now foreseeable. England's forests were denuded for charcoal used in smelting by the early eighteen hundreds. This is possibly the earliest example of resource exhaustion, a situation not unlike that faced by the world today with its depleting oil reserves.

The first mine shafts for coal extraction were sunk in the late middle ages. Records show that in 1684 near Bristol, England, there were 70 coal mines but only 123 miners.³ The industrial revolution, with its massive need for energy to drive the newly invented steam engines, heralded the steady growth of energy requirements.

Coal has been a major energy source throughout industrial history. It became the primary source of energy for both domestic and industrial use. It fired the steam engines that turned throughout the industrial revolution. By 1700 England was mining more than a million tons annually. Metalworkers and brick, tile, glass, and earthenware industries made extensive use of the high-energy content of coal. The early chemical industry used coal in refining processes for saltpeter, alum, and gunpowder.

By the nineteenth century, the United States was extracting and transporting large amounts of coal on steam engines used by the steel, chemical, and electricity-generating industries. Coal was also used for making gas to light homes and streets. Solid fuel was dominant until early in the twentieth century when oil and gas began to make inroads into the fuel market. Trains were pulled by diesel-fueled engines, and natural gas, along with electricity, eliminated the need for local coal justification. The use of coal declined until it hit a low point of 400 million tons in 1958. Electricity producers now burned oil because it produced little particulate pollution and no residue. By 1960, coal was the fuel of an earlier age, thought to be unfit for use in modern technology. However, the user attitudes changed as both industry and government realized that gas and oil reserves were not limitless. Coal began to receive renewed attention, and by 1970 the coal industry, after a 23-year slump, produced a record-breaking total of 602 million tons. By 1974, about 45 percent of the nation's electricity was produced from 400 million tons of coal.⁴

The OPEC oil embargo of 1974 was stark evidence that one of the basic elements of our economy, energy, was at the mercy of foreign powers. Coal and other energy alternatives then began to receive new attention.

Alternate Energy Sources

Since national security interests will be served by increasing domestic energy production, it is necessary to determine the best energy possibilities among several alternatives. Coal appears to offer the major short-term alternative to oil and natural gas, particularly for power generation and industrial use; furthermore, coal offers the most massive fossil fuel reserves in the world. The United States reserves of coal are estimated to constitute about 31 percent of the total world deposits, about 3.2 trillion short tons of the estimated world reserves of between nine and twelve trillion tons.⁵ With the general recognition that world oil production will probably peak and decline during the next 25 years, nations will be forced to exploit alternative energy sources. Coal is not as easy to extract, transport, or burn as nonsolid fuels so a transition to a coal-based economy will call for strong incentives and changes in attitudes toward coal. Making coal both available and acceptable will require major expansion of mining, processing, energy extraction, and research on utilization technology. Projections indicate that the nation will have to increase coal production from 60 to 300 percent to fill expected energy needs.⁶

Although one piece of coal may look much like any other, there are different grades and qualities, just as there are different grades of crude oil. Higher grades of coal have an energy value of up to 12,600 Btu per pound; lower grades have only half or a third as much. One system of coal grading divides coal into two broad categories, hard and soft. The ability of coal to form coke also varies widely. Since a major use of coal is in steelmaking, a second classification divides coal into thermal or metallurgical grade.

Worldwide coal production in 1977 was 3400 million metric tons. The United States accounts for more than half of all the coal used by the noncommunist countries. The use of coal in the United States has been falling steadily except for electricity production, which now accounts for more than 75 percent of current production; the next largest use is in the steelmaking industry.

Coal reserves are of all types, and with adjustments made for the inferior energy of some soft coals, the reserves are sufficient to support 200 years' consumption at present rates. Expressed in terms of oil equivalent, these adjusted coal reserves are equivalent to the energy content of about 3000 billion barrels, which is four to five times the current estimates of proven world oil reserves. Expressed in another way, the United States' coal reserves are equal to about 150 percent of the world's current oil resources. These resources would enable the United States to regain energy independence if it so chooses.

Constraints on Coal Use

Although coal is the most abundant fossil fuel resource, it is also potentially the most damaging to the environment. In April 1971, the federal government set primary ambient air quality standards to safeguard public health against six air pollutants: sulfur dioxide, total suspended particulates, hydrocarbons, nitrogen dioxide, carbon monoxide, and total oxidants. Coal combustion emits three pollutants affecting these standards: particulates, nitrogen oxides, and sulfur oxides. The technology for control of particulates is well advanced, and control systems provide high collection efficiencies with current fuels. Thus, meeting particulate emission standards is no problem for the future. The current retrofit technology for nitrogen oxide control is less advanced, and emission abatement systems are not yet available to reduce emissions to satisfactory levels. However, new coal-burning plants should be able to meet existing standards.⁷

A significant environmental problem is the emission of sulfur oxides. When mixed with water, sulfur oxides form sulfuric acid, a dangerous chemical that must be handled with extreme care. It is estimated that each year fossil fuel combustion releases 400 billion pounds of sulfuric acid into the environment. An acidic atmosphere is an obvious public health hazard, but the problem goes even further: acid attacks and corrodes metals. Thus bridges, outdoor stations, and other exposed structures are susceptible to acid deterioration. The resulting increased maintenance costs would be sizable.

Almost all this sulfuric acid falls as acid rain in the Northern Hemisphere. Acid rain runs off into the topsoil, leaching away calcium, a necessary plant nutrient. Studies have shown a definite decline in vegetative growth rate, both in Europe and in North America. An acidic water table can be detrimental to fish. In Norway and Sweden, which receive considerable acid rain, the rivers are becoming so acidic that commercial fish such as salmon and trout are ceasing to breed. In North America, fish kills have been reported in acidified lakes in Ontario, and in some parts of New Hampshire the rain is highly acidic.⁸

The principal means of combating current sulfur dioxide is by burning coal with low sulfur content. Unfortunately, most of the low-sulfur coal reserves in the United States are located west of the Mississippi River in the Rocky Mountain area, where transportation costs are significant. This coal is most easily removed by strip-mining, which is currently under strong attack by environmentalists. Thus, the possibilities for providing sufficient low-sulfur coal are opening new mines, desulfurization, and transportation of western coal to eastern markets.⁹

Desulfurization techniques available today are stack gas scrubbing, solvent refining, coal combustion processes, and precombustion sulfur removal. Several years ago it was assumed that stack gas-scrubbing systems would provide the least expensive method of sulfur dioxide emission control. These systems remove sulfur dioxide from flue gas and can be easily retrofitted to existing facilities. Although these systems have already been installed in several power-generating stations, their performance has been disappointing, and electric utilities are searching for other alternatives.¹⁰

The prospect of delays in the perfection of stack gas-scrubbing systems has increased interest in several alternative methods for precombustion removal of sulfur from coal rather than from effluent. Precombustion removal of sulfur from coal is probably more technologically feasible and cheaper than stack gas-scrubbing systems since the sulfur content of coal is more concentrated in the solid state than in gaseous form.

Currently, three processes are receiving attention in coal research and development programs: coal gasification, solvent refining, and coal liquefaction.

In addition to being a primary fuel, coal is a potential raw material for the production of synthetic gas and oil needed by major industry. In 1974 the Office of Coal Research provided a budget of $50 million for construction of three coal gasification pilot plants.

The idea of extracting gas from coal is far from new. There was a time when almost every city in the eastern half of the United States had a gashouse where town gas was produced for street and home lighting. The first American gas company was chartered in Baltimore in 1816, just four years after a gas company was established in London. By 1925 there were 150 international manufacturers of coal gasification equipment, and in the United States there were about 12,000 gasification plants in operation, consuming approximately 25 million tons of coal each year. However, virtually all of them disappeared with the availability of natural gas.

Today coal is still being gasified in Turkey, India, South Africa, Scotland, Morocco, Yugoslavia, and Korea.¹¹ However, the gas produced is of low Btu value but still environmentally acceptable. Low Btu gas derived from coal has several disadvantages. The conversion process might entail a loss of 25 percent in the original heating value of coal. Nor is it economically feasible to transport low Btu gas over long distances; therefore, the gasification plant must be located reasonably near the user. Finally, there is no method for storing large amounts of low Btu gas; thus fuel supply is very critical.

The major attraction of low Btu gasification is that it provides an ideal fuel for gas turbines in advanced combined-cycle power generators. In the combined cycle, stationary gas turbines are linked with steam turbines to yield a very high thermal efficiency. It is estimated that the combined system can compete economically with conventional fossil fuel plants equipped with gas stack scrubbers.

Existing technology for low Btu gasification of coal has served as a basis for efforts to develop gas of a high Btu content pipeline quality from coal. High Btu gas can be used as a substitute for natural gas and will be economical to transport over pipelines. In both high and low Btu coal gasification techniques, sulfur is transformed to hydrogen sulfide, which is easily removed by already commercially available methods.¹² However, in both gasification techniques (on an energy-equivalent basis), the cost would be $24 a barrel, or about twice the current price of a new, regulated interstate natural gas.

Solvent refining is a method of rendering high sulfur coal into an environmentally acceptable fuel at economical prices. In this process, coal is crushed, dissolved in a solvent, and then a purification stage removes the sulfur. The purified slurry can then be either dried into a low-sulfur coal or transported by slurry pipeline. Solvent refining of coal also allows for separation of coal conversion facilities and the final user, thus permitting flexibility in the location of these facilities.¹³

Coal liquefaction was pioneered by the Germans during World War II. Essentially, the process involves a chemical reaction of coal with hydrogen at high temperatures and pressures to yield a variety of products. Most liquefaction processes yield two or three barrels of sync rude for every ton of dry coal feed. For the United States, with its large coal reserves, the production of synthetic fuels from coal could be an attractive alternative to rising imports of oil and liquefied natural gas. The advantages of staying with liquid fuels are obvious: no great changes in technology are necessary by the consumer. The burden of investment is on the energy processors and producers. Today, $24 per barrel is the floor under the world price, with most exporters between $25 and $30 per barrel.

Many conditions will have to be met before coal can again fill a growing share of the world's energy needs. Implicit are an awareness of the long-term energy outlook, policy decisions by governments to encourage both the production and use of coal, and public attitudes that make such policies feasible. Extensive facilities for mining, transporting, and burning coal must also be built. The construction of such facilities will call for a huge capital investment.

Individual national governments will have to decide the extent to which they will encourage or discourage the expansion of coal-consuming systems. Since long lead times are needed in shifting away from an energy system dominated by liquid fuel, decisions must be made soon if such a shift is to be made before oil becomes less and less available and even more costly than it is today. Choices made in the next few years will influence the energy industry for the next century.

For the United States coal is not a scarce resource. Thus the nation could possibly become an energy exporter. Exporting coal would have a positive effect on economic development, employment, and the balance of foreign trade payments.

If coal is to serve as a significant energy source, governments will soon have to adopt necessary policies to allow and encourage its use. Both public and private investment decisions will be needed to provide funds for opening new extraction sites, building transportation facilities, and developing the infrastructure for handling and burning of coal by consumers. The expanded exploitation of coal will call for satisfactory solutions to the technical, economic, social, and environmental problems associated with the extraction and burning of coal.¹⁴

Grissom AFB, Indiana

We are grateful to the Alabama Environmental Quality Association for use of the accompanying photographs.

1. Robert H. Connery and Robert S. Gilmour, The National Energy Problem (Lexington, Massachusetts: Lexington Books, 1974), p. 76.

2. Joseph J. DiCerto, The Electric Wishing Well (New York: Macmillan, 1976), p. 2.

3. Ibid.

4. Ibid.

5. Edward D. Griffith and Alan W. Clarke, "World Coal Production," Scientific American, January 1979, p. 13; John Hagel III, Alternative Energy Strategies: Constraints' and Opportunities (New York: Praeger, 1976), p. 27.

6. Connery and Gilmour, pp. 171-72.

7. Ibid.

8. DiCerto, p. 17.

9. Connery and Gilmour, p. 173.

10. Hagel, p. 32.

11. DiCerto, p. 13.

12. Hagel, pp. 31-33.

13. Hagel, p. 32.

14. Griffith and Clarke, p. 47.

Lieutenant Colonel Robert J. Jamsky, DC (B.A., Pennsylvania State University; D.D.S., Temple University) is assistant base dental surgeon, Grissom Air Force base, Indiana. He has published an article in Oral Surgery and is a contributor to the textbook Diseases of the Oral Mucosa. Lieutenant Colonel Jamsky is a graduate of Air Command and Staff College and Industrial College of the Armed Forces.

Disclaimer

The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.

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