Coal
Consisting of altered remains of plants, coal is a widely used fossil fuel. Generally, the older the coal, the higher the carbon content and heating value. Anthracite coal ranks highest in carbon content, then bituminous coal, subbituminous coal, and lignite (as determined by the American Society for Testing Materials). Over 80% of the world's vast reserves occur in the former Soviet Union, the United States, and China. Though globally abundant, it is associated with many environmental problems, including acid drainage, degraded land, sulfur oxide emissions, acid rain, and heavy carbon dioxide emissions. However, clean coal-burning technologies, including liquified or gasified forms, are now available.
Anthracite, or "hard" coal, differs from the less altered bituminous coal by having more than 86% carbon and less than 14% volatile matter. It was formerly the fuel of choice for heat purposes because of high Btu (British Thermal Unit) values, minimally 14,500, and low ash content. In the United States, production has dropped from 100 million tons in 1917 to about seven million tons as anthracite has been replaced by oil, natural gas, and electric heat. Predominantly in eastern Pennsylvania's Ridge and Valley Province, anthracite seams have a wavelike pattern, complicating extraction. High water tables and low demand are the main impediments to expansion.
Bituminous coal, or "soft" coal, is much more abundant and easier to mine than anthracite but has lower carbon content and Btu values and higher volatility. Historically dominant, it energized the Industrial Revolution, fueling steam engines in factories, locomotives, and ships. Major coal regions became steel centers because two tons of coal were needed to produce each ton of iron ore. This is the only coal suitable for making coke, needed in iron smelting processes. Major deposits include the Appalachian Mountains and the Central Plains from Indiana through Oklahoma.
Subbituminous coal ranges in Btu values from 10,500 (11,500 if agglomerating) down to 8,300. Huge deposits exist in Wyoming, Montana, and North Dakota with seams 70 ft (21.4 m) thick. Though distant from major utility markets, it is used extensively for electrical power generation and is preferred because of its abundance, low sulfur content,
| Coal Production From 1950–2000 |
| Date | Anthricite | Bituminous | Lignite | Subbituminous |
| Coal production from 1950 through 2000. MMst stands for million short tons. |
| 1950 | 44.08 | 516.31 | 0.00 | 0.00 |
| 1960 | 18.82 | 415.51 | 0.00 | 0.00 |
| 1970 | 9.73 | 578.47 | 8.04 | 16.42 |
| 1980 | 6.06 | 628.77 | 47.16 | 147.72 |
| 1990 | 3.51 | 693.21 | 88.09 | 244.27 |
| 2000 | 4.51 | 548.47 | 88.74 | 433.78 |
and good grinding qualities. The latter makes it more useful than the higher grade, but harder, bituminous coal because modern plants spray the coal into
combustion chambers in powder form. Demand for this coal skyrocketed following the 1973 OPEC
oil embargo and subsequent restrictions on natural gas use in new plants.
Lignite, or "brown" coal, is the most abundant, youngest, and least mature of the coals, with some plant texture still visible. Its Btu values generally range below 8,300. Although over 70% of the deposits are found in North America, mainly in the Rocky Mountain region, there is little production there. It is used extensively in many eastern European countries for heating and steam production. Russian scientists have successfully burned lignite in situ, tapping the resultant coal gas for industrial heating. If concerns over global warming are satisfied, future liquefying and gasifying technologies could make lignite a prized resource.
Resources
Books
Hartshorne, T., and J. W. Alexander. Economic Geography. 3rd ed. Englewood Cliffs, NJ: Prentice-Hall, 1988.
Periodicals
Young, G. "Will Coal Be Tomorrow's Black Gold?" National Geographic 148 (August 1975): 234-259.
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