Coal | Research & Encyclopedia Articles

Coal

Scientists are unsure as to when it was discovered that coal could provide heat when burned; however, coal has probably been used as a fuel since prehistoric times. The ancient Chinese mined coal hundreds of years before the Christian era, and developed the world's first coal industry around 300 A.D., when they began using coal from shallow deposits for heating buildings and producing metals. By 1000 A.D., coal had begun to replace charcoal--which is made from wood--as the leading fuel in China. One of the earliest records of coal's economic value appears in a poem written by Shen Kua, a Chinese scientist of that era.

In Europe, coal was mined in Germany about 1,000 years ago. During the 1200s, coal was produced commercially from open pits in England and Belgium. Mainly, it was used for smelting and forging metals; blacksmiths, for example, took advantage of coal's hot flame to shape their products. Because of the pungent smoke given off by burning some coals, wood and charcoal remained the preferred fuels in Europe until the 1600s. However, the manufacture of bricks, glass, salt, and soap consumed huge quantities of charcoal, and, when a severe shortage of wood developed, most factories were forced to switch to coal. To meet this demand, England and other European countries sharply increased their output of the fuel. By the end of the 1600s, England was the world's leading coal producer, a position it would hold for some 200 years.

In North America, native peoples had learned to use coal long before the first settlers arrived. The Pueblos dug it from hillsides and burned it to bake pottery. European explorers discovered coal in the New World as early as 1673, but because wood was so plentiful, only a few coal mines were opened during the 1700s.

Coal is found in every continent on Earth, but the greatest amounts occur in the United States, China, Ukraine, Russia and Kazakhstan. Today's coal resources were created long ago, when much of the Earth was covered by shallow swamps where plant life flourished. As these plants died, they accumulated at the bottom of the swamps and were buried by sediments--sand and other mineral matter--before decaying completely. The heat released by burning coal actually comes from the energy of the Sun, which was stored by these ancient plants in the form of carbon compounds. In some coals, plant fibers can still be seen under a microscope.

Most coal began to form during the Carboniferous period, about 300 million years ago. At first, plant matter was changed into peat, a moist, spongy material that is still harvested and burned as fuel. Through the ages, as the overlying layers of sediment thickened, the peat was compressed and gradually hardened into coal.

Coal is ranked according to its carbon content, which generally corresponds to its age. Lignite, or brown coal, is the youngest and softest type of coal. It contains the least amount of carbon and the most moisture. Next is subbituminous coal, then bituminous coal, which is by far the most abundant type. Bituminous coal ignites easily and produces the most heat. Anthracite is the hardest coal, and the least plentiful. It burns cleanly but is difficult to light.

Bituminous coal is the only kind suitable for making coke, a special fuel used to smelt iron (extract it from its ore by melting). In the late 1600s, British brewers discovered that coal could replace charcoal as a fuel for drying malt, beer's essential ingredient. But airtight ovens had to be developed to eliminate the undesirable gases released from burning coal. These gases, along with vaporized coal tar, were drawn out of the new ovens, leaving coke--a porous, hard mass of nearly pure carbon. Soon coke fuel was being used to smelt copper and lead. Then in 1709 Abraham Darby (1678-1717), a British ironmaker, substituted coke for charcoal in blast furnaces for smelting iron. The price of charcoal had been going up, and the size of Darby's blast furnaces--and thus their efficiency--was limited by charcoal's fragility. At his Coalbrookdale ironworks, Darby had access not only to local supplies of iron ore, but also to bituminous "coking" coal. Darby's new process was successful, and coke gradually replaced charcoal as the fuel of choice for ironmaking.

The spread of coke-fueled iron smelting, along with the development of the steam engine in the 1700s, marked the beginning of the Industrial Revolution in England. During the 1800s, this revolution spread throughout Europe and into America. With steam engine power, factories were able to increase production enormously, but the engines used up huge amounts of energy. Because coal was the only fuel plentiful enough to meet these requirements, it became a determining factor in worldwide industrial growth. Countries without coal lagged behind in their development.

Coal became essential not only to smelting and manufacturing but to transportation as well. The establishment of the great railroad networks during the 1800s represented a milestone for the coal industry. For the first time, coal could be easily transported to distant markets, and the steam locomotives themselves burned large amounts of coal. Ships were also powered by steam, requiring huge boilers that also consumed great quantities of coal. The fuel also came into widespread use for home heating, and with the advent of gaslights, people began to depend on coal for lighting as well. Gas manufactured from coal became widely available in cities and towns. By the late 1800s, a thriving coal-gas industry was supplying extensive gas lighting systems in many industrial nations.

Coal gas is just one of many valuable by-products of coal. This gas and many other substances made from coal serve as raw materials for manufacturing everyday products such as vitamin s, fingernail polish, perfume, detergent, paint, and plastic. When coal is baked into coke, some of the gases turn into liquid ammonia and coal tar, while others change into light oil. Coal tar was first produced commercially in the 1700s, for preserving wood. It was not until the mid-1800s that coal's value as a rich source of organic chemicals began to be exploited. Coal's by-products contain substances that are used today in an amazing variety of products including medicine, fertilizers, dyes, synthetic rubber, insulation, herbicides, and insecticides. Coal tar can also be used for roofing, road surfacing, and protective coatings for pipelines.

Until the early twentieth century, coal enjoyed nearly total dominance of the energy market, in the U.S. and the rest of the industrial world. Coal was fully established as society's all-purpose fuel: it provided heat, light, and mechanical power, as well as raw materials for the chemical industry. And during this century, as electricity pervaded modern life, coal became--and still is--the major fuel for electric power generation.

The introduction of the automobile in America symbolizes the beginning of today's diverse energy market. Although only a few thousand cars ran on gasoline in 1900, the unparalleled growth of the American automotive industry since then has stimulated demand for oil products. In the transportation industry, trucking began to compete with railroads, and the trains themselves were increasingly operated on diesel fuel. Oil displaced coal as a shipping fuel even more quickly and also began to compete in certain industrial applications. At the same time, the natural gas industry in America, spurred by advances in pipeline technology, captured the heating market from coal.

Despite all its setbacks, the coal industry has continued to grow overall, thanks to America's escalating demand for electricity. From 1945 to 1955 alone, consumption of coal by U.S. power plants almost doubled. More than two-thirds of all coal mined in America is now used for power generation. Most power plants burn coal to produce steam, which spins turbines that drive electric generators. Coal's main drawback is air pollution. Coal combustion releases sulfur dioxide, a major cause of acid rain, carbon dioxide, a major cause of the greenhouse effect, as well as soot and smoke. Today, many power plants are required to treat their exhaust gases with expensive "scrubbers" to remove these pollutants.