Geology Reference
In-Depth Information
1.1. The Formation of Coal
Ann G. Kim
Coal seam (photo center) exposed in the
New River Gorge, West Virginia.
Photo: National Park Service, http://nps.gov/neri/NatureScience/geologicformations.htm
Introduction
C
oal formation has been described as
(Barghoorn, 1952) when carbon from
plants remains in terrestrial sediments and is not recycled to the atmosphere (Figure 1.1.1). Coal is, by definition, a
readily combustible rock containing more than 50% by weight and 70% by volume of carbonaceous material
(Schopf, 1966). Another definition describes coal as a combustible solid, usually stratified, which originated from
the accumulation, burial, and compaction of partially decomposed vegetation in previous geologic ages (Hen-
dricks, 1945).
“
an inefficiency in the carbon cycle,
”
Coal has been used for over 3000 years, in China, in Bronze Age Europe, and by Plains Indians in America
(Cassidy, 1973). During the Middle Ages, coal use became more common, for forges, kilns, and breweries, as well
as domestic heating (EIA, 2002). In 1306, King Edward issued a royal decree banning the use of coal in London,
but the ban was ineffective because charcoal made from wood was in short supply. The development of brick
chimneys 100 years later alleviated the problem to some extent (Hessley et al., 1986). In the United States, wood
was the primary fuel used by the colonists. It was abundant and relatively easy to obtain. In 1850, coal was used to
fuel the steam engine and became the principal source of energy until 1950 when it was surpassed by petroleum for
use in automobiles and by natural gas for home heating (Figure 1.1.2). Since 1984, coal has produced about one
third of the energy consumed in the United States (EIA, 2002). And 92% of the coal mined in the United States is
used to produce over 50% of our electricity (EIA, 2006). Projections by the US Department of Energy indicate that
coal consumption will continue to increase as demand for electricity increases (EIA, 2008).
As of 2005, world coal consumption was 5883 million mt (metric tons) of which China consumed 2339 million mt,
the United States
493 million mt (EIA, 2008). World coal consumption is projected
to grow by 2.5% per year to 9583 million mt (EIA, 2006). In spite of the environmental problems associated with
coal mining and coal use (acid mine drainage, coal fires, greenhouse gas emission, air pollution, etc.), it seems that
coal will continue to be a major source of energy for the foreseeable future.
—
1086 million mt, and India
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