Page 148 - Synthetic Fuels Handbook

134 CHAPTER FIVE

Thus, coal remains in adequate supply and at current rates of recovery and consump-
tion, the world global coal reserves have been variously estimated to have an R/P ratio of
at least 155 years. However, as with all estimates of resource longevity, coal longevity is
subject to the assumed rate of consumption remaining at the current rate of consumption
and, moreover, to technologic developments that dictate the rate at which the coal can be
mined. And, moreover, coal is a fossil fuel and an unclean energy source that will only add
to global warming. In fact, the next time electricity is advertised as a clean energy source,
consider the means by which the majority of electricity is produced—almost 50 percent of
the electricity generated in the United States is from coal (EIA, 2007).
Current projections are that the use of coal as an energy source will diminish by the
year 2020 (Fig. 5.5) with natural gas use increasing as petroleum use also declines as a
percent of the global energy production. However, the current author is of the opinion that
coal use will increase as more liquids and gas (synthesis gas) are produced from coal and
as environment technologies evolve and are capable of ensuring that coal is truly a clean
and nonpolluting fuel.

100%
18
80% 22 26

60%
49
44 40
40%
20% 29 26 24

0%
1071 1997 2020
Coal Oil Natural gas Nuclear Hydro Other renewables
FIGURE 5.5 Estimated use of energy sources in the year 2020.

5.2 FORMATION AND TYPES

5.2.1 Coal Formation

The precursors to coal were plant remains (containing carbon, hydrogen, and oxygen)
that were deposited in the Carboniferous period, between 345 and 280 million years ago
(Fig. 5.6). As the plant remains became submerged under water, decomposition occurred
in which oxygen and hydrogen were lost from the remains to leave a deposit with a high
percentage of carbon. With the passage of time, layers of inorganic material such as sand
and mud settled from the water and covered the deposits. The pressure of these overlying
layers, as well as movements of the earth’s crust acted to compress and harden the deposits,
thus producing coal from the vegetal matter.
The plant material (vegetal matter) is composed mainly of carbon, hydrogen, oxygen,
nitrogen, sulfur, and some inorganic mineral elements. When this material decays under