For most of the past 50 years, since the birth of environmental awareness, coal has been the "black sheep" of the power-production family.
Now, thanks to more efficient furnaces, better exhaust-scrubbing systems and other technological advances, coal is regaining favor in the world's energy markets.
However, the biggest factor in coal's recent price surge is steadily increasing demand for the fossil fuel - in power generation and steel-making - aided by rising costs for other types of fuel, like oil and natural gas.
