Coal is the one fossil energy source that can play a substantial role as a transitional energy source as one moves from the petroleum and natural gas based economic system to the future economic system based on nondepletable or renewable energy systems. For coal to remain competitive with other sources of energy in the industrialized countries of the world, continuing technological improvements in all aspects of coal extraction have been necessary. Coal has many important uses, but most significantly in electricity generation, steel and cement manufacture, and industrial process heating. Despite the long-term importance of oil and gas use, coal will remain a major pillar of the world's energy supply. Developing countries use about 55% of the world's coal today; this share is expected to grow to 65% over the next 15 years. The main objective of the present study is to investigate the contribution of coal to global energy demand and its share in global energy sources by presenting its historical development. In addition, this paper describes and summarizes environmental impacts of coal consumption and present status of several clean coal technologies.