Focus on Coal

Coal is a fossil fuel formed in ecosystems where plant remains were preserved by water and mud from oxidization and biodegradation, thus sequestering atmospheric carbon. It is composed primarily of carbon and hydrogen along with small quantities of other elements, notably sulfur. Coal is extracted from the ground by coal mining, either underground mining or open pit mining (surface mining).

Coal is the largest source of fuel for the generation of electricity world-wide, as well as the largest world-wide source of carbon dioxide emissions. Carbon dioxide is a greenhouse gas and these emissions contribute to climate change and global warming. In terms of carbon dioxide emissions, coal is slightly ahead of petroleum and about double that of natural gas

Four Basic Varieties of Coal:

Anthracite: Sometimes also called "hard coal," anthracite was formed from bituminous coal when great pressures developed in folded rock strata during the creation of mountain ranges. Anthracite has the highest energy content of all coals and is used for space heating and generating electricity. Anthracite averages 25 million Btu per ton.

Bituminous: Bituminous or "soft" coal formed when greater pressure was applied to subbituminous coal. This is the type most commonly used for electric power generation in the U.S.. It has a higher heating value than either lignite or subbituminous, but less than that of anthracite. Bituminous coal averages 24 million Btu per ton.

Subbituminous: Subbituminous coal formed from lignite when it came under higher pressure. This coal is a combustible mineral formed from the remains of trees, ferns and other plants that existed and died during the time of the dinosaurs. A dull black coal with a higher heating value than lignite that is used primarily for generating electricity and for space heating. Subbituminous coal averages 18 million Btu per ton.

Lignite: Increased pressures and heat from overlying strata caused buried peat to dry and harden into lignite. Lignite is a brownish-black coal with generally high moisture and ash content and lower heating value. However, it is an important form of energy for generating electricity, particularly in the American Southwest. Lignite averages 14 million Btu per ton