Coal is a usually known as a fossil fuel formed as a result of the thriving ecosystem over the years where plant remains were hoarded by water and mud from the process of oxidation of the material and constant biodegradation. Coal is a willingly Combustible fuel source. The emission in the likes of coal is somewhat higher than petroleum. The fossil fuels are extracted by means of mining. The hauling of the fuel is fundamentally carried out in terms of deep pit mines. Usage of coal as a fuel is almost obsolete over the years apart from the very few industries that still continue to use it for their highly price advantageous sense.

Coal Mining

The quality of coals in Colombia is quite high. The moisture content of the Colombian coal is generally low. Ash yields range from less than 1 to 21 percent, but average around 6 percent on an as-received basis. Sulfur contents are also low, most values are less than 1 percent. Gross Calorific Values are generally all over 11,000 Btu/lb (6,111 Kcal/Kg) on an as-received basis. The majority of the ash oxides are silica and alumina. Iron oxides are highest in the Guachinte Formation, which has high pyritic sulfur content. Quartz and kaolinite were the predominant minerals, but the Guachinte coal also contained pyrite, marcasite, hematite, and smectite, which were not significant in the Golondrinas coal. CaO is significantly higher than most samples in the Puerto Bolívar Coal - Cordoba sample, which also has a higher SO3 value. SO3 and Fe2O3 are also high in the Cauca coalfield.

Coal Classification

Coal is a readily combustible rock containing more than 50 percent by weight of carbonaceous material formed from compaction and indurations of variously altered plant remains similar to those in peat.

After a considerable amount of time, heat, and burial pressure, it is metamorphosed from peat to lignite. Lignite is considered to be "immature" coal at this stage of development because it is still somewhat light in color and it remains soft.

• Lignite increases in maturity by becoming darker and harder and is then classified as sub-bituminous coal. After a continuous process of burial and alteration, chemical and physical changes occur until the coal is classified as bituminous - dark and hard coal.

• Bituminous coal ignites easily and burns long with a relatively long flame. If improperly fired bituminous coal is characterized with excess smoke and soot.

• Anthracite coal is the last classification, the ultimate maturation. Anthracite coal is very hard and shiny.

¹⁾ Volatile matter - dry mineral matter free basis. In coal, those products, exclusive of moisture, given off as gas and vapor determined analytically.

Anthracite coal creates a steady and clean flame and is preferred for domestic heating. Furthermore it burn longer with more heat than the other types.

Typical Sulfur Content in Coal

• Anthracite Coal : 0.6 - 0.77 weight %

• Bituminous Coal : 0.7 - 4.0 weight %

• Lignite Coal : 0.4 weight %

Typical Moisture Content in Coal

• Anthracite Coal : 2.8 - 16.3 weight %

• Bituminous Coal : 2.2 - 15.9 weight %

• Lignite Coal : 39 weight %

Typical Fixed Carbon Content in Coal

• Anthracite Coal : 80.5 - 85.7 weight %

• Bituminous Coal : 44.9-78.2 weight %

• Lignite Coal : 31.4 weight %

Typical Bulk Density of Coal

• Anthracite Coal : 50 - 58 (lb/ft³), 800 - 929 (kg/m³)

• Bituminous Coal : 42 - 57 (lb/ft³), 673 - 913 (kg/m³)

• Lignite Coal : 40 - 54 (lb/ft³), 641 - 865 (kg/m³)

Typical Ash Content in Coal

• Anthracite Coal : 9.7 - 20.2 weight %

• Bituminous Coal : 3.3-11.7 weight %

• Lignite Coal : 4.2 weight %