Coal

Coal is a combustible black or brownish-black sedimentary rock fossil fuel, usually occurring in rock strata in layers or veins called coal beds or coal seams, created from the remains of plants that lived and died about 100 to 400 million years ago, when parts of the Earth were covered with huge swampy forests. The energy we get from coal today comes from the energy that plants absorbed from the sun millions of years ago. All living plants store solar energy through a process known as photosynthesis. When plants die, this energy is usually released as the plants decay. Under conditions favorable to coal formation, however, the decay process is interrupted, preventing the release of the stored solar energy. The energy is locked into the coal.

2. Where can I find Coal?
Estimated that more than 930 billion tons of coal reserves around the world. It means there is enough coal reserves to last for another more than 147 years. Coal is located worldwide, can be found on every continent in over 70 countries, with the largest reserves in the United States, Russia, China and India. Potential coal resources in Indonesia is very abundant, especially on the island of Kalimantan (Borneo) and Sumatra, while in other areas can be found even in small amounts, such as West Java, Central Java, Papua and Sulawesi.

3. Coal Mine
There are two ways to remove coal from the ground—surface and underground mining. Surface mining is used when a coal seam is relatively close to the surface, usually within 200 feet. The first step in surface mining is to remove and store the soil and rock covering the coal, called the overburden. Workers use a variety of equipment— draglines, power shovels, bulldozers, and front-end loaders—to expose the coal seam for mining

4. Types of Coal
Coal is classified into four main types, depending on the amount of carbon, oxygen, and hydrogen present. The higher the carbon content, the more energy the coal contains.

- Lignite is the lowest rank of coal, with a heating value of 4,000 to 8,300 British thermal units (Btu) per pound. Lignite is crumbly and has high moisture content. Lignite is mainly used to produce electricity. It contains 25 to 35 percent carbon.

- Subbituminous coal typically contains less heating value than bituminous coal (8,300 to 13,000 Btu per pound) and more moisture. It contains 35 to 45 percent carbon.

- Bituminous coal was formed by added heat and pressure on lignite. Made of many tiny layers, bituminous coal looks smooth and sometimes shiny. Bituminous coal contains 11,000 to 15,500 Btu per pound. Bituminous coal is used to generate electricity and is an important fuel for the steel and iron industries. It contains 45 to 86 percent carbon.

- Anthracite was created where additional pressure combined with very high temperature inside the Earth. It is deep black and looks almost metallic due to its glossy surface. Like bituminous coal, anthracite coal is a big energy producer, containing nearly 15,000 Btu per pound. It contains 86 to 97 percent carbon.

5. Uses of Coal
Coal has many important uses worldwide, primarily used as a solid fuel to produce electricity and heat through combustion. Other utilization of coal are use by paper industry, textile industry, metallurgy steel production, cement manufacturing and other industrial processes as well as liquid fuels.