Coal

• Coal is a rock that has so much carbon in it that the rock burns.

• Coal is old. It is millions of years old. It forms from the same processes that form all sedimentary rocks.

• Charcoal is different from coal. Charcoal is made by partially burning wood. It is made now, by people.

Coal is found in many places in the United States

Kinds of Coal

Peat: not coal yet, but burnable

Bituminous coal Anthracite Coal

Lignite Coal

Peat

• Peat is an accumulation of partially decayed vegetation matter.

• Peat forms when plant material, usually in marshy areas, is inhibited from decaying fully by wet and acidic conditions.

• Under the right conditions, peat is the earliest stage in the formation of coal.

Lignite Coal

• Lignite, often referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for steam-electric power generation.

• Lignite contains more moisture than higher ranked coal and when dried, it crumbles easily.

Bituminous Coal

• Bituminous coal is a relatively hard coal containing a tar-like substance called bitumen. It is of higher quality and rank than lignite.

• It is usually black, sometimes dark brown, often with well-defined bands of bright and dull material associated with sedimentary rocks.

Anthracite Coal

• Anthracite is the highest rank of all coals. It is a high carbon, low sulfur and high BTU coal. Anthracite is a "smokeless" fuel unlike some of the lower grades of coal. It burns cleaner, hotter and longer than any other coal.

• Anthracite coal is a metamorphic rock and is considered to be a transition stage between ordinary bituminous coal and graphite.

Coals’ energy comes from the sun

• Plants in the biosphere store solar energy through photosynthesis by converting it into chemical energy in the form of organic (carbon-based) molecules.

• Energy that enters the biosphere nearly equals that lost by oxidation.

• A small percent is stored in the form of fossil fuels in sedimentary rocks

Formation of Coal

Steps to form coal

• Thick layers of nearly pure plant material are deposited.

• During compaction by overlying sediment, water and gases are squeezed out.

• The percent of carbon increases as the coal is compacted more, and the rank increases.

• The greater the carbon content, the greater the energy stored in the coal

• Coal also contains sulfur compounds and ash, the unburnable part, composed of sand, silt and clay.

The greater the time, heat and pressure of burial, the higher the rank of coal