Coal is a fossil fuel, just like oil and natural gas. The transformation of organic plant matter formed it, and it has been in existence for over 350 million years.
All it takes is a swamp at the edge of a sedimentary basin, such as a lake or lagoon. Tectonic activity increases sea levels, covering and killing vegetation. In sedimentation, plant debris is trapped under layers of sand and mud. This protects the debris and slows down its decomposition. The vegetation will grow back until the next flood.
The sedimentary basin slowly sinks beneath the sediments’ weight. As the temperatures rise, the layers of dead plants are gradual “cook”, which leads to their transformation. The various stages of sedimentation change cellulose, which is the main component of wood from peat to brown coal (brown), then to sub-bituminous, then bituminous, and finally anthracite. Anthracite is the most carbon-rich.
Timeline for the Formation of Coal
The Period of the Carboniferous (“coal-bearing”) was 360 million to 290 million years ago. This Period saw the most favorable conditions for coal formation. However, less coal was formed in certain parts of the Earth in subsequent periods, including the Permian (290 to 250 million years old) and the Mesozoic Era (265 million to 65 million years ago span>
The Tertiary Era’s accumulated plant matter, less than 65 million years old, is usually less mature. It’s often found in the form of lignite, which has a lower carbon and a higher content of volatile matter (bitumen, decayed wood) than the Tertiary Era. There is also Tertiary Era coal of higher rank, which was heated by plate tectonics and matured earlier. This includes Paleocene (65 to 55 million years ago) and Miocene (20 million years old), both in Columbia and Venezuela. Anthracite is found close to the surface in Indonesia because of its high geothermal gradient.
The Moscow Basin’s deposits have not yet reached the lignite stage. It is too cold!
Recent accumulations, which date back to 10,000 years ago, are rich in fibrous material known as peat. This allows for the identification of roots and branches. This material did not have enough carbon to be buried deeply.
Different Types of Coal
There are many types of coal. They are ranked according to their carbon and volatile matter contents:
- Anthracite contains 86-98% pure carbon and 8-3% volatile matter. Anthracite is still widely used for heating homes.
- Bituminous coal comprises 70 to 86% carbon and 46- to 31% volatile matter. It is used for making coke and in metallurgy.
- Sub-bituminous coke is between 70 and 76% carbon and 53 to 42% volatile material. It is used in industrial boilers.
- 65 to 70% of the carbon in lignite is volatile matter, while 63 to 53% is carbon. This low-grade fuel has high moisture content and is used in industrial boilers.
- Partially decomposed vegetation makes up peat. It is technically not coal. It is composed of only volatile matter and has a lower carbon content than 60%. It is a poor fuel, once used in Europe as dried briquettes to heat, but it is now only used in a handful of regions like Ireland.