Coal Energy: Formation, Types, Uses, and Environmental Mitigation

Fossil Fuel Energy Resources

Coal: Origin, Classification, and Utilization

Origin and Formation of Coal

Coal originates from the transformation of plant remains under reducing conditions. These remains undergo a process of carbonization, which enriches them with carbon.

Carbonization Process

Carbonization is performed by the action of certain anaerobic bacteria that ferment organic matter, producing CO2 and methane. This process enriches the plant remains with carbon. These materials are then covered by new sediments, which increases the pressure and temperature, causing diagenesis and forming different types of coal. For coal formation to occur, specific conditions must be met:

• Originates in areas with significant vegetation development.
• Occurs when accumulated plant debris is buried quickly.
• Specific pH of the waters.
• Sufficient depth to prevent oxidation and allow plant debris accumulation.
• Requires minimal terrigenous input.
• Continuous subsidence of the basin.

Types of Coal Origin

Coal originates in two primary types of basins:

• Paralic: Large basins.
• Limnic: Small basins.

Classification and Types of Coal

The classification criteria for coal are three-fold:

• Types: Based on the type of plant material they contain, two types of coal are distinguished:
  • Humic: Derived from woody plants.
  • Sapropelic: Derived from non-woody plant debris.
• Degrees: Based on the level of impurities they contain.
• Rank: Based on the degree of carbonification (evolution), the following types can be distinguished:

• Peat: A dark brown substance, composed of thick, loose fibers. It has the lowest proportion of carbon among coals and burns poorly.
• Lignite: More evolved than peat, it has a higher carbon ratio and a greater calorific value.
• Bituminous Coal: Primarily derived from large fern forests. There are two varieties: dry coal and fat coal.
• Anthracite: The oldest coal, with the highest carbon content and calorific value. It burns with difficulty. Further carbonization transforms this coal into graphite, which is not considered a type of coal.

Exploitation and Utilization of Coal

The uses of coal include:

• Electricity generation in thermal power plants and as fuel for domestic and industrial heating.
• Through the distillation of soft coal, various products are obtained:
  • Solid residue: Coke
  • Coke gas
  • Ammonia and coal tars
• Peat (often referred to as 'turba' or 'mob' in some contexts) is used as an organic fertilizer.
• Jet (a type of lignite) is used in jewelry.

Strategies to Minimize the Environmental Impacts of Coal

To mitigate the environmental impact of coal, several strategies can be employed:

• Replacing coal with fuels that have lower sulfur content.
• Pre-processing coal to remove as much sulfur as possible.
• Designing more efficient thermal power stations.