Coal extraction

Coal extraction, also known as coal mining, is the process of removing coal deposits from the earth for use as an energy source and industrial raw material. Coal has been one of the most important fuels for electricity generation, steel production, and various industrial activities. It remains a key component of the global energy mix, despite growing emphasis on renewable sources.
The extraction of coal involves locating coal seams, assessing reserves, and using different mining techniques depending on the depth, thickness, and geological conditions of the deposit.

Types of Coal

Coal is a sedimentary rock formed from the remains of ancient vegetation subjected to heat and pressure over millions of years. It exists in several grades, classified based on carbon content and energy value:

Coal-Bearing Regions in India

India has vast coal reserves, mainly concentrated in eastern and central states:

• Jharkhand – Jharia, Bokaro, Dhanbad.
• Odisha – Talcher, Ib Valley.
• Chhattisgarh – Korba, Raigarh.
• West Bengal – Raniganj, Asansol.
• Madhya Pradesh – Singrauli, Umaria.
• Telangana – Singareni Collieries.
• Maharashtra – Wardha Valley.

India ranks among the top five coal-producing countries globally, with Coal India Limited (CIL) being the largest producer.

Methods of Coal Extraction

Coal extraction is broadly divided into surface mining and underground mining, depending on the depth and location of coal seams.

1. Surface (Open-Cast) Mining

Definition: Surface mining involves removing overburden (soil, rock, and vegetation) to expose and extract coal deposits located close to the earth’s surface (usually up to 300 metres deep).
Types of Surface Mining:

1. Strip Mining:
   • Overburden is removed in long strips to expose coal seams.
   • Used in flat terrain or shallow deposits.
2. Open-Pit (Open-Cast) Mining:
   • Large pits are dug using heavy machinery such as draglines, shovels, and trucks.
   • Suitable for thick, horizontal coal seams.
3. Mountaintop Removal:
   • The tops of hills or mountains are blasted to access coal seams underneath.
   • Common in hilly regions (e.g., Appalachia, USA) but rarely used in India due to environmental concerns.

Advantages:

• High recovery rate (up to 90%).
• Low production cost.
• Mechanisation allows rapid extraction.

Disadvantages:

• Severe environmental degradation — deforestation, habitat loss, air and water pollution.
• Displacement of local communities.
• Landscape destruction and soil erosion.

2. Underground (Deep Shaft) Mining

Definition: Underground mining is used when coal seams lie deep below the surface, typically more than 300 metres. It involves tunnelling and creating shafts to reach coal seams.
Types of Underground Mining:

1. Room and Pillar Method:
   • Coal is mined in a checkerboard pattern, leaving pillars of coal to support the roof.
   • Later, some pillars may be extracted in a process called “retreat mining.”
2. Longwall Mining:
   • A long wall of coal (100–300 metres) is mined in a single slice by a mechanical shearer.
   • Hydraulic supports hold the roof as the coal face advances, and the roof collapses behind.
   • Highly efficient and commonly used in deep mines.
3. Drift, Slope, and Shaft Mining:
   • Drift Mining: Horizontal tunnels from hillsides.
   • Slope Mining: Inclined tunnels following the coal seam.
   • Shaft Mining: Vertical shafts with elevators to reach deep seams.

Advantages:

• Less surface disturbance compared to open-cast mining.
• Suitable for deep coal seams.

Disadvantages:

• Lower recovery rate (30–50%).
• High safety risks due to roof collapses, explosions, and gas emissions.
• More expensive and labour-intensive.

Coal Extraction Process (Step-by-Step)

1. Exploration:
   • Geological surveys, drilling, and sampling identify coal reserves and assess quality.
2. Planning and Design:
   • Feasibility studies, environmental impact assessments, and mine design determine the method of extraction.
3. Overburden Removal (in Surface Mines):
   • Earthmoving equipment (draglines, excavators, bulldozers) clear the overlying material.
4. Drilling and Blasting:
   • Explosives break the overburden and coal layers into manageable fragments.
5. Loading and Haulage:
   • Shovels and loaders transport coal to conveyor belts or trucks for processing.
6. Processing (Coal Washing):
   • Removal of impurities such as ash, sulphur, and stones to improve quality.
7. Transportation:
   • Coal is transported to thermal power plants or industrial consumers by rail, road, conveyor, or inland waterways.
8. Reclamation:
   • Post-mining, the land is rehabilitated by refilling pits, replanting vegetation, and restoring ecosystems.

Machinery Used

• Draglines and Power Shovels – for removing overburden.
• Continuous Miners – for mechanised cutting of coal underground.
• Roof Bolters – to support tunnel roofs in underground mines.
• Conveyors and Shuttle Cars – for coal transportation.
• Ventilation Systems – for air circulation and removal of hazardous gases.

Environmental Impacts

1. Land Degradation: Loss of fertile land due to excavation and dumping.
2. Air Pollution: Dust and particulate emissions from blasting and transport.
3. Water Pollution: Acid mine drainage contaminates groundwater.
4. Deforestation and Habitat Loss: Especially in open-cast mining areas.
5. Greenhouse Gas Emissions: Methane (CH₄) and CO₂ released during extraction.
6. Noise and Vibration: Affect nearby communities and wildlife.

Mitigation Measures:

• Reclamation and afforestation of mined areas.
• Use of dust-suppression systems.
• Treatment of mine effluents.
• Monitoring of air and water quality.
• Adoption of clean coal technologies.

Safety Measures in Coal Mining

• Proper ventilation and gas detection systems to prevent explosions.
• Roof support systems and ground control.
• Use of personal protective equipment (PPE).
• Emergency evacuation plans and rescue equipment.
• Regular training and compliance with safety standards (DGMS in India).

Coal Mining in India – Institutional Framework

• Coal India Limited (CIL): State-owned enterprise controlling over 80% of India’s coal production.
• Singareni Collieries Company Limited (SCCL): Joint venture between the Government of Telangana and the Centre.
• Private Sector Participation: Since 2020, commercial mining by private firms has been allowed to enhance competition and efficiency.

Future of Coal Extraction

With growing environmental concerns and global commitments to reduce carbon emissions, the future of coal mining is shifting towards:

• Cleaner extraction technologies.
• Underground gasification and carbon capture.
• Diversification into renewable energy by coal companies.
• Gradual reduction in coal dependence for electricity generation.