About Energy from Coal

If you had one ton of bituminous coal with an energy content of 25 million BTUs, the energy released upon combustion would still be approximately 25 million BTUs, regardless of how long it had been laying there, assuming it had been stored properly and retained its energy content.

Coal is classified into several types based on its carbon content, energy content, and degree of metamorphism. 

1. Anthracite Coal

- Carbon Content: 86-97%

- Energy Value: Approximately 25-35 million BTUs per ton.

- Characteristics: 

  - Highest rank of coal, hard and lustrous.

  - Burns cleanly with a high heat output and low smoke.

- Uses: Primarily used for residential and commercial space heating and in industrial processes where high energy content is required.

2. Bituminous Coal

- Carbon Content: 45-86%

- Energy Value: Approximately 24-35 million BTUs per ton.

- Characteristics: 

  - Soft and typically black, with a shiny appearance.

  - Contains volatile compounds and can produce more smoke than anthracite.

- Uses: Widely used in electricity generation and steel production (metallurgical coal).

3. Sub-bituminous Coal

- Carbon Content: 35-45%

- Energy Value: Approximately 18-25 million BTUs per ton.

- Characteristics: 

  - Lower carbon content than bituminous coal, generally brownish-black.

  - Contains more moisture and has a lower heating value.

- Uses: Primarily used in electricity generation.

4. Lignite Coal

- Carbon Content: 25-35%

- Energy Value: Approximately 8-14 million BTUs per ton.

- Characteristics: 

  - Also known as brown coal, has a high moisture content and is soft.

  - Has the lowest energy content among coal types.

- Uses: Mainly used in electricity generation, particularly in power plants close to mining sites.

Summary of Energy Values by Coal Type

| Coal Type         | Carbon Content (%) | Energy Value (Million BTUs per ton) |

|-------------------|---------------------|-----------------------|

| Anthracite           | 86-97               | 25-35                                

| Bituminous         | 45-86               | 24-35                                

| Sub-bituminous  | 35-45               | 18-25                                

| Lignite                 | 25-35               | 8-14                                 

Each type of coal has specific characteristics that determine its use and suitability for different applications. Higher-ranked coals (like anthracite) have higher energy values and are better for applications requiring high heat and low emissions, while lower-ranked coals (like lignite) are often used primarily for electricity generation due to their abundance and lower energy content.