What is the Difference Between Black and Brown Coal

The key difference between black and brown coal is that black coal has a comparatively low content of ash and moisture than brown coal.

Coal is a fossil fuel similar to natural gas and oil and is in a solid rock form. Coal forms from plant debris that collects in swamps. This process takes thousands of years. When plant materials collect on swamps, they degrade very slowly. Generally, swamp water does not have a high oxygen concentration; therefore, microorganism density is low there, resulting in minimum degradation by microorganisms. Plant debris accumulates in swamps because of this slow decaying. When these are buried under sand or mud, the pressure and inside temperature convert the plant debris to coal slowly. Coal is considered a non-renewable natural resource. This is because when we mine out coal and use it, it does not regenerate again easily.

CONTENTS

1. Overview and Key Difference
2. What is Black Coal (Bituminous Coal)
3. What is Brown Coal (Lignite)
4. Black vs Brown Coal in Tabular Form
5. Summary – Black vs Brown Coal 

What is Black Coal?

Black coal, also known as bituminous coal, is a type of coal consisting of a tar-like substance named bitumen. Sometimes, this substance appears in dark brown color while it is mostly black colored in nature. It has well-defined bands of bright and dull material within its seams. Typically, it is hard and friable.

Bitumen, also called asphalt, is a naturally occurring dark, thick liquid that is highly viscous and sticky. Sometimes it can be found in the semi-solid state as well. Bitumen also forms as a byproduct in refining processes. The naturally occurring form of bitumen is often referred to as “crude bitumen.” It has a viscosity that is similar to the viscosity of cold molasses. The synthetic form of bitumen is named “refined bitumen,” which is obtained from the fractional distillation of crude oil at high temperatures.

Primarily, this type of coal is important in electrical power generation and in the steel industry. This substance is also suitable for smelting iron, which must be low in sulfur and phosphorous. Moreover, this substance commands a high price compared to other grades of black coal that are useful in heating and power generation.

Black coal can release a large amount of firedamp in the coal mining industry. Firedamp is a dangerous mixture of gases that will cause ground explosions. Furthermore, the extraction of black coal demands high safety procedures, which involve attentive gas monitoring, good ventilation, and vigilant site management.

What is Brown Coal?

Brown coal or lignite is a soft, brown, combustible sedimentary rock that forms from naturally compressed peat. This substance has about 25-35% carbon content. It is considered to be one of the lowest ranks of coal because it has a relatively low heat content. We can mine lignite all around the world and, it is mainly useful for steam-electric power generation.

The inherent moisture content of lignite is about 75%, while ash content ranges from 6 – 19%. Therefore, the carbon content of this substance is typically about 25-35%. However, the energy content produced by this material can range from 10 to 20 MJ/Kg. The content of volatile matter in brown coal is comparatively high. It makes it easier to convert into gas and liquid petroleum products compared to higher-ranking coals.

The major use of brown coal is the generation of electricity, while there are some other uses such as its use in agriculture, in the chemical industry, in the jewelry industry, as a fuel, as an industrial adsorbent, etc.

What is the Difference Between Black and Brown Coal?

Black coal is also known as bituminous coal, and it is a type of coal consisting of a tar-like substance known as bitumen. Brown coal or lignite is a soft, brown, combustible sedimentary rock that forms from naturally compressed peat.  The key difference between black and brown coal is that black cola has a comparatively low content of ash and moisture, whereas brown coal has a comparatively high content of ash and moisture.

The below infographic presents the differences between black and brown coal in tabular form for side by side comparison.

Summary – Black vs Brown Coal

Black coal is also known as bituminous coal, and it is a type of coal consisting of a tar-like substance known as bitumen. Brown coal or lignite is a soft, brown, combustible sedimentary rock that forms from naturally compressed peat.  The key difference between black and brown coal is that black cola has a comparatively low content of ash and moisture than brown coal.

Reference:

1.“Black Coal.” Geoscience Australia.

Image Courtesy:

1. “Coal bituminous” (Public Domain) via Commons Wikimedia
2. “Lignite-coal” By Edal Anton Lefterov – Own work (CC BY-SA 3.0) via Commons Wikimedia