Question

What is the superior quality of coal called?
A. Peat
B. Lignite
C. Bituminous
D. Anthracite

Answer 1

Hint: We know that coal is a combustible rock and, along with oil and natural gas, it is one of the three most important fossil fuels. Higher carbon content is associated with coal that has spent a longer time forming, while lower carbon content is a characteristic of younger coal. The coal which has higher carbon content, that coal will be of superior quality.

Step by step answer:
We should know that coal is a primary energy source for more than a century. It began to form during the Carboniferous period, which took place between 360 million and 290 million years ago. Coal is formed when dead plant matter decays into peat and is converted into coal by the heat and pressure of deep burial over millions of years. We should know the following factors that make up the good coal:
1. The type of vegetation the coal originated from.
2. The coal’s depth of burial.
3. Temperatures and pressures at that depth.
4. How long it took the coal deposit to form.
All of the above factors determine the carbon content that determines a coal’s rank. Higher carbon content of coal will be of superior quality. Now, we look at the options and we will identify the superior quality of coal.

A. Peat is a soft, crumbly, dark brown substance that is formed from generations of dead and partially decaying organic matter. We should know that peat is the first step in the formation of coal, and slowly becomes lignite after pressure and temperature increase as sediment is piled on top of the partially decaying organic matter. In order to be turned into coal, the peat must be buried from 4-10 km deep by sediment. Peat exhibits the lowest carbon content (less than 60%) and has an energy density of 15 mega joule per kilogram.

B. Lignite or brown coal is brown in colour and the lowest quality of coal. The carbon content of lignite ranges from 65-70%; therefore, compared to other types of coal it contains the greatest amount of compounds other than carbon, such as sulphur and mercury. We should know that lignite is the youngest fossil fuel produced, with an age of approximately 60 million years. Its relatively short lifespan means it exhibits quite a low energy density at 18 megajoule per kilogram. Lignite's high moisture content and lower carbon content results in more carbon dioxide emissions than harder black coals.

C. We should know that bituminous coal is the second highest quality of coal, with a carbon content that ranges from 76-86%. It is the most abundant type, and one of the longest buried fossil fuels—with an age of approximately 300 million years old. Therefore, its energy density is relatively high at 27 mega joule per kilogram. The high carbon and low moisture content of this particular type of coal makes it ideal in the production of steel and cement, as well as in electricity generation and coke production.

D. Anthracite is a dark black form of coal and the highest quality coal. We should know that it is very hard, has low moisture content, and a carbon content of nearly 95%. When burned, anthracite can reach a very high temperature. In addition we should note that anthracite is usually the oldest type of coal, having formed from biomass that was buried 350 million years ago. Its prolonged burial time means it exhibits a very high energy density of 33 megajoule per kilogram. It has the highest energy density of any type of coal. Since so much energy is released when burned, this fuel is exceptional at heating up quickly and burning very hot. Anthracite is used for space heating as it is one of the cleanest types of coal to burn, producing less smoke than other types. Its clean burning properties allow anthracite to burn longer than wood, making it appealing to use in home heating stoves.

From the above discussion, we know that anthracite is the coal of superior quality.

Note: Increasing our use of coal would increase concern over several environmental issues. Two main environmental concerns associated with the use of coal are:
Pollution, caused by emissions of contaminants such as sulphur dioxide, nitrogen oxides, and mercury, which affects human and environmental health.
Greenhouse gases, emissions of which contribute to global warming.