Some people are unaware that not all coal is the dark black coal we are used to seeing.
There are actually different types of coal, with different properties, and they might be used in slightly different ways.
Summary – Types Of Coal (& Uses)
- Coal comes in various types, from the softer brown coal with higher moisture content and lower amounts of carbon, to various stages of harder black coal with less moisture and more carbon
- We mainly use coal in society for energy generation for electricity, but also for key products and processes like steel production
- Different coal types have different properties, and have different emission rates of both carbon dioxide and air toxins
Major Types Of Coal
Coal might be broadly categorised into black and brown coal. But, the major types of coal are:
- Anthracite – hard and black. Contains a high percentage of fixed carbon and a low percentage of volatile matter.
- Bituminous – has a high heating (Btu) value and is the most common type of coal used in electricity generation in the United States
- Sub-bituminous – black in color … and has a higher heating value than lignite
- Lignite – aka brown coal, is the lowest grade coal with the least concentration of carbon
Coking coal or coke is also made by heating coal or oil with the absence of air.
- Over time, coal progresses in rank from lignite, to sub-bituminous coal, to bituminous coal and finally to anthracite; a process known as coalification. As the coal increases in rank, the carbon content – and hence the energy content – increases, whilst the moisture content decreases
Coal is formed when plant material is subjected to high temperatures and pressures lasting millions of years. Several stages are involved in the formation of coal. These are:
- Plant material, wood
- Brown coal (lignite)
- Black coal (sub-bituminous, bituminous and anthracite)
Each successive stage has a lower water content and a higher energy content. This means that when the same quantity of each material is burned, a greater amount of heat is released for each successive stage.
Other Materials Often Related To Coal
These materials might not be coal technically, but they are often related to coal:
- Charcoal – is man made, whereas coal is naturally formed
- Peat – not actually coal. But, it is the first step in the process of a material becoming lignite/brown coal. High pressure and heat turns peat into coal
How The Different Types Of Coal Are Used
Coal has a major use as an energy source for electricity (burning of coal creates heat, the heat boils water, and steam from the water moves large turbines to create energy).
But, how the different types of coal are used depends on the country and region they are used in.
The type of coal found in a particular region and how abundant and cheap it is might determine how it’s used.
For example, even though brown coal tends not to have as much energy per unit as black coal, it might be cheaper to use in some countries and regions and might be used in coal power plants there (as it can help supply cheap electricity).
It can depend on logistics and other factors.
Aside from using black or brown coal for energy and fuel, coal can be used for:
- Making steel – coking coal is used in steel production
- Used as an ingredient in making other chemicals and products
- Black coal is also used in cement manufacture, alumina refining, paper manufacture and for other industrial purposes (ga.gov.au)
Read more about the uses of coal at https://www.worldcoal.org/coal/uses-coal
Emissions From The Different Types Of Coal
OurWorldInData.org has a good graph/chart showing how much carbon dioxide each type of coal fuel source emits per unit of electricity produced – view it at https://ourworldindata.org/fossil-fuels
In order of most to least emissions:
- Sub Bituminous Coal
Something to note is that more brown coal (in quantity) might need to be burnt compared to black coal to get the same amount of energy, and this can contribute to higher carbon emission rates. So, the inefficiency of brown coal might contribute to it’s higher carbon release rate per unit of electricity.
A Note About How Coal Types Can Differ Even Further
Apart from the general types of coal described above, coal can also differ based on where it is found in the world.
For example, certain types of Chinese coal might have slightly different properties than certain types of Australian coal.