There’s different types of coal, with black and brown coal being two of the major types.
These types of coal are formed during a certain process over time, and can be further broken down into different sub categories of coal.
In the guide below, we list and explain the different types and ‘ranks’ of coal, how they are formed, their different properties, and other relevant information.
Summary – What Is Coal, & What Are The Different Types Of Coal?
What Is Coal?
Coal is a combustible sedimentary rock that is formed over long periods
Different Types Of Coal
Coal is mainly categorised into being either black coal, and brown coal
But, coal can further be categorised in the different ‘rank’ of coal it is, depending on how far along the coal formation process it is, and also the traits it has.
We provide more information on the different types of coal and their potential traits below.
What We Use Coal For, & Why It Might Be Important
Coal is generally used for energy generation for electricity
It may also be used as a fuel.
But, it also has a range of other uses, with it’s use in steel production also being a key use across society.
Read more about why coal is important and what we use it for in this guide
What Is Coal, & What Is It Made Of?
Coal might best be described as a ‘combustible sedimentary rock’
Is usually consists mostly of carbon, but may contain other elements too, such as hydrogen, nitrogen, sulfur and oxygen
It comes in different colors and forms, with brown coal and different variations of black coal being the main types of coal
How Is Coal Formed?
Various reports indicate that the formation of coal happens over a period of millions of years.
These reports indicate that coal comes from organic materials such as plant matter and the remains of dead organisms.
These organic materials build up over time in layers, and are covered by sediments.
The geological process then subjects this organic matter to heat/high temperatures and pressure, and changes the organic matter physically and chemically
The end result of this formation process (sometimes referred to as ‘coalification’) is differing ranks of coal
Major Types Of Coal
Coal might be broadly categorised into black and brown coal.
There are different forms and ranks of black and brown coal though
The form and rank of coal can depend on geography (where the coal is found), but also how far along the formation process the coal is
‘Rank’ might refer to the quality of the coal – with lignite being a lower ranking coal, and anthracite being a higher ranking coal
Chronologically, the different forms of coal that are created over different times spans, from the forms that happen first to the forms that happen latest in the formation process, are:
– Before coal is formed it starts as organic material
– Organic material progresses into peat
– Lignite (brown coal) (peat progresses into Lignite)
– Sub-bituminous (black coal)
– Bituminous (black coal)
– Anthracite (black coal)
From the above data, lignite is a younger form of coal than the various forms of black coal which might take longer to form.
Over time, coal progresses in rank from lignite, to sub-bituminous coal, to bituminous coal and finally to anthracite …
According to environmentvictoria.org.au, the several stages involved in the formation of coal, in order from first to last, are:
Plant material, wood
Brown coal (lignite)
Black coal (sub-bituminous, bituminous and anthracite)
Different Traits & Features Of The Different Ranks Of Coal
The different ranks of coal may differ in regards to some of the following traits, features and performance/output:
– The water content/moisture content of the coal
– The energy content of the coal
– The carbon content of the coal
– The % of volatile matter in the coal
The high the quality or rank of the type of coal, the more energy and less water content it might have, and the less of it might have to be burned to get the same amount of energy as a lower rank or lower quality type of coal.
According to environmentvictoria.org.au:
… 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.
According to ga.gov.au:
As the coal increases in rank, the carbon content – and hence the energy content – increases, whilst the moisture content decreases
Emissions From The Different Types Of Coal, & Related Materials
In their guide, ourworldindata.org has a good graph/chart showing how much carbon dioxide each type of coal fuel source, and related materials emit per unit of electricity produced
Our own comments about the information they present is that the lowest ranking and lowest quality forms of coal may have the highest emission rates, whilst the higher ranking and higher quality forms of coal may emit less.
Some reports indicate that the emission rate difference might be in the vicinity of around 9-10%.
Paraphrased from ourworldindata.org, the order of the most emissions to least emissions is:
Charcoal (most emissions)
Sub Bituminous Coal
Bitumen (least emissions)
Something else to note is that if more brown coal (in quantity) might need to be burnt compared to black coal to get the same amount of energy, this may also 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 generated.
Coal May Also Differ By Geography & Geologic Variables
Apart from the general types of coal described above, coal may also differ based on where it is found geographically in the world.
One example of this might be that some reports indicate that certain types of Chinese coal might have slightly different properties than certain types of Australian coal
This can be due to geologic and other local variables that impact the coal.
How The Different Types Of Coal Are Used
What Coal Is Generally Used For
The primary use of coal across society might be for energy – specifically electricity production.
Coal is combusted, which creates heat, which boils water and creates steam, which moves large turbines to create electricity
Read more about the other uses for general coal in this guide.
What The Different Types Of Coal Are Used For
Different types of coal may also be used more heavily for different things in different countries
Some types of coal for example are abundant in some regions more than others
This abundance might mean coal is cheaper in that region, and so it might be used for some purposes/applications more heavily
An example of this might be the heavy use of brown coal for electricity generation in regions where brown coal is abundant
Because of it’s abundance, the local supply of brown coal might be cheap, and this might mean cheaper and more affordable electricity
In other regions where brown coal is as abundant, more efficient forms of black coal might be used (as black coal usually has more energy per unit)
Are Coke & Coal The Same Thing?
Several reports indicate that coke and coal aren’t the same thing.
The main difference is that ‘Coke’ is derived from coal (so, they are still closely related)
It’s created during a a process called ‘coking’.
This involves coal (some reports say specifically bituminous coal is used) being heated or baked in the absence of oxygen.
This process may essentially reduce the impurities of the coal and refine it.
Coke might be the primary source of carbon used for steelmaking.
What Are Charcoal & Peat?
Both charcoal and peat can be mentioned by various reports in conjunction with coal.
However, these materials might be considered to be technically different to coal.
As we mentioned in the sections above in this guide, peat is the material that precedes lignite in the coal formation process, but comes after organic material like plants and the remains of dead organisms.
Made via a man made process of burning wood, peat, and other materials at high temperatures in an environment (such as a steel or clay box) with little to no oxygen
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