Coal is graded by rank: lignite, sub-bituminous, bituminous and anthracite. Rank shows how far the coal has matured underground. Higher-rank coal has more carbon, less moisture and more energy per tonne. Lignite sits at the bottom, anthracite at the top.
The best grade is not always the highest. Power plants, cement kilns and steel mills each need different properties, and the right choice balances energy, impurities and delivered cost.
The four coal grades at a glance
| Grade | Carbon content | Energy | Moisture | Main uses |
|---|---|---|---|---|
| Lignite | About 25% to 35% | Lowest | Very high | Power plants next to the mine |
| Sub-bituminous | About 35% to 45% | Moderate | High | Power plants, industrial boilers |
| Bituminous | About 45% to 86% | High | Low | Power, cement, and coking coal for steel |
| Anthracite | About 86% to 97% | Highest | Very low | Heating, specialist industrial uses, some steel processes |
Lignite
Lignite, or brown coal, is the youngest and softest coal. It holds a lot of water, so it has the lowest energy per tonne and is expensive to transport. Most lignite is burned in power plants built right next to the mine. It is rarely traded by sea.
Sub-bituminous coal
Sub-bituminous coal has more energy than lignite but still carries significant moisture. Its big advantage is that it is often low in sulphur and ash, which helps power plants meet emission limits. Much of Indonesia’s export coal is sub-bituminous, which is why it is so widely used in Asian power plants. See our guide to Indonesian coal.
Bituminous coal
Bituminous coal is the most widely traded grade. It covers two very different products:
- Thermal (steam) bituminous coal, burned in power plants and cement kilns for its high energy
- Coking (metallurgical) coal, a type of bituminous coal that softens and swells when heated without air, forming the coke used in blast furnaces
Australia, Colombia, Russia, South Africa and the US are major sources.
Anthracite
Anthracite is the hardest, highest-carbon coal. It burns hot with little smoke and is used for heating, water filtration and some industrial processes. It does not make coke, so steel mills use it only in limited roles, such as injection into the furnace or sintering. See anthracite vs bituminous for steelmaking.
Which coal grade suits which industry?
| Industry | Usually uses | What matters most |
|---|---|---|
| Power generation | Sub-bituminous or bituminous thermal coal | Calorific value matched to the boiler, sulphur, ash, moisture |
| Cement | Bituminous or sub-bituminous thermal coal | Energy, ash chemistry, sulphur |
| Steelmaking | Coking coal, plus some PCI and anthracite | Coking properties, low ash and sulphur |
| Industrial boilers | Sub-bituminous or bituminous | Steady, reliable quality and price |
For power plants, see coal suppliers for power plants. For steel, see coal in steel production.
How export coal is graded in practice
In trade, thermal coal is described by its specification, not just its rank. The key figures are:
- Calorific value (CV), in kcal/kg, quoted on a stated basis such as GAR (gross as received) or NAR (net as received)
- Total moisture
- Ash
- Total sulphur
- Volatile matter
- Size
Indonesian coal, for example, is often traded as 3,400, 4,200, 5,000 or 5,800 kcal/kg GAR, linked to the Indonesian Coal Index. Read how to assess coal quality for a step-by-step check.
How to choose the right grade
- Start with your equipment. Ask your boiler or kiln supplier for the design coal range.
- Compare cost per unit of energy, not per tonne. A cheaper, lower-CV coal can cost more per useful kcal once freight is added.
- Check impurities against your emission limits. Sulphur and ash matter as much as energy.
- Agree the basis. Make sure the CV in the contract is stated on the same basis (GAR, NAR or ADB) your plant uses.
- Insist on independent inspection at loading.
Buying Indonesian coal through Agromer
Agromer holds mandates for Indonesian thermal coal for power plants and industrial buyers. We work with an end-buyer LOI, payment by 100% DLC or SBLC, and SGS inspection at loading. Send us your specification, monthly quantity, contract length and discharge port. See our Indonesian coal supply page.
Frequently asked questions
What are the four grades of coal?
Lignite, sub-bituminous, bituminous and anthracite, ranked from lowest to highest carbon and energy content.
Which coal grade is best?
It depends on the use. Anthracite has the most energy, but most power plants burn sub-bituminous or bituminous coal, and steel mills need coking coal.
What coal is used in power plants?
Mostly sub-bituminous and bituminous thermal coal, matched to the boiler design.
What coal is used for making steel?
Coking coal, a type of bituminous coal that forms coke when heated. Some anthracite and PCI coal are also used.
What grade is Indonesian coal?
Most Indonesian export coal is sub-bituminous, typically 3,400 to 5,800 kcal/kg GAR, with low ash and sulphur.
What is GAR and NAR?
GAR is gross calorific value as received. NAR is net calorific value as received, which subtracts energy lost to moisture. NAR figures are lower than GAR for the same coal.