Sub-bituminous coal

Sub-bituminous coals may be dull, dark brown to black, soft and crumbly at the lower end of the range, to bright jet-black, hard, and relatively strong at the upper end. They contain 15-30% inherent moisture by weight and are non-coking (undergoing little swelling upon heating). The heat content of sub-bituminous coals ranges from 8,300 to 11,500 Btu/lb or 19.3 to 26.7 M J/kg. Their relatively low density and high water content render some types of sub-bituminous coal susceptible to spontaneous combustion if not densely packed during storage to exclude airflow.

A major source of sub-bituminous coal in the United States is the Powder River Basin in Wyoming.

Sub-bituminous coals, in the United States, typically have a sulfur content less than 1% by weight, which makes them an attractive choice for power plants to reduce SO₂ emissions under the Acid Rain Program.

Sub-bituminous coals release large quantities of greenhouse gases when burned, compared to higher grades of coal.