The majority of the mines that are used to extract the coal to produce electricity in the WB6 countries is the lower quality lignite type of coal. Due to its abundance and relatively easy access, as it generally is found closer to the surface makes this mineral among the most widely used in electricity production. Due to its low energy density and high ash content as well as other minerals that are harmful to the environment particular heavy metals, make this resource as one of the most polluting and environmentally damaging source of energy. Bosnia and Herzegovina, Serbia, Kosovo, Macedonia and Montenegro, all rely heavily on lignite coal for their energy production. There are other types of coal mines, such as sub-bituminous coal or even more rarely anthracite coal mines that due to cost and them being less accessible and less bountiful makes the use of them expensive and unfeasible for electricity generation. Bosnia and Herzegovina has large amounts of sub-bituminous coal compared to other countries, which is usually mined using underground methods. This type of coal is higher in calorific value than lignite, and is widely used there for electricity. Coal mines have a dramatic impact on the environment and the landscape as they tend to change the structure of the soil completely, degrade it and make it unusable. The strip mining of the earth with heavy machinery has very long term consequences, particularly to the nearby residents. Most of the time the ash that is used in the combustion of power plants is put back in the mine when the coal is removed thus creating long term complications.