Brown coal accounted for electricity to the tune of 162 billion kilowatt hours, equivalent to about 25% of Germany’s total electricity production of 629 billion kilowatt hours in 2013, industry group Arbeitsgemeinschaft Energiebilanzen said.

Environmentalists, reports AP, criticized the mounting use of coal, saying it is a “dirty” source because of the large amount of carbon dioxide released when it is burned.

They are now asking for energy reforms to increase the costs of operating coal-fired power stations –especially those that use brown coal, a highly polluting fuel.