Tagebau Garzweiler near Grevenbroich, Lignite, often referred to as brown coal, is a soft brown combustible sedimentary rock that is formed from naturally compressed peat. It is considered the lowest rank of coal due to its relatively low heat content. It is mined in Bulgaria, Greece, Germany, Poland, Serbia, Russia, the United States, Canada, India, Australia and many other parts of Europe and it is used almost exclusively as a fuel for steam-electric power