At the end of mining process, large number of small pieces of coal are left as residue. These pieces of coal are combined with other materials like bentonite, molasses and sodium silicate to bind them. Then they are pressed and dehydrated in special briquetting machine to form uniform shaped briquettes. They are used as a substitute of costly solid fuels like firewood, charcoal, etc. Coal briquettes are preferred as they give high calorific value compared to other fuels.