Alkaline desulfurization is more effective in removing pyritic sulfur from coal, which is the less abundant form than the organic sulfur. Lignite and coal samples from Turkish resources were extracted with an aqueous alkaline solution obtained from the water-soluble fraction of biomass ash. By this method, high sulfur removal from lignites was possible. The effect of temperature, the amount of biomass ash used, and stirring speed were studied in the ranges 10 to 50 g, 350 to 550 K, 0.042 to 1.8 MPa, 15 to 60 min, and 300 to 600 rpm, respectively. The effect of pyritic and organic sulfur removal were investigated. This process removed 33.1, 35.3, and 37.2% of total sulfur content; 52.3, 53.6, and 60.7% of pyritic sulfur content; and 4.6, 22.1, and 18.0% of organic sulfur content from the lignite samples, respectively.