In this study, cofiring of high ash and sulfur content lignite with hazelnut shell and cotton residue was investigated in 0.3 MWt METU Atmospheric Bubbling Fluidized Bed Combustion (ABFBC) Test Rig in terms of combustion and emission performance of different fuel blends. The results reveal that cofiring of hazelnut shell and cotton residue with lignite increases the combustion efficiency and freeboard temperatures compared to those of lignite firing with limestone addition only. CO2 emission is not found sensitive to increase in hazelnut shell and cotton residue share in fuel blend. Cofiring lowers SO? emissions considerably. Cofiring of hazelnut shell reduces NO and N2O emissions; on the contrary, cofiring cotton residue results in higher NO and NO emissions. Higher share of biomass in the fuel blend results in coarser cyclone ash particles. Hazelnut shell and cotton residue can be cofired with high ash and sulfur-containing lignite without operational problems.