Biomass species such as the rice husk and the olive milling residue, and a low quality Turkish coal, Soma Denis lignite, were burned in a thermal analyzer under pure oxygen and dry air up to 900 degrees C, and differential thermal analysis (DTA) and derivative thermogravimetric (DTG) analysis profiles were obtained. Co-combustion experiments of lignite/biomass blends containing 5-20 wt% of biomass were also performed. The effects of the oxidizer type and the blending ratio of biomass were evaluated considering some thermal reactivity indicators such as the maximum burning rate and its temperature, the maximum heat flow temperature, and the burnout levels. FTIR (Fourier transform infrared) spectroscopy and SEM (scanning electron microscopy) were used to characterize the samples, and the variations in the combustion characteristics of the samples were interpreted based on the differences in the intrinsic properties of the samples. (C) 2012 Elsevier Ltd. All rights reserved.