The co-firing of coal and biomass was studied using DTG assays. Blends of coal of different ranks and pine charcoal (obtained through pyrolysis of biomass at 1000°C) were prepared. Combustion profiles and characteristic temperatures (IT, PT and BT) were obtained and compared. To detect deviations, the experimental burnout curves for each blend were compared with weighted averages calculated from the conversion profiles obtained for the individual fuel samples and the blend composition. Positive and negative deviations were obtained which can be predicted from the differences in the reactivity of the blend components and their relative proportions.