Woody biomasses such as ash tree (AT), hybrid poplar (HP), and rhododendron (RD) were subjected to torrefaction and carbonization at temperatures of 200 degrees C and 400 degrees C. Likewise, several lignite samples were carbonized at 750 degrees C. Various binary fuel blends such as raw lignite/raw biomass, raw lignite/biochar, lignitic char/raw biomass, and lignitic char/biochar were prepared where the fraction of biomass or biochar was 10 wt% in the blends. The cocombustion characteristics of these blends were investigated through a thermal analysis method from the synergetic point of view considering the fuel properties and the combustion performance. Some parameters relevant to the combustion reactivity such as ignition point, maximum rate, peak temperature, and burnout temperature were commented to figure out whether synergistic interaction or additive behavior governs the combustion characteristics of the blends. Also, the combustion performance indices such as ignition index (C-i), burnout index (C-b), comprehensive combustibility index (S), and the burning stability index (D-W) were estimated. It was concluded that the combinations of the additive behavior and the synergistic interactions governs the cocombustion process, and the kind of the fuels and their thermal history determine the reactivity and the interactions during cocombustion.