The pyrolysis behavior of Turkish biomass samples such as hazelnut shell, almond shell, and sunflower stalk residue was studied using a thermogravimetric analysis (TGA) laboratory-scale setup. Biomass samples were characterized using the standard method of the Van Soest detergent analysis, and both the virgin biomass and fractions were investigated. The reaction temperature was increased to 900 °C with a heating rate range between 2 and 60 °C min−1 in the TGA experiments. Seven solid-state reaction models were applied to evaluate the obtained experimental TGA results. The heating rate was not the only parameter affecting the values of activation energy and the ratio of the main components such as the cellulose and lignin of the virgin biomass samples (almond shell, sunflower stalk, and hazelnut shell) also affected the value of the activated energy values. It was determined that a model fitting mechanism gives limited information to determine the exact activation energy values for the samples. The reaction order model provided straightforward and decisive results for all the biomass and lignin samples. Models of two- and three-dimensional diffusion were better suitable for the cellulose devolatilization. It was also determined that the activation energy of the lignin samples was similar regardless of the types of biomass. According to the kinetic calculations, the cellulose samples showed the highest activation energy values and the lignin samples had the lowest.