Investigations were launched under atmospheres of different N2/CO2 ratios for thermo-degradation of lignocellulosic biomass and its chlorinated derivative that typically contains 10 wt.% poly(vinyl chloride) (PVC) over thermogravimetric analysis. Two degradation stages were found where CO2 was inert in stage one but changed to be reactive in stage two. Lignocellulosics were less reactive than their chlorinated derivatives. Non-isothermal thermogravimetric data were used for evaluating kinetics using Ozawa-Flynn-Wall and Vyazovkin methods. The values of apparent activation energy in stage one were 200-250 kJ/mol with less variance but varied greatly in stage two for different scenarios concerning CO2 proportion and PVC presence. These values were used to determine the reaction mechanism of each stage by master-plots method. Most processes were kinetically characterized by diffusion and reaction order models. The results afford a theoretical groundwork for the resourceful utilization of lignocellulosics derived from municipal activities and the development of their thermochemical conversion systems.