The work presented in this thesis explores the thermochemical methods (pyrolysis and gasification) for co-conversion of biomass with plastics and tires into value added products. Numerical study was performed on steam co-gasification of sawdust and plastics (PE and PP) using Aspen Plus. The study determined the synergistic effects of mixing PE and PP (0-30%) with lignocellulosic biomass. Highest hydrogen concentrations of 64.58 % and 62.87 % were obtained respectively for PE-biomass and PP-biomass gasification at 30% plastic content and 750 oC. Experimental research was carried out on co-pyrolysis of sawdust and tires using Quartz Wool Matrix (QWM) reactor over zeolite and novel biochar-based catalyst. Design Expert version 11 was used to obtain the optimal process conditions. Both catalysts showed great catalytic performance in terms of de-oxygenation and denitrogenation reactions. With the biochar-based catalyst, selectivity of aromatics was increased to more than double (25.53 %) as compared to the non-catalytic process (11.48 %).