The co-steam gasification of biomass (straw) and Refuse-Derived Fuel (RDF) presents a promising pathway for sustainable waste management and renewable energy production, with significant implications for environmental protection. This study investigates the co-gasification of straw and RDF to optimize syngas production and minimize undesired by-products. The optimization of the S/M ratio and gasification temperature is crucial for efficient RDF gasification. The optimal S/M ratio and temperature balance syngas yield, quality (LHV), and process efficiency (carbon conversion efficiency and cold gas efficiency), while minimizing environmental hazards from solid residues. The carbon conversion efficiency of co-gasification of RDF increased by 12.7 % at the S/M 0 f 0.75 and gasification temperature of 800°C, a significant improvement compared to the efficiencies observed for the separate gasification of straw and RDF. Additionally, the gas yield and the cold gas efficiency were increased by 14.43 % and 26.42 % compared to the separate gasification processes, respectively. These results demonstrate the synergistic effects of co-gasifying straw and RDF, enhancing gasification performance and reducing tar formation. The study underscores the potential of co-steam gasification of straw and RDF as a technologically viable and environmentally friendly approach to waste-to-energy conversion, emphasizing the importance of operational optimization for achieving superior energy recovery, resource efficiency, and reduced environmental impact.