Disruption in feedstock supply due to seasonal availability, and logistics problem poses a threat to smooth biomass gasification. To mitigate this problem, cogasification of different biomass feedstocks may be a reliable and efficient means of syngas production. Furthermore, the oil palm trunk (OPT) has been neglected in conducting thermochemical studies due to its high moisture and nature of availability compared to oil palm frond (OPF), despite its abundance during replanting periods and remarkable thermochemical properties. Hence scarce information is known on its gasification and co-gasification studies. In this study, OPT and OPF were co-gasified using a lab scale downdraft gasifier, to evaluate the influence of blending ratio on co-gasification performance and syngas quality at a temperature of 800 C, particle size of 5-10 mm, and an airflow rate of 2.5 L/ min. The blends utilised were OPT/OPF at ratios 30/70, 50/50 and 70/30 for cogasification, whereas pure OPT and OPF were used for gasification. The optimum blend was 30OPT/70OPF, as it produced the highest gas constituents of CO, H 2 and CH 4 , compared to the other blends. It also produced the highest gas yield and heating value, 1.47 Nm 3 /kg and 6.85 MJ/Nm 3 , respectively. Its cogasification efficiencies were also higher for both cold gas (56.35%) and carbon conversion (68.53%). In the gasification study, OPT was 7% higher than OPF in H 2 yield, whereas OPF was higher in CO yield by 20%, and in terms of CH 4 both yielded almost same results. The gas yield and heating values of syngas produced in OPT and OPF gasification were comparable as the difference in both cases was not more than 5%. It is deduced that there exists positive synergistic effect in 30 OPT/70 OPF blend as evident from the results obtained, and that OPT is a capable gasification fuel that can complement OPF in case of supply shortage. K E Y W O R D S blending ratio, co-gasification, gasification, oil palm frond, oil palm trunk, syngas 1 | INTRODUCTION Gasification refers to a thermochemical process for the transformation of carboniferous fuels into syngas in the presence of a gasification medium and within a reactor called gasifier, usually at a temperature range of 700 C to 1000 C. The typical gasification process reaction is described in Table 1. 1,2 The products of gasification are syngas, char and ash, with the syngas being the major product consisting of CH 4, H 2 , CO, CO 2 and an unwanted