Biomass gasification often encounters the shortage of biomass supply for continuous operation. Co-gasification of different biomass materials is a promising solution that can address the shortage of biomass supply for the continuous gasification process. However, the effectiveness of co-gasification is not well understood. Furthermore, there is nearly no reported work of co-gasification of two or more biomass materials. In this study, two Malaysian local biomass materials, wood residual and coconut shells were co-gasified in a 33.6 kW thermal capacity downdraft gasifier to investigate the effect of blending ratio the on quality of the producer gas. The results show that producer gas composition increased as coconut shells proportion increased in blends of up to 60. A blend of 40:60 W/CS results in a synergetic effect as compared to discrete gasification of both feedstock. The maximum H2 and CO were obtained as; 11.46 vol. and 23.99 vol. respectively at 40:60 W/CS blending ratio. The results achieved from 40:60 W/CS blend were 16.70 and 10.96 higher as compared to pure wood gasification for H2 and CO respectively. It is concluded that coconut shells can be utilized a substitute of wood residual in form of blends or as discrete feedstock for the continuous gasification process without the change in gasifier geometry. © 2018 The Authors, published by EDP Sciences.