The formation of tar during biomass gasification is a main barrier to establishing reliable gasification technologies. Different catalysts are being used for tar abatement from the biomass gasification. In this study, catalytic and noncatalytic cogasification of wood-coconut shell blends was carried out in a downdraft gasifier. The effect of the operating parameters on syngas quality, performance of cogasification, and tar reduction was investigated. The biomass blending ratio (BR) was varied as W20:CS80, W50:CS50, and W80:CS20, equivalence ratio (ER) was varied from 0.19 to 0.35, gasification temperature from 700 to 900 °C and catalyst loading (CL) from 5 to 30. Dolomite, limestone, and Portland cement were used as a catalyst. The results revealed that under noncatalytic conditions, the blend with higher proportion of coconut shells produces better syngas composition with higher HHV and lower tar content. The high ER reduced H 2 , tar formation, cold gas efficiency and gas yield. It also improved the carbonaceous gas species and carbon conversion efficiency. Increasing gasification temperature significantly improved the syngas quality, cogasification performance and reduced the tar content. The 30 CL significantly improved the gas composition content, gas yield, cold gas efficiency and reduced the tar content up to 52. Better syngas quality and cogasification performance was possible with calcined cement catalyst whereas a reduction in tar content was observed in the presence of limestone. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 688�698, 2019. © 2018 American Institute of Chemical Engineers