Steam gasification of dried coffee grounds (about 10 wt% water) was investigated in a laboratory-scale bubbling fluidized bed gasifier coupled to a pneumatic transported bed char combustor. The effects of steam-to-fuel ratio and Ca additive in two different forms, physically mixed or impregnated, were tested to examine their potential to increase gasification efficiency and eliminate tars. This examination was also conducted in a two-stage bubbling fluidized bed gasifier having a secondary stage of fluidized particles in the gasifier's freeboard. The results showed that increasing steam-to-fuel ratio only slightly increased the gasification efficiency expressed by fuel C conversion and cold gas efficiency, while the accompanying decrease in tar evolution was also not significant. Calcium additive exhibited pronounced upgrading effects on gasification efficiency and tar elimination only in the impregnated form. It increased the fuel C conversion from about 70% to 90% and decreased the tar content in the produced gas from 40 to 10 g/m(N)(3) at a reaction temperature of about 1073 K. This kind of high activity to facilitate fuel gasification and enhance tar reforming/destruction was attributed to the high degree of dispersion of impregnated Ca throughout the fuel matrix. The CaO physically blended into the fuel was poorly dispersed, resulting in its low activity to affect gasification reactions. The two-stage bubbling fluidized bed gasifier allowed increased gasification efficiency and suppressed tar evolution to some extent, but it was hard to eliminate further the tars generated in gasifying the Ca-impregnated fuel. This indicates essentially that the tars from the Ca-impregnated fuel are more difficult to degrade than those from coffee grounds only. This study also found that the fuel C conversion and tar content in product gas correlate with the H-2/CO molar ratio of the produced gas.