The influence of reaction conditions on light gas species (CO, CO2, H-2 and light hydrocarbons from CH4 to C3H8) and tar compounds during devolatilization of dried sewage sludge (DSS) was investigated. The tar content in the gas was characterized by the gravimetric tar as well as by GC MS analysis of 36 aromatic compounds (from benzene to perylene). Experiments were performed in a laboratory fluidized bed (FB) where the temperature of the dense bed was varied from 500 to 900 degrees C, the temperature of freeboard was varied from 600 to 900 degrees C, and the DSS particle size was varied from 1 to 5 mm, at fixed gas residence time. The temperatures of the two zones were adjusted independently to specifically study the yields of volatiles (light gas species + tars) generated from the fuel particles in the dense bed and the extent of secondary conversion of these volatiles in the freeboard, with special concern on tar compounds. It was found that higher dense bed temperature promoted the yields of light species but its influence on heavy polyaromatic tar hydrocarbons (PAR) was not significant provided that the freeboard temperature was kept below 700 degrees C. The increase in freeboard temperature enhanced the secondary conversion of volatiles, reducing the yield of gravimetric tar while increasing dramatically the yields of light gas and heavy PAH. The yields of tars were found to be insensitive to particle size within the investigated range. Additional tests were conducted using wood pellets to compare the results of DSS with a typical woody biomass. Although the magnitude of the yields was found to depend on the fuel type, the variation of tar compounds with the temperature of dense bed and freeboard followed similar trends for both fuels, suggesting that the same mechanisms of volatile conversion occur regardless of the parent fuel structure.