Cleaning and upgrading of the hot raw gas from a-biomass gasifier, bubbling fluidized bed type, is studied at small pilot plant scale (10 kg biomass fed/h) using a calcined dolomite located downstream from the gasifier. Gasification is made with steam-oxygen mixtures at 800-850 degrees C and atmospheric pressure. Main variables studied are the gas residence time in the bed of dolomite and the gas atmosphere composition, which depends on the gasifying agent (H2O + O-2)-to-biomass and H2O/O-2 ratios. H-2 and CO content in the flue gas increases by 16-23 vol % and decreases by 15-22 vol % (dry basis), respectively. Although CH4 conversion (elimination) higher than 30 vol % has never been reached, tar conversion (elimination) of 90-95 vol % are obtained with space times of 0.06-0.15 kg calcined dolomite h(-1) m(-3). A detailed study is here presented on how the calcined dolomite significantly cleans and upgrades the flue gas, increasing also the gas yield by 0.15-0.40 m(3)(STP)/kg daf biomass fed.