Applicability of gulfweed as feedstock for a biomass-to-liquid (BTL) process was studied for both production of gas with high syngas (CO + H-2) content via gasification of gulfweed and removal of gaseous impurities using char obtained in the gasification. Gulfweed as aqueous biomass was gasified with He/CO2/O-2 using a downdraft fixed-bed gasifier at ambient pressure and 900 degrees C at equivalence ratios (ER) of 0.1-0.3. The syngas content increased while the conversion to gas on a carbon basis decreased with decreasing ER. At an ER of 0.1 and He/CO2/O-2 = 0/85/15%, the syngas content was maximized at 67.6% and conversion to gas on a carbon basis was 94.2%. The behavior of the desulfurization using char obtained during the gasification process at ER = 0.1 and He/CO2/O-2 = 0/85/15% was investigated using a downdraft fixed-bed reactor at 250-550 degrees C under 3 atmospheres (H2S/N-2, COS/N-2, and a mixture of gases composed of CO, CO2, H-2, N-2, CH4, H2S, COS, and steam). The char had a higher COS removal capacity at 350 degrees C than commercial activated carbon because (Ca,Mg)S crystals were formed during desulfurization. The char simultaneously removed H2S and COS from the mixture of gases at 450 degrees C more efficiently than did activated carbon. These results support this novel BTL process consisting of gasification of gulfweed with CO2/O-2 and dry gas cleaning using self-supplied bed material. (C) 2013 Elsevier Ltd. All rights reserved.