The effect of lignocellulosic biomass composition on gasification of biochar in a pilot-scale fluidized-bed reactor was studied. First, three biomass samples from agroindustrial sectors of Colombia were pyrolyzed. These biochars were then subjected to gasification. The biomasses, biochars, and gasification residues were subjected to various physicochemical and morphological analyses to study the evolution of the carbonaceous structure and syngas composition. In the case of sugar cane bagasse and rice husk, the high contents of cellulose and hemicellulose promoted the thermochemical conversion of the biochar into syngas; however, in the palm kernel shell, its high lignin content made thermochemical pyrolysis and gasification difficult as a result of the recalcitrance of the lignitic structure, which forms a more organized carbonaceous structure.