Synthesis of activated carbon (AC) from sawdust of Algarroba wood was performed as a function of the temperature under CO(2) and N(2) flow. Characterization was performed by adsorption-desorption N(2) isotherms, FTIR, XPS and SEM. Functional acid or basic groups were detected on the surface of AC. For both studied atmospheres, the maximum value of surface area was obtained at 800 degrees C. A monotonic correlation between temperature and mean pore diameter was detected being the higher the activation temperature the lower the mean pore width of AC. Ultramicroporous AC with pore diameters of 6.7 angstrom and 5.3 angstrom were obtained at 900 degrees C under CO(2) and N(2) flow, respectively. It can be concluded that pore diameter and the functionalization of the AC surface can be controlled easily controlling the temperature of activation, independently of the gas atmosphere. The present results suggest that waste biomass is a potential source for the synthesis of carbon materials with potential novel applications. (C) 2011 Elsevier B.V. All rights reserved.