In this study, the optimization of the palm shell based activated carbon production using combination of chemical and physical activation for methane adsorption is investigated, response surface methodology (RSM) in combination with central composite design (CCD) was used to optimize the operating parameters of the production process. Physical activation temperature, chemical impregnation ratio and physical activation time were chosen as the main process variables and the amount of methane adsorption was selected as the investigated response. Phosphoric acid and carbon dioxide were used as chemical and physical agents, respectively. The optimum reaction conditions were found to be a physical activation temperature of 855 degrees C, H3PO4 impregnation ratio of 9.42 g of phosphorous per gram palm shell and physical activation time of 135 min. The results exhibited significant increase in methane adsorption after physio-chemical activation. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.