Cellular structured activated carbon samples were prepared with the aid of alkali carbonates X2CO3 (X = Li, Na, K, Rb, or Cs) from dry bread yeast with a milling procedure. The resultant carbon possesses a very large adsorption amount even for supercritical methane. The activation with Cs2CO3 gave the greatest surface area of 2420 m(2) g(-1) from the subtracting pore effect method. The activation efficiency of X2CO3 (X = Li, Na, K, Rb, and Cs) was associated with the order of Gibbs free energy Of X2O (X = Li, Na, K, Rb, and Cs) which should play an important role in the gasification. The carbon activated with Rb2CO3 gave the greatest adsorption amount of supercritical methane of 90 mg g(-1) at 0.9 MPa at 303 K. (c) 2007 Elsevier Inc. All rights reserved.