Activated carbons were prepared from LFG (wastes generated during Lactic acid Fermentation of kitchen Garbage). Activated carbons were prepared by conventional steam activation and via the acid treatment prior to the steam activation. Porous properties of the prepared activated carbons were evaluated from nitrogen adsorption isotherms at 77 K. Activated carbons prepared by steam activation from LFG had much more mesopores than a commercial activated carbon, and had unique broad-shaped pore size distributions. It was evident from the ultimate analysis at each preparation stage of the carbons that the activated carbons prepared from LFG contain much nitrogen as carbonaceous materials. It was found that the burnoff of nitrogen during steam activation of LFG contributes to the formation of unique pore size distributions of the activated carbons. Activated carbons prepared via the acid treatment had not only more mesopores but also more micropores than the commercial activated carbon. It was suggested that LFG was useful as a resource for practical activated carbons, especially, for mesoporous activated carbons. It was also beneficial to apply the acid treatment to improve the porous properties of the prepared activated carbons.