Phase-separated two-stage anaerobic process was examined and evaluated using artificial organic solid waste in laboratory scale. Acidogenic process, which was combined with subsequent methanogenic process using packed-bed reactor, was operated emphasizing on either hydrogen production, or solublizing efficiency of solid materials. In either effluent from hydrogenogenic, or solublizing operation, maximum allowable OLR achieved at methanogenesis was higher than the single methanogenic process. Hydrogenogenic operation was more suitable to combine methanogenic process than solublizing operation, since retention time of hydrogenogenic operation was much shorter than the solublizing operation, obtaining almost the same levels of overall removal efficiency in both COD and VSS. The combination of hydrogenogenic operation in acidogenic process and methanogenic process produced approximately 442 mmol 1-reactor(1) days(-1) of methane and 199 mmol 1-reactor(1) days(-1) of hydrogen at 25 h of total retention time indicating 82% of COD removal with 96% of VSS decomposition. (c) 2006 Elsevier Ltd. All rights reserved.