The feasibility has been shown for a novel hybrid system of solid state fermentation (SSF) with recycle for organic solid waste in which a part of solid is washed to suppress accumulation of glue-like material and resulting reaction breakdown. The optimum washing rate in the SSF reactor was examined. The water content and pH in the SSF reactors were also monitored throughout the operation. The decomposition rate of the reactors at 187.5 and 250 ml/day maintained the high value. These reactors reached a near steady state at 0.07 g VM/(g VM day) at constant rate. Washing conditions less than these rates resulted in breakdown of the reaction. A decrease of decomposition rate was observed in drier conditions of < 40% of water content and a good correlation between decomposition rate constant and water content in the SSF reactor was observed. (c) 2005 Elsevier Ltd. All rights reserved.