The purpose of this experimental study was to clarify the effect of the number of the vertical perforated pipes on the composting rate and the extent of organic matter degradation. To achieve this target, composting was performed on the simulated organic solid waste, blended with wood chips and inoculums using a laboratory-scale composting reactor equipped with the vertical pipes as air suppliers for the passive aeration. The dog food (DF) was used as a simulated organic waste to be composted. For the aeration purposes, two, four and six vertical perforated pipes, which top wall was heated at the initiation phase, were embedded in the reactor at Runs A, B and C, respectively. The composting was monitored by regularly measuring the bed temperature at different points during the composting process. Thermophilic temperatures, about 55°C, were observed within the bed during each of the composting runs. The final conversions of carbon were, approximately, 86 to 96%. On the basis of a simple heat balance obtained under a steady reaction proceeding, the composting rate was analyzed. The composting reaction rate increased in increasing in the number of the vertical pipes during the composting process. The reaction rate was expressed as a first order equation and the reaction rate constant was calculated.