Composting is an approach to convert typically organic waste into soil amendment for nutrient enhancement and plant growth. The composting of cow dung and spent mushroom for 13 days to study the potential of degradation of organic matter at different size of laboratory scale. The compost bed size is crucial to study because larger amount of raw materials will reduce the O2 concentration inside the compost bed. In this study, the aerobic compost bed size of 2, 4 and 6 kg were prepared at 60 % of initial moisture content, 20 mm particle size and 28:1 of initial C/N ratio. Temperature, moisture content, porosity, pH, C/N ratio and total organic carbon were analysed to evaluate the degradation process. All compost beds recorded the mesophilic phase (>30 ℃) upon composting of initial total organic carbon of 35 to 37 %. Moisture content reduced to lower than 43.9 %, total organic carbon reduced to less than 25 % and compost beds were nearly neutral (pH 7) at the end of composting. The findings show that, all the compost beds follow the first-order kinetic reaction as R2 larger than 0.880. The degradation rate constant of 2 kg compost bed showed the largest value, 0.0503 day-1 indicates the best composting process and results the smaller compost bed is preferable for mesophilic phase composting.
