Optimization on co-composting of horse manure with pineapple waste composition using Response Surface Methodology (RSM)

Abstract

Horse manure (HM) content of nitrogen and phosphorus can improve soil nutrient as organic fertilizer. Biodegradable pineapple waste (PW) contains high organic carbon, which is also a good bulking agent if appropriately treated with HM through co-composting to optimize the better quality of the co-compost product. The study objective was to optimize the composting quality of HM with PW via response surface methodology (RSM). Twenty treatments based on 3 level codes (-α, 0, +α) of three compositing factors, namely co-composting period (20, 25, 30 days), percentage of composition HM: PW (85:15, 90:10, 95:5) and particle size of PW (0.25, 0.50, 0.75 cm), respectively were designed using the central composite design (CCD). At the end of composting period, the carbon to nitrogen ratio (C/N), dry matter (DM), organic matter (OM), moisture content (MC), bulk density and pH were determined as co-compost qualities (dependent responses). The optimum results indicated that the Day 20 of composting period, composition 95:5 (HM: PW) and 0.25 cm of particle size had significant optimum values of 27.2 % DM, 72.8 % MC, 90.3 % OM and pH 6.7. No significant interaction of the three factors was found on C/N ratio and bulk density by RSM analysis. Subsequently, the significant results of optimum value developed a prediction model for co- composting HM and PW.