Optimization of pilot-scale in-vessel composting process for various agricultural wastes on elevated temperature by using Taguchi technique and compost quality assessment

Abstract

Rapid treatment processing for agricultural waste is of the utmost importance with the boom in the agriculture sector of China. This research aimed to examine the influence and optimize the applied temperature and allowed processing time in accelerating the degradation and mineralization rates of the in-vessel composting of agricultural wastes. Under the umbrella of Taguchi technique, total 09 experiments were conducted with three levels of temperature (55°C, 65°C, 75°C) and time (15h, 18h, 22h) in a pilot-scale composter equipped with control systems for temperature, aeration, agitation, and humidity for the composting of poultry manure (PM), vegetable waste (VW), and rice straw (RS) mixed at ratio 5.5:3.5:1 respectively. Results showed that among all treatments, the combination of temperature 65°C and time 18h was an optimal treatment based on S/N ratio and experimental data analysis. Material Loss Analysis of this most stabilized compost showed final masses of mixed raw material, dry matter, moisture contents, TN, and TP were reduced by 78 %, 50 %, 93 %, 23 %, and 41 % of initial masses respectively. Elimination rates of volatile fatty acid and NH+4-N were observed at 98 % and 79 %, respectively. Little higher pH (8.3) showed slight alkane nature of the optimal compost having 26wt.% moisture content, 9.9±0.5wt. % of dm total nutrients (N+K2O+P2O5), and acceptable limits of heavy metals. All these physiochemical characteristics were within limits of the Chinese Standards of Organic Fertilizer (2012). Overall medium size particle distribution was observed under the macroscopic analysis.