Optimization of process parameters for kitchen waste composting by response surface methodology

Abstract

The optimization of process parameters for decomposition of kitchen waste into mature, stable compost was investigated using response surface methodology (RSM). RSM and central composite designs were applied to evaluate and optimize the key factors namely fly ash, bulking agent for moisture optimization and temperature, inoculum size and lime concentration for C/N optimization, which affect the stability of compost. Moisture and C/N ratio were selected as response variables. The experimental data of response variables were fitted into quadratic polynomial model using the multiple regression analysis and found it was statistically significant quadratic model. Box–Behnken design under RSM was used to optimize their interaction between bulking agent (40 %) and fly ash (15 %) has significant effect on moisture optimization and temperature (35 °C), lime (3 %), and inoculum size (10 %) were the best for C/N ratio optimization and compost maturity. These optimized conditions were used and recorded the 50 % moisture reduction, and 8.43 C/N was achieved; indicates the stable and mature compost in minimum time. A significant correlation was also found between C/N ratio, humic acid, fulvic acid and degree of polymerization during compost formation. It was fleetingly concluded that optimization of compost parameters promote the decomposition rate and humification process.