Ethanol production from kitchen garbage using response surface methodology

Response surface methodology based on central composite design (CCD) was utilized to optimize the conditions of simultaneous saccharification and fermentation (SSF) for ethanol production from kitchen garbage. Both open and close fermentation were carried out in this study to test their effects on ethanol production. In this study, the result showed that open fermentation without undergoing heat treatment was better due to the unspoiled nutrients inside. Maximum ethanol concentration of 33.05 g/L was obtained with the optimum conditions of time of 67.60 h, pH of 4.18 and temperature of 35 °C. Second order polynomial models were developed to quantify the relationships between variables. It showed that linear effect of pH, cross-effect between time and pH, square effects of time and pH showed trivial influence on ethanol production. The result of conformation experiment under the optimum conditions agreed well with the model predictions (34.21 with 33.05). The ethanol yield could reach 0.23 g ethanol per dry gram garbage, which showed the technology could be an ideal method to utilize kitchen garbage. Ethanol production from kitchen garbage by open fermentation could to a large extent save the cost and eliminate threats of solid-waste.