Optimization of process parameters for enhanced methane production from banana peduncle by thermal pretreatment

Abstract

Anaerobic digestion of lignocellulosic biomass such as agricultural residues has gained interest due to its abundant presence in rural areas. However, anaerobic digestion of such biomass requires pretreatment to increase its digestibility. The effect of thermal, alkali, and extrusion pretreatments on the biomethane potential (BMP) of the lignocellulose-rich banana peduncle was studied with an automated methane potential test system (AMPTS II). The raw banana peduncle was characterized, and it was observed that the cellulose, hemicellulose, and lignin contents were 53.44, 19.83, and 14.25%, respectively. The BMP of the shredded banana peduncle was estimated using a AMPTS and found to be 184.32 mLN/g of volatile solid (VS) added. Further to increase the methane yield, the banana peduncle was subjected to bioextrusion, alkali, and thermal pretreatment. The thermally pretreated banana peduncle showed a maximum BMP of 377.60 mLN/g VS, compared to the BMP of alkali and extruded banana peduncle (298.9 and 248.02 mLN/g VS, respectively). Scanning electron microscopy (SEM) images showed the deconstructed cellulose structure of all the pretreated samples. As thermal pretreatment was effective, further optimization of pretreatment parameters was carried out using Response Surface Methodology (RSM) with temperature and time as independent variables and BMP as the response. Based on the experiments, thermal pretreatment of banana peduncle at 120 °C for 35 min yielded the maximum BMP of 532 mLN/g of VS added. First-order kinetic, modified Gompertz, and logistic models were used to study the methane potential kinetics. The modified Gompertz model was proved to be the most suitable model for modeling the methane production kinetics.