Optimization of microwave pretreatment parameters of elephant grass by response surface methodology and kinetic study of its biomethanation

Abstract

The optimization of microwave pretreatment parameters of elephant grass and the kinetic study of biogas production from the pretreated feedstock were investigated. The elephant grass was characterized and pretreated in a microwave power system. The pretreatment parameters (energy and time) were optimized using response surface methodology. The pretreated elephant grass was decomposed by anaerobic digestion to produce biogas. The biogas compositions were determined using a digital gas analyzer, and the kinetics study was done using a first-order kinetic model. The results revealed that microwave pretreatment improved the inherent properties of the elephant grass, hence enhancing biogas yield. The optimum values of the parameters for the thermal pretreatment were resident time of 15 min and microwave irradiation energy of 72 kJ with the optimal average degree of disintegration of 35.88%. The biogas contains a reasonable amount of methane gas which contributed to its high calorific value of 21.32 MJ/m3. The kinetic data for biogas production from microwave-pretreated elephant grass are a rate constant of 0.199 day−1 and lag time of 2.5 days. Therefore, microwave pretreatment has the potential to remove lignin from lignocellulose biomasses and enhance biogas yield.