Kinetic Study of Biogas Recovery from Thermo-chemically Pre-treated Rice Husk

Six simple kinetic models were used to perform comparative investigations of the kinetics of biogas production from thermo-chemically pre-treated rice husk which were heated at 155°C for 4 h prior to soaking in 15% aqueous ammonia for 48 h and finally subjected to anaerobic digestion. The process was operated for 45 days in the mesophilic conditions by comparing the performance of test digesters containing only inoculums, with control operated at similar condition. Kinetic modelling of the biogas production rate and cumulative biogas yield, revealed that thermo-chemical pre-treatment was effective in improving the kinetics of bio-gasification. Comparing linear, exponential and modified exponential models in terms of coefficient R², it was observed that biogas production rate followed exponential path whereas the cumulative biogas yield exhibited best fitting to the sigmoidal curve for Gompertz relation as compared to that of logistic growth model. Biogas production rate analysed with the Gaussian model revealed better correlation as compared to the linear exponential and modified exponential models where the plots were performed for ascending and descending limbs separately. As, biogas production rate followed exponential path, the Gaussian plot was found to be legible and more accurate.