Kinetics of biogas production from fermentation broth of wild cocoyam codigested with cow paunch in batch mode abstract
Mathematical models are useful in solving the stability problems often exhibited by anaerobic digestion process. Kinetics of batch anaerobic digestion of cocoyam waste mixed with cow paunch for biogas production in batch mode was studied for 30 days hydraulic retention time (HRT). Data from cumulative biogas yield obtained during the experimental stages was fitted to C-NIKBRAN mathematical model based on first order reaction which adequately predicted the kinetic behavior of the substrate’s anaerobic biodegradability. The validity of the applied model was also verified through application of the regression model (ReG) (Least Square Method using Excel Version 2003) in predicting the trend of the experimental results. Comparative analysis of Figs. 7-10 show very close alignment of curves which precisely translated into significantly similar trend of data point’s distribution for experimental (ExD), derived model (MoD) and regression model-predicted (ReG) results of cumulative biogas yield. Also, critical analysis of data obtained from experiment and derived model show low deviations on the part of the model-predicted values relative to values obtained from the experiment. This necessitated the introduction of correction factor, to bring the model-predicted cumulative biogas yield to those of the corresponding experimental values. Deviational analysis from strongly indicates that cumulative biogas yield was most reliable based on the associated admissible deviation of the model-predicted cumulative biogas yield from the corresponding experimental values); 9.2% within the pH range. The values of cumulative biogas yield within the highlighted deviation indicates over 90% confidence level for the applied model and over 0.9 effective dependency coefficients (EDC) of cumulative biogas yield on pH, chemical oxygen demand (COD), total viable count (TVC) and total dissolved solids (TDS). Also, deviation of model-predicted cumulative biogas yield from corresponding experimental results indicates a maximum deviation of 7.17%. This translated into over 92% operational confidence for the derived model as well as over 0.92 effective dependency coefficients (EDC) of cumulative biogas yield on pH, chemical oxygen demand, total viable count, and total dissolved solids