Empirical Model for Predicting Rate of Biogas Production

Rate of biogas production using cow manure as substrate was monitored in two laboratory scale batch reactors (13 liter and 108 liter capacities). Two empirical models based on the Gompertz and the modified logistic equations were used to fit the experimental data based on non-linear regression analysis using Solver tool in Microsoft Excel. The 13-liter reactor was used in Experiments1 & 2 and in Experiment 3 the 108-liter reactor was used. In all the three experiments, Gompertz model gave a better goodness of fit than the modified Logistic model. The cross correlation coefficients for experiment 3 are 0.9972 and 0.9965 for Gompertz and Modified Logistic models respectively. Atomic absorption spectroscopy (AAS) analysis of the biogas indicates that its methane content is above 70% in both reactors. Keywords : Empirical model, Non-linear regression, biogas production, cow manure.