Estimation of Biogas Potential of Liquid Manure from Kinetic Models at Different Temperature

The target when using models to analyse results of biogas yield from manure or similar substrate is mostly to determine their kinetic parameters, which help significantly in knowing the bioreactor behavior and efficiency. This work aims at utilizing experimental biogas data obtained at 25, 30, 35, 40 and 45℃ to estimate these parameters, including the biogas potential of liquid manure from existing biogas models, first and second order biogas rate equations and the basic arithmetic equations using Excel Solver coupled with POLYMATH by regression. Best models are Cone, Proposed model, Transference, Logistic and Modified Gompertz as they give high coefficient of determination and fits the measured biogas yield data at 25-45℃. Estimated biogas potential from Modified Gompertz model ranges from 7143-13584 mL/gVS; Logistic, 6556-12779 mL/gVS; Cone, 7713-14403 mL/gVS and; Transference, 35639-44932 mL/gVS, over the temperature range. The biogas potential parameter is not found in the Proposed model, first and second order biogas rate equations, linear, exponential and polynomial equations but are useful in finding fitted estimates of the empirical data. Most accurate or correct model among the best models obtained here, as per future studies, can be determined using model comparison parameters such as the Bayesian Information Criterion, Akaike’s Information Criterion and F-test.