KINETIC MODEL FITTING FOR ANAEROBIC CO-DIGESTION OF CHIBUKU BREWERY WASTE GRAIN WITH COW DUNG

A study of the anaerobic co-digestion of 25 wt% cow dung in chibuku brewery waste was carried out in a 1000 ml capacity Erlenmeyer flask at mesophilic conditions to determine its biogas potential and model fit its kinetics. The results showed that the first biogas production occurred 5 hours from the start-up, rose to its maximum on the seventh day and stopped on the eighth day. Further, the theory of chemical kinetics was used to model fit the biogas process. The data for the effect of time on biogas yield was used to determine the fractional yield. The fractional yield was then used to model fit the process by invoking linear regression on kinetic models of first, second and third orders of reaction. As a result, the first order kinetics was found to closely fit the kinetics with the rate constant of 0.4350 s-1 for the biogas process occurring in slurry at temperature of 35±5°C. This rate constant was best fitted by a linear regression coefficient of 0.8384. The study provides a way of determining the rate constant which could be used in the reactor design of an anaerobic co-digester.