Simulation of Anaerobic Codigestion of Cow dung and Fruit waste

Abstract

This work tends to model and simulate a codigestion process of cow dung and fruit waste to produce bio fertilizer. The raw materials (fruit waste and cow dung) for bio fertilizer production were analyzed for physicochemical properties. The model used was adopted from previous works and was modified by using four microbial kinetic equations: the Monod, the Moser, the Tessier and the Contois to represent the microbial behavior within the batch culture, other changes includes assumption of semi-batch instead of continuous process and addition of subroutines during the solution of the model to account for the biofertilizer production and quantification. The results from the physicochemical analysis showed a carbon/nitrogen ratio of cow dung to be 38.67 which exceeds the limit for optimum biogas production, COD values of 3244.26 mg/L and 426.67 mg/L for cow dung and fruit waste respectively were also obtained. The simulation results showed that the Tessier model fits best to the experimental data used for the comparison with a retention period of 40 days, it also gave a biofertilizer yield of 72.88% and a cumulative biogas production of 6.78 kg. The substrate/biomass profile that was obtained for the Tessier model compares well to the profile drawn from experimental data.