Modelling Cow-Dung and Grass- Clippings Isothermal Continuous Stirred Co-digester for Biogas Production using Modified Gompertz Rate Equation

The continuous search in renewable energy sources for industrial and domestic utilization is very imperative and motivated this study. The study of Cow- dung and grass clippings Co-digestion are important due to the fact that successful outcome of the studies will provide a basis for waste minimization and enhance renewable energy production for global consumption. This work therefore is focused by exploiting the modified Gompertz kinetic equation in developing design models for the simulation of continuous stirred co-digester(CSC) at isothermal condition. Co-digester functional dimensions such as volume, length, space time, space velocity and heat generation per unit volume were developed for Continuous Stirred Co-digester type..The developed models were simulated using Matlab codes programming technique using design basis of 50,000 metric tons of biogas per annum at 37oC isothermal condition. The developed performance models were solved numerically using MATLAB version 7.1 within the operational limit of conversion degree, XA = 0.1 to 0.9.The results obtained showed that increase in fractional dimensions of Co-digester volume VR, length LR and Space time SV­ increases with increase in fractional conversion at constant radius. Results of space velocity (SV­) and heat generation/per unit volume (q) showed inverse characteristic behavior as increase in fractional conversion decreases space velocity and heat generation per unit volumes.. Further careful examination of the results, demonstrated that at optimal yield of 0.9 degree of conversion, Co-digester volume value of 10.0m3 at constant radius was feasible. The results as obtained in this work proved dependable relationship with fractional conversion.