Simulation of Methane Gas Production Process from Animal Waste in a Discontinuous Bioreactor

Abstract

Due to the importance of environmental protection and the need to use new energy and alternative to conventional fuels, renewable energy has received much attention. Due to this necessity, a discontinuous bioreactor producing methane gas from animal waste has been modeled and simulated in this research. Monod kinetics was used to express the relationship between the growth rate of microorganisms and substrate concentration. The fourth-order Rong Kuta numerical method solved the substrate consumption and production of microorganisms and methane gas. The effect of the initial concentration of microorganisms on methane production has also been investigated. The initial concentrations of substrate and microorganisms are 74.51 g/L and 61.1 g/L, respectively. The results of this study showed that the mathematical model deviates about 53.8% from the laboratory data. According to the presented model, the amount of methane produced after 70 days is equal to 29.10 g/L. The decomposition rate of the substrate and methane gas production depends on the substrate's residence time. Increasing the initial concentration of microorganisms produces methane gas in less time. The amount of methane produced is independent of the initial concentration of microorganisms. The model presented in this study can predict the time required to perform the reaction, optimal bioreactor performance, design of relevant process equipment, and increase the scale of equipment, such as storage tank and proper control to produce high purity methane more volume. Suitable in bioreactors.