System dynamics modelling and simulation of biogas production systems

Design and management of biogas production systems require detailed information on both steady state and dynamic behaviour of the systems. Modelling efforts of steady state and dynamic biogas production systems are reviewed. A dynamic model of biogas production systems based on system dynamics methodology is presented. The model consists of four coupled nonlinear first-order differential equations, two microbial growth equations and the resulting equation for biogas production. The model was programmed in the dynamic simulation language professional DYNAMO suitable for micro-computers. The model's predictive ability is determined by comparing the model output with the observed values reported. Finally, the sensitivity analysis shows that gas production is sensitive to the influent concentration and retention time. It is demonstrated that system dynamics is the simplest and quickest route to the understanding of dynamic systems through models.