Mathematical Modeling and Simulation Analysis of a Bioreactor with Forced Aeration

Abstract

The composting process is commonly used in waste management as a method of converting or stabilizing organic waste. Due to the complex, non-linear nature of biological and physicochemical phenomena involved, this process is relatively difficult to predict and control. The control is usually aimed at obtaining the final product, that is, the compost that meets legal standards. The article presents a simple mathematical model of the composting process with forced aeration, which will potentially facilitate the control task. A second order model was developed, with two inputs signals. Based on the mathematical model in the form of the state equations, the computer model of the bioreactor was built in the MATLAB/Simulink environment, which was then used to conduct different simulation tests. It was shown that it is possible to control the process using forced aeration, directly influencing the temperature changes in the bioreactor, and consequently also the time of obtaining the final product of the reaction. The analysis of the dynamic properties of the process performed using its model linearized about some nominal state trajectory shows the changes in its internal stability—starting from the unstable character in the initial phases of the reaction, through stabilization in its intermediate phase, up to the asymptotic stability, ending in the stable equilibrium state.