Numerical Model to Find the Optimal Anaerobic Digestion Temperature in a Continuous Reactor without Hydrolytic Microbial Compartment

Abstract

Although the methanization process is already a relatively advanced and widely used technology, its control on an industrial scale is still the subject of extensive research. The search for appropriate models to be used in control theory is now a high priority to optimize fermentation processes and solve important problems related to process instability. The aim of this study is to prove how it is possible to find the digestion temperature for which biogas production is optimal, without going through an experiment. For this purpose, we have developed a numerical model based on mass balances, performed on microorganisms and on organic substrates. This model predicts the cumulative volume, volume flow rate and molar composition of biogas (methane and carbon dioxide) as a function of temperature. The influence of temperature on digestion was studied in the range of 20 to 40 °C in mesophilic regime. The results show that the daily production, the cumulative volume and the molar composition of the biogas are more influenced by the temperature inside the reactor. The cumulative volume of biogas increases as the temperature increases in the range of 20 °C-35 °C and peaks at 35 °C.