Optimal biogas production in a model for anaerobic digestion

We investigate a model for anaerobic digestion, a process used to produce biogas. The model, introduced in Weedermann et al. (J Biol Dyn 7:59–85, 2013), consists of differential equations describing the interactions of microbial populations involved in three main stages of anaerobic digestion: acidogenesis, acetogenesis, and methanogenesis. We show that this model predicts that an increased yield in biogas can be achieved in regions where operating parameters push the system into a bistable state. In some regions of bistability, biogas production occurs at only one of the steady states while in others both steady states result in biogas production with one state being more productive than the other. We demonstrate which operating parameters and state variables have the most significant impact on system performance. Surprisingly, the optimal biogas production does not always occur at a steady state where all classes of microorganisms coexist.