Nonlinear model predictive substrate feed control of biogas plants

Optimal substrate feed control of biogas plants is a complex and challenging task due to the nonlinearity of the anaerobic digestion process, which produces biogas from biodegradable input material. In this paper a nonlinear model predictive control (NMPC) scheme is applied to optimally control the substrate feed of an agricultural biogas plant. The implemented algorithms are investigated in a simulation study using a validated simulation model of a full-scale biogas plant. Process states are estimated using a recently developed state estimator. Results show that this approach is very feasible providing the plant operator with a gain of 550 € per day compared to previous operation.