Nonlinear Autoregressive Exogenous modeling of a large anaerobic digester producing biogas from cattle waste

•Anaerobic digester yields dynamic behavior under frequent changes in feed.•An empirical approach utilizing ANN has been used.•NARX network has been used to model the dynamic behavior.•Predictions of biogas produced compare well with plant data within ±8% deviation. In waste-to-energy plants, there is every likelihood of variations in the quantity and characteristics of the feed. Although intermediate storage tanks are used, but many times these are of inadequate capacity to dampen the variations. In such situations an anaerobic digester treating waste slurry operates under dynamic conditions. In this work a special type of dynamic Artificial Neural Network model, called Nonlinear Autoregressive Exogenous model, is used to model the dynamics of anaerobic digesters by using about one year data collected on the operating digesters. The developed model consists of two hidden layers each having 10 neurons, and uses 18days delay. There are five neurons in input layer and one neuron in output layer for a day. Model predictions of biogas production rate are close to plant performance within ±8% deviation.