A novel process simulation model (PSM) was developed for biogas production in anaerobic digesters using Aspen Plus (R). The PSM is a library model of anaerobic digestion, which predicts the biogas production from any substrate at any given process condition. A total of 46 reactions were used in the model, which include inhibitions, rate-kinetics, pH, ammonia, volume, loading rate, and retention time. The hydrolysis reactions were based on the extent of the reaction, while the acidogenic, acetogenic, and methanogenic reactions were based on the kinetics. The PSM was validated against a variety of lab and industrial data on anaerobic digestion. The P-value after statistical analysis was found to be 0.701, which showed that there was no significant difference between discrete validations and processing conditions. The sensitivity analysis for a +/- 10% change in composition of substrate and extent of reaction results in 5.285% higher value than the experimental value. (C) 2014 Elsevier Ltd. All rights reserved.