Modeling Dynamics of the Biogas Process Under Uncertainty: A Fuzzy Set Theory Approach

Global concern about climate change has led to a growing interest in exploring renewable energy sources, such as the biological conversion of biomass to methane in anaerobic environments. Anaerobic digestion model no. 1 (ADM1) is the most widely used platform for biogas process modelling. To describe the biochemical processes involved in anaerobic digestion, ADM1 employs a set of 35 differential equations. These equations can be solved simultaneously by knowing the appropriate initial values for the concentration variables. Biogas production has significant uncertainties in nature, as with many real-life applications, resulting in challenges in modelling and simulation. For instance, ADM1 is constructed on an ensemble of anaerobic biochemical reactions. Due to the possible variations and fluctuations in independent variables and parameters, the reaction rates cannot be calculated with absolute certainty. There are different approaches to classifying uncertainties in a system. The present paper proposes a mathematical framework to model biogas production’s uncertainties. Among different approaches and tools describing the system’s ambiguity, a possibilistic approach using fuzzy set theory has been employed. Based on the results, it is evident that the fuzzy model is able to capture and reflect the defined system uncertainties quite effectively. Using this mathematical tool, designers and decision-makers can gain a deeper understanding of the system.