Modelling and Simulation of an Electrochemically Mediated Biofilm Reactor Biogas Upgrading

Abstract

Marzieh Domirani et al. (2021) had developed the mechanistic model with the implementation of integration of microbial electrosynthesis (MES) with anaerobic digestion (AD) technology for biogas upgrading. The model's predictions varied significantly from the real-case scenario and required proper parameter estimation. Model modification and development of a new improved ADM1 based model with the bioelectrochemical CO2 reduction process in MES biofilm reactor was focused on this thesis to understand MES application. The model considered a single chamber MES biofilm reactor and the AD process also occurred on the same reactor. Microbially active CO2 reduction to CH4 was included in the MES biofilm model. The Nernst expression was incorporated as a Monod-type kinetic expression to formulate the reaction rate. For the biofilm reactor compartment (BRC) in AQUASIM, ADM1 was implemented solely as a set of differential equations (DE). Seven dynamics processes (DE) along with one equilibrium process, (input and initial condition as per ADM1) were activated on BRC along with disintegration, hydrolysis, and uptake subprocesses of AD.

The simulation was not achieved in AQUASIM due to a dynamic problem (DAZZL error) during simulation. Checking rate and input in BRC and changing the accuracy of state and program variables were recommended to rectify the error. The maximum CH4 content in upgraded biogas with optimized parameters was expected high (>87%) with efficient biogas yield. CO2 from external sources could reduce the pH inhibitory effect in the MES-BRC reactor. Furthermore, the possible simulation of the model identifies the key process parameter and understands MES application.