Biochemical Reaction modelling considering biomass growth in Underground Hydrogen Storage in Porous Media

Underground hydrogen storage is a method that promises a more sustainable future of energy supply, aiming to minimize the carbon footprint. Since hydrogen is used as a nutrient source for the biomass within the water of the formation and at the gaseous-aqueous phase interface, the modelling of biochemical reactions of biomass is one of the hot topics for the future of hydrogen storage. The desired outcome upon storage of hydrogen in the subsurface requires consideration of several conditions seriously, which will then be identified in this work. Utilizing the application PHREEQC, written in the C language, this study will simulate biochemical kinetic reactions of hydrogen due to microbial metabolism of the hydrogen consuming bacteria. The resulting geochemical models will identify the remaining purity of hydrogen, assessing stored volume losses and tracking the water production caused by bacterial growth. The models are based in equilibrium reactions for gas¿water¿rock interactions and kinetic reactions involving methanogenic- (Eq. (3)), sulfate-reducing- (Eq. (4)), acetogenic- (Eq. (5)), and iron-reducing bacteria (Eq. (6)). Numerous mathematical models, such as Monod, Moser, and Panfilov (Hagemann Birger, 2017), are examples taken from the literature and are being used to describe the microbial growth in underground hydrogen storage. Known as substrate-limited growth models, each bacterial species in these models is characterized by specific empirical parameters that govern growth and biochemical reaction rate. Single and dual Monod substrate-limited growth models are applied in this paper for both microbial activities to see the disparity between the potential results of each. Biomass for each process is produced, which is then transformed into a biomass concentration profile. Models with two bacteria will also be simulated to better understand the growth competition between them. The conclusion shows that MET and ACE are consuming the most hydrogen and SRB requires a high sulfate concentration to significantly increase its hydrogen consumption. Therefore, mineralogy and water composition greatly influence biochemical reactions, with carbon minerals favoring ACE and MET, sulfate minerals favoring SRB, and iron minerals favoring IRB.