Biohydrogen Production via Genetically Optimized Dual-Stage Fermentation with Directed CO₂ Capture and Biological Recycling: A Theoretical Framework

Microbial hydrogen production presents a compelling alternative to conventional methods such as steam methane reforming and electrolysis, offering the potential for low-energy, carbon-conscious fuel generation. This theoretical study proposes a dual-stage hydrogen production system utilizing genetically optimized strains of Clostridium butyricum and Rhodobacter sphaeroides within a vertically integrated bioreactor. The system is designed to maximize hydrogen recovery through sequential dark fermentation and photofermentation, leveraging glucose as the primary substrate and water as an additional electron source. Stoichiometric modelling of the full metabolic cycle predicts a hydrogen yield of 12 mol H₂ per mol of glucose, representing the complete recovery of all hydrogen atoms available from the substrate and water. This equates to 13.45% yield by glucose mass, or 8.41% when including water input. The design includes membrane-based gas separation and redirection of CO₂ emissions to biological sinks such as sugarcane plantations, bamboo forests, and algae bioreactors to enhance sustainability and carbon offset potential. While experimental validation is pending, this model establishes an upper-bound theoretical framework for microbial hydrogen recovery and CO₂ integration. Emphasis is placed on idealized assumptions regarding enzyme function, microbial conversion efficiency, and gas capture. The results are intended to guide future research into scalable, decentralized biohydrogen platforms aligned with global climate goals. (This model defines an idealized performance ceiling and includes realism-adjusted scenarios using expression and membrane correction factors.)