BIOHYDROGEN PRODUCTION FROM AGRICULTURAL RESIDUES VIA INTEGRATED PRE-TREATMENT AND DARK FERMENTATION: OPTIMISING YIELDS AND ESTABLISHING A SCALABLE ZEROWASTE CIRCULAR BIOECONOMY ROADMAP

In order to promote a zero-waste circular bioeconomy, this study assesses the production of biohydrogen from agricultural residues (rice straw and sugarcane bagasse) using optimised dark fermentation and integrated pre-treatment. According to recent reports, hydrogen yields from laboratory-scale hydrolysis and fermentation for optimised substrates and cultures were between 40 and 60 mL H₂·g⁻¹ volatile solids (VS). The experimental molar yields were close to the practical maxima reported for dark fermentation, ranging from approximately 1.2 to 2.3 mol H₂·mol⁻¹ hexose. Peak yields were increased and accessible sugars were increased by selective acid/biological pretreatments. Analyses of mass and energy balance show that there is a positive net energy output and that it is possible to integrate residual solids into anaerobic digestion or composting, allowing for almost zero waste streams. The study illustrates the role of biohydrogen in sustainable energy transitions by putting forth a scalable process flow and techno-economic roadmap for decentralised rural deployment.