Enhancing Dark Fermentative Hydrogen Evolution via Tailored Water Hyacinth Iron-Biochar Additives

Dark fermentation is a promising and sustainable renewable energy generating method, however poor hydrogen yield and unstable gas production limit its efficiency, requiring improved measures. Water hyacinth (Eichhornia crassipes), a common invasive aquatic weed, was used to generate biohydrogen in this study. Batch fermentation studies using sewage sludge in 400 mL reactors were performed. Heat-shock pretreatment at 90–100°C for 15–20 minutes suppressed methanogenic activity and enriched hydrogen-producing bacteria in the inoculum The substrate-to-inoculum ratio was 2 and the substrate concentration was 80 g VS/L. To promote acidogenic hydrogen-producing bacteria, the fermentation medium pH was set at 5.5.A control reactor with simply water hyacinth and inoculum produced 70–80 mL of gas per day. In comparison, the reactor with iron-loaded biochar produced 150 mL of gas in 24 hours, a nearly two-fold increase over the control. Due to fast acidogenesis and volatile fatty acid formation, the iron charcoal reactor pH decreased from 5.5 to 4.69 in 12 hours. To continue hydrogen production, the pH was readjusted to 5.5. Improved microbial activity, iron catalysis, and electron transfer processes boost gas generation. The results show that iron-loaded biochar improves water hyacinth biohydrogen generation and is environmentally friendly. Index Terms—Keywords: Biohydrogen production, Dark fer-mentation, Water hyacinth, Gas production, Sustainable bioen-ergy

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