Transforming orange peel waste into hydrogen: The effect of biocompound extraction and inoculum-to-substrate ratio on dark fermentation

This study investigates the effects of biocompounds extraction routes on hydrogen production from orange peel waste (OPW) through dark fermentation as a strategy to assess its potential to fit within a biorefinery framework. OPW underwent essential oils (EO) and pectin extraction before passing through dark fermentation at different inoculum-to-substrate ratios (ISR) to identify the best condition for hydrogen production yields. The findings indicate that OPW after EO extraction by hydro-distillation at ISR 0.6 provides the highest cumulative hydrogen yield (142.88 ± 2.90 mL H₂/g VS) and volatile fatty acids generation (13.10 ± 0.65 g VFA/L) that would follow its integration within the biorefinery context. Statistical analysis reveals that OPW processing routes and ISR are significant factors influencing hydrogen production and yield, emphasizing the importance of selecting processing routes for OPW. This work highlights the relevance of developing comprehensive outlines for OPW valorization, contributing to circular economy models.