Exploring sustainable biohydrogen production from dried food waste: Optimization strategies and environmental...

Biohydrogen production from food waste is a promising renewable energy pathway with environmental and waste management benefits. This study explored the potential of dried food waste (DFW) and DFW hydrolysate (DFWH) for biohydrogen production, examining DFW composition, process optimization, and microbial pathways through dark fermentation. Under the optimized dilute acid pretreatment condition (120 °C, 1.3% v/v H₂SO₄, 79.74 min and 10% TS), DFW achieved a total sugar concentration of 21.2 ± 2.0 g/L and an organic acid concentration of 8.4 ± 1.2 g/L. The theoretical sugar yield was 0.223 ± 0.001 g sugar/g DFW, closely aligning with the experimental yield of 0.212 ± 0.002 g sugar/g DFW. Particle analysis indicated that around 60% of volume density in DFWH had particle size below 0.01 μm, signalling effective biomass breakdown and improved enzymatic accessibility, which supports bioconversion. With a sugar concentration of 15 g/L and an initial organic acid concentration of 6.5 ± 0.6 g/L, DFWH achieved a 1.58-fold increase in hydrogen yield, producing 1.24 ± 0.02 mol H₂/mol glucose_equivalent. Untreated DFW yielded 0.78 ± 0.03 mol H₂/mol glucose_equivalent, with the shortest observed lag time of 14.6 ± 0.2 h. These results emphasize the advantages of dilute acid pretreatment in enhancing biohydrogen yield and production efficiency, even in the absence of additional nutrients. Microbial analysis of DFWH revealed a dominance of Clostridium puniceum at 66.9% relative abundance, followed by Clostridium butyricum at 8.55%, supported by sufficient micronutrients. This microbial composition is favourable for biohydrogen production, reinforcing DFWH's potential as a sustainable biohydrogen feedstock.