Effects of substrate component proportions on dark fermentative hydrogen production from food waste: performance, process parameters, and mechanistic Insights

The composition of organic substrates critically determines the efficiency of dark fermentative hydrogen production. In this study, food waste was used as the base substrate, and the content ratios of carbohydrates, proteins, and lipids were precisely regulated by adding cooked rice, peptone, and rapeseed oil respectively. Batch dark fermentation experiments were conducted to systematically investigate the influence patterns and underlying mechanisms of each component on hydrogen production performance and key process parameters. The results showed that carbohydrates were the core favorable component for hydrogen production, with the cumulative hydrogen production reaching a peak value of 167.72 mL/gVS at a carbohydrate content of 85%. Insufficient carbohydrate content led to inadequate energy supply from the substrate, while excessive content caused excessive acidification (pH < 4.0) of the system, inhibiting the activity of hydrogen-producing bacteria. Protein content exhibited a negative correlation with hydrogen production efficiency; the ammonia nitrogen generated from protein hydrolysis may contribute to the inhibition of hydrogen-producing bacteria and simultaneously raised the system pH to an unsuitable range. Lipids displayed a threshold effect: lipid content below 20% did not impair hydrogen production, whereas excessive lipids caused severe inhibition through the coating action of long–chain fatty acids on microbial cells and substrate particles. These findings established practical guidelines for regulating the three major components in organic waste to maximize biohydrogen production, offering a theoretical basis for feedstock pretreatment and co–digestion strategies.