Optimization of buffer adjustment strategies for enhancing stability and hydrogen yield in high solid-phase biohydrogen production systems

The transition towards low-carbon energy has intensified research on via photo fermentation biohydrogen production (PFHP), particularly using agricultural waste. However, high solid-phase PFHP (TS≥10 %) remains underexplored despite its advantages of lower operational costs and energy consumption compared to low solid-phase systems. This study addresses the critical challenge of rapid acidification in high solid-phase PFHP by evaluating phosphate, carbonate, and citrate buffer systems at varying initial pH levels (6–9) using corn straw as substrate. Results demonstrated that phosphate buffer at pH 7 optimally stabilized the fermentation system, maintaining pH within 5.5–6.5 and achieving the highest cumulative hydrogen yield (1317.56 ± 17.25 mL, 68.85 mL H₂/g TS) and peak nitrogenase activity (1425 ± 65 nmol C₂H₄/h). Kinetic analysis via the Gompertz model (R² > 0.99) confirmed the system’s efficiency, with a maximum hydrogen production rate of 25.15 mL/h at 20.08 h. Phosphate buffer also enhanced light energy conversion efficiency (12.58 % at 12–24 h) and mitigated volatile fatty acid accumulation. In contrast, carbonate and citrate buffers showed lower performance, with yields of 794.62 ± 19.21 mL and 1017.56 ± 18.25 mL, respectively. The study identifies 84 h as the optimal fermentation duration to balance productivity and energy efficiency. These findings provide novel insights into buffer-mediated pH regulation for scalable high solid-phase PFHP, emphasizing phosphate buffer’s role in optimizing biohydrogen production from lignocellulosic biomass.