Operational strategies for long-term biohydrogen production from sugarcane stillage in a continuous acidogenic packed-bed reactor

• Long-term biohydrogen production was assessed in a packed-bed reactor.
• Continuous hydrogen production was attained for 240 days of operation.
• Recovery capacity after performance losses was observed in the acidogenic reactor.
• Optimal results were observed for effluent pH values in the range of 5.1–5.2.
• pH control was imperative for continuous hydrogen production.

The use of packed-bed reactors for biohydrogen production often results in performance losses in the short term because of the negative effects of operational factors, such as biomass accumulation and inadequate pH conditions. Because packed-bed systems constitute a promising technology for biohydrogen production, studies on continuous hydrogen production over the long term must be carefully conducted by applying proper operational strategies. Therefore, this study assessed continuous biohydrogen production in a packed-bed reactor operated under thermophilic conditions (55 °C) using sugarcane stillage as the substrate. The results indicated that the acidogenic reactor presented a capacity for recovering from performance losses, regardless of their cause, and maintaining continuous hydrogen production rates under long-term operation (240 days). pH proved to be a key factor for obtaining continuous hydrogen production, and the optimal results were observed in a pH range from 5.1 to 5.2. Furthermore, an optimal specific organic loading rate of 6.3–6.4 g carbohydrates g−1 volatile suspended solids d−1 was observed, and this value is consistent with the results of previous studies focused on hydrogen production from fermentative systems.