Reactor start-up strategy as key for high and stable hydrogen production from cheese whey thermophilic dark fermentation

Using the right start-up strategy can be vital for successful hydrogen production from thermophilic dark fermentation (55 °C), but it needs to be affordable. Hence, three start-up strategies modifying only influent concentration and temperature were assessed in a reactor fed with cheese whey: (i) high temperature (55 °C) and a high organic loading rate (OLR_A - 15 kgCOD m^?3 d^?1) right at the beginning of the operation; (ii) slowly increasing temperature up to 55 °C using a high OLR_A and (iii) slowly increasing temperature and OLR_A up to the desired condition. Strategy (iii) increased hydrogen productivity in 39% compared to the others. The combination of high temperature and low pH thermodynamically favored H₂ producing routes. Synergy between Thermoanaerobacterium and Clostridium might have boosted hydrogen production. Three reactors of 41 m³ each would be needed to treat 3.4 × 10³ m³ year^?1 of whey (small-size dairy industry) and the energy produced could reach 14 MWh month^?1.