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

Abstract 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 (OLRA - 15 kgCOD m−3 d−1) right at the beginning of the operation; (ii) slowly increasing temperature up to 55 °C using a high OLRA and (iii) slowly increasing temperature and OLRA 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.