Thermophilic bio-hydrogen production from food industry wastes in suspended- and attached-cell reactors: preliminary screening in 0.12-L bioreactors and scale-up to a 19-L pilot reactor

Today there is growing a search for renewable, low-cost and low-emission energy sources. This work is aimed at assessing the technical and economic feasibility of a biological process of H2 production from food industry waste in thermophilic conditions. The production of H2 by 4 strains of the genus Thermotoga (T. neapolitana, T. petrophila, T. naphtophila, T. maritima) was studied at 77°C in batch bioreactors (120 mL) with glucose, molasses and whey as carbon sources. With all the substrates tested, T. neapolitana gave the best results, with an initial H2 production rate of 1.2–1.9 mmol Lmedium-1 h-1 and a selectivity of 1.6–2.6 mmolH2 mmolmonosaccharide consumed-1. Using T. neapolitana, further studies were conducted with cells immobilized on 4 types of porous supports (3 vitreous ones and a ceramic one). The best results were obtained with the ceramic support, characterized by the maximum interfacial area (2.1 m2 g−1). Further tests, aimed at simplifying the composition of the growth medium, gave encouraging results. For example, in the case of molasses a minimal medium composed only of NH4Cl, K2HPO4, NaCl, buffer and cysteine was identified. In comparison with the complete medium, the minimal medium was characterized by a 73% cost reduction and a 12% increase of the H2/substrate yield. Finally, the process scale-up to a 19-L reactor is in progress. Preliminary results indicate that, in the scale-up of the production of H2 from glucose with T. neapolitana, the values of the three monitored yields (H2/substrate, organic acids/substrate and biomass/substrate) showed no significant changes.