Pilot composite tubular bioreactor for outdoor photo-fermentation hydrogen production: From batch to continuous operation.

[Display omitted] • A novel 70 L tubular photo-bioreactor for biohydrogen production was constructed. • The LCE of 4% can be achieved by the method of the built-in light source. • Maximum hydrogen yield of 7 mol H 2 /mol glucose was obtained in the batch stage. • The average hydrogen production rate can reach 22.8 mL H 2 /(L·h) at HRT of 5 d. A novel 70 L composite tubular photo-bioreactor was constructed, and its photo-fermentation hydrogen production characteristics of batch and continuous modes were investigated with glucose as the substrate in an outdoor environment. In the batch fermentation stage, the hydrogen production rate peaked at 37.6 mL H 2 /(L·h) accompanied by a high hydrogen yield of 7 mol H 2 /mol glucose. The daytime light conversion efficiency is 4 %, with 37 % of light energy from the sun. An optimal hydraulic retention time of 5 d was identified during continuous photo-fermentation. Under this condition, the stability of the cell concentration is maintained and more electrons can be driven to the hydrogen generation pathway while attaining a hydrogen production rate of 20.7 ± 0.9 mL H 2 /(L·h). The changes of biomass, volatile fatty acids concentration and ion concentration during fermentation were analyzed. Continuous hydrogen production by composite tubular photo-bioreactor offers new ideas for the large-scale deployment of photobiological hydrogen production. [ABSTRACT FROM AUTHOR]