Enhancement of hydrogen production from glucose by nitrogen gas sparging

The effect on hydrogen yield of N2 sparging was investigated in non-sterile conditions using a hydrogen-producing mixed culture previously enriched from soya bean meal. A continuous stirred-tank reactor (CSTR) at 35°C and pH 6.0 was operated on a mineral salts-glucose (10 g l−1) medium at a hydraulic retention time (HRT) of 8.5 h, and organic loading rate of 27.02 g glucose litre reactor−1 day−1. Results are reported from an 8 week period of continuous operation, and the enrichment culture gave stable results over an extended period. A hydrogen yield of 0.85 moles H2/mole glucose consumed was obtained after 5 HRT, the gas produced being 53.4% H2. With N2 sparging at a flow rate approximately 15 times the hydrogen production rate, the hydrogen yield was 1.43 moles H2/mole glucose consumed. The specific hydrogen production rate increased from 1.446 ml hydrogen min−1g−1 biomass to 3.131 ml hydrogen min−1 g−1 biomass under sparging conditions. It is suggested that hydrogen partial pressure in the liquid phase was an important factor affecting hydrogen yield. Energy could be recovered as hydrogen from processes generating volatile fatty acids for fine chemicals and liquid bio-fuels or from acidification reactors preceding normal anaerobic biological treatment of sugary wastewaters