Fermentative hydrogen production at ambient temperature

The hydrogen productivity of a chemostat-type anaerobic reactor operating without pH control on a glucose-mineral salts feed at ambient temperatures (15–34°C) was examined. The reactor, with an inoculum from sewage sludge, operated continuously for 330 days at solids retention times (SRTs) varied manually in response to the progress of the fermentation. SRTs of 2.5, 2.0, 1.5, 1.0, 0.5 and 0.25 days were used at the temperatures of 15–18°C, 16–19°C, 24–28°C, 25–29°C, 28–32°C and 30–34°C, respectively. The sewage sludge microflora (dominated by Clostridium species) produced hydrogen during anaerobic acidogenic conversion of glucose at ambient temperatures. At the shortest tested SRT of 0.25 days, the organic loading rate was 416 mmol-glucose/l/day, the hydrogen productivity peaked with each mole of glucose in the temperature-uncontrolled fermenter converted into 1.42 mol of H2; each gram of biomass produced 0.214 mol of H2 per day. The experimental results show that without temperature control the anaerobic sewage sludge microflora could be acclimated to produce hydrogen. Moreover, we prove the stable performance characteristics of a hydrogen-producing fermenter using anaerobic sewage sludge microflora.