Biological hydrogen production from CO: Bioreactor performance

This paper presents an alternative solution to the current problem faced by the world; diminishing of fossil fuel. Bioconversion of synthesis gas to hydrogen as clean fuel was catalyzed by a photosynthetic bacterium, Rhodospirillum rubrum. The clean fuel production was biologically mediated by the water–gas shift reaction in a 2 l bioreactor. The work performed was on agitation effects on hydrogen production, KLa and power consumption. The results show that 500 rpm was the suitable agitation rate to be employed. The hydrogen production was optimized at 0.44 ± 0.023 atm giving a KLa of 86.4 ± 3.5 h−1. The production rate was 9.6 mmol H2/h. The maximum light conversion efficiency at agitation speed of 800 rpm, light intensity of 500 lux (732 kW/m2) and 4 g/l inlet acetate concentration was about 10.84 ± 1.73%. At this condition, the maximum CO conversion efficiency was found to be 81 ± 5.6%. The ratio of power per volume was calculated to be 322.30 ± 12.14 kW/m3 and foaming problem was successfully avoided. The corresponding power consumption was estimated to be about 0.64 ± 0.03 kW, while the output hydrogen energy was determined to be 643.2 ± 26 kW. A prolonged operation of continuous hydrogen production employing a microsparger showed stable behaviour for a duration of 27 days.