Biocatalytic conversion of syngas to liquid biofuels using Clostridium acetobutylicum

This study aimed to develop a pilot-scale bioreactor for ethanol production from syngas produced from biomass gasification and evaluate its performance. Gasification of characterized feedstock, namely Casuarina wood and coconut shell, is performed in a 2 kg hr-1 downdraft gasifier and the produced gas is cooled in a heat exchanger and scrubbed in a scrubbing bed to produce syngas free of moisture, tar and particulates. The syngas are fermented to produce biofuels in a 5 L capacity bioreactor with Clostridium acetobutylicum strains. The percentage yield of acetone, butanol and ethanol was verified with the standard concentration and found to be 12%, 5% and 7% from casuarina wood and 13%, 7% and 6% from coconut shell respectively. The syngas components viz., carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H), are fermented to produce acetone, butanol and ethanol along with larger proportions of acids. These acids can be converted into bio-alcohol if the fermentation period or gas-liquid transfer is enhanced. The pretreatment of feedstock is not required in syngas fermentation as it is a major process in conventional bio-alcohol production methods. This pays a way to superior technology in terms of cost and time.