11-19: Biodiesel and H2 production from CO2 by sequential use of microorganisms in bioreactors

Photoconversion of light energy and waste CO₂  into an array of biofuels by sequential use of microorganisms in bioreactors was studied.  First the oil production by microalga Chlorella vulgaris was investigated in a batch culture and in a photobioreactor using waste CO₂.  Both flasks and a photobioreactor were illuminated with fluorescent light continuously. Algal biomass was recovered by centrifugation with subsequent drying under 80^◦C.  Algal oil was extracted with hexane.  High oil content (50%) was found in Chlorella cells.  Algal oil was converted into biodiesel by transesterification.  A simple photobioreactor for biodiesel generation from microalgae was made from parallel clear PVC 10 feet tubes (6’ diameter) with a small slope (10%).  The gas mixture (5% CO₂ and air) flowed up from bottom of PVC tubes to the top as large gas bubbles.  Next, glycerol, a by-product of biodiesel production, was used as a substrate for making biohydrogen (H₂) by bacterium Enterobacter aerogenes in batch culture and in a bioreactor.  Higher H₂ production rates for up to 1600 mL g^-1· DW· h^-1 were observed than bacterial cells grew in the presence of 1% glycerol compared to 10% and 0.1% on a simple medium containing inorganic salts.