Potential of wastewater treating Chlorella minutissima for methane enrichment and CO2 sequestration of biogas and producing lipids

An algal biorefinery approach is today's need for commercialization of microalgal biodiesel production. In the present study, an indoor photobioreactor with Chlorella minutissima was evaluated to upgrade biogas produced from anaerobic digestion of cow dung. The potential of C. minutissima was assessed in two different growth media viz. BG 11 and wastewater. The significant CO2 absorption reported by C. minutissima was in the range of 75-85.4% at 1296 μmol m−2s−1 of light intensity and 0.33 vol per volume per minute (vvm) gas flows. The present study demonstrated that there is an increase in methane content from 63.5 to 86.4% in the effluent biogas. The highest biomass productivity was observed at 1296 μmol m−2 s−1 light intensity with the same gas flow and the productivity of 0.18 gL−1 and 2.2 gL−1 in the BG11 medium and wastewater respectively. Further, we reported that total lipid content based on dry biomass of C. minutissima were 22.4% and 26% in the BG11 medium and wastewater, respectively. The gross calorific value of treated biogas was also higher (8.15 kWh m−3 and 8.63 kWh m−3) in both BG11 and wastewater, respectively.