Urban photobioreactor for CO2 sequestration and microalgal biomass production

The growth system of microalgae photobioreactors (PBRs) has drawn a lot of interest as a viable and sustainable method for generating quality biomass for value-added products and biofuels. The objective of this research work is to cultivate micro-algae species Chlorella vulgaris in a photobioreactor that was designed, fabricated, and powered by solar energy system. Three experimental conditions were compared with 1:4 ratios of microalgae culture (40L) and fresh water (10L) having 100mL of media (nutrients) used in each experiment with control sample (ambient air aeration) experiment # 1, injecting 200 g of CO2 for 15 sec (experiment # 2), and 300g of CO2 for 25 sec (experiment # 3) on alternate days during the cultivation period. All experiments showed the reduction of nutrients concentration (orthophosphate and nitrate) and enhancement of biomass productivity with respect to 10 days of cultivation period. Experiments 1, 2 and 3 showed removal of orthophosphate as 50 %, 41.74 % and 60.78 % respectively, whereas nitrate removal was 22 %, 48 % and 58 %. Biomass productivity from experiments 1, 2 and 3 after 10 days of cultivation period were 196.63 mg/L, 203.43 mg/L, 318.76 mg/L respectively. Statistical analysis revealed that supplying CO2 from external source in experiment # 2 and experiment # 3 have same pattern of statistical significance with co-relationship between two groups of means with p-value of 6.306 × . The maximum microalgal biomass was recovered from experiment # 3, with 7.98 % by weight protein content yield and lipid content yield 37.4 % by weight (1.87/ 5 g of dried biomass). Kinetic study showed volumetric mass transfer capacities of and were found to be 1.763× /s and 1.676× /s, with better result of gas transfer capacity of the system. In the extracted lipids favorable qualities of fatty acids for the production of microalgae biodiesel were found such as myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), oleic (C18:1), linoleic (C18:1), and linolenic acids (C18:3). The use of urban micro-algae photobioreactors is an environmentally sustainable strategy that can contribute significantly to the bio-based economy and reduce the negative effects of traditional fossil fuel usage on the environment.