Development of a Microalgae based System for Biogas Upgrading and Oil Production from Waste Biomass

Abstract

A study of a system for carbon dioxide reduction from biogas to increase the methane and accumulate oil in the form of lipid in the Chlorella vulgaris TISTR 8580 was proposed. The system coupled together with the CO₂ reduction and oil production systems. Microalgae were cultivated in a photobioreactor bubble column with cell turbidity at 540 nm, where the specific growth and doubling time of the algae were calculated. Biogas was produced from the cow manure, which was injected directly into the C. vulgaris culture system with the different flow rates. The optimum biogas flow rate to affect the highest carbon dioxide fixation efficiency and methane content was tested. By applying the flow rate of 100 mL/min and a concentration of 1.9 x 10⁷ cell/mL of C. vulgaris culture, which is shown that the maximum efficiency of CO₂ reduction was 84.48%, while the methane in the biogas effluent increased to 89.40%. The highest biomass productivity, lipid production and content levels of 0.33 mg/L d^-1, 4.74 mg/L d^-1 and 14.35 % were achieved, respectively. These results show that the utilization of microalgae C. vulgaris is the effective alternative process for reducing the carbon dioxide content, while the biogas methane volumes are increased. The lipids accumulation in the microalgae C. vulgaris culture were 75.22% of unsaturated fatty acid.