Growth pattern of Chlorella vulgaris and Arthrospira platensis using CO₂ in biogas from anaerobic digestion of tofu wastewater: A preliminary study

Abstract Liquid waste from tofu production can be treated by anaerobic digestion to produce biogas. The main components of biogas are CH4 (methane) and CO2 (carbon dioxide), but usually, biogas also contains water, H2S (hydrogen sulfide) or other sulfuric compounds, and other trace gases and impurities. Therefore, purification and upgrading the biogas are necessary to improve its quality as a fuel. One of the alternative methods of biogas purification is by reducing CO2 content using microalgae culture, which involves the ability of microalgae to use the CO2 in biogas for photosynthesis. In this research, Chlorella vulgaris and Arthrospira platensis were tested for their ability to grow under biogas produced from anaerobic digestion of tofu wastewater aeration in a batch system. The results indicated that Chlorella vulgaris could grow better than Arthrospira platensis on the same flow rate of input biogas. Despite the ability of Chlorella vulgaris to use CO2 in biogas, the cell numbers in culture aerated with biogas were lower than with air, which indicated an inhibition by biogas on Chlorella vulgaris growth.