Biogas‐Assisted Growth of Chlorella vulgaris in an Open Raceway Pond: Proof of Concept and Economic Assessment

Abstract

Microalgae are a promising source of renewable fuels and value-added chemicals but are hampered by the high cost of cultivation. Sparging CO 2 in water bodies can increase the yield and reduce the cost. This work studies the feasibility of synergistically integrating a biogas digester with a microalgae cultivation system. Raw biogas is sparged through the microalgal culture to increase the microalgae yield while also purifying biogas for further use. At laboratory scale, Chlorella vulgaris was cultivated in a 1-L batch, and biogas was sparged for 3 h per day. For a demonstration-scale 4000-L raceway pond, a special contacting device was used to supply biogas to the microalgal culture. On the laboratory scale, C. vulgaris concentration increased by 30 % when sparged with biogas. Moreover, the protein and lipid contents were higher than in an air-sparged control batch. The cultivation cost of microalgae decreased by 20 %.