The kinetics of Scenedesmus obliquus microalgae growth utilizing carbon dioxide gas from biogas

• Biogas is a viable carbon source for microalgae growth.
• Biomass production rate and characteristics were assessed.
• Scenedesmus obliquus can adjust to grow with high concentration of CO2 in the carbon source.

Microalgae Scenedesmus obliquus was cultured in a laboratory photobioreactor to determine the efficacy of using biogas as a carbon source for the microalgae's growth. The biogas contained ∼60% CH4 and ∼40% CO2, and was derived from an anaerobic digester operating from animal wastes, and an anaerobic reactor utilizing high strength wastewater. The results showed that biogas is a viable carbon source for microalgae growth and that significant portions of the biogas' CO2 can be utilized for algae growth, resulting in a biogas having a high concentration of methane. This paper develops the kinetic expressions for the algae's growth by assuming an autocatalytic reaction between carbon substrate and microalgae. The maximum specific growth rate and biomass productivity of S. obliquus were 0.56 d−1 and 0.145 g L−1d−1 respectively. The biomass contained 51.8% carbon and higher heating value (HHV) was 22.9 MJ kg−1.