Growth characteristics of Chlorella sorokiniana in airlift and bubble column photobioreactors

► Determination of suitable CO2 concentration for the cell growth of C. sorokiniana. ► Modifying std. TAP [-acetate] medium to control pH drop at higher CO2 concentration. ► Modeling and simulation of the growth profile using logistic equation. ► Comparison of growth profile in airlift and bubble column photobioreactor. ► Comparison of mixing time and KLa in airlift and bubble column photobioreactor. The present study investigated the feasibility of bioCO2 sequestration using Chlorella sorokiniana. It was found that 5% CO2 (v/v) in air was the most suitable concentration for the growth of this organism. At this concentration, the maximum rate of CO2 sequestered and the biomass obtained were found to be 1.21gL−1d−1 and 4.4gL−1 respectively. Modeling and simulation of the growth profile was obtained using the logistic equation. Further, at higher CO2 concentrations, pH drop in the growth media, TAP [-acetate], was prevented by replacing NH4Cl by NaNO3. Additionally, the study evaluated the performance of two reactors namely: bubble column and airlift reactor based on their growth profile and transport properties like KLa and mixing time. The growth profile was better in airlift reactor and it provides cyclic axial mixing of media. KLa of downcomer was significantly lower than the riser in airlift reactor.