Use of concentric-tube airlift photobioreactors for microalgal outdoor mass cultures

A vertical concentric-tube airlift photobioreactor (ALP) was used to cultiv ate Phaeodactylum tricornutum UTEX 640 in outdoor continuous mode during th e summer. A mathematical model is developed to estimate the irradiance prof ile and average irradiance inside the culture, and hence, to compare the bi omass production capability of the airlift device with a horizontal-loop tu bular photobioreactor (HLTP) located at the same place as the ALP. The maxi mum biomass productivities were similar in both photobioreactors in spite o f the higher light availability in HLTP; thus, the photosynthetic efficienc y was higher in ALP. This behavior was attributed to photoinhibition in HLT P and the negative effects of an inappropriate light-dark cycling. (C) 1998 Elsevier Science Inc.