Microalgae-based anaerobic fermentation as a promising technology for producing biogas and microbial oils

Abstract

Abstract This study assessed the potential of using microalgae anaerobic fermentation as a novel choice for producing microbial oils and biogas. Microalgae biomass (Chlorella vulgaris) was used for volatile fatty acids (VFAs) production at three organic loading rates (OLR = 6, 9, 12 g COD/Ld). Regardless of the OLR, anaerobic systems displayed similar organic matter conversion yields into VFAs (VFAs-COD/CODin = 38%) and VFAs distribution profiling. Obtained digestates were further used with a two-fold purpose, producing microbial oils from the VFA rich liquid fraction, and generating methane from the remaining solid spent. The yeast Yarrowia lipolytica was able to grow on VFAs concentration up to 17.6 g/L while the highest VFAs concentration (24.2 g/L, digestate obtained at 12 g COD/Ld) resulted inhibitory. Despite of that, Y. lipolytica exhibited remarkably high lipid content (15–23%) when grown in digestates. The three spent solid fractions (corresponding to the 3 OLRs) reached the same methane potential.