Pre-treated digestate as culture media for producing algal biomass

•A pre-treated digestate was used as potential culture medium for microalgae growth.•Chlorella sp. and P. tricornutum grew with success on pre-treated digestate.•High nitrogen removal was obtained with both algae tested.•Growth rate and biomass profile were similar to those obtained in standard media.•Accumulation of lipids and carbohydrates was obtained during N-starvation phase.

An agro-zootechnical ultrafiltered digestate (UF) coming from an anaerobic digester plant was used to grow two strains of microalgae: Chlorella sp. and Phaeodactylum tricornutum, in a comparison with standard substrates. Chlorella sp. and P. tricornutum were able to grow on UF with similar growth rates (μ) to those obtained using standard substrates, i.e. μ of 0.216 d−1 and of 0.200 d−1 for Chlorella sp., and of 0.128 d−1 and 0.126 d−1 for P. tricornutum, on synthetic media and UF, respectively. Algae grown on UF showed similar final biomass composition to those obtained by using synthetic media. Algae were able to remove nitrogen from UF, i.e. 92% and 71%, for Chlorella sp. and P. tricornutum respectively. Microalgae can grow on UF producing good quality final biomass.