Coupling algal biomass production and anaerobic digestion: Production assessment of some native temperate and tropical microalgae

Coupling algal biomass production and anaerobic digestion is one of the most promising bioprocesses for economically viable algal production. This study assesses the production rates of some native microalgae growing in media supplemented with algal digestate, urban wastewater or digested sludge. Native microalgal populations isolated from temperate freshwaters (Scenedesmus spp.) and marine ecosystems (Nannochloris spp.) had the highest potential production rates (about 100 mg DW L⁻¹ d⁻¹) with algal digestate at about 20% loading ratio. However, no growth was measured for Nannochloris spp., when the ammonium concentration exceeded 100 mg L⁻¹ although Scenedesmus spp. appeared to be tolerant to higher NH₄⁺ concentrations. Very low production rates, or no growth, were measured when microalgae isolated from high salinity waters (Dunaliella salina, Lyngbya aestuarii) were used, suggesting that populations well adapted to extreme environmental conditions are not suitable candidates for growing on wastewater or anaerobic digestate.