Utilization of nitrogen-rich agricultural waste streams by microalgae for the production of protein and value-added compounds

Current food and feed production practices via agricultural processes generate waste streams often rich in nitrogen. Conversion of the nitrogen in agricultural waste into valuable products would prevent environmental pollution and promote a circular economy. Nitrogen in agricultural waste could remain in both water-soluble and solid forms. While microalgae could utilize several forms of water-soluble nitrogen in protein-rich biomass, many agricultural wastes would require pretreatment steps so that nitrogen and other elements could be made available for microalgal consumption. In addition to nitrogen recovery, several microalgae could also produce other highvalue metabolites (e.g., pigments, polyunsaturated fatty acids, etc.) using waste sources. This review explored the recent advances in microalgal cultivation using agricultural wastes to produce biomass rich in protein and other value-added metabolites for food and feed applications. Finally, the challenges and prospects of microalgal nitrogen recovery from various agricultural wastes are briefly discussed.