Harvest of algal biomass with bioflocculants for biofuel with upstream and downstream processes: State-of-the-art towards sustainable alternative

Abstract

Algal biorefinery development faces hindrances at upstream stages, such as algae cultivation, and downstream stages, such as biomass harvesting, followed by oil extraction for further transformation into biodiesel. The intensified utilization of bioactive compounds enriched algal biomass for biofuel production necessitates the scale-up of algae cultivation, which has been reported as a current challenge. Algal harvesting for biomass recovery from culture medium is a tedious process. The physical, chemical and biological methods are widely applied to harvest algae from suspended culture mediums. Owing to certain limitations such as high energy requirements, high cost involved and environmental toxicity, physical and chemical methods appear unfavourable relative to the biological method. Bioflocculation is considered an environment-friendly, low cost and highly energy-efficient method applied to a wide range of algal species. The present study aims to review contemporary algal harvesting methods, including physical, chemical, and biological approaches. The bioflocculation mechanisms associated with the flocculation of algal cells are comprehensively explained along with process parameters and the influence of nano-materials on algal biomass harvesting improving the upstream process and algal biofuels extraction enhancing the downstream process. The challenges of bioflocculation process of algae are also reviewed.

Graphical Abstract

Keywords

Bioflocculants / Algal biomass / Algal biofuels / Flocculation mechanism / Magnetic nanomaterials / Engineering / Environmental Engineering

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