Potential of microalgae cultivation using nutrient-rich wastewater and harvesting performance by biocoagulants/bioflocculants: Mechanism, multi-conversion of biomass into valuable products, and future challenges

Microalgae have been identified as one of the new feedstocks for renewable energy production. The conversion of microalgae into various valuable products has also been increasing in the last decade. Microalgae harvesting, one of the most important stages in microalgae production, has been studied and reviewed by many researchers. However, most harvesting methods still utilize chemicals during the process, which make harvested biomass not directly ready for food/feed production and pharmaceutical-related processes. Biocoagulants/bioflocculants are emerging compounds that can be used during the harvesting of microalgae because their existence does not introduce toxicity in the harvested biomass. Considering its potential to produce ready-to-use biomass, biocoagulants/bioflocculants have a bright future in microalgal biomass production processes. This review article highlights simultaneous wastewater treatment and microalgal biomass production as an emerging method in accommodating a circular economy paradigm. This paper juxtaposes the utilization of chemical-based coagulants/flocculants and biocoagulants/bioflocculants in harvesting microalgae. Biodegradability, effectiveness, harvested biomass characteristics, and potential of medium reuse are emphasized in the discussion. The agglomeration mechanisms of microalgae during harvesting, recent advances in the microalgal biomass conversions, and future challenges related to the utilization of biocoagulants/bioflocculants are also described in detail. Microalgae harvesting by using biocoagulants/bioflocculants is a feasible and promising environmentally friendly technology for microalgal biomass production.