Multi-objective optimization of a novel microalgae harvesting method based on buoy-bead flotation and feasibility analysis by life cycle assessment

Abstract

Highly efficient microalgae harvesting is crucial for promoting the industrial application of microalgae bioenergy. In this study, positively charged sodium alginate microspheres (PCSAMs) were prepared, and the efficient harvest of Chlorella vulgaris (C. vulgaris) was realized based on the buoy-bead floatation method. A multi-objective optimization model was established to optimize the harvesting process, and the method’s feasibility was analyzed through life cycle assessment. The optimal harvesting efficiency and biomass concentration were 95.34% and 5.80%, respectively, and the corresponding costs were 5.13–5.16$/m3 and energy consumption was 0.065–0.066 kW h/m3. PCSAMs and C. vulgaris could form adhesion through electrostatic complementation, and poly dimethyl diallyl ammonium chloride (PDDA) long chain molecules formed “traps” on the surface of PCSAMs, improving the ability of PCSAMs to carry C. vulgaris. CO2 emissions during the harvesting process were only 0.065–0.066 kg/m3, which conforms to the carbon reduction policy and is more suitable for large-scale microalgae harvesting.