Low-energy microalgae harvesting using electrocoagulation and its process optimization

Microalgae represent a promising renewable resource due to their high productivity and metabolite-rich biomass. However, the high energy and cost demands of harvesting processes remain a major bottleneck for commercial application. This study examines the application of electrocoagulation (EC) using magnesium (Mg) electrodes as an energy-efficient and environmentally friendly method for harvesting Chlorella vulgaris. The process was optimized using a Box-Behnken experimental design with current density, initial pH, and processing time as independent variables, and recovery efficiency (RE), compression ratio (CR), and ash content (AC) as responses. The optimized conditions (12 mA/cm2, pH 9, and 7.21 min) resulted in a RE of 98.66 %, a CR of 4.78, and an AC of 1.73 %, with low energy consumption (0.649 kWh/kg biomass). ANOVA and model validation confirmed the statistical significance and predictive accuracy of the optimization model. FTIR and biochemical analyses showed minimal changes in the functional groups and primary metabolites of the harvested biomass, indicating the process preserved biomass quality. Mg incorporation was minimal and environmentally safe, with a post-process medium suitable for reuse. Compared to conventional methods, EC provided superior harvesting efficiency with significantly lower energy input and shorter processing time. The significance of this study lies in offering an effective, low-energy alternative to conventional harvesting techniques that also support environmental sustainability.