Due to the high expense and negative environmental effects of traditional synthetic flocculants (such as alum and chitosan), which contaminate biomass and ecosystems during downstream processing, microalgae harvesting continues to be a crucial bottleneck in large-scale biomass production. Efficient harvesting is necessary to concentrate diluted microalgal solutions into usable biomass and extract high-value bioproducts, including proteins, pigments, biofuels, and omega-3 fatty acids. This study explores waste-derived bio flocculants, such as pomegranate seed waste (PSW) and chicken eggshell membranes (CESM), as inexpensive, environmentally friendly substitutes for these problems. For Chlorella vulgaris harvesting under neutral settings (pH 7), this study assesses PSW and CESM as sustainable bio flocculants. The eggshell membrane's performance was hampered by decreased ionization of functional groups, but it was still able to achieve 35–40% flocculation effectiveness at 80 mg/L dosage by utilizing its protein-polysaccharide matrix and bridging processes. On the other hand, PSW showed strong versatility, with 65–72% effectiveness at 0.25–0.5 g/L dosage through synergistic polymer bridging and hydrophobic interactions. environmental compromises. CESM depended on partial charge interactions, mechanistic research showed that PSW's lignin-polysaccharide network enabled persistent floc production even in the absence of electrostatic supremacy. The feasibility of PSW (~1.1 USD/kg), which offers a 50% cost decrease over synthetic alternatives, was confirmed by cost analysis. These results highlight PSW's potential as a pH-flexible bioflocculant for systems that need to operate at a neutral pH while maintaining economic viability, biomass quality, and efficiency without sacrificing either the environment or chemicals.
