Evaluating the Efficiency of Modified Crop Residues based Flocculants for Harvesting of Microalgae

Abstract

The efficient and cost-effective harvesting of microalgae is a critical challenge in the field of sustainable biofuel production and environmental management. This study explores the potential of modified crop-residue-based flocculants as an innovative and economical solution for microalgae harvesting. Traditional methods for harvesting microalgae, such as centrifugation and chemical flocculation, are often cost-prohibitive and environmentally detrimental. Therefore, the development of eco-friendly and low-cost alternatives is essential for the feasibility of large-scale microalgae cultivation. In this study, crop residues, specifically wheat straw and biochar were subjected to chemical modification to enhance their flocculating properties. The modification involved treatment with 0.5 M magnesium chloride. The modified crop residues and biochar were characterized using Scanning Electron Microscopy (SEM), Atomic absorption spectroscopy (AAS), Elemental analysis and X-ray diffraction (XRD) were carried out to understand the changes in their chemical structure and surface charge. The flocculation efficiency of the modified residues was evaluated using a mixed consortia of microalgae mostly dominated with Chlorella sp. Parameters such as flocculant dosage, pH, time were optimized to achieve maximum biomass recovery. The results indicated that the chemically modified crop residues exhibited significantly higher flocculation efficiency compared to their unmodified counterparts. The best-performing modified flocculants achieved over 90% microalgae recovery at lower dosages, highlighting their potential as cost-effective alternatives. The research provides robust evidence that modified crop-residue-based flocculants are a highly effective, economical, and environmentally friendly alternative for microalgae harvesting. Their implementation has the potential to significantly reduce the cost and environmental footprint of microalgae-based biofuel production, paving the way for more sustainable and scalable bioenergy solutions. Future research directions should focus on optimizing the modification processes, scaling up flocculant production, and exploring their applicability in other areas of wastewater treatment and biomass recovery.