Harvesting of microalgae using Saccharum officinarum bagasse: characterization, process optimization, and evaluation of harvesting potential.

In microalgae downstream processing, biomass harvesting is a key step that requires a huge amount of energy. Microalgae harvesting can directly influence the microalgal biomass industry for its wide applications. In the present work, sugarcane bagasse (SB) was investigated as a plant waste-derived flocculant for harvesting microalgae. The SB with 40mg/L exhibited harvesting efficiency (HE) of 93.6% and 89.48% at pH 7.5 and 9.5, respectively. SB showed a negative surface charge, indicating that the flocculation mechanism in the present study is not primarily through charge neutralization. Elemental analysis of harvested biomass showed the presence of 27.07% of carbon, 6.83% of hydrogen, and 5.86% of nitrogen. Overall, results indicate the possible utility of SB as low-cost eco-friendly plant-based waste material for mixed microalgae harvesting. FTIR (Fourier-transform infrared), Zeta potential, SEM (scanning electron microscope), and EDX (energy-dispersive X-ray) analysis were performed to assess the characteristics of SB and mechanism of harvesting. The FTIR spectrum analysis of SB revealed the presence of multiple functional groups indicating their possible role in flocculation by bridging mechanisms. The SB has promising potential to be used at a demonstration scale for microalgae harvesting for various applications.