UTILIZATION OF BROWN SEAWEED RESIDUES AFTER FUCOIDAN EXTRACTION FOR THE PRODUCTION OF BIOFERTILIZERS

Abstract

This study explored the valorization of by-products generated during fucoidan extraction from brown
seaweed for producing a liquid biofertilizer suitable for sustainable agriculture. The by-products included
solid residues and potassium-rich alkaline wastewater obtained after hydrochloric acid extraction and
ultrafiltration with a 100 kDa membrane. Chemical analyses showed that the wastewater contained
significant levels of potassium (18.07–21.45 g/L), proteins, free amino acids, magnesium, and zinc, while the
dried residue retained 26.3% alginate. A liquid biofertilizer was successfully formulated by alkaline
oxidative hydrolysis of the residue, followed by nutrient blending using the wastewater. The final product
demonstrated enhanced germination and early growth of Brassica juncea under laboratory conditions. This
work highlights an effective circular bioeconomy strategy by transforming brown seaweed processing waste
into a high-value agricultural input for organic and sustainable farming systems.