The present invention, relates to a method for extracting liquid fertilizer and calcium alginate (phyco-colloid) from seaweed. The brown seaweed is collected, dried and mixed with water (1:5) followed by shaking for 5 hours, overnight fermentation, and centrifuged to get supernatant as liquid fertilizers. The leftover residue is used for calcium alginate extraction by addition of Na2CO3 and kept in room temperature for one hour with manual intermediate stirring followed by shaker water bath at 60°C for 10min at constant stirring at 60 rpm. This is allowed to cool down to 30°C. After that incubation is carried out in shaker water bath at 80°C for 2 hours at constant stirring at 60 rpm. Then the mixture is allowed to cool down at room temperature which results in settling of higher viscosity sodium alginate.