The effect of mechanical expressions on red algae yield, Kappaphycus alvarezii L. Doty

Abstract

Commercial seaweed cultivation has been introduced to numerous parts of the world. Significant research is dedicated to its improvement of cultivation and processing. Kappaphycus alvarezii, a macroalgae, has spread throughout Southeast Asia and has been cultivated in many regions. The reliable cash income supports many coastal fishing communities. Separation of the solid-liquid fractions of fresh seaweed may provide additional value to seaweed farmers. Seaweed prices fluctuate due to variations in seaweed quality at the farm level. In addition, seaweed mostly grows better during the rainy season when there is a lack of sunlight to facilitate drying required for trade. If the seaweed can be immediately processed without drying and two products are obtained from liquid and solid separation, it will save space for drying and cost for adding new drying infrastructures. The liquid is used for agriculture fertilizer and the dry cake is used as an aquatic feed additive. Six factors were studied to improve liquid extraction with mechanical expression using a fractional factorial design with two levels. The high levels of factors are coded +1 and lower levels coded as-1. The lower level Comitrol™ blade space (1 mm blade space), low level initial temperature (22 oC), low initial weight (20 gram) and high level final pressure (2800 Pa) gave the highest liquid recovery from Kappaphycus alvarezii. Speed of pressing and time held at final pressure had negligible effect on liquid recovery. The economic analyses showed that a 250Mg per year solid liquid processing facility is a profitable investment given a Minimum Attractive Rate of Return of 20%, because the Internal Rate of Return was shown to be 30.23%. An increase of 10% in variable costs over ten years decreases net cash flow (-$100.17); but an increased the selling price of 2.5% restored the IRR to 30.23%.