Optimization of algal methyl esters using RSM and evaluation of biodiesel storage characteristics

Abstract

Background: This paper deals with the production of biodiesel from the brown seaweed Sargassum myriocystum, a third-generation biodiesel from the Gulf of Mannar, Rameshwaram, India. The optimization of reaction parameters was done using Design-Expert software version 8.0.7.1. Algal oil was transesterified using methanol and sodium hydroxide. The effect of oil:alcohol ratio, catalyst amount, temperature, and time on biodiesel yield was investigated by response surface methodology using central composite design. Results: It was found that the maximum biodiesel yield was obtained at 60°C for 1:6 (v/v) oil:alcohol ratio, 0.4 (w/w) catalyst amount, and 120 min. The R2, adjusted R2, and predicted R2 values are 0.9977, 0.9956, and 0.9923, respectively, which implies that experimental values are in good agreement with predicted values. The fatty acid profile of S. myriocystum biodiesel was determined using gas chromatography. Algal biodiesel was stored in dark and light conditions. Fuel properties like kinematic viscosity and acid value were determined. It was found that the samples exposed to light led to an increase in kinematic viscosity and acid value with some sediment formation. Conclusions: The acid value and kinematic viscosity of the samples stored in the dark environment had only marginal increase in fuel properties which were within the range specified by the American Society of Testing Materials (ASTM D6751).