Synthesis and optimization of ethyl esters from fish oil waste for biodiesel production

Fish oil is a sustainable, abundant, and low-cost raw material, as it is extracted from fish processing waste. This work suggests that fish oil is appropriate for biodiesel production and evaluates its potential through ethyl esters (EE). Initially, fish oil showed an acid value of 10.86 +/- 0.05 mg KOH g(-1). But after a neutralization reaction, the acid value was reduced to 0.68 +/- 0.01 mg KOH g(-1). Alkaline trans-esterification reactions were performed on a laboratory scale, using a central composite rotational design with three variables and a triplicate over the center point. We studied the appropriate concentrations of ethanol and catalysts, and the temperature that provide the best EE yield. The results showed the optimal condition is with 0.7% of a NaOH catalyst, a temperature of 54 degrees C, and an ethanol:oil molar ratio of 11.7:1. In such conditions, it was possible to acquire an EE yield of 96.4% with a low acid value of 0.32 +/- 0.08 mg KOH g(-1), which presented physicochemical properties consistent with the parameters by the Petroleum National Agency's (ANP). In the conditions studied, the results showed high levels of EE from the residual fish oil. This suggests that this raw material, rich in unsaturated fatty acid, can be beneficial for biodiesel. (C) 2018 Elsevier Ltd. All rights reserved.