Synthesis and RSM Optimization of Methyl Ester from Waste Fish Oil by Transesterification Using Potassium Hydroxide Catalyst

Abstract

Renewable energy is vital for countering fossil fuel depletion and pollution, offering flexibility through its diverse and sustainable sources. Biofuels, derived from renewable organic materials, are a major renewable resource with a low carbon footprint, non-toxic, biodegradable, and sulfur-free, reducing emissions and health risks. Salmon oils pose environmental hazards and are challenging to dispose of properly. Therefore, it was proposed to convert them into biodiesel fuel as a sustainable solution. The process applied transesterification, employing methanol and potassium hydroxide as the catalyst to convert the oil into methyl ester. The impact of four parameters—reaction time, temperature, methanol and catalyst concentration were investigated. Experiments were conducted through various ranges for each variable: temperature was studied from 40 °C to 65 °C in increments of 5 °C, methanol concentrations from 10 % to 20 % in increments of 5 % wt./wt., catalyst concentration from 0.25 % to 1.5 % in increments of 0.25 % wt./wt., and reaction time from 15 to 90 minutes in increments of 15 minutes. The optimal conditions were determined using the Response Surface Methodology (RSM) model in Design Expert 13, based on optimization procedures for the settings of factorial variables, aiming for the minimum temperature, time, and catalyst concentration, with a methanol range of 10 % to 20 % by wt. The optimal production of fatty acid methyl esters (FAME) occurred at a reaction temperature of 50 ℃, with 20% methanol by weight and 0.875% potassium hydroxide by weight, for 60 minutes, getting a maximum yield of 89.07%.