Production of fatty acid methyl esters from an olive oil industry waste

Abstract

This work studies the synthesis of fatty acid methyl esters (FAME) using crude olive pomace oil as raw material and zinc stearate as catalyst. Pomace oil is a non-edible by-product of olive oil production. The oil was characterized. In order to reduce the plant pigment content in the oil, the liquid was contacted with a modifed clay. An experimental design was applied to determine the optimum operating conditions to achieve the minimum pigment concentration and the maximum amount of recovered oil. Response surface methodology was used to study the relationship between process variables and the selected response variables. A mixed-level factorial design was used, and the studied responses were triglyceride and free fatty acid (FFA) conversion and FAME yield at 30 min of reaction time. Under optimum conditions (temperature (T): 140°C, catalyst loading (C): 3 wt%, initial molar ratio of the reactants (MR): 30), 98% and 67% of triglyceride and FFA conversions were achieved, with 84% of FAME yield. This study shows that pomace oil can be used as a raw material for biodiesel production. At short reaction times and under moderate operating conditions, it was possible to convert triglycerides and fatty acids selectively toward FAME.