Oxidation Stability: The Bottleneck for the Development of a Fully Renewable Biofuel from Wine Industry Waste

Abstract

Wine industry generates a large amount of biowaste, such as grape marc and wine lees, which is considered in the Directive (EU) 2018/2001 as an adequate feedstock to produce advanced biofuels. Grapeseed oil fatty acid ethyl esters (FAEEs) can be obtained from oil extracted from grape marc and bioethanol distilled from wine lees or wine surplus. Although FAEE still has no specific standard, grapeseed oil FAEE would fulfill all of the properties set by the standard EN 14214, except oxidation stability. This work analyzes the effect of natural antioxidants on the oxidation stability of grapeseed oil FAEE, using grapeseed oil fatty acid methyl esters (FAMEs) as a reference for comparison. On the one hand, the biofuel, produced with conventional transesterification, was mixed with FAME and FAEE produced via in situ transesterification. On the other hand, antioxidants extracted from grapeseed or defatted grapeseed flour were added to the biofuel. The results show that (1) FAEE has worse oxidation stability than FAME, (2) in situ transesterification improves the oxidation stability, and (3) addition of natural antioxidants is hindered by their low solubility in alkyl esters. Finally, the concentration of antioxidants, measured by UV–vis spectroscopy, showed a correlation between the absorbance at 285 nm (characteristic of phenolic compounds) and the induction time (IT) of the samples.

Survey on Antioxidants Used as Additives to Improve Biodiesel’s Stability to Degradation through Oxidation

“…Hydro-peroxides formed are unstable compounds and continuously decompose, forming aldehydes and short-chain organic acids as oxidation products. These compounds progressively form insoluble gums through polymerization reactions that increase the acid value and viscosity [45,46]. Consequently, when biodiesel is oxidized, a series of changes occur that most often reduce the quality of the biofuel and, thus, the engine performance is affected.…”

Improvements in the stability of biodiesel fuels: recent progress and challenges

“…Tocopherols prolonged the induction period of several types of fatty acid methyl esters. Furthermore, natural antioxidants perform better than synthetic antioxidants (Donoso et al 2020 ).…”

The role of antioxidants in improving biodiesel's oxidative stability, poor cold flow properties, and the effects of the duo on engine performance: A review

“…As a result, a series of changes occur when biodiesel is oxidized, often compromising biodiesel quality and hindering engine performance. Therefore, the structural composition of fatty acid and environmental factors such as luminosity, humidity, high temperatures, metal contaminants, and oxygen in the form of singlet and triplet [ 26 ], catalyzed the initiation of the oxidation process by generating free radical from the alkyl chain [ 27 ]. Below are some of the main oxidation actors, responsible for oxidation stability in biodiesel.…”

“…The produced peroxyl radical (ROO • ) is less reactive than the carbon-based free radical (R • ), but further reacts and propagates to the second step by quickly abstracting another hydrogen from a methylene moiety to form hydroperoxide (ROOH) and another carbon radical as shown in Eq. (9) , which is subject to fragmentation easily by heat or UV-light [ 26 ]. …”