Purification of Residual Glycerol from Biodiesel Production as a Value-Added Raw Material for Glycerolysis of Free Fatty Acids in Waste Cooking Oil

K. A. Viraj Miyuranga, Udara S. P. R. Arachchige, Randika A. Jayasinghe and Gamunu Samarakoon ()
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K. A. Viraj Miyuranga: Department of Civil and Environmental Technology, University of Sri Jayewardenepura, Pitipana 10206, Sri Lanka
Udara S. P. R. Arachchige: Department of Civil and Environmental Technology, University of Sri Jayewardenepura, Pitipana 10206, Sri Lanka
Randika A. Jayasinghe: Department of Civil and Environmental Technology, University of Sri Jayewardenepura, Pitipana 10206, Sri Lanka
Gamunu Samarakoon: Department of Process, Energy and Environmental Technology, University of South-Eastern Norway, 3918 Porsgrunn, Norway

Energies, 2022, vol. 15, issue 23, 1-20

Abstract: The crude glycerol produced as a byproduct of transesterification synthesis has very few applications because it comprises of significant amounts of methanol, catalyst, and soap. On the other hand, transesterifications of highly acidic oil in the presence of an alkaline catalyst are problematic due to the presence of high amounts of free fatty acids. In this study, the free fatty acid level of high acid oil, which was initially determined to be 19.25%, was decreased to permit the direct production of biodiesel via glycerolysis with pure glycerol, making direct transesterification feasible. Through a process of purification, crude glycerol was refined to 92.5% purity. It was revealed that the physiochemical parameters of density, moisture content, ash content, matter organic non-glycerol content, pH, and Na/K concentrations of generated purified glycerol are equal to those of commercially available glycerol. In contrast, glycerolysis treatment successfully decreased the free fatty acid level to less than 2% under optimal conditions, which were determined to be 200 °C, a glycerol-to-oil molar ratio of 4:1, and a KOH catalyst concentration of 1.6 wt.% at 350 rpm. The inclusion of hexane as a co-solvent accelerated the glycerolysis process, and the weight ratio of oil-to-hexane was 8:1. Moreover, it was viable to use waste methanol for biodiesel synthesis and purified crude glycerol as a raw material in a variety of industries, including biodiesel production. In addition, compared to acid esterification, the FFA concentration of oil with a high acid value fell significantly.

Keywords: biodiesel; biofuel; free fatty acid; glycerol; glycerolysis; purification; renewable energy; sustainability; value-added; waste cooking oil (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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