https://doi.org/10.15255/KUI.2023.062
Published: Kem. Ind. 73 (11-12) (2024) 439–447
Paper reference number: KUI-62/2023
Paper type: Original scientific paper
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The Influence of Qualitative Parameters of Waste Cooking Oils and Fat on Fatty Acid Methyl Esters Yield

M. Ostojčić, M. Cikoja, I. Flanjak, B. Bilić Rajs, T. Moslavac, M. Benšić, M. Brekalo, I. Strelec and S. Budžaki

Abstract

Due to the growing demand for alternative green fuels, biodiesel remains a focal point of scientific research. While chemical biodiesel production, mostly from edible oils, has been established worldwide for years, enzymatic synthesis and the utilisation of raw materials like waste or inedible oils and fats are increasingly preferred, primarily due to economic and environmental considerations. The aim of this study was to perform enzymatic biodiesel synthesis with Burkholderia cepacia lipase using selected waste cooking vegetable oils and animal fat, and to correlate the resulting fatty acid methyl esters (FAME) with lipase substrate specificity and main specific characteristics of the selected waste feedstock (such as fatty acid profile, free fatty acid content, peroxide and iodine values). The listed characteristics of the oils/fat were determined using standard methods, while biodiesel was synthesised through transesterification of the selected waste oils/fat with methanol in the presence of a lipase catalyst. Analysis of FAME during 24 h of biodiesel synthesis from waste cooking vegetable oils revealed that a one-hour reaction time was sufficient to achieve a yield of over 97 % of FAME. Conversely, when utilising waste cooking animal fat as a substrate, the minimum yield of 96.5 %, as per European standard (EN 14214), was not achieved even after 24 h of synthesis. According to the correlation matrix, the highest positive correlation was found between iodine value and the resulting FAME. The waste cooking vegetable oil with the highest iodine number (123.88 ± 2.41 g I₂/100 g) yielded the highest proportion of methyl esters after 1 h of synthesis. A statistically significant positive correlation was found between FAME and the iodine and peroxide values, suggesting these parameters as indicators of waste oil suitability for biodiesel synthesis. This study is a contribution to further research on potential substrates for biodiesel synthesis from waste streams.

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Keywords

biodiesel synthesis, iodine value, waste cooking vegetable oil, waste cooking animal fat, Burkholderia cepacia lipase