Oxidation Stability of Biodiesel Produced from Non-Edible Oils of African Origin 2011-01-1202

Mono alkyl esters of long-chain fatty acids derived from renewable lipid feedstock, such as vegetable oils or animal fats, also known as biodiesel are well positioned to replace mineral diesel. The outstanding technical problem with biodiesel is that it is more susceptible to oxidation owing to its exposure to oxygen present in the air and high temperature. This happens mainly due to the presence of varying numbers of double bonds in the free fatty acid molecules. The chemical reactivity of esters can therefore be divided into oxidative and thermal instability, which can be determined by the amount and configuration of the olefinic unsaturation in the fatty acid chains. Many of the plant-derived fatty oils contain polyunsaturated fatty acids that are more prone to oxidation.

Increasing production of biodiesel from vegetable oils (edible) places strain on food production, availability and price and leads to food versus fuel conflict. Hence, this study evaluates biodiesel derived from low cost non-edible oils, primarily available in African continent, namely croton megalocarpus, moringa oleifera and jatropha oils. The fuel related properties and oxidation stability of croton oil methyl ester (COME), moringa oil methyl ester (MOME) and jatropha oil methyl ester (JOME) were determined and compared with global biodiesel standards such as ASTM D6751 and EN 14214. Oxidation stability of COME, MOME and JOME with and without antioxidants was analyzed using Rancimat method. The results showed that most of the properties of COME, MOME and JOME fulfilled the minimum requirements specified in the ASTM D6751 and EN 14214 biodiesel standards. However, COME and MOME did not fulfill the oxidation stability requirements specified in EN 14214 (6 h), while JOME displayed a remarkably high oxidation stability of 10.43 h. Also, this study examined the effectiveness of three antioxidants namely 1, 2, 3 trihydroxy benzene (PY), 3, 4, 5-tri hydroxy benzoic acid (PG) and 2-tert butyl-4-methoxy phenol (BHA) on COME, MOME and JOME. The result showed that, the effectiveness of these antioxidants was in the order of PY≻PG≻BHA.