A REVIEW OF BIODIESEL PRODUCTION FROM NON-EDIBLE RAW MATERIALS USING THE TRANSESTERIFICATION PROCESS WITH A FOCUS ON INFLUENCE OF FEEDSTOCK COMPOSITION AND FREE FATTY ACIDS

The main resources needed for an alternative fuel are availability and renewability, that is, less dependence on restricted raw materials accompanied by no or less pollution. Due to being eco-friendly and non-toxic to nature, biodiesel is attracting more and more interest. Biodiesel has many important technical advantages compared to petroleum diesel, such as inherent lubricity, low toxicity, derivation of renewable and domestic raw materials, biodegradability, insignificant sulfur content, and lower exhaust emissions. However, they have some important disadvantages that include the high cost of the raw material, lower storage and oxidative stability, lower volumetric energy content, lower low-temperature operability, and in some cases, higher NOx exhaust emissions. One of the major challenge obstacles is the high cost of refined vegetable oil as raw material, which consists of almost 70% of the total production costs. Therefore, in order to reduce the cost of biodiesel, non-edible sources such as residual cooking oil (WCO), algae oil, non-edible vegetable oil, and residual fats are commonly used for the production of biodiesel due to its low cost and don't affect the food chain. The most common method used in the production of biodiesel is the transesterification of vegetable oils and animal fats. Production and process are influenced by several factors, such as temperature and reaction time, the molar ratio of alcohol to oil, and type and concentration of catalyst. Therefore, this review focuses on the recent discovery of the transesterification of inedible sources for biodiesel, the influence of the composition of the raw material on the quality of biodiesel, and the possible solutions to its disadvantages for the production of biodiesel.