A REVIEW ON WASTE COOKING OIL BIODIESEL AS A VIABLE FUEL FOR DIESEL ENGINES: EXISTING CONCEPTS, EMERGING TRENDS AND FUTURE PROSPECTS

The world is in an irreversible process of switching to alternative fuel sources for diesel engines. This has been necessitated by accelerated depletion of fossil diesel resources coupled with the detrimental impact of exhaust emissions on the environment. Biodiesel is a standout amongst other possible fuel options for diesel engines that have been discussed in the literature. Biodiesel is regarded as a clean source of fuel because its combustion results in a decrease in most harmful emissions when compared with fossil diesel fuels. However, some feedstocks for biodiesel are not feasible due to the exorbitant cost of acquisition and their negative impact on food supply channels. A switch to waste cooking oil (WCO) is viewed as the most encouraging option for biodiesel feedstock despite its disadvantages, like its high free fatty acid (FFA) and water content. In this paper, existing concepts used for WCO biodiesel production process in regard to feedstock pre-treatment, production technologies and purifications methods are analysed, highlighting the merits and demerits of available options. Furthermore, emerging trends and prospects of WCO biodiesel production technologies are presented.