Experimental studies of natural antioxidant additive with used cooking oil methyl ester in a compression ignition engine

Abstract

The rapid increase in population has led to the massive consumption of energy from fossil fuels. Diesel engines are widely used in various sectors such as industries, agriculture, transportation, power generation, etc. Increased prices, limited reserves, and generation of harmful pollutants have provoked the need for the search of alternate fuels. Vegetable oil is a suitable alternative source for diesel fuel. However, its direct usage invokes many operational problems like fuel filter plugging, injector clogging, and incomplete combustion despite its increased viscosity and density. The reduction of viscosity can be obtained by various methods, among which transesterification is found to be effective. Fatty acid methyl ester or biodiesel obtained as a result of transesterification is found to have properties similar to that of diesel fuel which facilitates its direct usage in diesel engines. However, biodiesel poses problems such as oxidation which reduces its storage stability and also increased NOx emissions. These issues can be overcome with the addition of antioxidants that contain phenolic compounds. Free radicals contribute to oxidation and they are scavenged by the addition of antioxidants which not only improves the storage stability but also reduces NOx emissions. Many experimental works have been carried out with synthetic antioxidants on the effect of biodiesel storage stability and NOx emissions. Usage of synthetic antioxidants leads to detrimental effects like cancer together with the increased cost which directs the research towards the usage of natural antioxidants. The advantages of using natural antioxidants are their extensive availability, nontoxicity, and reduced cost. An expeditious increase in the population goes hand in hand with the massive number of restaurants that lead to a huge generation of used cooking oil. Direct disposal of used cooking oil has damaging effects on the environment. It can be converted to Used Cooking Oil Methyl Ester (UCOME) through transesterification. The presen