COMPARATIVE STUDY ON THE EFFECTS OF OXYGENATES ON BIODIESEL FROM FRESH AND USED COOKING OIL

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CHAPTER 1:     Introduction

The recognition of global warming and depletion of fossil fuels has led to the search for other energy options which are environmental friendly and sustainable. Emission of greenhouse gases from fossil fuels has led scientists to turn to biofuels as an alternative source. Biofuels are fuels made from different types of biomass such as cellulose, algal oil, corn, soy, sugar cane, jatropha, camelina, rapseed, animal fat, methane, paper waste and the likes. These sources create different fuels such as bioalcohols, plant based biodiesel and kerosene, biogas, solid biofuels and the likes (Webb & Coates, 2012).

                    Biodiesel

Biodiesel has grown quite a name for itself since its inception in the 20th century. It is a liquid biofuel composed of simple alkyl esters of fatty acids made from the trans- esterification of vegetable oils and animal fats which are renewable and nontoxic. It is known for its production of low greenhouse gases as compared to fossil fuel (Fangrui & Milford, 1999). The biodiesel produced is independent of the starting material which makes any material containing free fatty acids a suitable feedstock (Michael, Andrew, Winnie, & Thomas , 2006).

Biodiesel production has increased considerably in the last thirty years due to its properties that confirm it environmentally suitable. It is now being accepted in the commercial world as several institutions adopt its use such as businesses, governmental

organizations, schools and the likes. This trend is expected to continue over the years to come (Michael, Andrew, Winnie, & Thomas , 2006).

                    Advantages of biodiesel

The advantages of biodiesel over conventional diesel have been proven to be very essential in curbing emissions of carbon dioxide, sulfur oxide, particulate matter, and polycyclic aromatic hydrocarbons due to the fact that it has 10-11% oxygen by weight and allows for complete combustion of the fuel (Arjun, Chris, & Rafiqul, 2008). Its use comes with lower health problems which is possible since it has a reduced emission of carcinogenic substances. The environment is safer even with biofuel spill due to its high degradability and low toxicity (Romano & Sorichetti, 2011). Reports have suggested that the life cycle of carbon dioxide emissions have been cut down to 30% with the use of biodiesel as compared to conventional diesel (Gerard, Bruno, Dominique, Laurent, & Jean-Alain, 2003). As promising as biodiesel is there are limitations to it that need improvement.

                    Biodiesel production

Biodiesel is synthesized from animal or vegetable fat via trans-esterification. The Fig. below shows a schematic of the production path involved in the synthesis. During the trans-esterification process, triglyceride is converted to methyl or ethyl esters with the aid of an alcohol usually methanol and a base catalyst, potassium hydroxide which is more efficient than sodium hydroxide. An excess of alcohol drives the reaction towards the production of methyl or ethyl esters. The equation below shows the mechanism of conversion involved in the production of biodiesel (Encinar, Gonzalez, Martinez, & Pardal, 2010).

Figure 2: Schematic representation of biodiesel production pathway (U.S. Department of Energy, 2014) Equation 1: Trans-esterification of vegetable oil (Encinar, Gonzalez, Martinez, & Pardal, 2010)

                    Waste vegetable oil as feed stock

The feed stock for biodiesel production is a controversial topic due to the fact that it takes up food meant to be eaten like using soy, palm kernel, castor oil and the likes. This causes a debate on which is important, food or fuel? The use of waste vegetable oil, jatropha and other nonedible oil, producing plants for the production of biodiesel is a very popular topic most especially waste cooking oil which has virtually

no cost in securing it as a feed stock. 70-95% of the cost of producing biodiesel comes from the feedstock and using waste oil takes care of that cost (Arjun, Chris, & Rafiqul, 2008). The use of waste cooking oil in the production of biodiesel allows for its recycle seeing as its disposal holds serious damages in public sewers, waste water and even streams of flowing water (Nor, Sulaiman, & Nurrul, 2013).

                    Limitations of Biodiesel

Though biodiesel has promising prospects, in order to be fully accepted as an alternative to fossil fuel, its properties need to be improved upon such as the cetane number, energy density, viscosity, flash point and the likes. Modifications of the fuel properties can enable it to be well matched to that of conventional diesel. There have been a handful of researches that investigate the effect oxygenates have on biodiesel most especially the blends with diesel (Imtenan, et al., 2014).

                    Aims, Objectives and Significance

Oxygenates with good fuel properties such as ethanol, diethyl ether and methanol may be efficient in improving the properties or characteristics of biodiesel. The aim of this study is to investigate the properties of biodiesel produced from fresh cooking and waste cooking oil blended with oxygenates such as ethanol, methanol and diethyl ether. This study will create awareness on the modifications that can occur when biodiesel is blended with oxygenates and this can further help the biodiesel industry to flourish.