Abstract
Biodiesel is a renewable fuel that will soon be fully accepted in the commercial world
but there are limitations to its use that need improvement. The use of oxygenated
additives have improved the burning/fuel qualities of conventional diesel and gasoline.
These oxygenates may also improve the qualities of biodiesel. This paper focuses on
comparing the fuel qualities such as the density, specific gravity, heat content, flash
point, and kinematic viscosity of oxygenate-biodiesel blends. The biodiesel was
produced from fresh and waste cooking oil and they were characterized and compared to
ASTM standards. The oxygenated additives (ethanol, methanol and diethyl ether) were
blended in the percentages 10, 20, 30 and 40% with biodiesel from fresh and waste oil.
The physicochemical properties such as kinematic viscosity, density, specific gravity,
flash point and heat content were analyzed for the blends. The density and specific
gravity values were within the range of 0.7
: 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).
1.1 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 transesterification 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
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organizations, schools and the likes. This trend is expected to continue over the years to
come (Michael, Andrew, Winnie, & Thomas , 2006).
1.2 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.
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Figure 1: Effect of biodiesel use on emissions (U.S. Department of Energy, 2014)
1.3 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).
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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)
1.4 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
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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).
1.5 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).
1.6 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.