Production, characterization and performance of biodiesel as an alternative fuel in diesel engines – A review

doi:10.1016/j.rser.2017.01.001

Renewable and Sustainable Energy Reviews

Volume 72, May 2017, Pages 497-509

https://doi.org/10.1016/j.rser.2017.01.001 Get rights and content

Abstract

Due to the finite stock of fossil fuels and its negative impact on the environment, many countries across the world are now leaning toward renewable sources energies like solar energy, wind energy, biofuel, hydropower, geothermal and ocean energy to ensure energy for the countries development security. Biodiesel is one kind of biofuel that is renewable, biodegradable and has similar properties of fossil diesel fuel. The aim of this paper is to provide the substantial information on biodiesel to the researchers, engineers and policy makers. To achieve the goal, this paper summarizes the information on biofuel development, feedstocks around the world, oil extraction technic, biodiesel production processes. Furthermore, this paper will also discuss the advantages of biodiesel compared to fossil fuel. Finally, the combustion behavior of biodiesel in an internal combustion engine is discussed and it will help the researchers and policy maker and manufacturer. To determine the future and goal of automotive technology the study found that, feedstock selection for biodiesel production is very important as it associates 75% production cost. Moreover, the test of fuel properties is very important before using in the engine which depends on the type of feedstocks, origin country, and production process. Most of the researchers reported that the use of biodiesel in diesel engine reduces engine power slightly but reduces the harmful emission significantly. Finally, the study concludes that biodiesel has the potential to be used as a diesel fuel substitute in diesel engines to solve the energy and environment crisis.

Introduction

Transportation system plays an important role to develop the economy of any country in the world. Nowadays the key issue for worldwide transportation sector is the energy supply, which is being fulfilled by fossil fuels such as gasoline and diesel fuel. Globally, an average consumption of energy in the transport sector is increased by 1.1% per year due to the development of motorization industry. It has been reported that only the transportation sector have 63% share in the step up of total global liquid fuel consumption from the year of 2010–2040 [1]. Also, the significant growth of worldwide motorization industry has resulted in the increase of harmful pollutant emissions to the earth. It is very important to mention that, there are about 22% of global GHG (greenhouse gas) emission comes only from the transportation sector. Not only the International Energy Agency (IEA) predicted the emissions of GHG (carbon dioxide) from transport sector will be increased by 92% between 1990 and 2020 and it is also estimated that 8.6 billion metric tons carbon dioxide (CO₂) will be released to the atmosphere from 2020 to 2035 [2]. Vehicular emissions such as particulate matter (PM), hydrocarbon (HC), carbon dioxides (CO₂), carbon monoxides (CO) and nitrogen oxides (NOx) are hugely responsible for the air quality deterioration [3]. Fig. 1 shows the predictive share of transportation sector global energy consumption and CO₂ emission [4].

In Malaysia, the consumption of both petrol and diesel has been increasing rapidly with growing motorization and increasing dependence on private modes. At present, transportation sector consumes about 36% of the total national energy. Transportation sector consumes the largest portion of energy in Malaysia, and it's increasing every year. Energy consumption by transportation sector was increased from 1928 ktoe in 1978 to 17,180 ktoe in 2012. Fig. 2 shows the energy consumption by sectors in Malaysia [5]. Transport sector of Malaysia produced 42.4 million metric tons of CO₂ that shares 22.9% of total CO₂ emission in Malaysia. An increased number of registered motor vehicles is expected in years to come, which will certainly further increase the emission. It can be seen that CO₂ emission had increased from about 15 million metric tons in the early nineties to 42.43 million metric tons in 2012. As per calculation, transport sector needs to reduce CO₂ by 9.17 million metric tons to reduce 40% emission by the year 2020. Shares of different transport modes to total CO₂ emissions from the transportation sector are shown in Fig. 3 [6]. The road transportation has the major share (85.2%) of total GHG emission from transportation followed by the aviation, shipping, and other small sectors. Therefore, the major reduction of CO₂ emission should be achieved in road transportation.

Recently, worldwide researchers are trying to find out cleaner energy source for transportation sector that will come from the renewable energy source and will meet the energy and environment crisis [7]. Among the renewable energy sources, the biodiesel is considered as the most feasible cleaner fuel worldwide [8]. Fig. 4 shows the sectors in which biodiesel can be used as a diesel fuel replacement [9]. It is seen that biodiesel can be used as a substitute for diesel fuel in all the sectors including light vehicles. Heavy vehicles, equipment machinery, marine sectors, and remote generation. Thus the main aim of this paper is to study the potential of biodiesel as an alternative fuel in the transport sector.

Section snippets

Development of biodiesel

Vegetable oil (peanut oil) has been used as a fuel in a diesel engine by Rudolph Diesel on August 10, 1893 [10]. In 1853, a group of researchers first converted the vegetable oil into methyl ester through transesterification process. The concept of biodiesel was proposed for the first time in 1937, and a patent ‘‘Procedure for the transformation of vegetable oils for their uses as fuels” from a Belgian scientist G. Chavanne was granted. A Brazilian scientist Expedito Parente applied for the

Potential sources of biodiesel

Oil crops are the main pillar for biodiesel production. It is very important to choose the suitable feedstock for biodiesel production as feedstock alone costs 75% of biodiesel production cost [11]. At present up to 350 oil-bearing crops have been identified worldwide for biodiesel production which is categorized as edible oil, non-edible oil [13]. The most common edible oil sources are: peanut oil, soybean oil, sunflower oil, safflower, corn oil, rice bran oil, palm oil, coconut oil, used

Oil extraction techniques

Preliminarily processes need to be done to extract the oil from the seeds. First, the seed needs to be separated from the fruits. Then the drying process is done in the oven or under the sun to expected moisture contents. To extract oil, it is very important to grate the kernel to get a higher percentage of oil. The main techniques available to extract oil can be classified by (a) mechanical extraction (b) chemical extraction (c) enzymatic extraction. Besides some other techniques has also been

Characterization of crude oils

The characterization of vegetable oil is necessary to evaluate their viability for biodiesel production. The vegetable oils are mainly characterized by some of the fuel properties such viscosity, density, calorific value, flash point, acid value, cloud point, pour point, carbon residue and oxidation stability [25], [26]. Different vegetable oils have different properties. Among the vegetable oils, some oils have higher viscosity, density and some have a lower viscosity as shown in Table 3 [27],

Effect of fatty acid composition of vegetable oils

Fatty acid composition of any source of biodiesel is a very important parameter which helps to select the efficient method to produce biodiesel. The fatty acid composition mainly depends on the type and quality of the source and also the geographical condition in which the plant grows [8], [37], [38]. The available fatty acids in vegetable oils are palmitic (16:0) and stearic (18:0) acids. Some of the vegetable oils also contain other fatty acids such as lauric (12:0), myristic (14:0),

Production of biodiesel

According to the literature, vegetable oil cannot be used directly in diesel engines because of its higher viscosity which causes a problem such as poorer atomization of the fuel spray and less accurate operation of the fuel injectors in the engine [23], [25]. Table 5 shows the problem that causes in the engine due to the use of vegetable oil. However, some process could be used to produce biodiesel as well as reduce the viscosity of vegetable oils. The available techniques are pyrolysis,

Characterization of biodiesel

The characterization of its fuel properties determines the quality of fuel [36], [37]. The key fuel properties of biodiesel fuels are density, viscosity, flash point, calorific value, cloud point, oxidation stability and cetane number. A brief discussion of key fuel properties of biodiesel fuel is given in the following section. Table 7 [67], [68], [69], [70], [71], [12], [14], [31], [63], [72], [73], [74], [75], [76], [77], [78], [79] shows the key fuel properties of different biodiesel fuel.

Advantages and disadvantages of biodiesel

The biodiesel has numerous benefits as well as some shortcoming [11], [124], [140], [141], [142], [143], [144], [145], [146], [147], [148], which have been listed below. The major benefits of using biodiesel as a fuel is:

i.
Biodiesel emits fewer emissions such as CO₂, CO, SO₂, PM and HC compared to diesel
ii.
Producing biodiesel is easier than diesel and is less time consuming.
iii.
Biodiesel can make the vehicle perform better as it has higher cetane number.
iv.
Biodiesel prolongs engine life and reduces the

Performance and emission behavior of biodiesel in internal combustion engines

Labeckas and Slavinskas [149] studied the performance and emission of a diesel engine fuelled with (5–30% by volume) blends of rapeseed and jet fuel at 1400 and 2200 rpm. Their results indicated that brake thermal efficiency (BTE) of blended fuels were 1–3.6% higher than neat jet fuel. Engine emissions result showed that NOx, CO, smoke increased significantly with J10 fuel with a small reduction of unburned hydrocarbon. Altaie et al. [150] found that enriched biodiesel blended fuel shows lower

Combustion behavior of biodiesel in internal combustion engines

Agarwal et al. [178] studied the effect of different Karanja biodiesel blends (10%, 20%, 50%) on the combustion characteristics of a single cylinder diesel engine at constant 1500 rpm and different injection pressures (300, 500, 700 and 1000 bar). They found that all fuel blends increased the maximum cylinder pressure with the step up of injection pressure. Combustion duration of lower biodiesel blends was shorter than diesel fuel, but B50 showed higher combustion duration. Ozturk [145] reported

Conclusions

Biodiesel is an environment-friendly fuel and offers many social and economic benefits. This paper provides the comprehensive information on biofuel development, feedstocks around the world, oil extraction technic, biodiesel production processes, and advantages of biodiesel. Finally, the combustion behavior of biodiesel in internal combustion engine has been discussed which will help to the researchers and policy maker and manufacturer. Summary of this study can be discussed as follows:

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