A review of biodiesel production from Jatropha curcas L. oil

https://doi.org/10.1016/j.rser.2011.02.013Get rights and content

Abstract

The demand for petroleum has risen rapidly due to increasing industrialization and modernization of the world. This economic development has led to a huge demand for energy, where the major part of that energy is derived from fossil sources such as petroleum, coal and natural gas. However, the limited reserve of fossil fuel has drawn the attention of many researchers to look for alternative fuels which can be produced from renewable feedstock.

Biodiesel has become more attractive because of its environmental benefits and it is obtained from renewable resources. There are four primary methods to make biodiesel: blending, microemulsion, pyrolysis and transesterification. The most commonly used method is the transesterification of triglycerides (vegetable oil and animal fats) with alcohol in the presence of a catalyst. There is a growing interest in using Jatropha curcas L. oil as the feedstock for biodiesel production because it is non-edible and thus does not compromise the edible oils, which are mainly used for food consumption. Non-edible oils are not suitable for human consumption because of the presence of toxic components. Further, J. curcas L. seed has a high content of oil and the biodiesel produced has similar properties to that of petroleum-based diesel.

In this paper, an attempt has been made to review the different approaches and techniques used to generate biodiesel from Jatropha curcas oil. The main factors affecting the biodiesel yield, for example the molar ratio of alcohol to oil, catalyst concentration, reaction temperature and reaction time are discussed. Lastly, the environmental considerations and economic aspects of biodiesel are also addressed.

Introduction

The major part of all energy consumed in most parts of the world comes from fossil sources such as petroleum, coal and natural gas. However, these non-renewable sources will be exhausted in near future. Thus, the search for alternative sources of renewable and sustainable energy has gained importance with the potential to solve many current social issues such as the rising price of petroleum crude and environmental concerns like air pollution and global warming caused by combustion of fossil fuels [1].

Biodiesel fuel is of recent growing interest recently and has been strongly recommended as a substitute for petroleum diesel. The name biodiesel was introduced in the United States in the year 1992 by the National Soy Diesel Development Board which has pioneered the commercialization of biodiesel in the United State. Biodiesel can be blended with petroleum diesel as it has similar characteristics with lower hazardous exhaust emissions [21]. Biodiesel is processed from renewable biological sources such as vegetable oils and animal fats. The oils from vegetable crops and animal fats are extracted or processed to obtain the crude oil. It usually contains free fatty acids, phospholipids, sterols, water, odorants and other impurities. The free fatty acids and water contents have significant negative effects during the transesterification reaction of glycerides with alcohols using alkali or acid catalysts since they causes soap formation, consume catalysts and reduce its effectiveness and result in a lower conversion [1], [2]. Many researches have been undertaken on vegetable oils as a source for diesel fuel which includes palm oil, soybean oil, sunflower oil, coconut oil, rapeseed oil and so on. However, animal fats with high saturated fatty acids which normally exist in a solid form at room temperature may cause problems in the production process, causing its processing cost to be significantly higher than for vegetable oils [5]. Thus, vegetable oils are more favourable and draw a higher attention than animal fats for the fact that they are renewable and potentially an inexhaustible source of energy [1].

This paper reviews the production of biodiesel using vegetable oils, mainly of non-edible Jatropha curcas as potential feedstock, the technologies implemented, the process variables, economic aspects and environmental consideration of biodiesel production.

Vegetable oils, also known as triglycerides, are becoming one of the promising renewable feedstocks for biodiesel production and have become more attractive recently because of its environmental benefits. Due to it being renewable with energy content similar to diesel fuel after undergoing some chemical modifications, vegetable oils are becoming a promising alternative as a substitute for diesel fuel. The advantages of vegetable oils are renewability, biodegradability, liquid nature-portability, higher heat content (about 88% of diesel fuel) and lower sulphur and aromatic content. Edible vegetable oils like canola, soybean, rapeseed, sunflower and corn have been used for biodiesel production and found to be good as a diesel substitute. The non-edible vegetables oils such as madhuca indica, Jatropha curcas and Pongamia pinnata have also found to be suitable. Edible oils are widely used and more commonly used for biodiesel production [3], [4], [11]. Table 1 shows the fatty acid composition for different vegetable oils. More than 95% of biodiesel production feedstock comes from edible oils in developed countries because the properties of biodiesel produced from these oils are very similar to petroleum-based diesel [5]. In view of their several advantages, vegetable oils have a great potential to replace petroleum-based fuels in the long run [1], [6].

It is well-known that vegetable oils are candidates as alternative fuels for diesel engines as they have high heat content. However, the direct use of these vegetable oils leads to various problems. The high viscosities of vegetable oils which are about 10 times higher than of Grade No. 2D diesel fuel leads to poor atomization of the fuel, incomplete combustion, coking of the fuel injectors and so on. These disadvantages together with the usage of unsaturated vegetable oils that may result in engine damage can be solved by chemically modifying the biodiesel, which has similar characteristics to diesel [8], [9].

The free fatty acids (FFAs) and moisture content have negative impacts on the transesterification of glycerides with alcohol when an alkali catalyst is used. High FFA content is unfavourable in an alkali-catalysed transesterification reaction because the FFA will react with the catalyst to form soap and the separation of products will be extremely difficult, resulting in a lower yield of biodiesel. The Jatropha curcas oil quality will deteriorate due to improper handling and storage. Improper handling and exposure of the oil to atmospheric air and sunlight contributes to a rise in FFA concentration [20].

Crude Jatropha oil contains about 14% of FFA, which is far beyond the 1% limit for promoting transesterification reactions to occur using an alkaline catalyst [15]. It has been reported that transesterification will not occur if the FFA content in the oil is above 3% [6]. Many pretreatment methods have been proposed and established, including steam distillation, extraction by alcohol and esterification by acid catalysts. However, the esterification of FFA with methanol in the presence of acidic catalysts is the most commonly applied method because the process is simple and acid catalysts will utilize the free fatty acids in the oil and convert into biodiesel [5].

Much research work has been reported for the successful pretreatment of the high FFA of Jatropha oil. Patil and Deng [6] have achieved a high yield of biodiesel from Jatropha curcas oil with pretreatment conditions using a methanol to oil ratio of 6:1, 0.5% (v/v) of H2SO4 at 40 °C after 120 min. The FFA content of crude Jatropha oil was also reduced successfully to less than 1% with a 60%w/w methanol to oil ratio in the presence of 1%w/w of H2SO4 (based on weight of oil) as an acid catalyst in a 1 h reaction at 50 °C [20]. Azhari et al. [10] have conducted an optimization study to lower the FFA content of crude Jatropha oil via an esterification process using H2SO4 as a catalyst. The final FFA of the Jatropha oil was reduced from 25.3% to 0.5% at 60 °C under atmospheric pressure, using a 60%w/w of methanol to oil ratio, a catalyst loading of 1%w/w (based on weight of oil) and 180 min of reaction time. Further, Tiwari et al. [15] utilized the central composite rotatable design (CCRD) arrangement of response surface methodology (RSM) to predict the optimized reaction variables for the pretreatment process. The optimum combination for reducing the FFA of Jatropha curcas oil from 14% to less than 1% was found to be 1.43% v/v of H2SO4 acid catalyst, a 28% v/v methanol to oil ratio and 88 min of reaction time at 60 °C.

Another pretreatment approach for high FFA feedstock is to use a solid acid catalyst. Solid acid catalysts offer some advantages for eliminating separation, corrosion toxicity and environmental problems, but the rate of reaction in the esterification process is slower as compared to conventional liquid acid catalysts [5]. Lu et al. [14] have performed the FFA pretreatment process of crude Jatropha curcas oil, catalysed by liquid H2SO4 and a solid acid catalyst SO42−/TiO2 prepared by calcining metatitanic acid. Under the conditions of 12%w/w of methanol to oil ratio, a 1%w/w of H2SO4 (based on weight of oil) at 70 °C, the acid value of the oil was lowered from 14 mg KOH/g of oil to below 1 mg KOH/g of oil in 2 h. The FFA conversion achieved 95.6%. As for the solid catalyst, the optimum condition for pretreatment of Jatropha curcas oil were 20:1 for a molar ratio of methanol to FFA, 4 wt% of solid catalyst at 90 °C in 2 h. The conversion of FFA reached 97%. Both catalysts are able to reduce the FFA content of Jatropha curcas oil effectively. However, due to the lower activity of the solid catalyst, a higher molar ratio, catalyst loading and reaction temperature are required for the solid catalyst to achieve comparable efficiency.

Currently, the most common feedstock for biodiesel production is edible oils such as soybean, rapeseed, canola, sunflower, palm, coconut and also corn oil. However, this practice has raised objections from various organizations, claiming that biodiesel is competing for resources with the food industry. In many countries, such as India or China, edible oils are not in surplus supply and therefore it is impossible to use them for biodiesel production as they are needed more for food supply [11], [12]. India accounts for 9.3% of world's total oil seed production and is considered to be one of the promising edible oil producing countries. Even so, about 46% of edible oil is imported to cater the consumption need. The same goes for China with an annual import of 400 million tons of edible oils for the country's needs [13], [14].

Among various oil bearing seeds, Jatropha curcas has been found more suitable for biodiesel production as it has been developed scientifically to give better yield and productivity [13]. This non-edible oil is explored as a source for biodiesel production without compromising the food industry [3], [4]. In addition, the oil percentage and the yield per hectare are important parameters in selecting the potential renewable source of fuel. Production of non-edible oil seeds and the percentage of oil content are given in Table 2. Non-edible oils are not suitable for human consumption because of the presence of some toxic components in the oils. Therefore, Jatropha oil is considered a non-edible oil due to the presence of these toxic phorbol esters [5], [12].

Jatropha curcas is a drought-resistant tree belongs to the Euphorbiaceae family, which is cultivated in Central and South America, South-east Asia, India and Africa. It is easy to establish, grows almost everywhere even on gravelly, sandy and saline soils. It produces seeds for 50 years with a high oil content of about 37% or more. The oil from the seeds has valuable properties such as a low acidity, good stability as compared to soybean oil, low viscosity as compared to castor oil and better cold properties as compared to palm oil. Besides, Jatropha oil has higher a cetane number compared to diesel which makes it a good alternative fuel with no modifications required in the engine [3], [4], [13]. However, most non-edible oils contain a high level of free fatty acids (FFA) which is undesirable as it lowers the yield of biodiesel. This is because a high FFA (>1%w/w) will promote more soap formation and the separation of products will be difficult during alkali-catalysed transesterification. Eq. (1) shows the undesired saponification reaction which form soap and water when sodium hydroxide is used as the catalyst [5], [20]. Jatropha oil contains about 14% of FFA which is far beyond the acceptable limit of a 1% FFA level. Thus, pretreatment step to reduce the FFAs of feedstock is required for a better biodiesel yield [15].R1COOH(FFA)+NaOH(sodiumhydroxide)R1COONa(soap)+H2O(water)

Martin et al. [16] have identified Jatropha curcas as the most promising oil seed for biodiesel production in Cuba after comparison with various non-edible oil seeds because of the high oil yield of Jatropha at about 50%. Since Jatropha oils consist of mainly oleic and linoleic acids which are unsaturated fatty acids, the biodiesel produced has desirable good low temperature properties. Although Jatropha oil also has high free fatty acid content, methods to overcome this high FFA are well developed. Thus, Jatropha curcas oil has been highlighted as a potential biodiesel feedstock among the non-edible oils. Table 3 tabulates the composition and characteristics of Jatropha curcas oil.

Apart from being potential feedstock in the production of biodiesel as a diesel substitute, Jatropha oil has other uses such as producing soap and biocides (insecticide, molluscicide, fungicide and nematicide) [17]. Further, as the stability of biodiesel is highly critical to meet storage requirements, usually biodiesel requires the addition of an antioxidant. Appropriate blends of Jatropha and palm biodiesel have been established in order to minimize the dosage of antioxidant needed as Jatropha biodiesel has good low temperature properties but a poor oxidation stability, whereas palm biodiesel has a good oxidative stability with poor low temperature properties. The blending and combinations of Jatropha and palm give an additive effect on these critical properties of biodiesel [18]. Moreover, direct use of Jatropha oil without any modifications can be used in older engines and motors equipped with current technologies such as pumps and generators running at a constant speed [19].

Section snippets

Biodiesel and its properties

Biodiesel stands for a variety of ester based oxygenated fuels derived from renewable biological sources. In other words, biodiesel refers to a vegetable oil or animal fat-based diesel fuel consisting of long-chain alkyl (methyl, ethyl or propyl) esters or alkyl esters of fatty acids. It is a non-toxic, biodegradable and renewable fuel which can be used in compression ignition engines with little or no chemical modifications with significantly lower emissions than petroleum-based diesel when it

Main factors affecting the yield of biodiesel

There are few important variables that influence the transesterification reaction. In order to obtain maximum yield of biodiesel, these variables must be at their optimum.

Economic aspects of biodiesel

Biodiesel has become more attractive recently due to its environmental benefits and the fact that it is sustainable because it is made from renewable sources. It has several outstanding advantages as an effective alternative fuel with a lower level of pollution. However, the cost of biodiesel is the major challenge as it varies depending on the feedstock, processing, transporting, the price of crude petroleum and others [1], [21].

Vegetable oils are renewable and a potential source of energy

Environmental considerations

Biodiesel is considered to be carbon neutral because the carbon dioxide released into the atmosphere during its consumption as a fuel is been recycled and reused for the growth of vegetable oil crops [9]. Biodiesel has a higher cetane number than diesel because of its long chain fatty acids with 2–3 double bonds, it is without aromatics and contains 10–11% oxygen by weight. These characteristics of biodiesel reduce the emission of carbon dioxide (CO), hydrocarbon (HC) and particulate in the

Conclusions

The problem of diminishing petroleum reserves and the increasing awareness of environmental pollution from petroleum fuel emissions have led to the urge to find renewable alternative fuels as a substitute for petroleum based fuel. Biodiesel, which has environmental benefits and is produced from renewable resources, has become more attractive recently. Jatropha curcas is becoming a potential feedstock for biodiesel production due to its suitable characteristics. Jatropha oil has a higher cetane

References (52)

  • C. Martin et al.

    Fractional characterization of jatropha, neem moringa, trisperma, castor and candlenut seeds as potential feedstocks for biodiesel production in Cuba

    Biomass and Bioenergy

    (2010)
  • R. Sarin et al.

    Jatropha-palm biodiesel blends: an optimum mix for Asia

    Fuel

    (2007)
  • W.M.J. Achten et al.

    Jatropha bio-diesel production and use

    Biomass and Bioenergy

    (2008)
  • H.J. Berchmans et al.

    Biodiesel production from crude Jatropha curcas L. seed oil with a high content of free fatty acids

    Bioresource Technology

    (2008)
  • S.P. Singh et al.

    Biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of biodiesel: a review

    Renewable and Sustainable Energy Reviews

    (2010)
  • K.G. Georgogianni et al.

    Transesterification of rapeseed oil for the production of biodiesel using homogeneous and heterogeneous catalysis

    Fuel Processing Technology

    (2009)
  • A.S. Ramadhas et al.

    Biodiesel production from high FFA rubber seed oil

    Fuel

    (2005)
  • P. Chitra et al.

    Optimisation of experimental conditions for biodiesel production from alkali-catalysed transesterification of Jatropha curcas oil

    Energy for Sustainable Development

    (2005)
  • P.K. Sahoo et al.

    Process optimization for biodiesel production from Jatropha, Karanja and Polanga oils

    Fuel

    (2009)
  • A.P. Vyas et al.

    A review on FAMA production processes

    Fuel

    (2010)
  • X. Miao et al.

    Effective acid-catalyzed transesterification for biodiesel production

    Energy Conversion and Management

    (2009)
  • L.C. Meher et al.

    Technical aspects of biodiesel production by transesterification—a review

    Renewable and Sustainable Energy Reviews

    (2006)
  • N.U. Soriano et al.

    Biodiesel synthesis via homogeneous Lewis acid-catalyzed transesterification

    Fuel

    (2009)
  • S. Tamalampudi et al.

    Enzymatic production of biodiesel from Jatropha oil: a comparative study of immobilized-whole cell and commercial lipases as a biocatalyst

    Biochemical Engineering Journal

    (2008)
  • S. Hawash et al.

    Biodiesel fuel from Jatropha oil via non-catalytic supercritical methanol transesterification

    Fuel

    (2009)
  • Z. Ilham et al.

    Two-step supercritical dimethyl carbonate method for biodiesel production from Jatropha curcas oil

    Bioresource Technology

    (2010)
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