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Thursday, May 5, 2022

Limitations of Jatropha Curcas Seed Oil for Biodiesel Processing in Nigeria - Juniper Publishers

Recent Advances in Petrochemical Science - Juniper Publishers

Abstract

Scientists are looking far and wide for the raw material that will yield a new generation of advance biofuel, a source that does not divert food into energy, and is abundant enough to make a significant change in the oil market. In this paper, the process of refining the raw Jatropha curcas oil before transesterification was investigated. The study of its oil yield was also investigated with values of 17.43, 11.87% and 10.05% from different sources. The financial viability of Jatropha curcas seed oil for biodiesel production was evaluated and it revealed that the process consume much time and energy. This investigation revealed that, the use of Jatropha curcas oil for biodiesel production is not financially viable in Nigeria as at now. It was also found that the longer the oil is kept the more it deteriorates.

Keywords: Biodiesel; Jatrophacurcas oil; Limitation; Nigeria; Production

Introduction

Energy security, dependence on fossil oil and gas resources, and the negative consequences associated with global warming due to continuous greenhouse gas emissions have indicated serious concern. These have prompted significant interest in the development of low carbon and sustainable advance biofuels [1]. like biodiesel from nonfood feedstock. The Biofuels comprise of Solid, liquid and gas. The most commonly used of biofuels is the liquid among which are biodiesel, bioethanol and biobutanolin transportation sector. There is an increasing interest in alternative energy sources [2] because of their sustainability and environmental acceptability. Biodiesel has being discovered to be a good replacement for petroleum diesel because it has properties similar to fossil diesel [3]. In addition it lubricates the engine better than petro-diesel which can increase the engine life. Biodiesel reduces the lifecycle of carbon dioxide emissions by almost 70% compared to conventional diesel fuel [4]. The use of biodiesel will reduce the emission of greenhouse gas which is a major concern of scientists today. The use of biodiesel has been accepted worldwide in diesel engines though not 100% but as blend B20 in U.S and B10 in EU. With this blending formula the reduction in greenhouse emission is still achieved.

The first generation of biodiesel feedstock such as edible vegetable oils, remains highly contested and is currently the source of a heated debate on the threat that energy security poses to food security. This debate has stimulated a new interest in the exploration of the second generation of biodiesel feedstock, based on the conversion of non-edible vegetable oils biomass into energy. The second generation biodiesel feedstocks are sourced mainly from non-edible sources such as Jatropha, algae and Ceiba pentandra. A lot of nonfood feedstocks such as Simmondsiachinesis, Pongamia (Derris indica), Garcinia indica, Madhuca indica, Ricinuscommunis, Simaroubaglauca, Citrulluscolocynthis, Algae, etc. have been identified by centre for biodiesel production by renewable energy research scientists [5]. The second generation feed stocks are considered more sustainable as they generally offer greater levels of GHG reduction and do not use food crops as a feedstock. Scientists are looking far and wide for the raw material that will yield a new generation of advance biofuel, a source that does not divert food into energy, and is available abundantly enough to make a significant impact in the oil market.

Jatropha curcas Linnaeus, is a shrub and toxic tree with smooth gray bark, belongs to the family Euphorbiaceae [5]. Jatropha, a crop native to North American region is now distributed in several regions across the World [6]. The production of biofuel is driven by geopolitical concerns of fuel prices, realization that fossil fuel supply is finite and benefits for rural economies [7]. Since Jatropha curcas oil is non-edible the development of biodiesel in Nigeria has focused around Jatropha curcas seed oil. Cultivation of Jatropha for biodiesel production is desirable however; there are currently concerns about the low quantity of oil yield [8]. So far Jatropha boom has produced more losers than winners [9]. According to Matlack [7], Jatrophacan indeed grow on barren land, it doesn’t flourish there. Without moisture it does not seed or it seeds extremely poor. Jatropha curcas seed oil has a lot of free fatty acid [10] and phorbol ester a toxic substance which rendering it non-edible as presented in Table I.Jatropha curcas has two major genotypes; the toxic and non-toxic. The toxic genotype has phorbol ester a toxic substance. The non-toxic Jatropha curcas variety is only found in Mexico and is phorbol ester free [9].

Phorbol ester (phorbol 12-myristate acetate) has been identified as the major toxic compounds in Jatropha curcas seed and seed oil [11]. According to Ahmed and Salimon, [10] this phorbolester can cause biological effect in man and animal such as growing tumor. According to Li et al. [11] phorbol ester promotes tumor growth following exposure to sub carcinogenic dose of carcinogen. It has also been reported that phorbol esters in Jatropha curcas oil exhibit insecticidal and mulluscicidal activities over wide range of living organisms [11]. Other toxic substances in Jatropha oil including; saponins, lectins (curcin), phtates, protease inhibitors and carcalonic acid which is a strong purgative [10].

In this study, Jatropha fruits were harvested from the farm of National Research Institute for Chemical Technology (NARICT), Zaria Nigeria, shelled and oil was pressed out. The oil yield and the oxidation of un-kept oil were investigated. Also, some quantity of Jatropha seeds was bought from Institute for Agricultural research (IAR) Ahmadu Bello University, Zaria and Kano-Nigeria and their oil yields were also investigated. The Investigation on the process of refining the oil for biodiesel production was carried out. Also the cost per litre of its oil was investigated at the time in this study.

Materials and Methods

Materials

The materials used in this study include; mortar and pestle, grinding machine, oil pressing machine, weighing balance, sulphuric acid, methanol and CaO catalyst.

Method

Seed processing: After harvesting from the farm the fruits were shelled to obtain the seeds. These were done manually by breaking the hull and free the seeds. The seeds were pilled to obtain the kernels which were weighed and bagged ready for pressing.

Oil Processing: 30kg mass of freshly harvested seeds were mechanically pressed to obtain oil direct from oil pressing machine shown in Figure 1. The oil obtained direct from the pressing machine contained particles of the cake which was kept for two days to settle. After settling, the oil was decanted and filtered to obtained clean oil. The sediment was further pressed to obtain more oil locked in it. Later more oil was extracted from two bags of dry Jatropha seeds brought from Kano weighed 66.67kg by the same pressing process though age after harvest unknown. 21.3kg of three years old Jatropha seed from Institute of Agricultural Research (IAR) Ahmadu Bello University, Zaria was pressed too. The oil samples from wet and dry Jatropha curcas seeds obtained were weighed to determine their yields. The process is diagrammatized in Figure 2.

Refining of raw oil for biodiesel production: 1.5g of Jatropha oil was diluted in 25mL of isopropyl alcohol and was titrated against 0.1 M KOH to pink. From the titre value the percentage Free Fatty Acid (%FFA) was calculated from Equation 1 and acid value from Equation 2. The oil was esterified with methanol and sulphuric acid. The quantity of methanol required for esterification was calculated from Equation 3. The quantity of sulphuric acid was calculated from Equation 4. Equation 5 expresses the esterification reaction [1]. The mixture of sulphuric acid and methanol was added to the oil at 60 °C and left at this temperature for 60 minutes. The esterified oil was transferred into separating funnel and left for at least two hours. It was separated out into oil and acid solution. The esterified oil was titrated as before to determine its new FFA. This process was repeated until satisfactory FFA of 0.5 obtained.

where, %FFA, is percentage free fatty acid, v is the titre value and m is the mass of oil sample.

The required amount of methanol using Gerpen et al. [1] method is expressed in eqn. 3,

m = 2.25 xmass of oil x %FFA (3)

The required amount of sulphuric acidis expressed in eqn. 4,

Monitoring the rise in FFA of Jatropha oil: Old Jatropha oil was tested for FFA as described above. It was left uncared for 4 weeks and its FFA was tested in the interval of 2 weeks.

Results and Discussion

Oil Yield

According to Biozio[12], good cultivation practices are the key determinants for achieving favorable yields from Jatropha. There is a misconception that the Jatropha plant requires little water and that it requires almost no inputs in terms of fertilizers and pesticides. The quantity of oil obtained from 30kg of the seed was 5229.2g (5.7 litres) making 17.43% the mass of seed. The mass of the oil yield from dry sample of 66.67kg collected from Kano (though the age of store and specie’s name were not known) was 7913.8g (8.6 litres) making 11.81% yield. 2.33 litres of oil was obtained from 21.3kg three years old seeds from Institute of Agricultural Research Ahmadu Bello University, Zaria. This yielded 10.05% oil as presented in Table 2. The first and the third samples were Jatropha curcas Linnaeus specie. These yields were too poor compared to exaggerated value of 30 to 40% [6]. Ahmed and Salimon [10] reported oil yield of 33.73%, 32.7% and 30.5% from Jatropha seeds from Malaysia, Indonesia and India respectively. The authors claimed to have used mechanical extraction method which is same process as ours. More close to fact was 22.97% oil yield claimed by Nakpong and Wootthikanokkhan [13]. Over enthusiastic or unscrupulous promoters have misled people about the prospect of Jatrophacurcas plant [7]. The claim of 10 tons of seeds per ha annually has never been found realistic. Jatropha is good for its short gestation period and regular seed harvest are possible within four years of establishment [14]. The yield depends on the care and inputs to the farm.

The FFA of the fresh seed oil was found to be 3. Freshly extracted Jatropha curcas seed oil has low free fatty acid content but not as low as edible oil. Acid content gradually increases as long as the oil is kept. The presence of light, heat and moisture catalyze the oxidation of the oil. Fatty acid compositions of Jatropha curcas seed oil vary according to the type of cultivation and storage mechanisms [15].

Jatropha curcas oil is highly acidic. A sample had free fatty acid value of 17.95took four times esterification to bring its acid value to 0.43. For solid base catalyzed transesterification, the free fatty acid value of oil has to be reduced to less or equal 0.5. This process is time and energy consuming and labour intensity. A little quantity of the original oil sample was kept after 14 days the oil was tested and was found to have 20.76 FFA. After another 14 days the FFA rise to 30.86. This indicates that the longer the oil is kept the more it oxidizes and deteriorates. Considering the cost of esterification of the oil, definitely the cost of production of the biodiesel will rise by using Jatropha curcas oil for biodiesel production. For homogenous catalysis, high acid value leads to saponification which inhibits the formation of methyl esters (biodiesel) and waste of catalyst [3,16] as shown in Figure 3. The acid value of the freshly extracted oil was found to be 3.0 therefore; it is cheaper to process the freshly extracted oil into biodiesel. This would reduce the quantity of alcohol, time and energy require for refining it for biodiesel processing. From Table 1, the major glyceril triglycerides in Jatropha curcas oil can be estimated as presented in Table 3.

Jatropha Oil Cost

In Nigeria there is no fixed price for Jatropha curcas seeds or the oil. The price depends on the bargaining power of buyer and seller. The Institute of Agricultural Research, (IAR) Zaria, sells N500/kg of seeds. This was the cheapest in Nigeria as at the time of this investigation. Individual farmers sold it at higher prices. Based on the cost price of IAR the wet oil from NARICT farm cost N2 631.58/L ($8.63/L).The dry seed oil bought from Kano cost N2 906.63/L ($9.53/L) and the three years old dry seeds bought from IAR cost N4 484/L (14.70/L) respectively on the N305 per $. Yet the cost of extraction of oil from the seeds is not included. At this cost in Nigeria the use of Jatropha for biodiesel production is not economically viable. The cost of Jatropha in Nigeria is too high compared to International market cost of $1.50/L, (N457.50/L) [17]. More indigenous seed oils should be explored for biodiesel processing.

Actually, the Jatropha boom has produced more losers than winners. Many projects have foundered as seed production has failed to meet expectations, as a result, India, China, and other countries have scaled back plans for additional planting [7]. Failure is not only on the seed yield but also the oil yield which is found here below 20% as against 30-40% claimed by some promoters. Jatropha can indeed grow on barren land but it doesn’t flourish there [12].

Biodiesel yield

Jatropha curcas oil has good biodiesel yield if it is well refined. Ibrahim et al. [18] carried out comparative study of biodiesel yield from Jatropha curcas oil and palm oil, under the same reaction conditions, Jatropha had a better yield. Endalew et al. [14] had 100% conversion of Jatropha oil to biodiesel catalyzed by CaO + Fe₂(SO)₃.

Conclusion

An investigation was carried out on the viability of Jatropha curcas seed oil for biodiesel production in Nigeria. The oil oxidizes progressively with time. Its refinement consumes much methanol or whichever alcohol is used for esterification which would raise the cost of biodiesel production. It is too expensive in Nigeria to use Jatropha oil. especially for biodiesel production. More other indigenous non-edible plant seed oils should be explored for biodiesel production. Well refined Jatropha oil yielded more biodiesel than palm oil under the same reaction conditions Ibrahim et al. [18], but rely on Jatropha alone cannot meet the demand for biodiesel.