A review of processing and machinery for Jatropha curcas L. fruits and seeds in biodiesel production: Harvesting, shelling, pretreatment and storage Bo Yuan Lim a , Rosnah Shamsudin a,n , B.T. Hang Tuah Baharudin b , Robiah Yunus c a Department of Process and Food Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia b Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia c Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia article info Article history: Received 6 November 2014 Received in revised form 15 May 2015 Accepted 11 July 2015 Keywords: Jatropha curcas L. Process mechanisation Harvesting Pretreatment Shelling process Seed storage abstract The harvested Jatropha fruits need to be cleaned, dehulled and stored properly as part of the production of Jatropha biodiesel. During processing, the oil yield and quality of the extracted crude oil can be further improved by removing the husks (outer coating) of the seeds before any necessary seed treatment. This report attempts to provide an insight into the major issues of the process from harvesting the Jatropha fruits to the final storage of the seeds and pretreatment of the Jatropha seeds prior to the oil extraction process in production. This report describes a few aspects of the processes including common methods, research and technologies involved so that some improving strategies can be devised. The final part of this report also describes current development trends and the future prospect of Jatropha as a biodiesel. The paper has determined that both the harvest and shelling processes are basically performed manually, especially in rural areas. These activities are time consuming and introduce a high labour cost (80% of the feedstock cost) that can potentially make the Jatropha oil economically uncompetitive. A solution consisting of process mechanisation and mechanical device development are proposed to improve the sustainability of the industry and to meet the increasing world demand. An improvement in oil yield can also be achieved by fruit/seed pretreatment such as drying, shelling and heating. However, improper control may lead to the formation of oxidation products such as free fatty acids which will affect the efficiency of biodiesel production. This is an important sustainability issue which is related to the future development of Jatropha biodiesel. & 2015 Elsevier Ltd. All rights reserved. Contents 1. Introduction ........................................................................................................ 992 2. Botanical description of Jatropha curcas L. ................................................................................ 992 3. Jatropha fruit harvesting .............................................................................................. 993 4. Jatropha fruit pretreatment ............................................................................................ 994 5. Shelling Jatropha fruits ............................................................................................... 994 5.1. Removal of outer shells from whole fruits .......................................................................... 994 5.2. Removal of husks from seed ..................................................................................... 995 6. The use of physical and mechanical properties of Jatropha for equipment design ................................................ 997 7. The use of shells and husks ........................................................................................... 998 8. Storage of seeds ..................................................................................................... 999 9. Suggested pretreatment steps for oil extraction ........................................................................... 999 10. The cost of Jatropha postharvesting ..................................................................................... 999 11. The current development of the Jatropha industry in Malaysia and future prospects ............................................. 1000 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews http://dx.doi.org/10.1016/j.rser.2015.07.077 1364-0321/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ60 3 89466366; fax: þ60 3 86567123. E-mail address: [email protected](R. Shamsudin). Renewable and Sustainable Energy Reviews 52 (2015) 991–1002
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A review of processing and machinery for Jatropha curcas L. fruitsand seeds in biodiesel production: Harvesting, shelling,pretreatment and storage
Bo Yuan Lim a, Rosnah Shamsudin a,n, B.T. Hang Tuah Baharudin b, Robiah Yunus c
a Department of Process and Food Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysiab Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysiac Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
a r t i c l e i n f o
Article history:Received 6 November 2014Received in revised form15 May 2015Accepted 11 July 2015
The harvested Jatropha fruits need to be cleaned, dehulled and stored properly as part of the productionof Jatropha biodiesel. During processing, the oil yield and quality of the extracted crude oil can be furtherimproved by removing the husks (outer coating) of the seeds before any necessary seed treatment. Thisreport attempts to provide an insight into the major issues of the process from harvesting the Jatrophafruits to the final storage of the seeds and pretreatment of the Jatropha seeds prior to the oil extractionprocess in production. This report describes a few aspects of the processes including common methods,research and technologies involved so that some improving strategies can be devised. The final part ofthis report also describes current development trends and the future prospect of Jatropha as a biodiesel.The paper has determined that both the harvest and shelling processes are basically performedmanually, especially in rural areas. These activities are time consuming and introduce a high labourcost (80% of the feedstock cost) that can potentially make the Jatropha oil economically uncompetitive. Asolution consisting of process mechanisation and mechanical device development are proposed toimprove the sustainability of the industry and to meet the increasing world demand. An improvement inoil yield can also be achieved by fruit/seed pretreatment such as drying, shelling and heating. However,improper control may lead to the formation of oxidation products such as free fatty acids which willaffect the efficiency of biodiesel production. This is an important sustainability issue which is related tothe future development of Jatropha biodiesel.
Fossil fuels such as crude oil, coal and natural gas have beenwidelyused for generating electricity and for vehicle power, heat and manyother purposes. However, the high reliance on fossil fuels for thedevelopment of the country has led to the problem of over usagewhich consequently means that fossil fuels are in danger of exhaus-tion. The price hikes and unstable supplies of fossil fuels in the globalmarket can also affect the economies of developing countries. In 2013,the usage of crude oil, coal and natural gas together reached morethan 80% of the total energy consumption of the World [1]. Further,the overall world energy demand is estimated to keep growing by 37%from 2013 to 2035 [2]. The statistics show the world strongly relies ontraditional fossil fuels as a primary resource to generate energy inorder to fulfil current demand.
The high demand placed on energy and fossil fuels as a mainresource has drawn attention towards developing sustainable energyto confront the fossil fuel depletion issue. Among the alternativeresources, biodiesel which has the same function as diesel, is gainingworldwide acceptance and has been reported as a promising sub-stitute for conventional diesel [3]. Biodiesel is derived from vegetableoil or animal fats for use in a compression ignition engine [4]. Blendsof 20% (B20) or lower of biodiesel can be used with minor or noengine modification [5]. Biodiesel also produces less carbon dioxide,carbon monoxide, sulphur dioxide, hydrocarbons and particulatematter [6]. Thus, the mix will directly reduce the dependence onfossil fuel as well as reduce the impact on the environment. Inaddition, the world trend shows the usage of fossil fuel based dieselis slowly being replaced by biodiesel.
Different vegetable oils are used in different countries for biodieselproduction. The United States is an exporter of edible oil. The countryuses soybean for biodiesel production. The European countries userapeseed oil as the raw material. Tropical countries such as Malaysiause palm oil or coconut oil for the purpose. However, India is trying toreduce its reliance on edible oils. Therefore, India prefers using non-edible oils such as Simarouba, Jatropha and Karanja to producebiodiesel [7]. In order to be a future prospective fuel, biodiesel mustbe readily available, economically competitive, technically feasible andenvironmentally friendly [8]. It has to compete economically withpetroleum diesel fuels. One of the means to reduce the cost is to usethe less expensive sources of fatty acids such as animal fats, wastefood oil, inedible oils and the by-products of refining vegetablesoils [9].
The plant sources that are currently used as the feedstock forbiodiesel production include coconut oil, palm oil, rapeseed, soyabean,jatropha and so forth. Most of them are edible and require a large areaof land for growing. Over usage of food based crops in the biodieselindustry will eventually cause a food crisis problemwhich can impacthuman life. Inedible vegetables oils, mostly produced by tree bearingoil (TBO) seeds and shrubs, can provide a more suitable alternative.The current world emphasis is focused in terms of food securityduring feedstock selection with ongoing bioenergy development. Thecultivation of biodiesel feedstock should not compromise future needsin terms of food supply [10]. Hence, with no displacement of foodcrops and disturbance of food production, the focus has shifted toJatropha curcas L. to be the energy crop of choice [11–14]. The wideacceptance of Jatropha is mainly due to the high adaptation ofJatropha trees to marginal or waste land. Moreover, the requirementfor nutrients and water is lower for Jatropha because it is a perennial
crop which has a deeper root system to help retain water andnutrients more effectively [15,16,89]. There are many benefits offeredby Jatropha including reclamation of waste land, control of erosionand stimulation of rural development [17–19].
There are few steps involved in the production of Jatropha biodieselincluding cultivation, harvesting, fruit pretreatment, oil extraction, oilpurification and biodiesel production [14,20] (Fig. 1). High productionof biodiesel is required to cope with the depletion of current energysources. Hence, a large amount of Jatropha seeds need to be preparedprior to the oil extraction process in order to meet the demand.
Jatropha is a promising crop for biodiesel production but thetechnology is still in its infancy [24,25]. The development is still inprogress but not much has been realised to date. Further, most of thestudies focus on Jatropha plantations, oil extraction and biodieselproduction. However, a comprehensive study on Jatropha post-harvesting has not been widely carried out at present. The objectiveof this review is to share the most recent knowledge of the processingof Jatropha prior to extraction. It is important to compile informationabout the collection and processing of seeds as the activities havebecome one of the major challenges in the Jatropha cultivationprogramme [90]. Within this context, the primary focus will be onthe fruit harvesting, fruit pretreatment, the shelling process and seedstorage as part of Jatropha biodiesel production.
2. Botanical description of Jatropha curcas L.
J. curcas L., also known as the physics nut, belongs to theEuphorbiaceae family [23,26]. It is a drought resistant shrub andis well adapted to arid and semi-arid conditions [27]. It can beplanted under a wide range of rainfall regimes from 250 mm/annum to over 3000 mm/annum [28,29]. It is a perennial crop. Theroots grow vertically and laterally into deeper soil and thisstructure helps the plant to efficiently store nutrients and water[15,30].
The shape of the fruit is ovoid oblong and resembles an “Americanfootball”. The outer shell is green when it is fresh [31]. J. curcas L. canbe propagated reproductively through direct seeding or transplantingby stem cutting [15]. Normally, it grows up to 5 m in height [15]. Aheight of 8 m or 10 m can be achieved under favourable conditions[14]. The tree is a succulent plant that sheds its leaves during droughtor under conditions of stress [29]. The Jatropha tree starts to producefruits after six months and the yield becomes stable when the plant is1–3 years old [32]. The lifespan in terms of seed productivity is in therange of 50 years [33]. The Jatropha is native to Mexico and SouthernAmerica countries such as Belize, Costa Rica, El Salvador, Paraguay,Bolivia, Honduras, Nicaragua, Brazil, Peru, Argentina and Guatemala[34]. It has beenwidely cultivated throughout tropical and sub-tropicalregions in China, Malaysia, Indonesia, India, sub-Saharan Africa,Tanzania etc. [6,7,14,15,19,27,34–38].
The seed yield has been reported as 0.2–12 t/ha depending on thegrowing conditions [7,17,32]. The oil yield can achieve 1590 kg/ha [19].Other research has stated that the oil yield of Jatropha seeds iscompetitive compared to soybean and rapeseed which both producelesser oil by weight [39]. Further, the Jatropha oil can be converted tobiofuel which easily meets the American and European standards[40,41]. The Jatropha seeds (2–3 seeds in each fruit) are covered byshells (the outer layer of fruit) in each fruit. The seed itself consists ofhusk (the outer coating of the seed) and kernel (the nucleus of the
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seed) as shown in Fig. 2. The fruits contain 35–40% of shells by weightand 60–65% of seeds by weight while the seeds consist of 40–42%husks and 58–60% kernels by weight [6]. The seeds are black and thepure kernels are white. Further, the seeds are toxic due to the presenceof phorbol esters [42]. Both the shells and husks do not contain any oil.Around 30–55% of the oil is stored in the nucleus that needs to berecovered using a screw press or by using the solvent extractionmethod for biodiesel production [14,31,43,44].
3. Jatropha fruit harvesting
The harvest starts in the third year after planting since the fruityield for the first two years is too low [45]. The fruits becomemature when the colour changes from green to yellow [22]. Themature fruits remain on the branches and become brittle and
black when dried under the sun [32]. Jatropha fruits are bestharvested when mature (yellow-brown) [15]. Jatropha seed yieldis still difficult to predict, the earlier reported yield showing a verywide range (0.4–12 t/ha/yr) [15,27].
Another issue is that the Jatropha fruit ripening is unevenmaking harvesting a challenging process. Basically the harvestingcannot be completed at one time, unlike for rice and other crops,due to the fact that the fruits ripen over a long period of time andrequire a few weeks to months of picking [23,46,91]. Further, thelow density of fruits in the field is a cause of concern because ofthe greater distance required to transport the fruits in the field.The fruits are basically hand-picked. Sometimes, the workers use along stick to hit the fruits or shake the tree during harvesting [32].This method is strenuous and can cause the fruits to fall on thegrass. Therefore, a long wooden stick, with a circular comb and abag at one end, has been invented to make the harvesting processeasier [21,47]. The fruits can be directly collected in the bag on thestick. In Tanzania, a pole is used to pull down the branches of a treeto reach the higher fruits [37].
In order to ensure quality harvesting, the proper tools andbaskets should be provided. In the Philippines, a harvesting shearhas been developed as shown in Fig. 3 [48]. The fruit is insertedinto the slots of the tool which is then pulled and the fruit shearedduring harvesting. A bucket is connected to the harvesting shearby a flexible hose in order to convey the harvested fruits directlyinto the bucket. Further, a motorised harvesting rod has also beendeveloped to pull the fruits from the tree using a rotating claw[48]. Training on the use of the tools has to be conducted in orderto improve the effectiveness of the harvesting activity. Further, theshading of neighbouring crops can be reduced through pruning tofacilitate harvesting [15,27].
There is a large variation in harvesting rate as tabulated in Table 1as it depends on the picking method and plantation strategies (space,nutrients, water) [17,49]. The fruits have to be harvested manually atregular intervals causing this step to be very labour intensive and thispotentially affects the production cost [27]. Mechanisation of theprocess has been proposed to mitigate the cost issue. FACT in 2010stated that Viridas PLC (a Brazilian company) gave a presentationabout a prototype mechanical harvester in Jatropha World Miami2008. The conceptual designwas based on a shaker design used in theolive industry. An American company, Oxbo International Corporation,introduced the Korvan 9240 mechanical Jatropha harvester, as illu-strated in Fig. 4, that utilised a dynamic rotor to pick the fruits andallowed continuous harvesting. On the other hand, a robotic armmight be an alternative method but it is not currently feasible due tothe low density of yield and low cost of the end product.
Mechanical harvesting ensures continuously efficient harvest-ing, as well as providing cost control and a strong ability to harveston demand. Although mechanical harvesting provides severalbenefits, a suitable and convenient technology has still to bedeveloped for harvesting [37] as mechanical methods can damage
Whole fruitMean size:25.3 x 21.4 x 20.5
Whole seedMean size: 18.4 x 11.2 x 8.8
Outer shell
Husk (Seed coating)
Kernel (seed nucleus)
Fig. 2. The components of Jatropha fruits (unit: mm).
To bucket
Fig. 3. A sketch of a harvesting shear (left) and motorised harvesting rod (right)developed by the University of the Philippines Los Baños [48].
Jatropha Cultivation Fruit Harvesting Pretreatment
(Cleaning, drying,
fruit decapsulation and seed dehulling)Seeds/kernels storageOil extraction
(Screw press or
Solvent extraction)
Biodiesel production(Transesterification)
Biodiesel storage
Crude oil purification
(Sedimentation, filtration and centrifuging)
Biodiesel purification(Separation of
glycerol and biodieselwashing biodiesel
and drying)
Fig. 1. Jatropha biodiesel production process flow [14,21–23].
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flowers and tend to harvest both mature and immature fruits atthe same time [39]. Therefore, the technology might work if all themature fruits are allowed to fall down when shaken withoutaffecting the immature fruits.
4. Jatropha fruit pretreatment
Before the shelling process can take place, the fruits need to bedried since the moisture content will affect the shelling rate [24,47,51].The decrease in moisture content (11.15% w.b. to 5.83% w.b.) couldincrease the shelling efficiency of the compression rollers by around18% for one pass and 15% for a dual pass as shown in Fig. 5 [51]. It hasbeen previously reported that fruits with low moisture content arebrittle and easily damaged bymechanical force [32]. Further, thewateradds to the weight and transporting cost so that drying is a necessarystep. Direct sunlight is preferred if the seeds are not used forcultivation [47]. The fruits should be spread over a concrete floor ora plastic sheet. A solid concrete floor canmake theworkmore efficient[23]. Further, the floor should be inclined to avoid stagnating in rainwater. Sun drying is free but the time taken (7–10 days based onMehla [21]) to reach the desired moisture content is highly dependenton the environmental conditions. Adding a fan can improve the dryingrate where an electricity supply is available. Another vital step is toensure the fruits are free from small stones or other solid impurities toprevent damage to the shelling equipment.
5. Shelling Jatropha fruits
Jatropha fruit shelling is a cleaning process in which the outershells are detached from the fruits to produce clean seeds. Theseeds can be further processed to produce white kernels byremoving the husks (outer coating) from the seeds. The technol-ogy of seed cleaning is well established for other crops such asbarley, coffee and beans [52–54]. The physical characteristics usedto separate the seeds include size, length, weight, shape andsurface texture [55]. The most effective differences between theseed/kernel and undesirable material should be firstly identifiedfor the selection of a suitable separation mechanism.
5.1. Removal of outer shells from whole fruits
The cleanness of seeds decides the efficiency of oil recovery so thatthe shells should be removed prior to the subsequent oil extractionprocess [56,57]. The presence of shells allows the diffusion of oil fromthe kernels to the shells during the oil extraction process as the shellscan retain the oil in the press cake [58]. Therefore, the separation ofshells from the seeds is now normal practice for better oil yield.Further, increased shell content could potentially increase the opera-tional pressure required in the mechanical expeller and hence causeenergy wastage [59]. The oil-free husks can also be a barrier to blockthe oil emerging from the kernels and this affects the oil yield.Therefore, the whole seeds should be processed into a broken formto allow greater exposure of the oil-rich kernels to the pressing toolduring extraction [60]. However, this is not a common practicecurrently. The whole seeds are basically produced and just storedinstead of producing the broken form. It is believed that the wholeseeds are more valuable to commercialise as compared to the brokenform since the broken seeds are typically related to poor quality.
The outer shell can be removed manually or mechanically. Themanual method uses a long stick or any hard tool to beat the driedfruits in order to loosen the outer shells [27]. It can also be undertakenentirely by hand, but it is time consuming. Some workers may use awooden board to press the dried fruits on a table or a concrete floor tosplit the shells [21]. The separation of the shells and seeds does notrequire any advanced technology as it can be achieved easily usingwinnowing and sieving [21] (Fig. 6). The rural areas basically rely onlabour to remove the shells manually. The production of a largequantity of seeds using a manual method is inefficient and requires alot of labour which is costly. Only 5 kg of seeds can be recovered in3.4 h as reported by Grimsby et al. [37]. The reported major costs forfruit treatment for Jatropha biodiesel production is the labour cost[45]. This issue can restrict the development of the industry.
Other than the manual method, the implementation of a mechan-ical system in the shelling process is encouraged since a motorisedmachine can be designed to have a higher capacity and thus reducethe requirement for manual labour. Table 2 shows that most of thecommercialised shelling machines in the Jatropha biodiesel industryproduce whole seeds from whole fruits by removing the shells. The
Fig. 5. Shelling efficiency for different moisture content (data are mean values7-standard deviation) [51].
Fig. 4. A sketch of a dynamic rotor in a Jatropha curcas mechanical harvesterKORVAN 9240 [50].
Table 1Manual harvesting rate in different countries[23,37].
Country Harvesting rate
Brazil 48 kg seeds/dayCongo 40–50 kg seeds/dayHonduras 40 kg seeds/dayIndia 8 kg seeds/hIndonesia (model based) 7.5 kg seeds/hNicaragua 18 kg seeds/hSudan 3 kg seeds/hSumbawa, Indonesia 30 kg fruits/dayTanzania 2–10 kg seeds/h
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whole seeds or broken seeds are normally produced without remov-ing the husks (the outer coating of the seeds). The steps to separatethe shells from thewhole seeds can be carried out by using a screen ormesh and a blower which uses the difference in terms of size anddensity as the basis to achieve separation. The other separationdevices which might be useful for this application include a spiral
separator, an inclined belt separator, a vibrator separator, a roll milland an aspirator since the shells and seeds are also different in termsof roundness and mass according to the physical properties measuredby Pradhan et al. [32].
Figs. 7 and 8 visualise the designs of a few Jatropha shellingmachines available in the market. In summary, the machines can becategorised into two types which are either hand operated ormotorised machines. Basically, the hand operated machines have asmaller footprint and are portable and useful in rural areas where noelectricity is available. All of the motorised machines consist of acracking unit (cracking roller, impact blade, shearing mesh or shearingblade) while some of the machines are combined with a separator(vibratory sieve or air-screen unit) for a one-stop shelling process asshown in Table 3. In the cracking unit, the shearing mesh and bladeprovide stress in the fruits against the fixed part while the design ofthe cracking roller and impact blade can generate compression and animpulsive force such that the shells can be detached from the seeds.
5.2. Removal of husks from seed
Just as for the shells, the husks also do not contain any oil. Thehusks are the hard and brittle coating of the kernels. The husks can
Table 2Summary of Jatropha shelling equipment in the market [23,32,61–65].
No. Machine Input Output Discharge Supplier/developer Capacity Footprint Status
1 Universal nut sheller Wholefruit
Mixture of seed anddetached shell
No Fully Belly Project, USA 50 kg/h Unknown Commercialised
2 Hand-operated Jatrophacurcas L. fruit decorticator
Wholefruit
Whole seed Shell Indian Institute of Technology 40 kg/h Unknown R&D
3 Hand-operated decorticator Wholefruit
Whole seed Shell Rajkumar Agro Engineers Pvt.Ltd., India
30–60 kg/h Unknown Commercialised
4 Jatropha curcas ShellingMachine
Wholefruit.
Whole seed Shell Thailand National Metal andMaterials Technology Center
NA Unknown Commercialised
5 Jatropha sheller Wholefruit
Whole seed Shell Mixa Foods and Beverages,Kenya
NA Unknown Commercialised
6 Jatropha decorticator Wholefruit
Whole seed Shell Rajkumar Argo Engineers Pvt.Ltd., India
500–700 kg/h
Unknown Commercialised
7 Jatropha fruit shellingmachine
Wholefruit
Broken seed Shell Universiti Putra Malaysia 43.16kg/h 0.6 m�1.6 m R&D
8 Dehuller Wholefruit
Whole seed No Projector Tempate, LeonNicaragua
1000 kg/h 70 cm�100 cm�150 cm Commercialised
Rotating inner piece
Fruit inlet
Outlet
Rotating blade with sieve
Lower sieve
Upper sieve
Fig. 7. Examples of hand-operated shelling machines [23,32].
Motor
Rotating mesh
Fig. 6. A sketch of separator used in the Gota Verde project in Honduras [23].
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become a blocking wall to obstruct the extraction of oil from insidethe kernels. This will affect the performance of the oil recovery.The removal of the husks is not a common practice because as yetno mature technologies are available to recover the kernels on alarge scale basis. The easiest way to improve the oil yield is torupture the whole seeds into broken form as the feedstock for theoil extraction process. This allows a greater exposure of kernels tothe press tool in order to increase the extraction efficiency. Thequality of the Jatropha crude oil is also an important issue since itcan affect the quality of the biodiesel production for use in vehicles[67,68]. The husk content tends to affect the colour of crude oiland contribute to the formation of sediment in the crude oil.Achieving low husk content will definitely reduce impurities in theextracted crude oil. The efficiency of any subsequent crude oilpurification process in biodiesel production can also be improvedsimultaneously.
Greyt et al. [69] revealed that a reduction in the amount of huskscould improve the oil yield, increase the protein content and reducethe fibre content as illustrated in Fig. 9. The reported oil yield could be
improved by around 20% by reducing the husk content to 5%.However, Greyt et al. [69] commented that a zero level of husk isnot encouraged since the consequent press on the soft kernels isdifficult. This might be due to slip and the pressed kernels may turninto a paste inside the press tool. With regard to this issue, Beerens[59] reported that a reduction of the husk content to 66% could reducethe oil recovery of BT50 press due to the slip of solid–oil mixture. Amodification of the press tool to process seeds with low husk contentis necessary. Further, the higher fibre content of the undehulled seedscan increase the wear of the press. Table 4 shows the effect of huskcontent on the level of oil recovery based on previous research. A zerohusk content could improve the oil yield by 26.8%. A high qualitycrude oil should be free of impurities or sediment such as huskparticles. Therefore, one of the direct ways to improve oil quality is toreduce the husk content. A seed cleaning process has been proposedto remove the husks from the whole seeds in order to produce kernelswith purity as high as possible prior to the oil extraction process forbetter oil quality. In addition, the presence of husk content leads tomore solvent required during solvent extraction process and thus the
Rotating blade with sieve
Cracking rollers
Vibratory sieve
Shaking Air-screen
Blower
Outlet
Fig. 8. Examples of motorised shelling machines [23,62–64].
Table 3Summary of separation mechanism to produce seeds from whole fruits for the machines in the market [23,32,61–66].
1 Universal nut sheller Fully Belly Project, USA Vertical mill No2 Hand-operated Jatropha curcas L. fruits decorticator Indian Institute of Technology Impact and shear Screen3 Hand-operated decorticator Rajkumar Agro Engineers Pvt. Ltd., India Impact and shear No4 Jatropha curcas shelling machine Thailand National Metal and Materials Technology Center Cracking roller Screen5 Jatropha sheller Mixa Foods and Beverages, Kenya Impact and shear Blower6 Jatropha decorticator Rajkumar Argo Engineers Pvt. Ltd., India Impact and shear Air-screen7 Jatropha fruit shelling machine Universiti Putra Malaysia Cracking roller Screen
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husk content should be reduced in order to save the solventextraction cost.
The technology to remove the shell from the whole seed isconsidered mature as there are many types of processing equipmentavailable. Separation between the shells and whole seeds is notchallenging due to the high difference in terms of mass (the seedsare 25% heavier than the shells) [6]. However, not many mechanicaldevices exist to separate between kernels and husks due to the greatdifficulty in dehulling seeds mechanically without causing crushdamage. Breakage free kernels can be obtained only if the force isselective and applied only to the husks. The Jatropha seed is oblong inshape, has fragile cotyledons and a tough covering wall with arelatively thicker ring around the edges [21]. Therefore, dehullingcan best be achieved by compression or impact associated with ashearing action [21].
Very few seed cleaning devices are found in the market, whichindicates that the technology is still at an emerging stage. In Ghana, agroundnut cracker was modified for cracking Jatropha seeds and thedesign of the sieve in the shelling drum is shown in Fig. 10. At anoptimal setting, the blower loss, capacity and cleanliness were 2.76%(mass of kernel loss over total mass of sample), 1037.90 kg/h and88.65% respectively [72]. In China and India, the seed cleaning processhas been achieved with a large and complicated system. The wholesystem combined a few individual machines and occupied a largespace in the production area. The system basically consisted of agrading machine, a feed elevator, a seed shelling and separationmachine, a sorting machine and an air classifier as stated in Table 5.Zhengzhou Amisy Trading Co., Ltd. claimed that their system couldachieve a 90% shelling rate.
In summary, most of the machines are designed for the purpose ofdetaching and separating shell from seed. If the removal of the husksfrom the kernels is required, another seed cleaning system/deviceneeds to be added. A concept has been proposed by Universiti PutraMalaysia to recover kernels directly from the whole fruits within asingle machine as demonstrated in Fig. 11. It involves two stages,namely cracking and separation processes. Both stages consist of adouble level cracking unit and a pneumatic separation unit completewith a blower and duct to supply air movement. Both stages have asimilar design but with different roller clearances and blower speeds.Based on preliminary testing reports, the shell and husk removalachieved were 100.00% and 45.46% respectively. A total of 2.40% of the
kernels were lost throughout the various stages in the process [75].However, the technology is not mature and is still under development.
6. The use of physical and mechanical properties of Jatrophafor equipment design
The physical andmechanical properties of the Jatropha fruits, seedsand kernels are important information required to design andfabricate particular equipment and structures for processing, handling,storage and transportation [31,76–78]. The physical properties dis-cussed include moisture content, fruit size, sphericity, porosity, surfacearea, bulk density, true density, 1000 unit mass and the composition ofthe fruits.
Fig. 10. A sketch of the sieve in the shelling drum for a Jatropha seed cracker builtby Kwame Nkrumah University of Science and Technology, Ghana [72].
Jatropha fruits
Discharge Collect
First stageSecond stage
Fig. 11. The concept to recover kernels directly from whole fruits [75].
Table 4The oil yield improvement along with the reduction of husk content.
Reference Reduction of husk content (%) Oil recovery improvement
[70] 50 4–5%[71] 95 Around 20%[72] 100 26.8%
0
10
20
30
40
50
60
Undehulled 30 25 15 5Husk content (%)
Perc
enta
ge (%
)
Oil Protein Fibre
Fig. 9. Effect of husk content during the oil extraction process [69].
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The information concerning the moisture content is useful todetermine the time required for the drying process [76]. Knowl-edge of the size and shape are useful when designing theseparator, harvester, sorting device and grinding machines [76].Further, the shape can be defined in terms of the sphericity andaspect ratio which can have an impact on the material flowcharacteristic in the machine [76]. The properties such as porosityand surface area affect the resistance to airflow over the bulkmaterial bed during the drying process [76]. Furthermore, the bulkdensity, true density and 1000 unit mass are useful in determiningthe size of the storage bins required and the structural loads [76].Further, the information concerning the fraction of each part of thefruit gives an overall idea of the composition of the kernels andshells which affects the oil yield of the product.
Based on Table 6, the seed fraction shows a higher value ofsphericity than the kernels. This indicates that the kernels are moredifficult to roll along a plane. The bulk density of the fruits is lowerthan the kernels, thus revealing that the fruits require more space perunit mass as compared to the seeds and kernels. The solid density ofthe seeds and kernels are close to each other, signifying that thedensities of the husks (the coat of the seeds) and the kernels are veryclose as well, thus causing the separation of the husks from thekernels to be difficult using mechanical means. From another reportthe bulk densities for the seeds and kernels are stated as 450 kgm�³and 420 kgm�³ respectively while the solid densities are 1040 kgm�³and 1020 kg m�³ respectively [76].
The porosity of the kernels is less than the seeds. However, theresults are different as per a report by Sirisomboon et al. and Karajand Müller [31,76]. In addition, Sirisomboon et al. [76] reportedthe static coefficient of friction of the kernels was the highest of allthe surfaces studied as compared to the fruits and seeds. This isbecause the kernels are softer and have a viscous surface and thusare more difficult to move within a machine [76]. Unlike thekernels, the whole seed is harder and has a slippery surface whichenables it to move easily on a plane surface [76].
The minimum force required for the shelling process and oilextraction can be determined through a study of the mechanical
properties such as the rupture energy, rupture force and hardness [76].The energy or work used to rupture the kernels is the lowest and thatof the fruits is the highest as shown in Table 6. This suggests that thekernels can be broken easily during the shelling process [76]. Thehardness and the rupture force of the seeds are the highest as theseeds consist of a hard skin [76]. The fruits have the least hardness dueto the weak connection lines of the outer shells [76]. Further, therupture force of the kernels is much lower due to the soft texture ofthe kernels [31,76]. The deformation ratio at the rupture point can beobtained by dividing the deformation at the rupture point by thedimension of the fruit components in the direction of the appliedforce at the loading point [76]. The fruits require a lower strain torupture compared to the seeds and kernels as the deformation ratio ofthe fruit is the lowest [76]. Moreover, the angle of repose of the fruitsor seeds decides the feeder and storage design [76].
7. The use of shells and husks
The oil free shells and husks are not used in biodiesel production.They are also not valuable as fodder. The concept of zero wasteagriculture for Jatropha production has been proposed [62]. Further,Marieke Bruins commented that Jatropha oil itself will likely nevergenerate much profit [25]. It is necessary to create higher value of itsby-products in order to make Jatropha a viable biofuel in the market[92]. Therefore, the unwanted shells have been utilised as the feed-stock for biomass production as it stores energy recorded at3123 kcal/kg [62]. For the husks, the reported gross energy is19.0 MJ/kg [43] and it also has potential to be used as a burningmaterial. The shell particles have the potential to be employed as afertiliser since they consist of high levels of potassium (7.1%) and somenitrogen (0.86%) and phosphorous (0.14%) [62,79]. The husks, whichconsist of potassium (1.9%), nitrogen (0.7%) and phosphorous (0.1%),can be applied as green manure as well [43]. Further, the conversionof the seed husks into charcoal is feasible if a large quantity of huskscan be collected during production [5] (Table 7).
Table 6A comparison of physical and mechanical properties between Jatropha fruits, seeds and kernels [32,76].
Properties Fruit Seed Kernel
Seed fraction (%)a E71.68 – –
Kernel fraction (%)a E44.73 E63.02 –
Shell/husk fraction (%)a E28.32 E37.13 –
Sphericitya Highest Higher LowestBulk density (kg m�3)a Lowest Higher HighestTrue density (kg m�3)a Lowest Higher HighestPorosity (%)HYPERLINK \l "MEP_L_tbl6fna" \o "aPradhan et al., 2010. "a Highest Higher LowestAngle of repose (filling) (deg)b Smallest Larger LargestAngle of repose (emptying) (deg)b Larger Smallest LargestRupture force (N)b Higher Highest LowestDeformation ratio at rupture pointHYPERLINK \l "MEP_L_tbl6fnb" \o "bSirisomboon et al., 2007 "b Lowest Higher HighestHardness (N mm�1)b Lowest Highest HigherEnergy used to rupture (N mm)b Highest Higher Lowest
a Pradhan et al. [32].b Sirisomboon et al. [76].
Table 5Summary of seed cleaning systems available in the market [73,74].
No. System name Supplier Capacity Footprint Status Components
1 Jatropha seedcleaning system
Zhengzhou Amisy TradingCo., Ltd., Machine, China
400 kg/h 2.8 m�11.4 m Commercialised Material loading hopper, elevator, grading screen machine, screwelevator, shelling and separating machine, sorting machine
2 Jatropha seeddehulling system
Goldin (India) EquipmentPvt. Ltd.
100–200 kg/h
Unknown Commercialised Feed elevator, Impact huller, three deck fine grader, air classifier
B.Y. Lim et al. / Renewable and Sustainable Energy Reviews 52 (2015) 991–1002998
8. Storage of seeds
One of the factors that make Jatropha suitable for small-scaleproduction is that it can be stored for a prolonged period of timeunder good conditions before further processing [81]. It faces lessdeterioration problems as compared to other crops such as oil palmand cassava. The long storage period eases production planning andcan ensure that the seeds are available for processing evenwhen thereis high demand. Most of the storage is in the form of whole seedswithout the outer shells. The outer shells are larger and can add to theweight. Therefore, storage in the form of whole fruits will increase thetransportation cost and require more storage space. The stored seedsmay be further processed to remove the husks prior to extraction.
The degradation of oil is basically caused by hydrolysis andoxidation reactions which are a function of storage temperatureand relative humidity [93]. The seeds must be properly storedbefore oil extraction to prevent the formation of oxidation pro-ducts and free fatty acids which can inhibit alkaline-catalysedtransesterification reactions during biodiesel production [93]. Themoisture content of the seeds for storage should be in the range 5–7% and not more than 8% [21,23]. This control is necessary toprevent the seeds from deteriorating which could result in theformation of free fatty acids during storage [23]. The dried seedsare basically stored in woven sacks and must be placed in a well-ventilated room [21]. A long storage period of more than 8 monthsand long exposure to the sun should be avoided since these candegrade the oil quality [23]. Another report suggested it is betterto store the extracted oil in closed containers to prevent it frombeing exposed to oxygen and light, rather than storing wholeseeds, especially under tropical climate conditions [93].
9. Suggested pretreatment steps for oil extraction
Before extraction, the seeds must be dried if they are too humid(48%) [23,47]. The seeds can be dried in an oven at 105 1C or sundried [36]. Beerens [59] reported that cooking seeds in water at80 1C for one hour could achieve the highest oil recovery based ona mechanical press (89% for BT50 and 91% for the Sayari expeller(dual pass)). However, the contact of seeds with water is risky asfree fatty acids may form. Further, the seeds must be free of sandand stones or any hard impurities which could destroy a mechan-ical expeller [47]. The thresher or vibrating sieve is most com-monly used to remove the stones and sand [23]. In a separatestudy, Mehla [21] stated that steaming is necessary to improve theoil extraction efficiency. However, Sirisomboon and Kitchaiya [82]reported that heat pretreatment by steaming did not improve theoil yield in a Soxhlet extractor. Drying in an oven at a highertemperature (40–80 1C) has been reported to improve oil yield(36.83–47.06% by weight) but resulted in a higher acid value [82].In conclusion, the control of temperature and moisture contentparameters during pretreatment is important so as to maintain theoil quality.
10. The cost of Jatropha postharvesting
The feedstock accounts for a large portion of the directbiodiesel production cost due to the fact that the major cost of
production, which is around 82.83% as shown in Fig. 12, is incurredat the seed production stage [45]. The major costs at this stage arethe salaries of the labour for fruit collection, treatment (handlingand capital cost) and the fertilisation cost. Openshaw [29] esti-mated that 95% of the cost of harvesting, fruit shelling and seedcleaning is the labour cost. Therefore, the cost of production wasreported to be almost directly proportional to the fruit yield asshown in Fig. 13 due to the fact that more labour hours would berequired to process a larger amount of mature fruits. On the otherhand, although the pretreatment of fruit/seeds, such as drying andheating, are suggested for the best postproduction, there is noestablished documentation for the cost distribution of eachprocess.
Table 8 shows that different costs are incurred in differentcountries. The lower labour cost in Tanzania contributed to thelower harvesting cost. However, the development of Jatrophausing manual harvesting and the traditional dehulling methodbecomes impractical for a large scale plant and in the countrieswhere the labour cost is relatively high such as Malaysia, Belize,Brazil, etc. The production of Jatropha biodiesel should be effectiveand low cost so that the Jatropha can be a sustainable alternativefor fossil fuels. Henning [47] stated that the economy of the oil isvery much dependent on the price of the seeds. The reduction inthe price of the seed from US$0.10 to US$0.08 per kg can decreasethe price of the crude oil from US$0.83 to US$0.67 per litre [47]. Asa result, the process of mechanisation has become the primarydevelopment trend to reduce the seed cost in the Jatrophabiodiesel industry. On the other hand, one of the best means ofreducing cost is to combine the steps in the various operations[83]. Therefore, simplification using a single machine, using lowcost components or combining two machines might be a furthertrend for the purpose of saving production space, material hand-ling time, reducing labour requirement and reducing the main-tenance cost. This is to make the feedstock preparationeconomically feasible and market-competitive [29].
82.83
6.1010.89
0.19 Seed production (%)
Oil extraction andrefining (%)
Transesterification (%)
Biodiesel distribution(%)
Fig. 12. Financial analysis of Jatropha curcas L. biodiesel [45].
0
10
20
30
40
50
60
Year 2 (0.50) Year 3 (1.25) Year 4 (2.50) Year 5 (5.00) Year 6 (7.50)Yield per ha (tonnes)
Cos
t (U
S$/h
a)
Harvest Remove shell Remove husk
Fig. 13. An estimation of the cost of the traditional harvesting and shellingprocesses. Adapted from Openshaw [29].
Table 7The potential uses of shells and husks [5,23,29,80].
Discharged fruit components Potential uses
Shells Fertilisers, combustiblesHusks Fertilisers, combustibles, charcoal production
B.Y. Lim et al. / Renewable and Sustainable Energy Reviews 52 (2015) 991–1002 999
11. The current development of the Jatropha industry inMalaysia and future prospects
The highly suitable climate and land availability in Malaysia hascreated great potential for the development of Jatropha biodieselproduction. The Malaysian Ministry of Plantation Industries andCommodities has launched a B5 biodiesel (5% of biodiesel blend)mandate in 2013 in order to achieve an annual demand of 500,000 t ofbiodiesel [94]. However, currently all the biodiesel is produced usingpalm oil. The Malaysian government has no immediate policy to boostthe development of Jatropha production as it may lead to a negativeimpact on palm oil plantation equilibrium [14,95]. Further, there is alack of a marketing channel and a price structure for Jatrophaproduction in the country. In addition, the Malaysian AgriculturalResearch and Development Institute (MARDI) has suggested theimplementation of a contract farming programme to boost interestamong farmers to plant Jatropha. Further, Bionas Sdn. Bhd. has offereda buy-back guarantee for thirty years with an initial price of RM1050per tonne of fruits [96].
Up to three projects have already been identified in Malaysia in2012 with around 259,906 ha of Jatropha plantation area as reportedby University of Lüneburg [97]. On the other hand, Bionas Sdn. Bhd.claims to have 600,000 acres of Jatropha planting area, 313 nurseriesand a collection centre in Malaysia with a total capacity of around850,000 t of Jatropha crude oil [98]. However, the development ofJatropha in Malaysia is relatively slow as compared to India, China, andthe Philippines which all have vast plantation land and cheaper labour.In fact, there is a trend for local companies to develop the Jatrophaindustry elsewhere outside of Malaysia. For example, Bionas Sdn. Bhd.has announced a plan to develop Bohol in Philippines as a Jatrophaproduction hub in the Philippines [99].
On the other hand, many Malaysian companies, universities andresearch institutions are keen on R&D and commercialisation ofJatropha-based products such as biolubricants and biofuel[14,98,100,101]. Further, research regarding the development of aneffective method of biodiesel production is ongoing. For example, anovel method using a pulsed loop reactor has been developed for amore effective transesterification reaction of Jatropha crude oil (JCO) toJ. curcas methyl ester (biodiesel) [102]. In addition, the nation isconcentrating on improving the oil yield per hectare rather thanexpanding Jatropha plantations due to the disadvantage of high landacquisition cost in the country [14]. For example, ARK Bio Sdn. Bhd. iscurrently focused on the development of enhanced genetic materialfor Jatropha to improve oil yield and quality. Further, the high labourcost and high reliance on foreign workers in agricultural works in thecountry has also encouraged the development of mechanical devicesfor any agro-based production, including Jatropha production in thecountry. As a result, R&D expertise in terms of Jatropha and plantationexperience can potentially lead the country to be a role model toimprove Jatropha cultivation by collaboration programmes with othercountries. An example is Kenya where the improvement of seedmaterial and local agronomic knowledge are much required [103].
It is a fact that Jatropha is one of the best candidates for futurebiodiesel production since it is one of the cheapest among theother potential biodiesel feedstocks as shown in Table 9. Apart
from that, the following are other factors that make Jatropha astrong candidate as a future biodiesel source [11,14,19,95,96]:
a. Unstable edible oil price depending on food demand andunstable conventional fuel prices.
b. Availability of marginal land.c. Lower carbon and emission of greenhouse gases.d. Launch of biodiesel mandate by government as shown in
Table 10.e. Jatropha biodiesel can meet ASTM standards and is suitable for
diesel engines.f. Fast growth – The first yield can be expected after 6 months of
cultivation. The tree has a long life expectancy of more than45 years.
g. Low maintenance due to lower nutrient and water require-ments and the use of pesticides is not required.
As a result, the cultivation and production of Jatropha biodieselcan be expected to offer environmental and economic benefitswhile playing a role to be a substitute for fossil fuels in tropical andsub-tropical region countries, especially for the top world oil netimporters such as India and Indonesia [105].
12. Conclusion
Attention needs to be paid to the harvesting and shellingprocess due to the fact that the majority of the cost of manualprocessing is introduced during the seed preparation stage inbiodiesel production. The reported labour cost was more than 90%of cost of harvesting, fruit shelling and seed cleaning [29]. Manualprocessing, which is time consuming and cost ineffective due tothe high reliance on workers, will cause the Jatropha industry tobe less sustainable especially when large scale production isenvisaged. In Malaysia, a total of 259,906 ha of Jatropha plantationarea have already been identified in 2012 [97]. Further, the cover-age of Jatropha plantations has been estimated to increase to9.0 million hectares worldwide in 2015 [84]. The processing oflarge quantities of Jatropha seeds cannot be accomplished effec-tively without the assistance of mechanisation. All of the above-mentioned machines or tools can play a role in the businessoperations and the technical activities that must be conducted sothat the technology is effective and profitable. Even though thereis no mature technology as yet to speed up the harvesting, the
Table 9A comparison of biodiesel prices from differentfeedstock [104].
Table 10Some Biodiesel targets and mandates in different countries [90,95].
Country Target
China Tax exemptionEU 20% of renewable content in diesel fuel by 2020India Meet 20% demand within 2011–2012Japan 5% Biodiesel blend by 2010Malaysia Target 5% of palm oil blend
Table 8Data concerning the harvesting cost (cultivation of 1 ha Jatropha for 5 years)adapted from Achten [49].
Country Cost (TSH/kg) Equivalent to USD(1 TSHE0.0006USD)
Reference
Global study 120–210 0.07–0.13 [84]Africa 210–471 0.13–0.29 [85,86]Tanzania 80–100 0.05–0.06 [87,88]
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seed production can be undertaken efficiently using a hand-operated or motorised shelling machine. Currently, a 1000 kg/hof shelling rate is achievable using a dehuller for whole seedrecovery. However, the further processing of Jatropha seeds toproduce cleaner kernels has turned out to be characterised byvarious bottlenecks such as the difficulty of separating the kernelsand husks mechanically. Dehulling seeds mechanically withoutcausing crush damage is a challenging task. Broken husks andbroken kernels tend to have irregular sizes and similar mass andthus they are not easy to be separated mechanically. The researchto achieve breakage free kernels has become a research gap thatneeds to be solved to further stimulate the growth of the Jatrophabiodiesel industry. Another concern is that process mechanisationcan require a high capital cost that can burden small-scale farmers.However, this is a fixed capital cost and can be solved providedsufficient support/subsidies are provided by the government if thebiodiesel industry is part of the development plan of the country.On the other hand, the seeds should be stored under the condi-tions with 5–7% of moisture content, less than 8 months of storageperiod, well-ventilated room and without exposure to the sun[23]. Proper storage and seed pretreatment can increase the oilyield. In contrast, any improper conditions (e.g. temperature andmoisture content) can contribute to the formation of oxidationproducts and free fatty acids leading to a degradation of theextracted crude oil.
Acknowledgement
The authors would like to thank the Prototype Research GrantScheme (Reference no. 5529200) from Universiti Putra Malaysiafor financially supporting this research.
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