Castor and jatropha oils : production strategies – A review

General Head, Embrapa Food Technology <lago@ctaa.embrapa.br> Abstract: The Brazilian bioenergy matrix is based on four platforms: ethanol, energy forests, residues and co-products and biodiesel. The food-energy dichotomy in the use of edible oils is one factor which has stimulated the search for non-edible oleaginous energy crops, such as many native palms. By the year 2000 Brazil had an annual deficit of 80 thousand tons of castor oil, making necessary to import oil from China and India. After a strong debate the National Program on Biodiesel Production (NPBP) was launched by December 2004. After an initial excessive enthusiasm, small producers being focused in the program, a more mature and realistic planning is undertaken. Production in semi arid lands is being stimulated, mainly castor (Ricinus communis) and Jatropha (Jatropha curcas). Apart from belonging to the same botanical family (Euphorbiaceae), both plants are well resistant to poor soils. Castor plant is well adapted to practically the whole country, except for some extreme areas (too low water availability or too much rain). Castor keeps being an alternative for the semi arid region but much more technology is requested to make it largely exploited. Following the petroleum crisis of 1980’s an ambitious research program on Jatropha curcas was initiated, later on discontinued and presently retaken by Embrapa and some Universities. Progress is slower than in the case of Ricinus communis. The first agronomical observations confirmed low productivity, problems with pests and diseases, high harvesting costs etc. Some strategic factors should be considered for the production of castor and Jatropha oils: 1. Production of raw materials; 2. Production of oils; 3. Detoxification and value aggregation to the extraction cakes and residues. Regarding raw material production, it is necessary a strong, long term research program on genetic breeding (short cycle varieties, with high productivity and allowing a sole harvesting), soil fertility, pest control, domestication and mechanization. Just to mention Embrapa, in 2007 a new cultivar (BRS Energia) was launched, characterized by low height and single crop per year, thus facilitating mechanized harvesting. In 2009, a new cultivar is expected to be launched, with high tolerance to gray mould, castor principal disease. Concerning oil quality, no significant difference is observed among cultivars, but for biodiesel purposes genetic material with lower ricinoleic acid content is welcomed. The oil production of both species results in nitrogen rich cakes. However, since the cakes contain toxic components making difficult or impeding its production in large scale, total elimination or inactivation of toxic compounds is mandatory before the cakes can be considered useful as animal feed, fertilizer, in waste water pretreatment or any other application. Physical chemical and/or bio detoxification methods are being carried on.


The Brazilian bioenergy program
In 2003 searching raw materials for biodiesel production the castor oil revival program was launched by the Ministry of Agrarian Development.Small producers in poorer regions, such as northeastern of Brazil were an important motivation for this initiative.
The Brazilian Energy Policy (Law n. 9478/1997) was established with some clear objectives such as: to promote energy security with lesser external dependency, to protect the consumer best interests through regulation mechanisms and surveillance at the Regulatory Agencies, to increase the share of biofuels in the national energy matrix, to promote free competition and to protect the environment.The Brazilian Bioenergy program comprised important premises or concerns including guarantee of internal supply, need of specific taxation model in order to stimulate its usage, expansion of production to supply the growing internal and external demand for ethanol and biodiesel.Transversally to these premises private investments should be stimulated.In 2006, following the publication of the Brazilian Energy Plan, studies were overtaken which ended by creating a new research centre: Embrapa Agroenergy, now being installed in Brasilia, representing the recognition of the bioenergy importance by the Brazilian Agricultural Research Corporation, Embrapa.
better income distribution as the social aspects of the program are important questions behind the idea of producing biofuels.
In Brazil, the use of biofuels meets differential regional motivation (figure 2).The North of the country is constantly submitted to degraded areas reclamation, the access to remote areas is quite difficult thus making important local energy generation as well as energy fuels for boats and prioritization of indigenous plant species (palm species, babassu, etc.).In Center West region, despite the biggest production of soybean there are still areas to be expanded for sugarcane and other energetic crops; transportation of conventional diesel from coastal regions of Brazil is less costing; and conditions for integrating agriculture and animal husbandry are favorable.The Northeast offers possibilities for increasing family agriculture through castor bean production and also for introduction of other energetic cultures such as Jatropha curcas.The region has a great appeal for implementation of government policies of social inclusion.Situation in South/Southeastern regions are different: the air quality in big cities must be improved through reduction of conventional Diesel emissions.Local utilization of soybean and other oleaginous seeds is well established and the integration of agricultureanimal husbandry and forest through production systems is a reality.
The Brazilian Agroenergy R&D program comprises four interconnected platforms: Biodiesel, Ethanol, Energetic Forests and Residues and Co-products, while the guidelines of Agroenergy plan are divided in three axes: agronomic technology development, industrial technology development and transversal studies (social, economic, market, management and public policies).

Biodiesel: Regulatory Framework
Law 11.097/2005 establishes minimum percentages to mix biodiesel to Diesel, and prescribes the need of monitoring the introduction of this new fuel into the market.Initially (2005-2007) 2% of biodiesel were authorized to be added to Diesel, requiring potential market of 840 million liters/year.Nowadays the 2% addition is mandatory and the sound market is of 1 billion liters/year.In 2013, 5% will be mandatory and this will represent a Sound Market of 2.4 billion liters/year.In 2008, there were produced, in fact, 1.6 billion liters, and the installed capacity fitted a 3% addition.The actual production of oils in Brazil (table 1) satisfies the volume needed for biodiesel utilization, but for the future should be increased.Feedstock diversity for biodiesel is represented by soybean, castor, sunflower, palm, cotton and Jatropha (table 2).Requirements for crop insertion in biodiesel production chain consists of development and establishment of agronomic technology, industrial technology and logistic and infrastructure.Soybean crop fulfills all these requirements while Jatropha none (table 3).Some other parameters must be fulfilled for incorporating any raw material in the agronomic production chain, such as agronomic zoning, existence of certified materials and seed production infra-structure, including storage and transportation.In Brazil, all these parameters have been established for soybean, just a few for oil palm, sunflower, castor and cotton and none for Jatropha (table 4).

Strategies for expanding biofuels production and mechanisms of sustainability
The main argument against the use of biofuels is the competition with food production.In Brazil, using degraded areas for expansion and applying rational technology it would not affect food production for domestic consumption.Besides that, the utilization of the coproducts (ex: soybean and sunflower cakes) would complement food supply either for human consumption or animal feed.In Brazil, 366 billion ha of land are utilized for agronomical activities from a total surface of 851 billion ha.Ninety billion ha (24.6% of the total) correspond to non cultivated area still available for expanding agricultural activities.One important date is that sugar cane is cultivated only over 6.  ding to 1.7% of the total area suitable for cultivation.
As the objective of biofuels utilization is environmental protection, different mechanisms of sustainability must be taken in account along its production chain.
In Brazil, the no-tillage production system is being used systematically whenever possible, thus protecting the soil and decreasing the use of agrotoxics.Moreover, Embrapa developed a series of production systems integrating croplivestock and forest and the technologies The factor most discouraging regarding the increase of the castor crop is its low price and productivity and of course its toxicity.
Castor seeds contain 45 to 52% of oil but the high viscosity of the oil (and consequently of its esters) due to the ricinoleic acid content does not impart to the oil good characteristic for biodiesel performance (table 5).Breeding studies apart from looking for improving agronomical characteristics also take in account the search for material containing less ricinoleic acid as the oil from a wild material that has been reported by Rojas-Barros [3] exhibiting only 10% of ricinoleic acid.
Protein and other nutrients content in the cake make it an excellent raw material for fertilizer or feed (table 6).However, other factors should also be considered especially for feed application as will be discussed further down.

Castor oil extraction
The processes for extracting castor oil are conventional, either pressing or combining pressing and solvent extraction.The temperatures needed for removal of the solvent reduces the ricin content.
A simultaneous process for extracting the oil and convert it to ethyl esters has been patented by Petrobras researchers [4].Nevertheless, two plants in operation by Petrobras utilize foreign technology using methanol as the transesterifying alcohol.Equipment able to de-shell 85% of the fruits, with an operational capacity of 650 kg seeds per hour has been adapted, being very useful for small producers (figure 3).

Co-products from castor oil processing
As shown in table 4 castor cake has excellent composition for fertilizer application.However, castor seeds contain highly toxic and allergenic compounds which severely limit or prevent its use as feed after oil extraction [5,6].
Ricin is a 62-66 kDa protein consisted of two polypeptide chains, approximately 32 kDa and 34 kDa in size, linked by a disulfide bond.
The estimated lethal ricin dose in humans is 1-10 μg/kg [5,7].Additionally, a set of strong allergens known as CB-1A has been described [8].In Brazil some work has been done on these compounds and lead to the identification of one of them, Ric c 3 [9].Later one 20 isoforms were described by Machado [10].
The allergenic set is composed by albumins 2S, formed by a heavy and a light subunities with molecular mass of 9 and 4 kDa, respectively [11].Biochemical and immunological data relative to nine different fractions of albumins 2S, seven of which exhibited allergenic potential has been reported [10].
Table 7 shows some values for oil, ricin and albumin 2S content in some Brazilian castor seeds varieties [12].
Once castor oil production is increased, either provoked by biodiesel or industrial use, a great amount of the cake will inevitably be produced.Even if its final destination is the landfill, it is necessary to eliminate the waste's toxicity and avoid contamination of the earth's soil and waters.In any case the cake has to be treated before use.
In Brazil, among other initiatives, two more relevant approaches are being undertaken for detoxification of castor bean and cake.In the first approach, solid-state fermentation (SSF) of castor bean cake was carried out with the lipase produced by Penicillium simplicissimum (maximum activity was 44.8 U/g).The fungus P. simplicissimum was able to reduce the ricin content to non-detectable levels and to reduce castor bean cake allergenic potential by approximately 16% [13].Thermoplastic extrusion is the main tool in the second approach.The technique, in association with 1 or 2% CaO, already tried by Rhee [14] was carried out to inactivate ricin and simultaneously deactivate allergenic compounds [12].Ricin was detected by denaturant electrophoresis (SDS-PAGE).For allergenic activity evaluation it was used degranula-tion of mastocites, isolated from the peritoneal cavity of rats and then incubated with serum containing IgE anti-albumins 2S, with treated and non treated samples.Degranulation was observed with optical microscopy.The treatment with CaO 1 and 2% redu-ced the 29 and 31 kDa bands content responsible for ricin toxic activity.The treatment with CaO 2% was more efficient since the reduction of degranulation of mastocites (63% to 47%) was superior to the 1% treatment (63 to 55%).Extrusion combined with 7% CaO was also carried out resulting in total elimination of toxicity and allergenicity.Data are not still available but to find a solution to the problem is essential for the success of biodiesel program.

Some general characteristics of Jatropha curcas L
Belonging to the Euphorbiaceae botanical family, as castor plant does, similarities between the two species should be expected (figure 4).In fact, they are both toxics but for different reasons.Jatropha finds medicinal and veterinary uses and as insecticide but the cake/ meal is non edible as well as the oil which can be used as purgative, for skin treatment and/or biofuel [15].
The data found in literature on agronomical, chemical and technological aspects of Jatropha curcas are very variable.One can attribute this variation to the lack of domesticated varieties.
For instance, productivity is reported as going  inhibitor and saponins.Makkar [18], gives a comprehensive report on the analysis of some of these compounds.Phorbol esters are analogues of diacylglycerol, activate protein kinase C (PKC) and are acutely toxic (even though they present quite different biological activities and chemical stabilities) and thermostable.They are partially removed during oil extraction but the efficiency of the process depends on the type of extraction, solvent extraction being more efficient than pressing.In the case of solvent extraction the removal of phorbol esters will depend on the solvent type and subsequent treatment [19].
In Brazil, research for detoxification of Jatropha seeds is in its early stages.

Perspectives
The future is very promising for Jatropha breedingthere is substantial variation and we can benefit from new technologies and "piggy-back" on knowledge gained from other crops to go after specific traits such as yield, architecture and disease resistance.Robust standards for describing genetic variation and "new" elite lines are needed.
A network of evaluation of elite genotypes of Jatropha curcas has been settled whose objective is to evaluate and select elite genotypes of Jatropha curcas adapted to different producing areas in Brazil.The assays comprise 20 genotypes in 6 areas of 0.3 ha/area (DF, PE, MS, RS, RJ, MG).First new variety is expected to be launched in 2011.
A lot of work has to be done and we should set ourselves challenging targets for "rapid domestication" of Jatropha and work together to achieve these for the benefit of all.

Figure 3 .
Figure 3. Castor Seeds treatment: the equipment permits deshelling 85% of the fruits, with an operational capacity of 650 kg seeds per hour.

Table 3 .
Requirements for crop insertion in biodiesel production chain.

Table 4 .
Requirements for raw material incorporation into the agronomical production chain.

Table 5 .
Fatty acid composition of castor seed oil from Brazilian varieties.

Table 6 .
Cake and shell characterization.

Table 7 .
Oil content, albumin 2S and ricin in different varieties of castor.