Castor and jatropha oils: production strategies – A review

ARTICLE

Auteur(s) : Regina CA Lago

General Head, Embrapa Food Technology

The Brazilian bioenergy program

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.

The Brazilian Energy matrix comprises: oil (38.4%), biomass (29.7%) – where sugar cane occupies 13.9% and wood/charcoal 13.1%; hydroelectricity (15.0%), natural gas (9.3%), charcoal (6.4%) and nuclear (1.2%) (figure 1).

Questions involved in biofuels increasing production

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 agriculture – animal 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

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).
Table 1 Brazil: oils and fats (1000 t).

Strategies for expanding biofuels production and mechanisms of sustainability

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 6.2 billion ha corresponding 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 crop – livestock and forest and the technologies involved are largely sprayed and utilized for either small or big producers. High level of agronomical technology ended up by recuperating degraded pasture as in the Cerrado (savanna) area, where 1 ha recuperated pasture is equal to 1.8 ha of preserved forest.

Also concerning sustainability, optimizing use of areas affected by anthropic action must be overtaken, as the reduction of pressure for slashing fragile or strategic biomes, and the reduction of erosion and water contamination and GG emissions. By other hand, C sequestration and soil biological activity must be increased, and water quality greatly improved.

Some general characteristics of castor plant

Relevant research institutions formed a consortium to develop agronomical technology for the plant such as Minas Gerais Agriculture Research Institute, Epamig; Agronomical Institute of Campinas, IAC, and Brazilian Agriculture Research Corporation, Embrapa.

However, castor plant has high intolerance to low O₂ incidence and low resistance to certain diseases. Consequently, there is a need for breeding studies in the search of new varieties with annual cycle, which offer potential for mechanization and are highly resistant to pests. In 2009, a new variety resistant to grey mould, will be possibly launched although exclusively for the areas affected by the disease [2].

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

Castor oil extraction

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

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

Some general characteristics of Jatropha curcas L

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 from 2.0 to 12.0 t/ha; oil content ranges from 46 to 60%.

Composition of Jatropha seed and nut is shown in table 8 and of nut, shell and meal in table 9. The possibility of fertilizer utilization is visualized from protein content.

The fatty acid composition of Jatropha curcas seed oil does not pose any problem for its transformation into biodiesel. Distinctly from castor seed oil its main component is oleic acid (34.3 to 45.8%), followed by linoleic acid (29 to 44.2%) and palmitic acid (14.1 to 15.3%), some minor constituents from C14:0 to C22:0 and no traces of ricinoleic acid. Martinez-Herrera [16] reports 41.5 to 48.8% (C18:1), 34.6 to 44.4% (C18:2), 10.5 to 13.0% (C14:0).
Table 8 Composition of Jatropha Seed and Nut.

The context of Jatropha curcas in Brazil

Many challenges are posed by the plant to be overcome before a relevant Jatropha oil production could be settled. Among these are heterogeneous and disperse ripening; broad range of oil content (23 to 35%); production costs, limited technical knowledge: varieties, pests, diseases; toxicity of the cake and oil. Although tolerant to draught and to low fertility, the plant presents low productivity under these conditions.

Jatropha has been promoted for its ability to grow on marginal lands but until now what we have are wild varieties in the current Jatropha plantations.

Despite the great potential there is tremendous lack of technology for Jatropha development.

Regarding sustainability three aspects should be considered: environmental, social and economical. In the first case the GHG & energy balance that depends on land use, cultivation intensity and downstream processing. In the social aspect the non-displacement of food production which is also dependent on land use is of less concern for Brazil as seen before. Nevertheless, related to rural income generation there is a need for more reliable data. In the third aspect reliable income generation is the main parameter which in turn is dependent on oil price and political factors.

In conclusion, more information is needed on energy inputs versus outputs to allow more sustainable practices.

Priorities for Jatropha R&D

Jatropha meal from “toxic” varieties therefore cannot be used as animal feed, due to its tumour promoting activity i.e., its influence on the increase incidence of tumour formation in the presence of carcinogens [17].

Strategies for increasing Jatropha’s production

Antinutritional and toxic compounds removal

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

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.

Acknowledgement

References

2 Severino LS. Personal communication, 2009.

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