Research and development of new, more sustainable chemical products are considered one of the major challenges facing the chemical industry today. “Green chemistry” seeks to find less polluting or renewable products derived from plant material, in order to replace polluting materials obtained from non-renewable sources. The recent development of products such as bioplastics and biofuels are examples of the current interest in researching new alternatives to those derived from petroleum.
Although the traditional chemical industry exerts significant pressure in the market, bioproducts currently represent a small but growing part of the energy and industrial materials market. One of the plant species being studied for these purposes is castor.
Castor (Ricinus communis L.) is one of the 7,000 species in the Euphorbiaceae family, possibly originating from Ethiopia, Africa. The castor plant grows wild in warm soils, except in very dry areas. Today, its cultivation is not only focused on tropical regions but also in many countries around the world with temperate climates. However, the optimal conditions for its cultivation are found in Brazil, Ecuador, and South Asia. Wild castor is a perennial plant in the form of a shrub or tree, while in temperate zones, the shrub variety is a much smaller and annual plant.
The optimal conditions for its cultivation are: absence of frost, well-drained soils, and plenty of light. The irrigation of the crop greatly influences its production, as increased irrigation translates to higher yields. Ideally, irrigation should be 450 liters/m², as excess moisture at the end of the growth cycle or during flowering can harm its maturation.
Through this plant, several by-products can be obtained, such as glycerin and fibrous remnants ideal for the production of organic fertilizers. The main product of this plant is the oil, known as castor oil in English. Depending on the variety of castor, the amount of oil contained in the seeds will vary. The quality of the oil will depend on the extraction method used. The main characteristic of this oil is that it possesses chemical properties that make it unique. It is composed of 90% of a single fatty acid (ricinoleic acid) that contains a hydroxyl radical, making it soluble in alcohol at low temperatures; it is very viscous and has special physical properties. It has a molecular weight of 298 grams/mol, a melting point of 5ºC, and a salting point of -12ºC to -18ºC. These characteristics make it a product of great interest for the chemical industry as a source of raw material.
Castor oil has a wide variety of applications in industry, such as in the composition of paints, varnishes, cosmetics, therapeutic products, lubricants, and aircraft fuels, plastics, nylon, etc. Currently, the properties of this oil are being studied for biodiesel production. The main consumers of castor oil are developed countries that use this product as an input for the chemical industry. However, the potential for biodiesel production from the oil will create a new market for this product. This market alone could absorb the entirety of the current production from producing countries. On the other hand, the major producers of castor are India, China, and Brazil. These three countries account for 93% of global production, thus dominating the market today.
As stated, castor oil currently constitutes one of the most important raw materials in the so-called “green chemistry” due to its wide use in industrial activities. Its high composition of ricinoleic acid makes it an interesting resource for the chemical industry, and there is a high demand from countries such as France, Germany, and the Netherlands. The high price of castor in the international market compared to other plant products and its growing demand encourage interest in expanding this crop in temperate areas, such as in Mediterranean countries.
