Natural rubber, chemically 1,4 cis-polyisoprene, is a polymer with some unique properties besides superior elasticity. Natural rubber is extracted from the latex produced by a tree, Hevea brasiliensis, indigenous to the tropical rainforests of Central and South America. Although there are thousands of lactiferous (latex vessel bearing) species in the plant kingdom, only about 2 500 species contain rubber in their latex. Among those, only around 500 were tried as a source of natural rubber. The Para rubber tree or Hevea brasiliensis of the family Euphorbiaceae is the largest source of commercial natural rubber, amounting to almost 99% of the natural rubber production in the world. Latex, of which rubber is a constituent, is synthesized and contained in specialized tissues called laticifers. Latex is present in almost all parts of the plant, but for the purpose of commercial exploitation it is harvested from the latex vessels concentrated in the bark in the proximity of vascular cambium. The process of careful extraction of latex through controlled wounding on the bark is called rubber tapping.
As a product from varieties chosen by our Group’s research department, productive and tolerant to wind and diseases, natural rubber is a renewable raw material with many advantages. Rubber trees are a significant carbon sink as well.
Rubber trees are a flowering plant that belong to the family Euphorbiaceae (spurge). It is the most economically important member of the genus Hevea.
Natural rubber results from the coagulation of the latex from the rubber tree. This latex, not to be confused with the sap, flows in a separate network of specialized vessels in the bark of the tree: the lactiferous vessels. Natural rubber is obtained from the first latex transformation or coagulated cup lumps in the field and does not contain any solvents.
Where does rubber grow?
Rubber is native to South America. Its cultivation has spread to all tropical regions, more specifically to Southeast Asia as well as West and Central Africa. The history of natural rubber production in Nigeria began in 1894 with the exploitation of Funtumia elastic, indigenous wild rubber. Rubber is grown in Edo, Delta, Ondo, Ogun, Abia, Anambra, Akwa Ibom, Cross River, Rivers, Ebonyi, and Bayelsa States where the amount of rainfall is between 1 800 mm and 2 000 mm per annum.
Since the mid-twentieth century, all plantations have used selected plant material obtained through grafting. Rootstocks are raised in nurseries for six months before receiving a graft. These small rubber trees are then transplanted into the field, with a density of about 500 to 550 trees per hectare. After six years, they reach physiological maturity and the vegetative stage allowing for the start of tapping, through a fine incision in the bark to extract the latex. The rubber tree has a lifecycle of almost 30 years: when the trees’ yield decreases, the timber can be used for furniture, pulp or even firewood, or else it can be left in the field to decay naturally and maintain a good level of organic matter in the soil.
Harvesting starts with a fine incision in the bark of the tree. This operation makes it possible to transect the lactiferous vessels, allowing the latex to flow. It is harvested into cups placed below the tapping notch. Generally, tapping is done every 4 days, and the latex in the lactiferous vessels is renewed after harvesting.
Rubber is harvested in a liquid state – latex – or after coagulation in the field (cup lumps) and is then taken to the rubber factory.
A simple and sustainable treatment process
At the factory, the cup lumps are stored in bunkers for several weeks before processing. Then this raw material is washed, mixed, granulated and dried several times before being pressed into 35 kg bales. Strict adherence to quality standards throughout processing ensures compliance with end-users’ requirements. The finished product is then labeled “Technical Specified Natural Rubber” (TSNR) globally or NOKO10 in Nigeria.
Natural rubber is desired for its physical properties:
- Low thermal conductivity.
- Impact resistance.
- Vibration and noise damping qualities.
Since the domestication of Hevea brasiliensis in 1870s, enormous research efforts have been made to develop rubber varieties suitable for commercial exploitation the world over. Okomu’s rubber plantation consists of a collection of rubber clones, carefully selected by the Socfin agricultural department, based on its suitability for the region.
Okomu is maintaining a collection of mother plants in the bud wood garden, which serves as the source of grafting scion for the development of new planting material. There are 32 different clones, with ascertained clone conformity, in our bud wood garden today. Also, there is a Large-Scale Clonal Trial (LSCT) plot with 24 clones laid out with the objective of continuous evaluation of their adaptability to the region in the long run.
Please have a look at our Research webpage and learn more about the various actions taken in the domain of rubber cultivation, among other things.