Features

Rubber for latex and wood: a long-term option

13 May 2014 - {{hitsCtrl.values.hits}}

It is unlikely that the rubber plantations, currently going through difficult times with profitability per hectare markedly eroded due to rapidly declining selling price of rubber and spiralling costs of production due to rising wages of tappers, will bounce back in the near future.

According to market analysts, the world’s biggest rubber producing region has insufficient funds to intervene in the market to stem a price slide that has pushed rubber futures to multi-year lows. Tokyo rubber futures have plunged more than 25 percent this year, hovering near their lowest in more than four years, while physical prices on Singapore’s SICOM are languishing near five-year lows.

Market confidence has been dented by a weaker economic outlook in top market China and swelling global inventories, while top producer Thailand has announced plans to sell 200,000 tonnes from its stockpiles.

The International Rubber Consortium (IRCo) grouping Thailand, Indonesia and Malaysia - who together account for more than 70 percent of global natural rubber output - appears hamstrung by a lack of cash and political will.

It has been said that there aren’t many options on the table. The three countries have to pump money into IRCo to do the stock management. It will run into billions, so it may not be feasible at this juncture.

Also, it is known that Thailand’s government is in caretaker mode, Indonesia is in election mode. Therefore, it is unlikely that anything will move now. These are the two major players that have to call the shots. Indonesia has suggested that IRCo could be expanded to include other rubber producing countries such as Vietnam, Cambodia, Laos and Myanmar.

Tools available for immediate action to the major players include curbing exports, reducing tapping by farmers or buying rubber for stockpiling and sale at a later date.

Long-term option
A long term option for countries like Sri Lanka, who are price takers and not fixers, is to go for dual purpose rubber planting: latex and rubber wood.
The emergence of rubber wood as an internationally established wood product has often been termed a `success story.’ Various factors have contributed to this development, first and foremost the fact that rubber wood represents a relatively sustainable alternative to tropical woods extracted from natural forests.

Furthermore, rubber wood has proven to be very versatile in its use in furniture manufacturing and the wood-based panels industry. Where forests are scarce, particularly in South Asia, the use of rubber wood as fuel wood continues to mitigate pressure on natural forest resources.

Environmental
Rubber wood discussions make frequent reference to the product’s environmental sustainability, due primarily to the fact that it is procured as a by-product of a tree plantation crop. In view of the potential availability of rubber wood from existing plantations and the increasing scarcity of tropical woods from natural forests, there is little doubt that rubber wood relieves pressure on remaining forest areas.

Agro forestry researchers are also paying increasing attention to the role of smallholder cultivation (sometimes called `jungle rubber agro forestry’) as an alternative to certain types of unsustainable food crop-based shifting cultivation systems. Jungle rubber agro forestry is widely practiced in Indonesia (Sumatra and Kalimantan) and Southern Thailand; similar approaches are being introduced in Vietnam and are being considered for Myanmar.

Aside from the role of rubber wood plantations vis-à-vis other land use forms, numerous studies have been carried out to evaluate the environmental impact of rubber plantations as such. While many of these may exaggerate in their favorable comparison of hevea ecosystems to primary forest, they all present convincing evidence of positive effects.

Research on the ecological impact of rubber plantations on soils degraded by shifting cultivation has demonstrated an improvement of soil properties after the establishment of Hevea. Rubber plantations adopting proper agro forestry management practices (including terracing; silt pitting and bunding; and the growth of leguminous cover plants between the rows to assist with nitrogen fixation) were found to help in the enrichment of organic matter, which consequently improved soil physical properties, such as bulk density, soil porosity, moisture retention and infiltration. An increase in organic matter was also observed. Nutrient removal in rubber is known to be comparatively, much low.

Similarly, it is known that of all the agro forestry cropping systems rubber plantations approximate closest to the rainforest system, in terms of canopy, leaf litter and in nutrient cycling . Fertilizer inputs are considered very low and soil surrounding rubber trees appears to be enriched by abundant leaf fall.
According to some researchers, the most understated aspect of Hevea cultivation is that of its role as a carbon sink. Physiological studies have shown that Hevea is more effective than teak grown in plantation conditions in taking up carbon dioxide . This is thought to be due to the extra energy required to produce the latex inside the tree: in contrast to a synthetic rubber plant which consumes energy and produces carbon dioxide to convert pure energy (crude oil) into elastomers, the natural rubber plant converts carbon dioxide into an elastomer.

The leaf area created by a mature rubber tree is also sizeable: the leaf area index of a mature rubber plantation can be as high as six or seven. Because of the high photosynthetic rate and leaf area index, the biomass production per unit land area within a given time is very high in Hevea. With a planting density of 450 trees per hectare, the canopy closes in less than five years.

Environmental considerations in the context of rubber wood plantations have also attracted the attention of certification/labeling schemes. In 1994, a United Kingdom do-it-yourself retailer contracted SGS Silviconsult and Certification to undertake a Forest Audit of a Malaysian firm’s Hevea plantations in Johor (southern tip of Peninsular Malaysia).

The audit, the first of its kind on sustainable management of rubber plantations in Malaysia, was carried out using the principles and criteria for forest management of the European Forest Stewardship Council. While the auditors recommended certification, they also found areas in need of improvement, including the storage and use of herbicides; health, safety and environmental issues at sawmill sites; biodiversity conservation; and the use of pesticides and fertilizers.

Rubber wood yield
Rubber wood yields per tree vary according to clone, site conditions and management. The global rubber wood study carried out by Indufor under the auspices of the International Trade Centre estimated yield at 140 to 200 m3/ha, with the higher ranges observed in countries where plantations are carefully managed, i.e. Malaysia, Thailand, India and Sri Lanka .

Estates and smallholdings can yield 190 and 180 m3 of greenwood per hectare, respectively. In the case of usable logs, estates recuperate about 57 m3and smallholdings about 54 m3 per hectare. After sawing, the estates and smallholdings produce about 18.1 m3 and 10.8 m3 of sawn wood, respectively. In another study, gross yield was quoted at 180 m3/ha, which included branches greater than 5 cm diameter. In smallholdings, where trees are generally of poorer form, average yields were found as low as 100 m3/ha. Net volumes suitable for sawn wood processing were 20 percent and 15 percent of total volumes for estates and smallholdings, respectively.

Research on the development of more productive varieties (clones) has been carried out in a only a few countries, where trials for identifying clones as suitable for large-scale introduction often last ten to fifteen years.

In 1998, for instance, Malaysia launched latex-timber clones that can produce timber in a shorter period of time compared to other tropical species and can be densely planted. The clones RRIM 2023, 2024, 2025 and 2026 have been reported capable of producing 0.81 to 1.87 m3of wood per tree, significantly higher than the 0.68 to 1.33 m3 of the earlier 2000 series clones. Values for Sri Lankan clones may not differ very much.

Rubber wood properties
The natural color of rubber wood is one of the principal reasons for its popularity. The air-dry density is between 560-640 kg/m3 and it has good overall woodworking and machining qualities for sawing, boring, turning, nailing and gluing. It also takes finishes and stains well. Its strength and mechanical properties are comparable to traditional timbers used for furniture making and woodworking. However, there are more than 20 clones of rubber trees used in commercial plantations and some of the variations between clones are reflected in wood characteristics.

Rubber wood is easy to saw and causes no significant blunting of the saw teeth. The presence of latex in rubber wood tends to clog the saw teeth, which can be reduced by using router bits with larger than standard clearance angles. Rubber wood slices or peels well when converted into veneer.
Rubber wood can be turned without burn marks or tear outs on standard lathes and the wood is easy to drill or bore. There are two common methods used for the primary breakdown of rubber wood logs. One is to break the logs into two halves, each of which is then converted into sawn wood. The other method is to cut a slab from one side of the log, then turn it 90 degrees to cut the sawn wood.

While rubber wood exhibits a number of physical weaknesses, many have been overcome through technological advances in processing. Where rubber wood makes a significant economic contribution, research institutions continue their search for feasible remedies.

Conclusion
Although it is considered a perfect plan to manage the rubber tree for both latex and rubber wood, such perfection rarely exists because under normal circumstances tapping rubber tree for latex affects plant growth significantly, yet focus on both of them in the same planting is considered to be prudent, under the current situation of uncertainty in rubber for latex only business.

(The writer can be contacted at [email protected])

Features

Rubber for latex and wood: a long-term option

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