Bamboo and Rattan/Rattan/Course-2 Unit-1a
6 HARVESTING, PROCESSING AND TREATMENT
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Since rattan is generally harvested from forest areas, it is important that proper procedures are followed during harvest of rattan from the forest. The forest land generally belongs to the government hence it becomes the responsibility of the government to ensure that exploitation of the forests is prevented. Moderation has to be practiced in the amount of rattan that is extracted at one time. Also spacing out in time is essential to ensure good regeneration. As users and people dependent on forest produce it is also our responsibility and in our interest that the forest is kept viable for harvest. This means that only a small part of the total growing stock of rattan is harvested each time and the rest is left to allow regeneration of the crop. This will ensure that every year an adequate amount of cane can be utilized without endangering the rattan species’ presence in that region.
Up to 10 per cent of the mature growing stock of rattans can be safely harvested at a rotation of three years from clumps of age 6 to 15 years. This means that all clumps should be marked for identification. And each time any harvesting is carried out the identity of the clumps should be noted down such that culms from the same clump are not harvested in the next two years. A single clump at about 15 years of age may yield about a quintal of canes. As the clump matures, the stem length as well as the number of stems increases, which is why older clumps are harvested as compared to younger clumps. Care should be taken to harvest only the mature stems/culms which exhibit loosening of leaf sheath and exposure of lowest part of the stem. Rattan being a climber wraps itself around trees that give it support, because of this harvesting is tedious. Unwinding the canes manually from the branches of supporting trees instead of pulling them is better so as to avoid breaking and wastage of the top portions. It is suggested that harvesting should be limited to the dry season (December to May). Why???? (Drs Renuka/ Haridasan) Use of clump versus culms: Its not clear since in a clump you’ll have culms of all ages – are you suggesting that culms of age 6-15 are only harvested? In India the responsibility to ensure proper harvesting rests with the State Forest Departments. Annual lessees, or harvest permits are issued to local societies of the rural folk, socially and economically backward communities, registered contractors, etc. They harvest the canes under close observation by the Forest Department field staff. Piece work rates (rate per bundle) or labour charges are fixed for bringing bundles of a fixed number of canes (usually 20) to appointed Forest Depots. As you read this unit please note how labour-intensive these processes are and how any entrepreneur can help to generate jobs for people by starting a rattan project, thus improving their livelihood. This can help to sustain so many people.
6.2.1 HARVESTING RULES
A selective felling system is adopted for the extraction of canes, with the following rules:
- Only mature canes should be removed from the clumps while immature or tender canes should not be collected or damaged.
- Digging of rhizome or roots is not permitted.
- No canes shall be extracted from outside the specified blocks – areas are identified each year and harvesting is permitted from only those specified areas.
- All the one-year-old culms and six culms of the second year shall be retained in the clump.
Not clear – since earlier you have said ages 6 years to 15 years!!!!
- Clumps consisting less than six culms shall not be worked on.
- Felling should be done at not less than 15 cm and not more than 30 cm from the ground level. Please explain why this is specified…….
6.2.2 HARVESTING TECHNIQUES
Under the present system, the stem is cut below the level of 30 cm height from the ground using a chopper, and dislodged from the canopy by dragging. When it is difficult to drag the entire stem in case of relatively tall rattans, cutters have the tendency to cut the stem at reachable height, which is often less than half the length of the stem, and leave the upper portion in the canopy as waste. But, harvesting the tall stem is very laborious and even 5-6 labourers find it hard to drag stems of 15 m length or more through the thick canopy. In undisturbed areas, canes of length 25-50 m are not uncommon. Presence of thorny leaf sheath is another problem, as it often causes physical injuries in working.
Check Your Progress Exercise 1
Image:RATTAN harvesttransport 01.png
Soon after felling, most thick (large diameter) canes are cut into 12 feet (3-4 m) length and small diameter ones into 15-16 feet (4-6 m) length at the felling site itself. Bundles of 20 pieces which are convenient to carry are made. These bundles are carried to an intermediate site, generally 2-5 km away from the felling site, and stacked beside the road for transport by truck. When the extraction is a small-scale operation, instead of trucks, workers are engaged for head-load transport by foot. These may be carried for distances ranging upto 10-15 km or more.
Image:RATTAN harvesttransport 02.png
Harvested canes have to be sorted and dried before delivery to the manufacturing units. For this they are generally unloaded from the trucks in a convenient intermediate site for sorting and drying. Rattan extraction is mostly carried out during relatively dry season between December and May (in which part of India? NEast?) in order to reduce the risk of fungal infection. But because of improper drying fungal infections continue to reduce harvests. The water content in the freshly harvested canes allows germination of the fungal spores.
In general at present no preliminary processing (including on-site preservative treatment) method is in practice. Therefore, to achieve profitable yield of harvested canes, it is best to adopt recently developed techniques of on-site prophylactic treatment, followed by preliminary and permanent processing which are extremely useful in preserving harvested cane stocks, in good quality. These techniques have been developed by xxxxxxxxx and their adaptation will prevent or reduce loss due to fungal infections.
Check Your Progress Exercise 2
6.4 On-site Prophylactic Treatment
Presently freshly harvested cane, need to be often stored for about two to three weeks or even a month before they are transported to the processing units. Thus, how the harvested cane are stored becomes very important – if not stored properly in a dry condition the cane often gets infected with fungi thus reducing their quality and loss in the selling price. You need to have some procedures in place that can reduce the fungal infection since the weather and hence the moisture level in the atmosphere is not controllable, since rattan has to be stored in the open at various sites. An effective on-site prophylactic treatment for freshly harvested green canes is necessary to prevent fungal infestation and subsequent staining and deterioration.
We said earlier that it takes up to a month for harvested rattan to be ready for transport, but we should realize that the moment the cane is cut it gets vulnerable to fungal infection and the physical invasion and growth of fungi occurs within 24 hours of extraction. Although, signs and symptoms of fungal staining do not appear immediately after the invasion of the fungi, fungal spores invade the cut end of the canes. If the fungi are not controlled at this stage, these will continue to grow within the internal cortical tissues at a very high rate and symptoms (stains, blemishes, rot) become evident on the fifth day onwards after exposure. Since most of the rattan poles might have been severely infected and discoloured, by the time they reach the processing units, hence, it is of utmost importance that prophylactic treatment should be given immediately after the extraction, at the harvesting sites itself, to obtain stain and blemish-free material.
Procedure for prophylactic treatment
Remove the leaf sheaths from the freshly cut rattan and cut the canes into pieces of desired length. Stack the poles vertically and allow the sap to drip off through the cut ends for at least half an hour. The treatment is essentially a soaking of the canes in a chemical solution.
- The soak treatment can be done in a dipping vat made of GI sheet, or a dipping pit dug on the ground and lined with polythene sheet (Fig. 15).A pit of 4.5 m long, 1 m wide and 0.6 m deep will serve the purpose.
- The edge of the polythene lining sheet should be about 30 cm above the soil surface so that the solution will not spill into the pit or ground. Place some soil on the edges and press the edges of the plastic sheet tightly against the soil surface.
The solutions that can be used are: aqueous solution of 4% copper sulphate or 1% sodium pentachloro phenate (Na PCP) or 0.05% a.i.(active ingredient) Busan 30.
- The tank should be filled with known volume of water, add calculated quantity of the chemical to get the desired concentration and mix thoroughly with a stick.
- The cane poles should be soaked in bundles (of 20 poles) in the preservative solution for about 10 minutes. Two plastic ropes can be placed across the tank to facilitate putting the rattan poles into the treatment tank as well as for taking out the treated poles.
The cost of treatment per large diameter rattan pole of about 4 feet length is estimated to be about Rs. 0.20 only.
Image:RATTANprimaryprocess 20.png Fig. 15. Treatment pit dug on the ground and lined with polythene sheet
6.4 PRIMARY PROCESSING
6.4.1 Why should we oil cure rattans in preference to air drying?
Usually, after harvesting, the canes are air-dried for many weeks to reduce their moisture content. This is a very slow process and the chances of infection of the canes by fungi are very high. Fungal infestation leads to sap stains/blemishes, which mar the appearance and drastically reduce aesthetic value and sale price of the cane. Oil curing, if performed on green canes immediately after harvesting, can reduce their moisture content dramatically, thus preventing fungal infection. Thus, oil curing, if performed at the right time and under optimized conditions can serve to increase utilizable yield of cane after harvesting.
To reduce the time delays inherent in transporting the canes over long distances, the curing should be carried out in the field itself. Hence, the curing unit needs to be established in a place or collection depot, very close to the harvesting region. Anything more than a few days lag between harvesting, transportation and curing is not desirable.
How does oil-curing improve the canes after harvest?
Immersing the large diameter canes in hot oil/oil mixtures (using specially designed curing tub) for specified duration just below the boiling point followed by cleaning and drying, yields
- uniform and reproducible ivory white colouration.
- no adverse effect on the physical and mechanical properties of the cured rattans so that the utilization value is not affected
- resistance to subsequent fungal attack.
Oil cured canes, therefore, have great domestic as well as export demand and fetch more price than uncured canes. Hence, adoption of this value-addition technique will ensure better marketability and profit from sales.
Fig. 1. Gradual color change of canes from green to ivory white during sun drying for a week after curing(in contrast to untreated canes, in the left side).
How do we oil cure rattans?
At present, there are a variety of oil mixtures and associated procedures used for oil curing. No clear distinction between the effects of different oil mixtures/combinations on the quality of canes had been established until the year 2001. Recently, Dhamodaran and Bhat (2002) standardized the oil curing technology and according to this study, a 9:1 ratio by volume of diesel and coconut oil or kerosene alone with a curing temperature below the boiling condition of the oil medium has been identified as the best curing condition.
Curing duration of:
- 20 minutes for small diameter canes
- 30 minutes for medium diameter canes
- 45 minutes for large diameter rattans
has been found to be effective in imparting the desired ivory white color to rattan skin without affecting their physical and mechanical properties. However, curing periods of shorter or longer duration as against the prescribed ones were found to have adverse effect on the properties of the treated canes.
As high temperature causes damage to rattans in terms of shrinkage and charring and also increases the risk of fire hazards, temperature needs to be maintained strictly below the boiling point of the oil medium.
Oil Curing Facility/Equipment
For the application of the cane curing technique, the primary requirement is a curing tub of appropriate dimensions (2.4 m - 3.6 m or 4.8 m long, width 0.75 m, height 0.75 m; made of mild steel of 2-4 mm thickness) (Fig. 2 & 3). For heating the oil mixture, source of heat can be firewood, kerosene or LPG depending on convenience and finances of the operator. According to the source of heat, the design of the heating system varies. Use of fire wood requires a mud hearth and chimney (Fig. 4 & 5) while use of kerosene or LPG requires stove type burners (Fig. 6 & 7).
Use of LPG as fuel is very convenient and effective for controlled heating, as longitudinal burners are available for its use (Fig. 8). This will ensure more uniform distribution of heat within the oil medium. As localized heating can be avoided by the use of longitudinal burners, the chances of fire hazards are effectively minimized and shrinkage of canes also is uniformly moderate only. Moreover, in the case of emergency, the entire supply of LPG can be cut off by the use of a single control valve.
Fire safety measure is a crucial aspect in the suggested curing system. Direct exposure of hot oil vapor to the flame and chances of any fire hazard are minimized by concealing the burners within a metallic bracket (Fig. 9). A dial type thermometer (Fig. 10) is attached to the curing tub to indicate the appropriate levels of temperature.
Fig.2. Drawing of the oil curing tub. Fig. 3. The newly designed tub for curing the canes
Fig. 4. The mud hearth and curing system designed for the use of firewood as heat source.
Fig. 5. An illustration of the mud hearth design - Longitudinal sectional view
Fig. 6. Curing tug system designed for the use of kerosene as heat source Fig. 7. Newly designed tub for using LPG as heat source.
Fig. 8. Gas pipes and longitudinal burner concealed within brackets. Fig. 9. Metallic bracket used for concealing the burners.
Fig. 10. Dial type thermometer. Fig. 11. Cane curing system with metallic chains for lifting the bundles.
Fig. 12. Raised wooden/Bamboo platform near the cane curing unit for rubbing the oil-cured canes with coir or gunny cloth.
Fig. 13. Some traditional tools used in cane processing.
- About half of the tub is filled with the chosen oil mixture.
- The tub is carefully and slowly heated to raise the temperature up to the boiling condition and then the temperature maintained at that level.
- In each batch, 2-5 bundles of 20 canes of full length (12-16 feet) can be cured. The bundles are kept immersed in the oil by using some weights above the bundles for the desired duration (20, 30 and 45 minutes for small, medium and large diameter canes respectively) and stirred occasionally by using some wooden sticks. Utmost care has to be taken in controlling the temperature and managing the flame so as to avoid any fire hazard. Maintenance of uniform temperature below the boiling condition has advantages of moderate shrinkage of cured material and prevention of fire hazard.
- After curing the canes in hot oil for the required duration, the bundles are lifted with the help of metallic chains provided (see Fig. 11) and placed either over the wooden poles placed across the tub or over the tightened chains to drain the excess oil to the tub itself. Gentle shaking of bundles using wooden sticks/hooks hastens the draining process.
- The canes are then transferred to an elevated wooden platform (made with bamboo poles) for rubbing with coir or waste gunny cloth (see Fig. 12). This process removes most of the mucilaginous or waxy substances and to some extent the silica deposits from the surface of the stems. The subsequent rubbing with dry gunny cloth imparts polish and improves the smoothness of the stem.
- The cured canes are then to be straightened by bending in opposite directions with the help of a wooden gig and end-trimmed by a specially designed scissors (Fig. 13). The scissors should be sharp enough to give a clean cut to avoid end splitting.
- The polished canes are spread out in the open area and sun-dried for a week. Through this entire procedure. Gradually, the skin color changes from green (or often straw color) to an ivory white (Fig. 1). While drying, it is essential to cover the canes with polythene sheets or plaited coconut leaves during nights to prevent dew deposits and subsequent fungal infection and staining.
The trimmed straight canes are tied into tight bundles of 100 pieces, neatly stacked and covered with polythene sheets/plaited coconut leaves for further transport to godowns and other storage areas. Generally, canes will be supplied to manufacturing units from such storage areas.
It has been found that the additional investment on curing, as compared to the rest of the cost, is very marginal (in the tune of 29% of the original value in the year 2002). In the context of improved quality and ready acceptance by the cane furniture manufacturers, this is well justified. Looking at particular cases, oil cured canes add aesthetic value and durability to furniture, and to traditional house-boats used in the eco-tourism industry. Also, international markets demand rattans of ivory white-to clear straw color, which consequently fetch more money on sale. Thus adoption of oil curing technique can be an important stepping-stone for achieving sustainable and profitable development of rattan sector by efficient and value-added utilization of the available resource.
Fig. 14. Oil-curing adds value to the furniture, handicraft products and traditional houseboats in eco-tourism industry.