Document Sample
                                            Sena Peiris
                       Cleaner Production Professionals Association of Sri Lanka


Rubber Industry is a major thrust industry in Sri Lanka, which has a significant contribution to
national economy. Also, Rubber Industry generates many employment opportunities to rural
population having lower level of education. The technology used by most of raw rubber
manufacturers is very old and this results in low productivity and high environmental damage
which people to do not tolerate any longer. A closer look reveals that rubber industry
consumes large volumes of water, uses tons of chemicals and other utilities and discharges
enormous amounts of wastes and effluents. The few cleaner production assessments and
implementation programs carried out in Sri Lanka has shown tremendous benefits. Some of
them are lesser usage of chemicals, energy and utilities including water, improvement in
productivity and profitability, lesser loads and volumes of effluent discharged to the
neighbourhood, better image and relationship with employees internally and with the
neighbourhood externally. These benefits should encourage many rubber industrialists to
follow a cleaner production program in their own places. Many have realised cleaner
production is the only way to survive in today's competitive market where cost of production is
on the increase and prices are dwindling.


Cleaner Production, Reduce, Reuse, Recycle, Rubber industry, Sri Lanka


For several decades rubber has been a main revenue earner for a large population of rural
masses in Sri Lanka until industries like tea, textiles and apparel, tourism became prime
attractions. Though high cost of production and fluctuating prices have affected the growth,
rubber industry is going to remain a major source of income and generator of employment to
people in the rubber growing areas, in the millennium too.
Sri Lanka has about 180 factories producing raw dry rubber, which is used in production of
tyres, tubes, toys, shoes, garden hoses and many others. Also, 15 factories produce
concentrated latex, which is the main raw material for surgical and household gloves, condoms
and balloons, rubberised coir mattresses etc. [1]
One third of the raw rubber production is consumed locally in rubber based manufacturing
industries and the balance is exported. The government has accepted the importance of rubber
industry in the local economy and its influence to the livelihood of rural poor. Therefore,

rubber is identified as a major ~t industry along with a few other industries. A five-year plan is
drawn to develop the industry and to consume 50% of the raw rubber production locally, in
value added industries for export [2].
Cleaner Production Assessments in Rubber Sector
In 1996 and 1997 under Industrial Pollution Reduction Program of UNDPI0 Cleaner
Production assessments were carried out in two crepe rubber factories and a rubber goods
factory. In 1998 and 1999 the author with the assistance of Project SMED (Small and
Medium Enterprise Developers) carried out preliminary assessment at two concentrated latex
and gloves manufacturing plants. Also, the Rubber Research Institute (RRI) together with
Rubber Development Department conducted a preliminary survey to find an alternative to
effluent treatment, where the author was fortunate to be involved in introducing Cleaner
Production. This paper presents a few key relevant findings of the above CP assessments and
at the survey.


As shown in Table 1 raw rubber is produced as Smoked Sheets, Sole Crepe, Latex Crepe,
Scrap Crepe and Technically Specified Rubber in the dry form and as Concentrated Latex in
liquid form [3].
The latex tapped from the rubber tree, which is called the field latex, is the basic raw material,
which undergoes many processes during its conversion to dry rubber or concentrated latex.
The tapping of latex, cleaning and caring for the tree as well as addition of chemicals are
important steps in the field latex production. Latex tapping is a skilled job, which requires
many attributes in performing. A tapper has to tap a block of 300 trees a day in 6 to 8 hours.
The operation covers collection of latex, cleaning cup lump and the tree lace, do a new cut, fix
the cup, and move to the next tree. The whole operation should be completed in less than 2
minutes. The small holders do their own tapping as part time employment or hire tappers.
Unfortunately, due to the low social status associated with the rubber tapping on one hand and
the low incomes generated compared to other employment on the other hand, only the poor
and illiterate of the rural areas, and mostly females, have remained as latex tappers in the

Item                   1987     1988    1989    1990    1991    1992    1993    1994    1995    1996
Total production       121.8    122.4   110.1   113.1   103.9   106.1   104.2   105.3   105.7   112.5
(million kg)
Smoked sheets          55.6     62.8    54.3    58.6    51.3    44.4    43.7    40.9    42.2    53.2
Sole crepe             4.7      3.0     2.6     3.7     2.4     3.6     3.8     4.0     2.7     3.7
Scrap crepe            9.1      5.0     3.7     5.0     7.4     5.6     4.1     4.4     2.9     4.1
Latex crepe            35.1     33.6    31.3    29.1    28.7    24.9    25.1    30.1    29.3    33.7
Latex                  5.7      3.8     4.8     6.7     7.2     12.2    13.1    14.5    5.6     6.7
T.S.R.                 11.6     14.2    14.0    9.9     6.7     15.5    13.9    11.5    14.5    11.1
Local usage            19.3     19.9    21.0    23.6    26.7    28.8    32.8    36.4    36.9    39.9
Exports                106.0    99.3    86.0    86.8    76.4    78.6    69.6    69.1    83.7    72.1
F.O.B. Price (Rs)      27.6     33.7    36.2    35.5    33.5    37.6    44.3    51.8    68.3    79.8
Cost of production     14.3     17.2    19.4    21.4    22.9    124.5   30.2    60.8    33.4    36.7

                               Table 1: Economic data of Rubber [4]


The waste generation in rubber industry ~ be categorised into three areas.
§ Waste in preparation of field latex
§ Waste in raw rubber manufacture – dry rubber
§     Waste in raw rubber manufacture – concentrated latex
§     Waste in rubber based goods manufacture

Waste in preparation of Field Latex

As mentioned earlier, the rubber tapping is a skilled job. Lack of skill in tapping leads to poor
yield of latex due to incorrect cuffing angle and depth. The damage to a tree can result in
unnecessary consumption of tree bark, which cannot be corrected other than by replanting.
Also, the tapper has to ensure that latex does not coagulate prior to reaching the factory by
adding chemicals to his yield. Generally, tappers add more chemicals than required which is a
main reason for many problems in a manufacturing plant.

Waste in Raw Rubber Manufacture- Dry Rubber

50% of total rubber production in Sri Lanka is smoked sheets (RSS). The RSS making is
simple and is carried out in many thousands of small rubber factories by tappers, small holders
and even untrained labourers. The main waste from RSS is wastewater and serum discharged
into nearby water drain. The small volumes at individual factories does not cause much
environmental harm but the serum and water carry chemicals and other useful non-rubber

particles. RSS when coagulated is rolled to get the sheets using a large volume of water in the
mills. The final sheet is then dried in a smoke chamber where smoke and heat is generated
using solid fuel (rubber wood).

The wastes generated in crepe rubber factories are large in quantities and affect the environment. In
crepe rubber factories the field latex is diluted to a predetermined strength in tanks called ‘bulking
tanks’ and chemicals are added. The white fractions which, is separated after 2 to 3 hours is used for
manufacturing of sole crepe and grade 1 crepe while the yellow fraction is used in lower grade. The
yellow fraction contains all non-rubber particles, carotenoid substances, rust, dirt and other impurities
gathered while collecting, handling and transporting latex from the field to factory. Many instances
were found where the tappers were using galvanised iron buckets and factories were using iron bowsers
to handle latex which adds rust and impurities to field latex. Also most of the factories use untreated
water from a nearby stream or a well where iron content and other impurities are high. The natural
consequence is a larger yellow fraction. The white and yellow fractions are then separately coagulated
in coagulation tanks by the addition of chemicals. The coagulum thus formed is then cut into size by an
employee who is immersed up to the waist level in the water in the tank. The blocks cut like that are not
of a uniform size.
These blocks are then milled in a set of different mills to make thin laces or mats. The widths
of these laces vary and the edges have to be cut off later. These mats are then dried in a drying
tower for several days. The drying tower is a large room where hot air is circulated into at 340
Celsius. Therefore all the laces in the room gets equal heat irrespective of the degree of their
dryness thus wasting heat and prolonging drying time. The dried laces are then processed into
blankets or bundles depending on the grade and requirement of the customer. The excess
width of the blanket is cut off at this stage resulting in scrap crepe of lower market value.
The tree laces and cup lumps are too brought to the factory and washed to remove sand and
dirt using large volumes of water and they too undergo a milling process to form them into
laces and dried in smoke rooms or drying towers. The scrap crepe has a very good market in
industries where quality of rubber is not very important and due to low price.

Waste in Raw Rubber Manufacture- Centrifuged Latex

In centrifuged latex factories the field latex is transported by bowsers, feed into bulking tanks
and add chemicals to preserve the latex until centrifuging. In recent years almost all
centrifuged latex factories either coated their bowser insides with epoxies or switched over to
stainless steel bowsers to prevent rust contamination of latex. In centrifuging a large volume
of scrum water is discharged. This serum water is rich in many products such as proteins,
carbohydrates and Nitrogen, Phosphorus, and Potassium (NPK). As a result the load
discharged in wastewater also is very high. The addition of lightly polluted wash water from
bowsers and tanks add to the volume making it difficult to handle the total effluent volume.
Tables 2 and 3 show the average chemical composition and effluent parameters of rubber
factory waste discharges [51.

                  Substance                    Percent content (5)
                  Proteins                     1
                  Free amino acids             0.018
                  Other organic acids          0.04
                  Nitrogenous bases            0.08
                  Inorganic anions             Trace amounts
                  Metallic ions                Trace amounts
                  Formic acid                  0.012
                  Un-coagulated rubber         1
                  Carbohydrates                2.3

         Table 2: Average chemical composition of rubber processing effluent [6]

Parameter            RSS          Crepe TSR           Latex       Dipped     Toleranc
                                                      concentrate products   e limits
PH                   4.9          5.0    5.7          3.7         7.2        6.5-8.5
Settable solids      50           45     155          100         200
Suspended            140          130    237          190         241        100
solids (mg/l)
Total solids         3745         3500   1915         7576        2457       1500 /
(mg/l)                                                                       1000
COD (mg/l)           3300         3500   2740         6201        2011       400
BOD (mg/l)           2630         2500   1747         3192        1336       50 / 60
Ammonical            75           80     66           401         126        300 / 40
nitrogen (mg/l)
Total nitrogen       500          550    147          616         180        300 / 60
Sulphates (mg/l)                                      1610        72         1000

                  Table 3: Effluent quality parameters and tolerance limits [7]

Waste in Rubber based Goods Manufacture

The waste streams in value added rubber goods industries vary from factory to factory
depending on the final product and the process used. The gloves factories showed a very high
consumption of energy and compressed air, heavy usage of water in leaching and washing and
high reject rates. A rubber band manufacturing factory showed high use of steam and
compressed air, fillers and chemicals and also high percentage of off-cuts.


Below we have looked at a selected few opportunities relevant to all raw rubber factories,
which can be applied without incurring high costs. However, the involvement of the
government in certain areas such as rubber tapper training, were highlighted at a recent
seminar held in Colombo.

Rubber Tapping and Transportation

A program for the training of tappers and elevating their social status has to be launched
immediately as most of the processing problems are rooted in tapping. A proposal to train a
batch of rubber tappers is being studied by the Vocational Training Authority.
Usage of traditional coconut shell as the cup for latex collection gives a large cup lump
increasing the scrap crepe. This is now being replaced by a plastic bowl and the traditional
galvanised iron bucket is replaced by plastic buckets. The overall national savings add up to
millions of Rupees (1$US = 70 Rupees approximately) by this simple conversion.
The addition of chemicals to the field latex is still a problem and training of tappers and other
personnel seems to be the main option available. The transportation of the field latex by mild
steel bowsers adds rust to latex. A coating of epoxy has proved to be very effective and many
factories have already carded out the above to eliminate rust contamination of latex. A
significant improvement is noticed in the output of grade 1 crepe by the above solutions.


The addition of water and chemicals in the bulking stage is inevitable but no rubber factory in
Sri Lanka has considered reuse or recycling of water as the water is freely available still. The
streams are fast drying up and recycling appears to be the most economic and viable option to
the water shortage.


A simple partitioning of the coagulation tank using wooden planks proved to be very effective
instead of cutting the coagulum to size by a knife. This saved labour involved and the blocks
were of uniform size, which produced uniform edged laces at milling.

Skim Coagulation

In centrifuging plants the scram water contains about 1% rubber [6] which is usually
coagulated using sulphuric acid. The addition of ammonia in the field as well as in the factory
prior to centrifuging results in high usage of acid for skimming and causes many problems in
final treatment of effluent. To get the most effective latex formulation and chemical dosing at

field and in the factory through controlled trials is the most appropriate solution to the
problem which is complicated and time consuming. The long-term benefits of this solution are
very attractive. Before skim coagulation, the de-ammoniation of effluent helps to reduce usage
of sulphuric acid.
In all centrifuged latex factories the scrum water from latex, centrifuge wash water and
bowser wash water is discharged as one stream. The segregation of these streams can help to
reduce final treatment cost and possibility of recycling of the wash water with a little treatment
for selected uses.

Energy Consumption

In the factories where CP studies were carried out the electrical consumption was monitored
and the milling programs were planned to reduce the operating time. The uniform edged laces
reduced the milling needs and blankets and bundles formed took lesser time. In the dryer
tower the internal partitioning and systematic passing of hot air from chamber to chamber
improved the drying efficiency. The total reduction of electrical and thermal power for the
same output was approximately 10%.
In a glove factory the reduction of waste heat from the drying chamber and reduction of
electrical energy through power factor correction and other measures also amounted to 11 %.

Scrum Water

The serum water has many nutrients and other substances, which can be of high commercial
value. Trials are being conducted to use serum water as a liquid fertiliser. The results of initial
trials are very encouraging. Another proposal to make an animal food out of serum water is
under consideration.

Quality Improvement of Finished Goods

The author wishes to highlight one instance where the quality of the final product- household
and surgical gloves- was affected by quality of field latex.
It was observed that the reject rate in a glove factory to be high around 8.5% where as
standard was only about 1.5%. The major reason for the rejects was pin poles. The
investigation revealed that the latex used for dipping had foam and froth which when
transferred to the mould result in pin holes. The laboratory analysis of the centrifuged latex
showed high dose of soaps and also the inferior quality of chemicals used in the field. By
testing the latex from individual suppliers the problem could be traced to two specific estates
and currently field trials are in progress to develop a revised chemical formulation for the
latex. A trial production run using revised formulation resulted in only 2.5% rejects whereas
the control trial using the factory latex under %me conditions resulted in 7.8% rejects.

Specific Techniques Used in Waste Reduction in Rubber Factories

The well known 3R's, Reduce, Reuse and Recycle is unheard of in rubber factories. In all
factories assessed, the consumption of water could be reduced by 20% and chemical usage by
10% without any interference to general operations and without incurring any expenditure.
Through segregation the water can be reused in selected non-critical operations. The mildly
contaminated water can be recycled at a very low cost for reuse.

A crepe rubber factory in a outstation village 90 kilometres away from Colombo was in a very
awful situation a year ago. The cost of production was high, the quality was poor, employee
motivation low and the factory could be rated amongst the dirtiest with absolutely no house
keeping and it was impossible to cross the area without closing one's nose due to smell
generated by factory discharges. In 1998 March, the divisional superintendent (D8), being in a
desperate situation realised some thing has to be done to prevent total disaster. He devised a
plan to implement a 5S program at the start. The employees were trained, teams formed and
leading by example the DS motivated the factory employees to develop. Now, after one year
the factory has transformed into a model factory with excellent house keeping. The employees
have reduced the obvious waste streams without any knowledge of Cleaner Production,
improved the quality of the final product, gained customer satisfaction through faster service
and now they are prepared to introduce a proper Cleaner Production Implementation program
in order improve the productivity and environment.

Final Treatment of Effluent

The techniques of cleaner production can reduce the total volume and the load of effluent
from the factory but a quantity of effluent remains to be treated at the end. Usually, the most
distasteful job of the rubber factory owner or manager is the final effluent treatment. Cleaner
production can be successfully applied at this stage too in a rubber factory. The treatment
plants installed at many factories spending millions of Rupees has failed to give satisfactory
results due to incorrect operation or ignoring salient parameters or due to operation of the
system intermittently. A treatment plant at the dipped glove factory mentioned earlier was not
discharging water at the permissible standard due to overloading of the plant as the influent to
the plant was having excessive loads. The Cleaner Production practices in the factory reduced
the total load at the effluent plant by 30-40% and the plant is now functioning according to the


The limited experience of Cleaner Production practice in the rubber industry in Sri LMM
shows potential for tremendous savings in waste cost and the elimination of long drawn battle
between the factory owners and the neighbourhood of environmental degradation. The impact
of the results of cleaner production can be felt nationally through the rubber sector which can
be an alternative to overcome the down trodden industrial sector of Sri Lanka.


[1]    Central Environmental Authority (1994). Industrial Pollution Control Guidelines- Booklet 1, p.1-8.
[2]    Department of Census and Statistics. Sri Lanka (1997). Survey of rubber Base Industries, p.3.
[3]    Central Bank of Sri Lanka (1997). Economic and social statistics of Sri Lanka p.35.
[4]    Central Bank of Sri Lanka (1997), Economic and social statistics of Sri Lanka, p35.
[5]    Department of Census and Statistics, Sri Lanka (1 997). Survey of rubber Base Industries
[6]    Dr W.M.G. Seneviratne (1 999).Wastewater treatment and allied industrial effluents, p.1
[7]    Dr W.M.G. Seneviratne (1 999). Wastewater treatment and allied industrial effluents, p.1


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