Toward Sustainable Manufacturing of Natural Rubber: The Case of a Concentrated Latex Mill

Natural rubber (NR) processing industry plays a critical role in the economies of many developing countries where the rubber exports have been one of the major foreign exchange earners. At present, the growth of NR processing industry has been challenged by low productivity, rising cost of production and many environmental issues (large volumes of wastewater, greenhouse gas emissions, etc.) occurred due to its material and energy intensive nature. In order to face these challenges, adapting sustainable manufacturing measures which address the use of less energy, water and materials, and producing less waste is crucial. Accordingly, based on a case study of a Sri Lankan concentrated latex mill, this study highlights the importance of using sustainable manufacturing techniques and tools to uncover the underlying potentials for improving performances in NR processing sector. This study consists of three steps; (i) Material and economic loss, and global warming potential (GWP) quantification through the deployment of material flow analysis (MFA), material flow cost accounting (MFCA), and life cycle assessment (LCA) in a gate-gate basis, (ii) Selection and proposal of improvement options with the help of Pareto and one-way sensitivity analyses, field interviews,and literature, and (iii) Validation of suggested improvement options through the re-execution of MFA, MFCA, and LCA. With the support of this methodical hierarchy, the underlying economic and environmental hotspots in the current manufacturing process can be identified, and moreover, the degree of improvement potential can also be evaluated. Final outcomes indicate that the current manufacturing process can considerably be improved to become more economically and environmentally sustainable. To conclude, this study`s research methodology and findings are believed to be enormously beneficial in both introducing and establishing a sustainable manufacturing model in NR processing industry to sustain its growth in the future.Keywords: Natural rubber processing, Sustainable manufacturing, Material flow analysis (MFA), Material flow cost accounting (MFCA), Life cycle assessment (LCA

Preliminary Investigations of an Oil Based Ethephon Mixture (Motex Plus) on Low Intensity Harvesting Systems of Rubber

Low intensity harvesting (LIH) systems facilitate to reduce the cost of production (COP)through the reduction in the cost of tapping and also to minimise the harvester requirement inrubber plantations. In addition, considerable financial benefits are expected due to theincrease in economic lifespan of trees caused by the reduction in bark consumption. Tocompensate the yield loss due to lowering the intensity, 2-Chloroethylphosponic acid(ethephon) is used as a yield stimulant in LIH to enhance the yield per tapping. Allcommercial formulations of ethephon available in Sri Lanka have been water based.Although such formulations have an advantage in preparing different dilutions by mixingwith water, their long term effectiveness in field application are often questionable. A new oilbased formulation (Motex plus) has been introduced to Sri Lanka and therefore, the studyrecorded here was focused to assess its effectiveness in application of LIH.Performance of three low intensity systems recommended in Sri Lanka i.e. S/2 d3 (half spiralbased once in three days harvesting), S/2 d4 (half spiral based once in four days harvesting),and S/4 d3 (quarter spiral based once in three days harvesting) was tested with application of2.5% Motex Plus, every two months interval except during wintering, monthly and every twoweeks intervals, respectively together with S/2 d2 (half spiral based once in two daysharvesting) system for comparison. Dry rubber content of latex in LIH systems were above35% whilst it was about 33% in S/2 d2 system. Yield per tree per year in S/2 d3, S/2 d4 andS/4 d3 systems were 5.69 kg, 5.48 kg and 6.19 kg, respectively showing a slight higher yieldover the S/2 d2 system. Therefore potential reduction in the dose of oil based formulation isalso discussed. Number of trees affected with tapping panel dryness was comparably lower inLIH systems. Although the bark consumption per tapping was slightly higher in LIH systems,overall bark consumption has dramatically been reduced due to lesser number of tappingdays.

Profitability of Adopting Extended Low Intensity Harvesting Systems for Rubber

In harvesting, rubber tree is generally tapped along the half of the circumference of the trunkwith the frequency of once in two days (S/2 d2). Low intensity harvesting (LIH) systems inrubber plantations appeared to be a practical solution to address the issues related to labour,high rate of bark consumption and cost of production. Low intensity of harvesting could beachieved by reducing either the frequency of harvesting or tapping cut length or both.Recently two extended low intensity systems i.e. S/2 d4 (tapped along the half of thecircumference of the trunk with once in four days frequency) and S/4 d3 (tapped along thequarter of the circumference of the trunk with once in three days frequency) wasrecommended for harvesting rubber in Sri Lanka. Generally no estate would adopt LIHsystems in its full extent. Therefore, profitability of adopting S/2 d4 and S/4 d3 systems in anestate with 500 ha at different rates was worked out for general information. In this case,effects on production cost, net income and harvester requirement were analysed withdifferent adoption rates.Adoption of S/2 d4 and S/4 d3 systems may reduce the total production cost at rates of 1.86and 1.73 million rupees per 10% increase in adoption extent with S/2 d4 and S/3 d4 system,respectively However, adoption of the total extent of a 500 ha estate will get the benefit ofreduction of the production cost in Rs.18.69 and 17.28 million annually compared to tappingthe total extent with S/2 d2 system.Net annual income gained from 500 ha of rubber harvested with S/2 d2 system will be Rs.95.57 Mn. Adoption in 10% of the extent with S/2 d4 and S/4 d3 harvesting systems mayincrease the net income of the estate in Rs.1.87 Mn and 1.73 Mn per year, respectively.Adoption of 100% of the area with S/2 d4 and S/4 d3 system may increase the annual netincome to Rs. 114.26 Mn and Rs. 112.85 Mn, respectively.Harvesting 500ha of mature extent with 400 tappable trees needs 333 harvesters per day at d2frequency. Adoption of 10% of the extent with d4 and d3 frequency may reduce the harvesterrequirement in 5% and 3%, respectively. However, adoption of 100% of this extent with S/2d4 and S/4 d3 harvesting systems reduces the daily required number of harvesters to 167 and222, respectively.

Time Course Variation of Some Latex Physiological Parameters Associated with Yield of Rubber (Hevea brasiliensis) Grown in Eastern Province of Sri Lanka

Rubber cultivation in Eastern Province, is predominantly in the intermediate zone of whichclimatic conditions are considered to be sub-optimal for growing rubber. Due to low level ofatmospheric RH%, latex flow tends to cease early after tapping in these areas. Turgidity oflatex vessels associated with the water content of latex vessels decreases with the sunrisewhen evapotranspiration increases. Hence, time of commencing tapping greatly influences onthe latex yield. Therefore, the present study was aimed to identify the best time of the day forlatex harvesting through an assessment on latex physiological parameters. In order to identify the best time for tapping, variations in several physiological parameterstogether with latex yield were assessed at different time intervals, i.e., 04:00, 05:00, 06:00,07:00 and 08:00 in two smallholder sites in the eastern Province. Latex volume, dry rubbercontent (DRC%), initial flow rate (IFR) and plugging index (PI) were analysed along with theenvironmental factors at the time of tapping. Latex volume per day (LVPD) was highly associated with the overall latex yield hence hadbecome the prime factor concerned. The highest LVPD was recorded between 05:00 to 06:00hrs. Dry rubber content of latex had increased after 06:00 h and that could be attributed to thewater status of the trees which was governed by evapotranspiration. During 05:00-06:00 hrstime period, RH% was almost 100% and temperature was around 23° C. When tappingcommenced after 06:00 h, the overall yield declined. There was a tendency of increasing theplugging index (PI) with the delay of tapping. Therefore, the study concluded that high yieldscould be obtained in this agro-ecological region if tapping is performed before 06:00 h. Keywords: Hevea, Intermediate zone, Rubber, Sub-optimal climatic conditions, Tapping tim

RESPONSE OF LOW FREQUENCY HARVESTING SYSTEMS OF RUBBER UNDER DRIER CLIMATIC CONDITIONS IN SRI LANKA

Escalating cost of production (COP) and inadequate supply of skilled harvesters are among the major issuesthat natural rubber industry face today. Low frequency harvesting (LFH) systems of which trees are tappedin a lesser frequency than once in two days, are considered to be one of the solutions to overcome theseissues. With the focus given to expand rubber in drier climates, the present study was aimed to investigateon the yield response of LFH systems, viz. harvesting trees once in three (d3), four (d4) and six (d6) days inthe intermediate zone (IZ) with the stimulation protocols developed for the wet zone (WZ). With thedecrease in harvesting frequency in IZ, yield per tree per tapping (GTT) increased, however yield per treeper year (YPT) decreased. No such declines were observed in WZ. Stimulation had no negative impact onpercentage dry rubber content in latex (%DRC) or incidence of Tapping Panel Dryness. Whilst only the S/2d3 system is acceptable for IZ in the present form, stimulation protocols are to be revised in other LFHsystems. Bark consumption was reduced significantly by LFH resulting in several long-term beneficialeffects. Effect of stimulation on latex physiology is also discussed.Keywords: Climate change, Ethephon, Hevea, Low frequency harvesting, Rubbe

STIMULANT LEVELS TO BE USED WITH TWO LOW INTENSITY HARVESTING (LIH) SYSTEMS OF RUBBER UNDER WET AND INTERMEDIATE ZONES OF SRI LANKA

Low frequency harvesting (LFH) systems of rubber (Hevea brasiliensis) result in reduction in labour use and cost. However, yield stimulants (viz. Ethephon) are to be applied to enhance the yield in each harvest as a compromise for the yield reduction due to less number of harvesting days. A system of harvesting the tree once in four days (S/2 d4) has recently been introduced and a weekly harvesting system (S/2 d7) is presently under investigation. In S/2 d4 and S/2 d7, the required doze of Ethephon has exactly not known and that would vary with the climatic condition. Therefore, the present study was aimed to identify the suitable concentrations of Ethephon required for S/2 d4 and S/2 d7 systems under two climatic regions, wet and intermediate zones of Sri Lanka.Ethephon was applied in four concentrations (i.e. 2%, 3%, 4% and 5%) and yield performance in each system was evaluated against that of the traditional harvesting systems of S/2 d2 (tapping the tree once in two days). In the Intermediate zone, S/2 d4 and S/2 d7 systems showed a yield increase of 7 and 14 grams per harvest per 1% increase in Ethephon concentration, respectively.  In the Wet zone, respective increases were recorded as 4 and 7 grams. The S/2 d4 system required ca. 3.7 % and 3.2 % concentrations of Ethephon in the Intermediate and Wet zones, respectively, to achieve the yields given by S/2 d2 system. In S/2 d7, 5% Ethephon was sufficient for both zones. Ethephon concentrations tested had no adverse effects on tree health. Needs for commercial scale studies with financial analyses are discussed

Timber production in high density planting of Hevea brasiliensis

The demand of natural rubber has increased continuously with the increase in population and living standards of the human being. Rubber plantations are also a major resource of timber and fuel wood. In order to meet the continuous increase in demand for latex, timber and fuel wood, the productivity of rubber plantations should be increased. Whilst producing high yielding clones for improved latex and timber yield per tree which is a long-term process in perennial crops, planting density could be adjusted to obtain high productivity in rubber plantations. The present level of planting density of rubber in Sri Lanka has been decided on the experiments conducted with the genotypes which are not in common use at the moment. Also, the optimum density should vary with different socio-economic conditions. Therefore, the present study was aimed to identify the suitable planting density for the recently developed and commonly used genotypes of rubber. This paper is focused to assess the timber production of rubber with respect to high density planting. The experiment was set up in Ratnapura district of Sri Lanka in 1992. Rubber was planted in three high densities, i.e., 600, 700 and 800 trees per hectare, with the presently recommended level of 500 trees per hectare. Also, three genotypes (clones) i.e., RRIC 100, RRIC 110 and RRIC 121 were incorporated with the statistical design of split plot where the planting densities were laid as the main plots whilst clones were in the sub plots. Five trees in each sub plot were selected randomly and were used for the measurements of total tree height (TH), crown height (CH), thickness of the untapped bark (BT) and tree diameter at breast height at 11 years after planting (11 YAP). Thereafter, stem volumes were determined using Newton’s formula. Both TH and CH did not vary significantly among planting densities tested. Though not statistically significant, there was a marginal decrease in tree diameter with the increase in planting density. Irrespective of the clone used, BT and mean merchantable timber volume per tree decreased significantly with increase in planting density. Nevertheless, this decline was compensated by increased number of trees in high densities resulting in comparable levels of merchantable volume per hectare among different densities. Total stem volume per tree remained same among four densities tested with that total stem volume per hectare increased significantly with the increase in planting density. Therefore, higher densities are more useful in the industries of fuel wood, pulp, MDF boards etc. Among the clones tested, the clone RRIC 121 outperformed in growth and timber production. The clone RRIC 110 was infected with Corynespora leaf disease hence showed poor performance in all densities. Despite the increase in total timber production with the increase in planting density, overall financial viability of different densities is to be assessed considering all cost components and valuing both timber and latex produced before making any firm recommendation