School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemAn investigation on peeling recovery and quality of senile plantation-grown rubber trees in Laos(Springer (part of Springer Nature), 2020)The study assessed the peeling potential of rubber trees past the prime latex-producing age when the latex yields become non-economical. Fifteen 25-year-old plantation-grown trees were harvested and peeled using spindleless lathe technology. Following peeling, veneer sheets were measured and graded to determine volume and quality recoveries. Relationships between billet characteristics and recoveries or quality were examined and a recovery predictive model proposed. Most of the main causes identified for downgrading face veneers were either processing-related issues or drying-induced defects. Thus, a combination of several optimisation techniques could annihilate most of the main causes of downgrading veneer, potentially leading to a substantial proportion of higher-quality veneers typically used where surface decorative appearance is a primary consideration. The results demonstrated that rubber trees past their latex-producing prime from unthinned and unpruned stands have qualities and desirable traits to potentially produce certain high-value engineered wood products. Senile rubber trees in Laos could represent significant additional revenue to growers and a source of raw material to the industry which, theoretically, could be converted into high-value products if other factors can be overcome.
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ItemTimber Trading and Pricing of Plantation Grown Teak (Tectona grandis Linn.F) in Laos(SPRINGER, 2021-12)The market demand and price of teak in Laos vary broadly and depend on several factors. The aim of this study was to assess timber trading and pricing based on a survey of teak buyers. The research investigated teak trading methods, markets and prices paid for particular timber types and quality grades. Three types of teak timber are commonly sold: 24.7% as standing trees, 39.6% as round logs and 35.7% as square logs. The main wood products produced from plantation teak include joinery products, door and window frames, and furniture (57.9%, 26.3% and 15.8% respectively). The end buyers of teak timber in Laos are sawmillers and wood manufacturer. Teak timbers supplied to end buyers from growers via the local traders account for 49.0%, followed by 41.3% by direct supply from teak growers and 9.7% via the local small sawmillers and wood manufacturers. The price of teak timber varies significantly based on four main factors: timber types, log sizes, log quality (grades) and distance from plantation site to road (for standing trees). The round log price of 250US$/m3, based on both log diameter size (D26-30 cm) and log quality grade (A grade), was much lower than the 321US$/m3 amount paid for the same size of round log (D26-30 cm) based on log diameter alone (no grading price). It can be concluded that there is a need to develop a clear system or standard for teak log grading and pricing in Laos.
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ItemPlaning characteristics of Papua New Guinea timber species from plantations and regrowth forests(SPRINGER, 2020-03)Although Papua New Guinea (PNG) has a rich and diverse forest cover, there is limited information on processing characteristics for plantations and regrowth forests available. Consequently, the PNG timber processing industry is restricted to a few species, producing low-quality products, which limits opportunities for the processors. Sound knowledge of machining characteristics based on some systematic methods has been identified as essential for assessing the ability in processing raw material into appearance products. Therefore, a testing program was conducted to assess the planing characteristics and most common causes for planing degrade of 25 species sourced from the Morobe and West New Britain provinces, PNG. A total of 18 wood species proved to machine very well with more than 90% of assessed boards being graded either “excellent and requiring very light sanding” or “good and requiring light sanding”. Eight species from this group obtained a perfect score, i.e. requiring very light sanding.
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ItemASSESSMENT OF PHYSICAL AND MECHANICAL PROPERTIES OF PAPUA NEW GUINEA TIMBER SPECIES(UNIV BIO-BIO, 2020-01)A comprehensive testing program has been developed to assess different physical and mechanical properties of 26 commercial and lesser-known PNG species from secondary and plantation forests. The impact of log position in a tree on the mechanical properties has also been assessed to optimize the utilization of timbers along the value chain. The results showed that stiffness and bending strength tend to decrease or remain unchanged along the stem. Shear strength and Janka hardness displayed a similar trend to a lesser extent where the position in the tree had a limited impact on compression strength properties. Thus, segregating based on log position can be of interest where desired mechanical properties and costs associated with segregating justify optimum mechanical properties for the intended end use. The properties of selected species from plantations and regrowth forests were generally lower than those found in the literature for timbers from old-growth forests. The size of specimens tested, the amount and provenance of tested material, and some adaptive traits for tropical tree species are some factors potentially explaining observed differences. However, a comparison with recent studies tends to confirm the overall reduction of physical and mechanical properties when compared with old-growth forests timbers.
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ItemA Wood Recovery Assessment Method Comparison between Batch and Cellular Production Systems in the Furniture Industry(AMER SOC TESTING MATERIALS, 2019)Abstract Enhanced wood recovery mirrors a successful wood manufacturing operation. Studies of wood recovery in secondary wood processing, however, are scarce, particularly in furniture manufacturing. Although recovery rates are under the continuous surveillance of sophisticated technology, this attempt to monitor wood recovery would be especially challenging for small- to medium-sized furniture enterprises, as the capital investment in such technology would be substantial. This would hinder the possibility for improvements in production efficiency of the furniture industry. A methodology of wood recovery assessment in the furniture industry has been developed and proposed but has not been validated with a cellular production system, a different layout process and distinctive machinery, species, and other customer requirements. The objective of this study is to assess the wood recovery protocol individually used in batch and cellular production systems, followed by examining the wood recovery of furniture manufacturing in these distinct production systems. Two Indonesian medium-sized furniture companies that individually operate batch and cellular production systems were employed, and two methods, mass and volume, were used to assess wood recovery at each furniture-making station. There was a significant difference in cumulative wood recovery rates between batch and cellular production systems. Based on species and product dimensions, the average individual and cumulative wood recovery rates of furniture manufacturing resulted in a significant difference at the resawing and edging station. Large-dimension product recorded higher wood recovery level than small-dimension product. The wood recovery rates at the resawing and edging, surface planing, thickness planing, and trimming stations were mostly influenced by species, the quality of sawn timber, and cutting bills. Meanwhile, wood recovery at other stations was affected by product dimension and design. The mass method was the most acceptable method according to the measurement systems analysis.
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ItemFurniture Production Efficiency in the Indonesian Context(International Conference on Wood Science and Technology, 2018-10-16)Most efficiency improvement strategies implemented in furniture manufacturing are data-driven methods. Due to a lack of production systems used in most Indonesian small and medium-sized furniture companies, the evaluation of production efficiency for future improvement seems rather difficult to perform. A wide range of existing evaluation tools and the varying capabilities of the companies to adapt the methods contribute to a problematic evaluation process. Research has been undertaken with the aim to develop a generic efficiency evaluation method and to prioritise a new potential metric to assess and control efficiency in furniture manufacturing. A basic production cost analysis with standardized variables has been demonstrated as a typical method to evaluate production efficiency in multi furniture companies, followed by applying a wood recovery assessment, a Pareto analysis, an X-Y matrix, and process capability analysis. The heartwood proportion of teak (Tectona grandis) has been determined as a key potential efficiency metric to control and monitor teak sawn board quality and its utilisation. Applying process capability analysis with a setting of lower specification limits to the population of teak heartwood rates produces a model to simulate optimal teak utilisation.
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ItemQuality assessment of the drying process for Eucalyptus delegatensis timber using greenhouse solar drying technology(Springer Verlag, 2019-01-24)The aim of this study was to investigate the process of drying Eucalyptus delegatensis in a greenhouse solar kiln. Specific objectives were to assess stress formation, moisture gradients and timber distortion, the moisture content distribution within various sections of the timber stack, and internal checking and collapse development within the boards. The maximal temperature and relative humidity (RH) during day time were set at 430C/72% RH. In the night time the temperature was at ambient condition with 90% RH. The strain measurements were undertaken before and after the samples were sliced. The timber quality at the end of drying was assessed based on Australian and New Zealand standard (AS/NZS 4787:2001). The moisture content values in the three different sections (front, middle and end) of 2400 mm long boards were compared by Analysis of Variance. The results showed that the mean compressive strain was -2 x 10-4 mm/mm in the core layers and the tensile strain was 14 x 10-4 mm/mm in the outer layers. All sample boards were within the acceptable limits for cupping, spring and bow, even though the relative humidity level did not reach the set value. However, the amount of twist in three out of twelve sample boards was above the acceptable limit. Mean moisture gradient was 0.6%. There was a significant difference in moisture content at end section compared to the front and middle sections. Internal checking, collapse and residual stress were graded as Class “C” (class A is the highest grade and D is the lowest).
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ItemDrying timber in a solar kiln using an intermittent drying schedule of conventional laboratory kiln(Taylor & Francis, 2018-10-01)The purpose of this study was to apply an intermittent drying schedule developed from a conventional kiln to a solar kiln. Implementing this experiment could help better understand the oscillation of the temperature inside a solar kiln and timber quality during drying progress. The theoretical recharge and discharge curves were used to predict the temperature inside the solar kiln using experimental data obtained previously using a solar kiln. The surface and internal checks were measured using ImageJ freeware, and the development of the Moisture Content (MC) profile was assessed by coring and slicing method for the Eucalyptus delegatensis boards during drying. The results showed that the recharge and dis-charge model can predict the temperature with less than 2 C error from the experimental data in the solar kiln. The total drying time to 12% MC was 87 days for the solar kiln. The drying rate was equivalent to the conventional kiln decreasing at an average rate of 0.2%per day. The surface check formation was found when the MC gradient between the core and the case of the board was greater than 42% at 9 days of drying in the solar kiln and conventional laboratory kiln. The applied drying schedule used in the solar kiln was success-ful and offered similar drying time. However, the oscillation of temperature in the intermittent drying will require further improvement to get closer conditions in a solar kiln.
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ItemPotential of Veneer Peeled from Young Eucalypts in Laos(North Carolina State University, 2018-08-23)In Laos and neighboring countries, opportunities exist for the production of engineered wood products such as plywood and laminated veneer lumber to supply the rapid growth of construction, furnishing, and joinery activities. The objective of the present study was to assess the potential of peeling fast-growing high-yielding pulpwood from managed eucalypt stands in Laos for veneered products. Eucalyptus pellita, Eucalyptus camaldulensis, and eucalypt clone K7 (E. camaldulensis × E. deglupta) stands were characterized based on veneer quality and recovery. The influence of log position, log geometry, and other log traits during recovery were also investigated. The selected taxa achieved green veneer recoveries that ranged between 57% and 67%. End splitting and branch-related defects were the most important grade-limiting defects that restricted veneer sheet quality to a lower grade of most sheets. However, simple timely silvicultural decisions, such as pruning, could significantly help improve the quality of veneer obtained. The obtained results could be used in the formulation of recommendations to adopt better management practices in Laos to improve the value of plantation-grown wood.
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ItemAchieving Long-Term Adhesion and Bondline Durability with difficult-to-bond Australian Hardwoods Species(Society of Wood Science and Technology, 2018-07-25)Australia has unique resources of native hardwoods producing a range of aesthetically and structurally attractive timbers suitable for high-strength structural applications and other products for internal and external applications. Amongst problems limiting broader hardwoods applications is their excessive susceptibility to hydrothermal movements in response to changes in the atmospheric moisture. This, in turn, produces excessive interfacial stresses between hardwood surface and glues, resulting in fast degradation of adhesion in products exposed to weathering. A range of Australian hardwood species also suffers from poor adhesion due to high bulk phenolic and surface lipophilic extractive content as well as high density. Research has been undertaken with the aim to improve the performance, durability, and designs flexibility of hardwood-based components for outdoor and indoor applications. The method relies on the application of eco-sustainable water-based formulations of functional polymer and chemical additives overcoming the impact of extractives and facilitating chemical bonding of designated connector chains to cellulose constituents. To date, results of adhesion bonding tests have demonstrated a significant increase in shear strength, wood failure, and durability compared to unmodified samples of Eucalyptus camaldulensis, Eucalyptus pilularis, and Eucalyptus regnans. The results could potentially facilitate the effective transformation of the housing and construction industry by targeting drastically increased use of hardwoods by the rapidly developing Australian prefabricated housing and construction industry.