Lumber Recovery Research Articles

The effects of sawing methods on the lumber recovery rate and lumber grading of Eucalyptus globulus at the small-scale sawmill enterprise, Addis Ababa, Ethiopia

The effects of sawing methods on the lumber recovery rate and lumber grading of Eucalyptus globulus at the small-scale sawmill enterprise, Addis Ababa, Ethiopia

Estimation of lumber recovery for small-scale mobile sawmills in Tanzania

Lumber recovery is an important parameter in determining the production efficiency and viability of mobile sawmilling operations. In this study, lumber recoveries for mobile sawmilling machines operating in four different locations in Tanzania were estimated. A total of 11 mobile sawmilling operations were studied. On each piece of mobile sawmilling machinery, data on log sizes, including bottom, mid and top diameter, and log lengths were recorded. Results showed that the number of logs per machine ranged from 5 to 40 with an average of 28 logs. The middle diameter of the logs ranged from 8 to 44.60 cm, with an average value of 20.58 cm. The number of lumbers produced for each log varied from 1 to 9 pieces, with an average of 3 pieces across all the sites. The lumber recovery (%), varied depending on the individual machine, machine type, source of logs and geographical site within Tanzania. For all the machines, the average lumber recovery (%) per machinery ranged from 16.15 to 62.79%. Among the three types of mobile sawmilling machinery, Wood-Mizer had relatively higher lumber recovery (56.2%) than Ameck and Ding-Dong. The overall average lumber recovery value for all the machines, irrespective of log sizes, site and source of lumber was 43.34%. Analysis of variance (ANOVA) indicated that site, source of lumber, machine type and size of logs had a statistically significant effect (p < 0.05) on lumber recovery (%). The study concluded that mobile sawmilling in Tanzania produces sawn timber with reasonable lumber recovery. However, further studies are recommended to examine technical aspects, such as productivity and taper, as well as cost of the mobile sawmilling operations.

Assessment of the rate of lumber recovery of Eucalyptus saligna at Gefere sawmill in Gimbi area, Ethiopia

Assessment of the rate of lumber recovery of Eucalyptus saligna at Gefere sawmill in Gimbi area, Ethiopia

Lumber Recovery Rate of Cupressus lusitanica in Arsi Forest Enterprise, Ethiopia

In Ethiopia, sawmills have poor capacity utilization primarily due to the outdated equipment that resulted in a low recovery rate and the production of a high amount of wastage. The lumber recovery rate is the output (lumber) of a log in the sawing process. In Ethiopia, Cupressus lusitanica is significantly used for lumber, for furniture production, construction, poles and posts. Sampled logs were processed according to the normal production rate and standard lumber dimension of the sawmill for the purpose of estimating the lumber recovery rate. The present study aimed to investigate the lumber recovery rate of C. lusitanica and the factors affecting it. A total of 26.93 m3 of lumber was produced by the sawmilling operation, representing 72.86% of the overall lumber recovery rate. Furthermore, the sawdust and slabs were recorded as 2.92 m3 (7.90%) of sawdust and 7.11 m3 (19.24%) of slabs, respectively. There were a number of factors that decreased the magnitude of the lumber recovery rate. It was observed that cutting using a wider saw kerf caused a reduction in the rate of lumber recovery owing to the generation of an increased quantity of sawdust. The lumbers were air-seasoned in the sawmill yard. Maximizing the volume of the lumber recovered from the logs can increase the sawmill profitability, lessen the effects of climate change, ensure the sustainable use of natural resources, enhance the energy efficiency and manage wood waste (e.g., recycling and prevention) for green economic development and industrial transformation. This species has a great demand in the wood industry of Ethiopia; hence, the plantation and yield of C. lusitanica must be expanded in order to provide sustainable forestry, protect valuable forest resources and safeguard the biodiversity in the country.

Effect of Sawing Variation on Hardwood Lumber Recovery—Part I: Volume

Abstract Sawing variation (SV), the degree of deviation from a specified target lumber size, is an unavoidable component of the sawing process. SV is influenced by several factors such as machine, material, set works, feed works, and cutting parameters. To account for these factors resulting in deviations from the desired target size, the target thickness of the lumber cut must be increased such that only a minimal number of boards is less than target thickness. Thus, the greater the amount of SV, the larger the target thickness must be such that a minimal quantity of undersized lumber is produced. Hence, with larger amounts of SV come greater waste and decreased opportunities for optimizing lumber recovery. However, the decrease in material loss due to a reduction in SV may not necessarily translate into a statistically significant increase in lumber product recovery by volume. This study explored the effect of varying degrees of SV on lumber recovery by volume for a range of hardwood log diameters using the US Forest Service's LOg ReCovery Analysis Tool sawmill simulation software. A minimal average recovery improvement of 3 percent due to reduced SV was observed across all kerf thicknesses, equating to a production value improvement of $336,000 for an 8 million board feet mill. Results indicate that the recovery gains realized by volume depend upon the log diameters sawn, the lumber target thickness, and the change (reduction) in SV.

Effect of Sawing Variation on Hardwood Lumber Recovery—Part II: Board Count

Abstract Sawing variation (SV) describes all variations that exist in the production of lumber due to machine, material, set works, feed works, and cutting parameters. The necessary oversizing of board thickness due to SV diminishes sawmill profits and hence efforts must be made to reduce the variation. However, such efforts are costly and sawmill personnel generally do not know at which point efforts to reduce (SV) become more costly than oversizing the boards. In an accompanying paper we examined the impact of SV on lumber volume recovery and found that volume recovery increased comparatively more for thinner than for thicker kerfs and that the effect of reduced SV became more pronounced as diameter increased. In this second manuscript, the effect of SV on the quantity of boards sawn for a range of hardwood log diameters using the US Forest Service's LOg ReCovery Analysis Tool sawmill simulation software was researched and compared with the volume improvement from an earlier paper. Results showed that significant differences in the number of boards obtained was dependent on the log diameters sawn, the lumber target thickness, and the change (reduction) in SV. A minimal average recovery improvement of 3 percent due to reduced SV was observed across all kerf thicknesses, equating to a potential production value improvement of $336,000 for an 8 million board feet mill. All sawmills can benefit from reducing SV, but mills that saw large-diameter logs might consider pursuing SV reduction more aggressively than a sawmill sawing mostly small-diameter logs.

Effect of natural tung oil on wood shrinkage during the thermal modification process

The non-negligible shrinkage and volume loss caused by heat treatment would reduce the availability and product value of wood. In this study, natural tung oil was innovatively used to alleviate heat-reduced shrinkage in thermal modification. The mass changes, dimensional shrinkage and volume loss, chemical structures, morphological characteristics, as well as pore structures of wood were studied. The results demonstrated that the volume loss was significantly reduced after tung oil heat treatment, especially at high temperatures (reduced by 85.27% at 210 °C for 6 h). Tung oil could separate oxygen and mitigate the thermal decomposition of wood components. Additionally, tung oil had impregnated the wood and occupied transportation passages of volatile degradation products, such as vessels and pits. Although severe shrinkage appeared in air heat-treated samples, the porosity increased and part of the micropores transformed into mesopores and macropores. While tung oil heat-treated samples had a lower proportion of macropores and porosity than that of the control and the air heat-treated ones. Overall, tung oil heat treatment was facile, eco-friendly and highly efficient in maximizing actual lumber recovery and improving the product value of wood without any harmful chemicals, as well as saving wood resources.

Online Measurement of Outline Size for Pinus densiflora Dimension Lumber: Maximizing Lumber Recovery by Minimizing Enclosure Rectangle Fitting Area

This paper proposes a non-contact, online, rapid, and non-destructive measurement method of Pinus densiflora S.et Z. (Pinus densiflora) dimension lumber based on an algorithm of maximizing lumber recovery by minimizing the enclosure rectangle fitting area. The method takes the full influence of multiple factors, such as the difficulty in measuring large-size dimension lumber, conveying deflection, etc. into account. Image splicing, object and background segmentation, and lumber size measurements are carried out. Compared to other current algorithms, it can decrease the measurement errors and improve measurement efficiency. The problems of slow image segmentation, large-size lumber measurement, and conveying deflection are solved. Through measurement tests and error analysis, the measurement accuracy of the lumber size can reach 0.8 mm/m. This method meets the requirements of high-speed lumber production and lays the foundation for the development of a lumber detection and evaluation system.

The Effect of Kerf Thickness on Hardwood Log Recovery

Abstract When sawing a log into lumber or other products, the saw blade removes material to separate the wood fibers between the resulting two parts, a loss of material that is commonly referred to as saw kerf. Thicker kerfs result in greater waste and less material available to produce lumber. Over the past decades, with the advancement of materials and technology, saw blade thickness has decreased. However, the reduction in material loss owing to a reduction in saw kerf may not always translate into a statistically significant increase in lumber product recovery. In this study, we explored the effect of saw kerf thickness on lumber recovery for a range of hardwood log diameters using the US Forest Service's Log Recovery Analysis Tool (LORCAT) sawmill simulation tool. Results indicate that the recovery gains realized depend upon the log diameters sawn, the lumber target thickness, and the change (reduction) in the thickness of the saw kerf.

Dynamics of beetle-killed snags following mountain pine beetle outbreaks in lodgepole pine forests

Snags (standing dead trees) are important components of forest ecosystems that, among other benefits, provide critical habitat for many species of wildlife, but also represent important safety concerns to firefighters, forest workers, and the public. We identified factors that influence the fall rates of lodgepole pines, Pinus contorta Dougl. ex Loud., killed by bark beetles during a severe regional-scale outbreak of mountain pine beetle, Dendroctonus ponderosae Hopkins, that occurred in 2004–2012. Data were obtained during annual assessments (2010–2019) of a network of 107 0.081-ha circular plots installed in P. contorta forests in Colorado, Idaho, Montana, Utah and Wyoming, U.S. A total of 3789 P. contorta snags were monitored, and in each case we recorded, among other variables, the year the snag was created and the year the snag fell to the forest floor. Among snag age classes (i.e., number of years since tree death), the highest number of snags (1046) were 12 years since death (YSD), and those 13 and 14 YSD exhibited the lowest fall rates to date (<10%) despite being the oldest in our study. Snags 13 and 14 YSD were among the largest in diameter. Snag fall occurred in every snag age class from 1 to 14 YSD, with the greatest proportion of snag fall events occurring 4–8 YSD. By 2019, 24.7% (937) of snags fell to the forest floor. We modeled snag fall using a Cox’s proportional-hazards model that included six covariates of interest: elevation (m), slope aspect (categorical, cardinal direction), slope (%), canopy cover (%), snag height (m), and snag height:dbh (m, diameter at 1.37 m in height). Slope aspect had the strongest influence on fall rates. Northern aspects, increased canopy cover, and taller snag heights decreased the probability of snag fall. Conversely, southern aspects and increased height:dbh ratios (i.e., taller, skinner snags) increased the probability of snag fall. The predicted half-life (i.e., the amount of time since death required for 50% of the snag population to fall to the forest floor) was ~16 YSD after which the function predicted a linear, ~0.04/year decline in snag survival probability 15–30 YSD. The observed longevity of P. contorta snags confers important ecological benefits for some wildlife, and may offer opportunities for extended periods of salvage. However, checking (cracks) rapidly occurred, and many snags 6 YSD and older had at least one check at 1.37 m and 5.5 m in height, which can negatively impact lumber recovery. The relatively slow snag fall rates observed in our study also lengthen concerns regarding hazard trees, human safety, and protection of critical infrastructure. The implications of these and other results to management of P. contorta forests are discussed.

Radio frequency vacuum drying of Eucalyptus nitens juvenile wood

Wood drying is an important process for adding value and manufacturing innovative products. Eucalyptus nitens wood is inherently difficult to dry because of its natural propensity for checking as well as collapse and shrinkage. Lumber recovery after industrial drying of eucalypts is also very low. This study measured the wood quality of E. nitens juvenile wood (13 mm thickness) after radio-frequency vacuum (RFV) drying and wood dried in a conventional kiln dryer (KD). Drying cycles were performed using a radio frequency vacuum dryer with a 3 m3 of capacity and convective kiln-dryer equipment with a 3.5 m3 of capacity. The results showed that the drying time using the radio frequency vacuum method was reduced by 47% when compared to conventional kiln drying. The shrinkage was significantly lower in the RFV than in the conventional KD. The volumetric collapse decreased by approximately 60% in the RFV drying. RFV drying of E. nitens juvenile wood improves the wood quality for solid wood products because the intensity of surface checking and collapse are reduced.

Musical instrument lumber recovery from Romanian resonance spruces

Increasing demand for resonance spruce has led to gradual depletion of resources in traditional areas. Consequently, to meet the need for raw material to manufacture musical instruments, sorting has become the key operation of exploitation. This study was completed on the largest Romanian resonance wood resource, to maximize outputs of flitches for violin, cello, and double bass instruments by optimizing traditional requirements regarding quality of raw material with its current level. Ten resonance spruces were felled and gradually turned into semi-manufactured musical instruments. The material was analysed for defects in all stages of conversion. The frequency of zero defective samples was 60%. Evolution of defects along the trees indicated the tree section from 1 m to 12 m above the ground for musical instruments manufacturing. Output in terms of flitches ranged from one tree to another: between 19 and 32% if calculated from logs volume, and between 13 and 30% if calculated from volume of the standing trees. The results advocated for relaxing traditional requirements on resonance logs, at least regarding buttress and knottiness. Thus, recommendations are made, from the perspective of increasing efficiency, on the admissibility of defects and size diversification of musical instruments.

RENDIMIENTO VOLUMÉTRICO Y CALIDAD DIMENSIONAL DE LA MADERA ASERRADA EN ASERRADEROS DE EL SALTO, DURANGO

Se realizó la evaluación del rendimiento volumétrico y la calidad dimensional de la madera en cinco aserraderos de El Salto, Durango, México. Para tal efecto, se dio seguimiento a los productos generados a partir de 412 trozas de pino con un volumen de 293.73 m3 rollo sin corteza; de ellas se obtuvieron 7,085 tablas de diferentes dimensiones y clases equivalentes a 169.01 m3 , con un rendimiento en madera aserrada de 57.5%, correspondientes a 244 pies tablares (pt) por metro cúbico de madera en rollo aserrada. El rendimiento volumétrico más alto por calidad se observó en tablas de la clase número 5 con 86.49 pt, mientras que por grueso nominal fue para las tablas de (7/8”) con 95 pt. Respecto a la calidad dimensional, el espesor promedio al que se asierra la madera no fue suficiente para obtener madera seca y cepillada con dimensión final de 22.23 mm (7/8”), en tanto que para el grueso de 31.75 mm (5/4”), las tablas aserradas en el ejido El Brillante resultaron sobredimensionadas y las tablas de 34.10 mm (6/4”) del ejido La Victoria tuvieron espesores compatibles con la dimensión óptima de corte estimada. Con base en los resultados de este estudio, se sugiere establecer un sistema de control que asegure una buena calidad dimensional en los productos aserrados.

Optimal power consumption and surface quality in the circular sawing process of Douglas-fir wood

Optimal cutting conditions that result in high cutting accuracy and low power consumption are critical in lumber recovery and quality for sustainable wood manufacturing. Despite the many research on wood machining for secondary processing applications, less emphasis has been put on the challenges faced in primary sawing applications. These challenges are associated with online monitoring of surface quality through waviness measurement and conducting full-scale wood cutting experiments under extreme conditions. This paper investigated the effect of feed speed, rotation speed, depth of cut, and the average chip thickness on the power consumption and waviness during the sawing process of green Douglas-fir wood. Power consumption and waviness were measured to find the optimal cutting conditions for energy efficient cutting with high cutting accuracy. Waviness was monitored online using laser displacement sensors and the acquired signals were filtered using the wavelet denoising method. The results showed that cutting power and waviness increased with feed speed. While increasing the rotation speed accounted for higher cutting power, it resulted in less waviness. The impacts of rotation speed on cutting power and the waviness of the sawn lumber were discussed. The waviness is significantly greater at the board top as it is close to saw rim, which is characterized by higher blade deflection. For an identical chip thickness, energy efficient cutting was obtained under low-speed conditions, whereas high-speed conditions improved the waviness. There is a trade-off between productivity, cut quality, and power consumption.

The use of the first industrial X-ray CT scanner increases the lumber recovery value: case study on visually strength-graded Douglas-fir timber

Industrial computed tomography scanning of logs provides detailed information on timber quality prior to sawing. A sawing simulation—considering log rotation angle and knot size accuracy—revealed an average value increase of up to 20% for the best angle compared to the conventional horns-up position. Computed tomography (CT) scanning has the potential to improve the value of products sawn from logs and meets the increasing demands of the wood industry for detailed information on log quality prior to processing. In a validation step, automated measurements of knot cluster variable DAB (DIN 4074-1:2012-06) using CT were compared with manual measurements. In a second optimization step, the hypothesis that the value of the sawn products is increased by sawing at the best rotation angle as opposed to the horns-up position was tested. A sample of 36 Douglas-fir logs were scanned in an industrial CT scanner, and sawn into boards. Knots on the boards were manually measured, and compared with the corresponding knots on virtual boards created from the CT data. The error of the DAB was measured by comparing CT data to manual measurements. An optimized sawing simulation was performed, using the measured DAB error to account for CT measurement errors, as well as a rotational error to account for errors in the log turning equipment. Using the results of the sawing simulation, Monte Carlo simulations were performed to show the potential and benefit of an industrial CT scanner. The three largest DABs measured by the CT showed good correlation to the measurements on the manual boards. The simulation revealed an average increase of value from 4 to 20% compared to the conventional horns-up position depending on the relative price differences between the strength grades. By using a CT scanner to optimize sawing, sawmill owners can process logs in a better way to produce final products with increased added value.

Wood Quality of Old-Growth Koa Logs and Lumber

Abstract Acacia koa trees are ecologically, economically, and culturally significant to the Hawaiian Islands. Koa wood is one of the most valuable species in the world and sale of koa products represents a majority of all the Hawaiian wood products sold by Hawaiian retailers. Today, there is concern in Hawaii among foresters, forest landowners and managers, wood products manufacturers, and the public that the remaining old-growth koa resource has become scarce, is suffering from declining health and diseases, and is characterized by poor growth form. Current practices require harvest of only dead and dying trees and using downed material in wood products manufacturing. We examined lumber volume and value recovery from logs sawn from dead and dying trees and from relic logs (logs that have been on the ground) from four sites on the island of Hawaii. Gross lumber recovery from all study logs was 71 percent. Log size did not significantly influence lumber volume recovery. Forty-five percent of the lumber manufactured from relic logs was below grade compared with 26 percent of the lumber sawn from standing dead and dying trees. Variables that affect lumber quality, such as different defects and heartwood proportion, were measured. Decay-type defects were the most prominent.

An Analysis of the Differences among Log Scaling Methods and Actual Log Volume

Abstract Log rules estimate the volume of green lumber that can be expected to result from the sawing of a log. As such, this ability to reliably predict lumber recovery forms the foundation of log sales and purchase. The more efficient a sawmill, the less the scaling methods reflect the actual volume recovery and the greater the overrun factor. Using high-resolution scanned log data and the RAYSAW hardwood log sawing simulator, we compared recovery results for a 32-log sample with data from other mills and examined the overrun factors for common log scaling methods. With the sample logs, we saw underruns as low as −31.9 percent and overruns as high as 159.4 percent depending on log rule and log characteristics. Given the measurement accuracy of laser profiling systems and computing speed, it is relatively easy to determine log volume and recovery both quickly and with heretofore unknown accuracy. The log rules commonly in use today were all developed over 100 years ago: Doyle in 1825, Scribner in 1846, and International ¼-Inch in 1906. Both the logs from the forest and processing methods and equipment in the mills have changed since then. As such, the log rules are not as relevant to modern mills and today's timber supply as they once were. Given modern developments in laser measurement systems, mill operators have much better tools available to access log supply.

Análisis del rendimiento y utilidad del proceso de aserrío de trocería de pino

En este estudio se determinó un tamaño de muestra de 87 trozas para lograr una confiabilidad del 95%, con base en la variación del coeficiente de aserrío de una premuestra de 30 trozas. De la trocería procesada, un 43% se clasificó como de alta calidad, un 26% de clase media y un 31% de baja calidad. Respecto al diámetro, el 89.65% se ubicó en un rango de 30 a 55 cm. Se determinó un coeficiente de aprovechamiento nominal de 51% y una proporción de costeras y recortes de 27% y el porcentaje de aserrín de 22%. La calidad y diámetro de las trozas no influyeron en el coeficiente de aserrío, pero sí se presentó una relación directa entre la calidad de las trozas con la calidad de la madera aserrada, la trocería de 1a y 2a, generó un 31.70% y un 19.44% de madera de clase; la trocería de 3ª generó un 33.60% de madera de 3ra; la trocería de 4ª y 5ª un 34.79% y un 29.18% de madera de 4ª y 5a respectivamente. Se determinó un costo de la trocería de $432.00 por m3r, un costo de aserrío de $216.68 por m3 ($510.95/ por mpt). Relacionando los costos de estos dos conceptos con los precios de venta de la madera, se determinó una utilidad de $410.58 por m3 ($968.16 por mpt).

Efecto del sistema de aserrío tradicional en las características de la madera de encinos

El proceso de aserrío de encinos se considera una fase importante de su industrialización y de la calidad de la madera generada. Se analiza el control de calidad del proceso de aserrío, el sistema de corte tradicional con el radial y su efecto en los coeficientes de aprovechamiento, en los tiempos de procesamiento y en la proporción de dimensiones en anchos de la madera generada. Se utilizaron trozas de Quercus laurina, Q. candicans y Q. acutifolia, que se procesaron en un aserradero banda de 8 plg de ancho, con sierras tradicionales para pino. La variación del corte (St) fue de 3,93 mm, que se considera alta y refleja una mala calidad del aserrío, la media fue de 25,36 mm y la dimensión óptima de corte de 28,71 mm, la diferencia indica que un porcentaje considerable de las tablas producidas (80 %) no se puede clasificar en el espesor de la categoría de 3/4 plg. Los coeficientes de aserrío del sistema tradicional fueron de 55,83 % y en el radial de 52,31 %. El tiempo de aserrío para procesar 1 000 pies tablas en el sistema tradicional fue de 73 minutos y en el radial de 103 minutos, lo que representa un 41 % más del tradicional. Con el sistema se aserrío radial, se generó una proporción alta (77 %) de tablas angostas (4 plg y 6 plg), y un porcentaje bajo (23 %) de tablas con anchos mayores de 8 plg. Con el aserrío tradicional, las proporciones se invierten significativamente, para los anchos mayores a 8 plg representaron un 88 %.

Carbon sequestration for different management alternatives in sweet chestnut coppice in northern Spain

This paper provides an innovative approach to assessing carbon sequestration in sweet chestnut coppice taking into account the importance of carbon fluxes in the whole forest-industry value chain in the mitigation of climate change. The goals of this study were: to evaluate the baseline carbon capture of sweet chestnut forest in the north of Spain; to assess the effect of thinning and extending the rotation period on carbon storage; and to evaluate the substitution effect of using sweet chestnut products as an alternative to other materials. The CO2FIX model was used to estimate carbon content in different forest components: aboveground and belowground biomass, soil and wood products, under five different thinning and rotation scenarios. Model parameterization as a function of stand age was carried out using growth data, climate data, litterfall rates, sawmill processing data, and data on the lifespan of products and their final end. Sawmill efficiency was measured in situ using the Lumber Recovery Factor.The scenarios in which only one thinning was made resulted in more total carbon accumulating than the baseline, especially when the 40 years rotation was increased by 20 years. In contrast, scenarios involving two thinning did not even reach the baseline value of total carbon. Additionally, a positive impact on GHG emissions was found for using wood to substitute other materials, i.e. cement and fossil fuel. Taken together, these results highlight the sustainability of thinning and rotation treatments in terms of carbon storage in sweet chestnut coppice, and quantifiably supports the environmental benefits of the substitution effect of sweet chestnut wood products. As such, it provides valuable information for forest managers and policy makers who wish to address climate change mitigation in forest management planning.