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- Ah Shenga, Pedro
(författare)
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SAWING STRATEGIES FOR TROPICAL HARDWOOD SPECIES : Simulation studies based on industrial conditions of Mozambique
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The harvesting of Mozambique tropical hardwood species is considerable higher than the natural regrowth in the forest and the stock is decreasing drastically. Therefore, it is important to improve the material recovery when the wood is refined (i.e., in sawing and further refinement to products such as joineries, furniture etc.) to reduce the waste and to re-utilize efficiently the by-products to increase the added value. The wood processing industry is an important means to boost the industries in the rural areas and also to generate incomes for the local communities by creating jobs and business opportunities.The majority of the logging that can be used for sawmilling in Mozambique is exported as roundwood due to the inability of companies to meet the product standards set for export and to generate profit. The lack of capabilities of the local sawmills to generate profit, also foments the illegal logging because of the higher price of roundwood for export which contributes to increase the number of unlicensed individuals in harvesting. This threatens the law enforcement and thus the degradation of the local wood industry. An alternative to increase the profit and empower the local community could be to export more refined wood products such as sawn timber, parquet, and veneer instead of the roundwood.The objective of the work was to investigate alternative sawing strategies of tropical hardwood species that could increase the profitability of the Mozambique wood industry in general and at sawmill in particular. The subject was approached using a database of virtual logs and together with a sawing simulator. The thesis has two main focus areas: (1) creating the log database with the corresponding algorithms for sawing simulation, and (2) investigations of alternative sawing strategies.The first focus was to build the database of surface-scanned logs and develop the algorithm for the saw simulation. The results are a database of 15 logs models describing the logs outer shape in which 10 jambirre (Millettia stuhlmannii Taub.) and 5 umbila (Pterocarpus angolensis DC.), and the algorithm for the sawing simulation. The algorithm use “brute force” i.e., determines all volume yields of sawn timber from the combination of all settings of log-positioning parameters (offset, skew and rotation) and selects the maximum value of volume yield. From simulation, using three sawing patterns (cant-sawing, through-and-through sawing and square-sawing) combined with two positioning parameters (offset and rotation) it was found that the sawing pattern has great impact on volume yield and that the square-sawing gave higher yield followed by through-and-through sawing pattern.The second focus was on alternative sawing strategies; having in mind that the optimal volume yield is achieved by aid of computerized production systems and that these resources are not yet in use in Mozambique. Hence, the objective was to find the positioning parameters that can be set manually and improve the volume yield. The result have shown that the rotation is the most affecting parameter followed by offset and skew, and that the volume yield can decrease by between 7.7% and 12.5% from the optimal positioning when the logs are manually positioned with the knowledge about the optimal log position. In another study, using crook-up or horns-down positioning as alternative to the optimal positioning, the volume yield decreases by between 10% and 13% from the optimal positioning. By using bucked logs , the optimal volume yield increased by between 8% and 13% in relation to full lengths logs, and the volume yield of bucked logs when using crook up positioning decreases 2% in relation to optimal positioning of full length logs.It is concluded that there is an unexploited value potential in the wood chain which can be reached using alternative positioning and modern measurement techniques and that the grading of wood will facilitate and improve the sawing process.
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| 2. |
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| 3. |
- Hesselman, Jonas, et al.
(författare)
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Jämförelser mellan metoder för fastvolymbestämning av stockar
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In 2008 a new method for automatic measurement of solid volume under bark (m3sub) of sawlogs was introduced in southern Sweden. In this method the diameters at 10 cm intervals are used, thus producing a section-wise volume (m3sub-sw). The scanners used are programmed to leave out bumps and indents when diameters are calculated. The objective of the study was to compare this method with two other methods used on the Swedish wood market; a) volume based on top and butt end diameters (m3sub-tb) and b) volume based on top end diameters and conversion factors to solid volume (m3sub-cf). The conversion factors are arranged as a matrix based on diameter and length of the logs. Volume m3sub-tb is the most widely used method for measuring m3sub in Sweden. M3sub-cf is partly used for payment but more widely for planning purposes, for example when the logs are priced as a cylinder volume based on top end diameter. The study was performed on spruce (Picea abies). The three different volume estimates as well as the diameters obtained from the log scanners were evaluated on 435 manually measured control logs from five different mills. For an additional 180 000 automatically measured logs from four of the sawmills the m3sub-sw and m3sub-cf volume estimates were compared. The results showed only minor differences between the methods. The volume m3sub-sw was, for the 180 000 logs, 0.6 % greater than the volume m3sub-cf. The analysis of the matrix for conversion factors showed that, if the matrix was to be revised, this should be done as slightly increased factors for small diameter logs and for big diameter logs. However, it was concluded that it would mean less implications for the wood market if the section-wise volume could be reduced to make this volume equal to m3sub-tb and m3sub-cf. This to achieve that all three methods, given a sufficient number of representative logs, would give the same volume
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| 4. |
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| 5. |
- Hultnäs, Mikael, et al.
(författare)
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Dual-Energy X-Ray Absorptiometry Analysis for the Determination of Moisture Content in Biomass
- 2010
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Ingår i: Journal of Biobased Materials and Bioenergy. - : American Scientific Publishers. - 1556-6560 .- 1556-6579. ; 4, s. 363-366
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to describe and validate a novel method able to fast, accurately and with a high precision determine the moisture content of biological materials ranging 10% to 70%. A calibrated Dual X-ray photon absorptiometry technique is validated against moisture content in wood chips. Conventional criteria such as the Pearson correlation coefficient, the root mean square errors of calibration and coefficient of variation were used for the evaluation of the method. The method is independent of the thickness and density of the object but dependent of the effective atomic number of the material. The results shows that this photon absorptiometric method gives accurate (<2%) and precise (<1%) results for moisture content determination in wood chips.
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| 6. |
- Hultnäs, Mikael, et al.
(författare)
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Predicting the green density as a means to achieve the volume of Norway spruce
- 2013
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 28:3, s. 257-265
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Tidskriftsartikel (refereegranskat)abstract
- All roundwood that arrives at pulp mills in Sweden is measured manually to obtain the volume. Shortened times between the harvest of the wood and its transportation to the mill have decreased the variation in the green density of wood and have increased the appeal of a method that combines the prediction of green density and weight scaling of the trucks with wood to obtain the volume. The aim of this article is to create a statistical model that can predict the green density of Norway spruce (Picea abies (L.) Karst.) pulpwood with the help of density data from earlier years for a certain mill and meteorological data from the wood supply area of the mill. To create the model to predict the green density, stepwise regression was used. The results showed that the model can explain the variation in green density by 89%, and can predict the density with a mean error of 00.019 ton/m3. The average standard deviation of the ratio between the measured observations and the predicted density was 7% on a yearly basis with variations over the year. From October to March, the model showed results that were at the same level to the result for the volume measurement performed in Sweden today.
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| 7. |
- Johansson, Tord, et al.
(författare)
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Micropropagation and establishment of triploid birch and yield and wood properties
- 2006
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Rapport (populärvet., debatt m.m.)abstract
- A triploid birch (Betula pendula f. gigas) from Valls Hage, Gävle, Sweden has been cloned and micropropagated. Small (30 cm high), tall (90 cm) and magnum (> 120 cm) were produced and planted in the field in autumn or in next spring.Three localities were used: Hedemora, Sala and Uppsala. The experiments were located on former farmland. In a parcel, 25 seedlings of triploid birch was planted in a spacing of 3x3 m. Between the triploid seedlings, pendula birches (Betula pendula Roth) was planted. Close to the experiment a parcel with hybrid aspen (Populus tremula x Populus tremuloides) was planted. The same spacing as for triploid birch and mixed with pendula birch. Hybrid aspen was used as control.The percentage surviving seedlings differed between localities but also between planting years. As a mean 85-100% of the triploid birches planted five years ago were still alive. The highest triploid birches were found in Hedemora, 150-250 cm high. In Sala the heights differ between 120 and 160 cm and in Uppsala between 70 and 220 cm. The pendula birches were shorter, 75 to 200 cm high, and the aspens were 100 to 160 cm high.The diameter and height of older triploid birches was measured and compared with pendula birch. The triploid birches had grown faster than the pendula birches. A small group of triploid birches growing on a site in southern Sweden, Ekebo, had a a site index of 28-30 m (H40).Studies on wood qualities among others basic density and fibre length were made. There were no significant differences between the studied factors for triploid birch and pendula birch.Some practical implications were made.
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| 8. |
- Johansson, Tord, et al.
(författare)
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Överlevnad och produktion hos triploid björk
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A triploid birch (Betula pendula f. gigas) from Valls hage, Gävle, Sweden has been cloned by micropropagation. Mini (8 cm), small (30 cm) and tall (90 cm) seedlings were produced and planted in autumn or in spring 2001-2004. Three localities were used: Hedemora (Lat. 60° 15’ N.), Sala (Lat. 59° 95’ N.) and Uppsala (Lat. 59° 58’ N.). The experiments were located on former farmland. In a parcel, 25 seedlings of triploid birch were planted in a spacing of 3x3 m. Silver birches (Betula pendula Roth) was planted between the triploid seedlings. Close to the experiment a parcel with hybridaspen (Populus tremula x Populus tremuloides) was planted. The same spacing as for triploid birch and mixed with silver birch. The percentage surviving seedlings differed between localities but also between planting years. As a mean 85-100 % of the triploid birches planted five years ago were still alive. The tallest triploid birches examined five years after planting were found on parcels planted in spring 2003: Hedemora, 297 and 323 cm tall, Sala 117 and Uppsala 162 and 202 cm. The silver birches growing on the same parcels were shorter than the triploid birches on trials in Hedemora and Sala, 284 and 306, 87 and 121 cm respectively, but taller in Uppsala: 191 and 245 cm. When the trials were examined 2014 the heights for triploid birch ranged between 5 and 10 meters in Hedemora, between 3 and 5 meters in Sala and around 8 meters in Uppsala. The tallest triploid birches were growing on parcels planted in spring 2003. Silver birches were taller or had the same height as triploid birches on all localities. The height of hybridaspens ranged between 4 and 11 meters in Hedemora, 3.5 and 4 meters in Sala and 6 and 8 meters in Uppsala. Silver birches mixed with hybridaspens growing in Hedemora and Sala had the same height as hybrid aspens but were taller than hybridaspens in Uppsala (10 m). Diameter at breast height ranged between 40 and 78 mm for triploid birch and 29 and 81 mm for silver birch in Hedemora; between 13 and 33 mm and 22 and 29 respectively in Sala and 58 and 60 mm and 72 and 84 mm respectively in Uppsala. The diameter and height of older triploid birches (28-51 years of age) was measured and compared with a silver birch tree. A triploid birch (51 years old) micropropagated from a birch in Edsbyn had a site index of 28 m (H50), a triploid birch from Ekebo 32 m and a 30-year-old silver birch 34 m. Over all the studies did not reveal any differences in growth between triploid birch and silver birch. Key words: Farmland, growth, hybrid aspen, micro propagation, plantation, silver birch, survival, triploid birch, height
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| 9. |
- Klemedtsson, Leif, 1953, et al.
(författare)
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Skogaryd – Integration of terrestrial and freshwater greenhouse gas sources and sinks
- 2010
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Ingår i: 1st COST meeting ‘Belowground carbon in Europeanforest’, Birmensdorf, Switzerland, 26–28 January 2010..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Forests play an important role in the global carbon (C) cycle, and management as well as climate can cause major effects on the balance of C between the atmosphere and the plant/soil system. With re-gard to our commitments to the Kyoto and post-Kyoto actions on climate change, we need reliable predictions on how this balance is affected by management and climate. In 2006 the Skogaryd Research Forest was established in the southwest of Sweden (58°23’N, 12°09’E). The overall goal is to quantify net greenhouse gas (GHG) fluxes from drained spruce forest, by determining the individual fluxes and pools of C and nitrogen and elucidating their connection to site fertility, drainage status and abiotic parameters and then use the generated data in GHG models, for model validations and ultimately emissions predictions. During 2006-2009 the research has fo-cused on two sites, mineral and organic, dominated by Norway spruce (Picea abies). Both sites are drained fertile soils but with different land-use history that have affected their physical properties. Measurements includes: net ecosystem exchange of CO2, Shoot photosynthesis and respiration at different locations within the canopy, stem respiration, emissions of N2O and CH4 using manual cham-bers, soil respiration with automatic chambers including a trenching experiment where root-, mycelia-, and heterotrophic respiration are separated, fine root production using minirhizotrons, and mycelia production. The organic site also includes a wood ash experiment. From 2010 the research will be expanded to the whole watershed, from the mire system via streams, riparian zones, forests, to lakes and the subsequent exchange between the atmosphere and surface waters. Different terrestrial and limnic ecosystems will be linked holistically, using site specific tech-niques at different scales, from aircraft (km2) to chambers (m2) to create integrated models that can be used to quantify net GHG flux for management strategies.
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