Quality of imported spruce and birch wood from the viewpoint of end users

Transcription

1 Barents Forest Forum Preconditions for Forest Sector Investments in the Norhern Europe Quality of imported spruce and birch wood from the viewpoint of end users Henrik Heräjärvi & Erkki Verkasalo Metsäntutkimuslaitos Skogsforskningsinstitutet Finnish Forest Research Institute

2 Background Considerable increase in the volumes of imported spruce and birch logs during the 1990 s Mill. m 3 2,5 2 1,5 1 0,5 0 Saw and veneer log imports to Finland Spruce logs Birch logs Year Source: Metla

3 Quality of spruce sawn timber Main goals and methodology Materials from the southern part of Republic of Karelia (including a small sample from Novgorod), with a reference to Vologda and three regions in Finland (East = Savo-Karelia, West = Pirkanmaa-Satakunta, North = Kainuu) 1. Principal bending properties in advanced structural products: density, modulus of elasticity, strength destructive lab tests 2. Principal visual, physical and tooling properties and kiln-drying and splitting performance in the main joinery products non-destructive evaluation, destructive lab tests and industry experiments 3. Relationships with the commercial grading rules and standards (visual and strength grading), and technical suitability in selected segments of further processing and end-uses grading trials

4 Quality of spruce sawn timber Empirical log materials Log sampling* for the five regions by log diameter class from the true lots of Finnish saw mills, altogether 1162 logs ( logs per region) Measurement of log length, lengthwise diameters, bark removal in the mantle surface, log volume (o.b. & u.b.), maximum diameter and number of knots; record of, splits, decay, deviation from straightness, visual evaluation of straightness and overall quality Time of log sampling and measurement: Nov 2005 Feb 2006 => affects bark removal during wood procurement operations * Even number of logs per diameter class in sampling regional comparisons possible only on diameter basis

5 Quality of spruce sawn timber Log dimensions and quality (statistically differing regions in italics): Top diameter (cm, o.b.): Russian Karelia & Novgorod Vologda 24.2, Finnish regions 23.8 Volume (dm 3, o.b.): Russian Karelia & Novgorod Vologda 310, East-Finland 300, West-Finland 294, North-Finland 293 Percentage of straight logs: East-Finland 79, Vologda 79, West-Finland 78 Russian Karelia & Novgorod 72, North-Finland 72 Percentage of high-quality logs (overall visual quality): Butt logs: East-Finland 89, Vologda 85, West-Finland 83 Russian Karelia & Novgorod 77, North-Finland 69 Middle and top logs: East-Finland 88, West-Finland 86, Vologda 83, North-Finland 78, Russian Karelia & Novgorod 76 Volumetric loss in mantle area due to removed bark, %: Vologda 1.0, North-Finland 3.4, West-Finland 3.6, East-Finland 5.2 Russian Karelia & Novgorod

6 N of annual rings per log Quality of spruce sawn timber Growth rings (at log ends): number (left) and width (right) Annual ring width, mm East Fin West Fin North Fin Vologda Novgorod & Russian Karelia East Fin North Fin Novgorod West Fin Vologda & Russian Karelia

7 Quality of spruce sawn timber Heartwood percentage Heartwood proportion, % East Fin West Fin North Fin Vologda Novgorod & Russian Karelia

8 Density of spruce sawn timber Air dry density of wood by region Air dry density (kg/m3) East Finland West Finland North Finland Russian Karelia and Novgorod Vologda

9 Quality of spruce sawn timber Centre yield, visual grade distribution (NT) East East Finland West West Fin North Fin Vologda Novgorod* Russian East Karelia Karelia Finland Finland A B C D * A sample of only 17 logs

10 Quality of spruce sawn timber Centre yield, strength grade distribution (INSTA 142, visual evaluation) % T30 T24 T18 Reject HYL 0 East Finland West Finland North Finland Vologda Novgorod* Russian Karelia * A sample of only 17 logs

11 MOE (MPa) Modulus of elasticity of spruce sawn timber Modulus of elasticity by region IEast Fin West Fin North Fin Ru Karelia and Vologda Novgorod Modulus of elasticity of 44x200 mm boards by region East Fin West Fin North Fin Ru Karelia and Novgorod Vologda MOE (MPa) Surface Pith Surface Pith Surface Pith Surface Pith Surface Pith

12 Bending strength (MPa) Bending strength by region Bending strength of spruce sawn timber East Finland West Finland North Finland Ru Karelia and Novgorod Vologda Bending strength (MPa) Bending strength of 44x200 mm boards by region Ru Karelia East Fin West Fin North Fin and Novgorod Vologda Surface Pith Surface Pith Surface Pith Surface Pith Surface Pith

13 Strength grade distribution, by destructive measurement of true strength (volume-%) Strength classes 100 % 80 % C50 60 % C40 40 % 20 % 0 % East Finland West Finland North Finland Russian Karelia & Novgorod Vologda C30 C24 C18 C14 Reject

14 Added value of sawn timber comparing the results from visual strength grading (INSTA 142) and destructive strength tests (Strength) with the results from visual sorting (NT) prices: summer 2007 Region INSTA 142 vs. NT Strength vs. NT East - Finland West Finland North Finland Russian - Karelia & Novgorod Vologda

15 Change of species!

16 Quality of imported birch Study objectives: Determine the variation in quality of imported birch plywood logs and, subsequently, veneers, in comparison to the raw material obtained from domestic cultivated birch stands of second commercial thinning Simulate the timber assortment recoveries and grades when bucking the stems into a) veneer logs, and b) saw logs

17 Quality of imported birch, materials Measurements on stands and standing trees, logs, veneers and wood discs from Russia and Finland: Russian Karelia: 3 stands, logs imported to Joensuu for peeling experiments Leningrad region: 3 measured stands, logs for peeling experiments from 2 stands Vologda region: no field measurements, veneer log samples to Joensuu from 2 train stations in Vologda Finnish North Karelia: 4 measured stands, logs for peeling experiments from 2 stands

18 Materials, birch sample stands Measured sample stands Departure stations of train samplings

19 Saw log reduction* Saw log reduction, % Russian Karelia Leningrad region Finnish North Karelia Veneer log bucking Saw log bucking * Saw log reduction = the volumetric percentage of log-dimensioned timber that cannot be accepted as log due to the defects (calculations based on measurements of standing trees)

20 100% Distribution of timber assortments, veneer log bucking Average stem volume, dm % 80% 70% 60% 50% 40% 30% 20% 10% 0% Russian Karelia Leningrad region Finnish North Karelia Knot free veneer log Veneer log Pulpwood Waste

21 Peeling Peeling experiments 9 lots, ca m 3 each => totally ca. 500 m 3 of peeled logs

22 Veneer grade distributions 100 % 80 % 60 % 40 % 20 % 0 % Russian Karelia Leningrad region Vologda region Finnish North Karelia Domestic Imported Better surface veneers Other surface veneers Middle veneers

23 Tensile strength tests of veneers Test specimen Three butt logs from each study stands (1 small, 1 medium-sized, 1 large log) The second peeler bolt from each log Peeling using the same peeler and lathe setting Three veneer pieces were sampled from the veneer: from the beginning (near to the bolt surface, in the middle, and near to the end of the sheet (close to the peeler core) 3 defect free specimens (50 x 100 mm) were cut from each veneer piece Thickness measurement of the specimen Strength test with a pneumatic tensile tester Altogether 243 specimens

24 Tensile strength tests of veneers Tensile strength perpendicular to the grain, MPa 1,95 1,9 1,85 1,8 1,75 1,7 Core veneers Middle veneers Surface veneers All Imported Domestic All

25 Conclusions, birch Quality of imported birch timber strongly depends on the supplier of the material Percentage of waste (at mill) varies from 1 to 20 Regional differences cannot be estimated based on this case study Differences between the imported lots vary considerably in comparison to the domestic cultivated birch stands So far, the average stem size is smaller in cultivated birch stands than in Russian final felling stands As a consequence, the proportion of better surface veneers is smaller => raw material should be allocated by the product palette of the plywood mill accordingly: Imported birch => higher proportion of valuable surface veneers => logs to mills that produce uncoated boards for visual end uses Cultivated birch => average veneer grades => logs to mills that produce film coated boards