Willow wood
| pasture | |
|---|---|
 |
|
| Tree species |
White Willow (also mourning, cricket and yolk pasture), Crack Willow , willow , wicker , purple willow , Reif Weide |
| origin |
Europe, North Africa, Asia |
| colour |
Sapwood whitish to yellowish white, heartwood light brownish to reddish brown. |
| Material properties | |
| Bulk density mean | 560 kg / m³ |
| Raw density limit values | 330-590 kg / m³ |
| Axial shrinkage | 0.5% |
| Radial shrinkage | 3.9% |
| Tangential shrinkage | 6.8% |
| Flexural strength | 31-37 N / mm² |
| Compressive strength | 28-34 N / mm² |
| tensile strenght | 46-64 N / mm² |
| Thermal conductivity | 0.113 W / (m K) |
| Fuel properties | |
| Calorific value | 19.7 MJ / kg |
As willow wood is wood of various kinds of pastures (genus Salix ) denotes, as useful and firewood be used. In Europe, this is mainly the white willow ( Salix alba ) and various subspecies and varieties such as the weeping willow , the cricket willow and the yolk willow. It is used for various applications, in particular as round , industrial and sawn timber , and considerable amounts are used for energy (as biogenic fuel in heating plants, among other things ). Willow wood, like poplar wood , is increasingly being produced not only in the forest , but also in short rotation plantations .
According to DIN 4076, "WDE" is the abbreviation for the white willow.
properties
The willow genus, which is represented by numerous species, breeds and hybrids, can be divided into tree willows and shrub willows due to their growth forms. Most of the species grow shrub-like at different heights, only a few species form trees with continuous tree trunks. This is mainly the white willow, as well as limitations to the Crack Willow ( Salix fragilis ) and the goat willow ( Salix caprea ). The former is by far the most frequently used type of willow. Shrubby willows do not play a role as suppliers of wood, but they can be important as wicker and connective willows. The wicker ( Salix viminalis ) and the purple willow ( Salix purpurea ) as well as the introduced American willow ( Salix amaricana ) should be mentioned here.
Under favorable conditions, white willows grow into medium-sized trees with heights of 20 to 30 meters and 1 meter in diameter with a straight, cylindrical trunk, usable shaft length of 10 meters. In the wild, however, the trunks are often crooked. Willows are fast-growing, like poplars, and mature after 30 to 50 years. A willow stand can produce an increase of 15 to 25 solid cubic meters of wood per year and hectare under good conditions . For comparison: Beeches create an increase of 6 to 8 solid meters in good locations.
The willows are among the heartwood trees with color core formation. The sapwood zone is usually wide and whitish to yellowish-white, the core is light brown to reddish brown. The annual rings are noticeably wide and well set off from one another, to which a dense latewood band contributes. The longitudinal surfaces are accordingly flattened in the tangential section or striped in the radial section. The pores are fine and scattered as individual pores or in small groups, they are only visible with a magnifying glass.
The wood of different types of willow cannot be visually distinguished from one another and is also similar in terms of physical properties; it is also very similar to poplar wood. It is coarse-grained and very soft with a bulk density of 560 kg / m 3 at 12 to 15% wood moisture. It is not very elastic and not very firm, but at the same time very light. The shrinkage is moderate and it is very susceptible to fungus and insect attack, impregnation is good in sapwood and only moderately feasible in heartwood.
The structure of the wood makes it easy to work with, but it frays easily and forms woolly surfaces. It is easy to saw, slice and peel and is very easy to split. The bending properties are unsatisfactory, gluing and screwing are problem-free.
use
Material use
Willow wood is used in the same application areas as poplar wood. It is mainly used as round , industrial and sawn timber , and considerable amounts of it are used for energy (as biogenic fuel in heating plants, among other things ). It is processed into chipboard and chipboard molded parts as well as peeled veneers and used as blind wood for furniture. Like poplar wood, it is also processed in the match industry; plywood , plywood for curved molded parts, chip baskets for fruit and vegetables and gift packaging are also produced from peeled poplar veneer . Also Sliced veneer is made of poplar wood.
The wood is also processed into drawing boards , household appliances, toothpicks and snow shovels. It is also well suited for making fibreboard and making pulp and paper . Willow wood is also processed into wood wool . In England in particular, willow wood is the material used to make the pickguards of cricket bats and has the task of dampening the impact of the ball at speeds of up to 130 km / h (this is how the cricket willow, a subspecies of the white willow, got its name).
Energetic use
As with poplar wood, the calorific value of willow wood is 19.8 MJ / kg between that of spruce and beech wood. Due to the low density, the energy yield of the wood in relation to the wood volume (e.g. per ster or per cubic meter ) is lower than that of other firewood.
In addition to poplars, willows are the most important tree species for cultivation in short-rotation plantations as fast-growing tree varieties . In the case of willow wood from short-rotation plantations, which are harvested after a few years, the ash content is 1.8%, around three times that of spruce wood from the forest.
supporting documents
literature
- D. Grosser, W. Teetz: Beech . In: Arbeitsgemeinschaft Holz eV (Ed.): Local timber (loose-leaf collection) . No. 7 . Information service wood, wood sales fund - sales promotion fund of the German forest and wood industry, 1998, ISSN 0446-2114 .
Individual evidence
- ↑ Peter Niemz: Investigations into the thermal conductivity of selected native and foreign wood species . In: Building Physics 29 . tape 29 , no. 4 . Ernst & Sohn Verlag for Architecture and Technical Sciences GmbH & Co.KG, Berlin 2007, p. 311-312 , doi : 10.1002 / bapi.200710040 .
- ↑ Martin Kaltschmitt, Hans Hartmann and Hermann Hofbauer (eds.), 2009: Energy from biomass. Basics, techniques and procedures. Springer Verlag, 2nd edition, p. 360, ISBN 9783540850946
- ↑ a b c d e D. Grosser, W. Teetz: Weide . In: Arbeitsgemeinschaft Holz eV (Ed.): Local timber (loose-leaf collection) . No. 15 . Information service wood, wood sales fund - sales promotion fund of the German forest and wood industry, 1998, ISSN 0446-2114 .
- ^ Agency for Renewable Raw Materials (2007): Handbuch Bioenergie-Kleinanlagen. ISBN 3-00-011041-0 ( pdf )