Wood

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Wood (from Germanic * holta (z) , 'wood', 'wood'; from Indo-European * kl̩tˀo ; original meanings, derived from Indo-European * kel- , 'to beat': 'cut off', 'split', 'beatable wood') In common usage, it refers to the hard tissue of the shoot axes (trunk, branches and twigs ) of trees and shrubs . Botanically , wood is defined as the secondary xylem of the seed plants produced by the cambium . According to this definition, however, the woody tissues of palms and other higher plants are not wood in the narrower sense. Here, too, the storage of lignin in the cell wall is characteristic . In a broader definition, wood is therefore also understood as lignified ( lignified ) plant tissue.

From a cultural and historical point of view, woody plants are probably among the oldest plants in use . As a versatile, but especially renewable raw material , wood is still one of the most important plant products as a raw material for further processing and also a regenerative energy source . Objects and structures made of wood (e.g. arches and shields , charcoal , pit wood , railway sleepers , wooden boats , stilt houses , forts ) as well as the timber industry were and are part of human civilization and cultural history.

The deforestation of forests along the coast of the Mediterranean was one of the first major human interventions in an ecosystem . Deforestation was the first step towards making the largely forested Europe arable .

Different types of wood, from top to bottom: Weymouth pine , wenge , ramin , macassar ebony , maple burl , bog oak

Origin of wood

0  mark , 1  annual ring border , 2  resin canals , 3  primary  rays , 4  secondary rays, 5  cambium , 6  rays of the  bast , 7  cork cambium , 8  bast , 9  bark

Wood is formed by the cambium , the tissue between wood and bark (secondary growth in thickness ).

In the division of cambial two emerge cells , one of which is their ability to divide reserves and a new initial cell grows. The other becomes a permanent cell that divides one or more times. Wood (secondary xylem) emerges from the cells that later differentiate into conduction , strengthening or storage tissue . Bast outwardly is formed ( phloem , that is phloem), from which the inner bark is and later from the from the phellogen formed bark produced. The production of xylem cells exceeds the production of phloem cells many times over, so that the bark portion of the entire stem is only about 5 to 15 percent.

In the northern temperate zone, there are four growth phases due to climatic conditions :

  • Rest period (November to February)
  • Mobilization phase (March, April)
  • Growth phase (May to July): Wood cells that arise during this time of year are large , thin-walled and light in color and form what is known as early wood
  • Deposition phase (August to October): Wood cells that arise during this time of year are small-lumen , thick-walled and dark in color and form what is known as late wood (or autumn wood)

This cyclical growth behavior results in annual rings that are clearly recognizable in a cross section through a trunk (see also dendrochronology ).

structure

Wood has a species-specific anatomical structure so that wood species can be distinguished from one another on the basis of their macro and micro structures. The scientific description of wood structures and the determination of wood types is the task of wood anatomy .

  • Different wood structures

  • Spruce wood ( Picea abies ) in the SEM

  • Oak wood ( Quercus robur ) with rows of pores (cross section)

  • Beech wood ( Fagus sylvatica ) with rays (tangential cut)

  • Wood of the sycamore fig ( Ficus sycomorus ) with axial parenchyma (light microscope image)

Chemical constituents

Composition of the cell wall in
Central European conifers and hardwoods
substance Softwood Hardwood
cellulose 42-49% 42-51%
Hemicellulose 24-30% 27-40%
lignin 25-30% 18-24%
Extract substances 2-9% 1-10%
Minerals 0.2-0.8%

The lignified cell wall of deciduous and coniferous woods contains the structural substances cellulose , hemicelluloses and lignin as well as, to a lesser extent, so-called extract substances . Cellulose and hemicellulose are often grouped together under the term holocellulose . Microfibrils are the essential structural element of the cell wall .

The proportions of lignin and hemicellulose are different in conifers and hardwoods. The elementary mass fractions of dry wood are around 50% carbon, 43% oxygen, 6% hydrogen and 1% nitrogen and other elements.

Softwood

In terms of developmental history, softwoods are older than hardwoods , so they have a simpler anatomical cell structure than these and only have two types of cells.

  • Tracheids : elongated (prosenchymatous) cells tapering to a point at the ends, which are only filled with air or water. They combine management and strengthening functions and make up 90 to 100 percent of the wood substance . The exchange of water between the cells takes place via so-called pits or pits . As transverse tracheids in the wood rays, they ensure the transport of water and nutrients in a radial direction. They make up 4 to 12 percent of the total wood substance.
  • Parenchyma cells : In a longitudinal section, mostly rectangular cells that take on the management of nutrients and growth substances as well as the storage of starch and fats . In the radial direction they form the majority of the ray tissue as ray parenchyma . The parenchymal cells surrounding the resin canals act as epithelial cells and produce the resin that they secrete into the resin canal .
  • Softwood and hardwood

  • Spruce wood

  • Pine wood

  • Cherry wood

  • Rosewood

Hardwood

The developmentally younger hardwood tissue is much more differentiated than that of softwood. It can be divided into three functional groups.

  • Conductive tissue: vessels ( trachea ), vascular tracheids , vasicentric tracheids. The latter two are intermediate stages in the development from the tracheid to the vessel.
  • Strengthening tissue: libriform fibers , fiber tracheids
  • Storage tissue: ray parenchyma cells, longitudinal parenchyma cells, epithelial cells

The vessels that do not exist in conifers are characteristic of hardwoods . They can often be seen with the naked eye as small pores in the wood cross-section and as grooves in the tangential section . According to the arrangement of these tracheas one differentiates:

The growth zones ( annual ring pattern ) and the species-specific arrangement of pore and parenchymal strands result in the characteristic grain of the wood species.

Coreing

We speak of the nucleation of wood when the inner waterways of the trunk are interrupted and the cells die. In the case of conifers, this is done by closing the pits in the courtyard and in the case of numerous deciduous trees, by thinning the cell lumen at an age of approx. 20–40 years. After that, phenolic core ingredients are formed and stored in the cell walls, which often leads to an increase in natural durability . If the core area is clearly recognizable by a dark color, one speaks of heartwood trees (e.g. oak , pine , Douglas fir , larch , robinia ). If no color difference can be seen, but it can be concluded from the reduced moisture content that the interior is cored , we speak of mature wood trees (e.g. spruce , fir , linden , pear tree ). Mature wood is real heartwood.

Numerous trees, on the other hand, tend towards facultative nucleation (e.g. ash, beech, cherry). The core is contrasted in color, but one speaks of a false core , since the core formation does not take place endogenously and regularly, but is triggered by exogenous influences (injuries). The false core does not have increased durability. As sapwood is referred to the area of the trunk, the activity on the water - and nutrient transport participates and storage.

Tropical wood

The term tropical wood is defined by the origin of the wood and is therefore outside the plant classification . Under tropical timber which is mainly heartwood tropical hardwood species understood. Tropical woods usually contain a species-specific, characteristic arrangement of pores and parenchyma . Many tropical woods are characterized by advantageous mechanical properties due to the so-called alternating twist and by higher durability due to a very high core material content . The color or grain is often perceived as appealing ( precious wood ). Due to the more constant climate in the tropics, the structure of tropical woods is more even than the structure of wood from the temperate latitudes, which is characterized by tree rings . The consumption of tropical wood has been discussed critically in the industrialized countries since the 1970s, since the existence of tropical rainforests is endangered by overexploitation, among other things . On the other hand, wood is an important economic factor for many tropical countries and is (as in the temperate zones) an important source of income for the rural population. Environmental groups criticize, however, that this part of the population benefits the least from all logging in the tropics.

Indonesia has a high rate of deforestation : According to the Food and Agriculture Organization of the United Nations (FAO), the annual net loss of forest between 2000 and 2005 was around 1.8 million hectares , an area the size of Saxony . (The net increase in forest in China during this period was around four million hectares per year.) According to the FAO, the largest proportion of global tropical forest loss is caused by shifting cultivation and the use of firewood . The latter accounted for around 83 percent of logging in tropical countries in 2000. To protect the tropical rainforests , environmental protection organizations such as WWF , Greenpeace , NABU and BUND have played a key role in initiating FSC certification. Other organizations like Pro Rainforest , Rainforest Rescue and Watch Indonesia! call for the complete abandonment of tropical wood to protect the last remaining rainforests, as they are of the opinion that a protective seal cannot guarantee ecologically responsible and socially acceptable forest management.

With careful wood selection and proper planning in terms of durability, tropical woods can always be replaced by native woods; you just have to do without the special optical characteristics of tropical woods.

Examples: Meranti , mahogany , teak , balsa wood , rosewood , Bangkirai (Yellow Balau), Bongossi , Abachi , Framiré , Merbau , Ovangkol , Ramin , Afzelia , Wengé

properties

The properties of wood are characterized by its organic nature, its porosity , its anisotropy and its hygroscopicity . Wood properties are basically species-specific, but also vary within a species due to the origin of the wood. Sapwood and heartwood differ only in terms of permeability and durability, but mostly not in their technical properties.

Hygroscopic properties

The hygroscopic property of wood - d. H. its tendency to absorb or give off moisture from the environment - causes its comparatively low dimensional stability with changing ambient humidity . The wood moisture adjusts to the ambient climate. Changes in humidity below the fiber saturation range (depending on the type of wood 25–35% wood moisture content ) are accompanied by dimensional changes ( swelling and shrinkage ). Some types of wood such as B. Teak have a low degree of shrinkage due to the inclusion of hydrophobic substances . A technical process for reducing hygroscopicity is wood modification .

Anisotropy

Almost all wood properties differ in the three anatomical basic directions of the wood (axial, radial, tangential). This causes z. B. an uneven shrinkage of the wood during drying . For the Central European timber types , the maximum shrinkage is on average 0.3% axially, 5% radially and 10% tangentially. When drying, wood shrinks tangentially (parallel to the annual rings) about twice as much as it does radially (parallel to the wood rays), so that radial cracks ( shrinkage cracks ) easily develop, especially in large-sized wood . The swelling / shrinkage coefficient indicates the change in dimension per percent change in wood moisture content ( shrinkage ).

Dense and elastomechanical properties

Properties of selected types of wood
Wood species Gross
density
(kg / m 3 ) 		Shrinkage
coefficient 		Strengths (N / mm 2 ) Modulus of elasticity
(N / mm 2 ) 		Durability
class
(DIN
EN 350-2)
radial tang. Pull
(axial)		 Pressure
(axial)		 Bend
(transverse)		 Thrust
(axial)
Spruce 470 0.15 0.32 80 40 68 7.5 10,000 4th
jaw 520 0.15 0.30 100 45 80 10 11,000 3-4
larch 590 0.20 0.44 105 48 93 9 12,000 3-4
birch 650 - - 137 60 120 12 14,000 5
beech 690 0.19 0.34 135 60 120 10 14,000 5
Oak 670 0.15 0.26 110 52 95 11.5 13,000 2
Ash 690 0.19 0.34 130 50 105 13 13,000 5
Black locust 730 - - 148 60 130 16 13,500 1-2
Sipo 590 0.22 0.25 110 58 100 9.5 11,000 2
Azobé 1060 0.32 0.42 180 95 180 14th 17,000 1

The so-called gross density of the wood fluctuates with the wood moisture. With a wood moisture content of 12% (normal moisture content in heated interiors), the bulk density, depending on the type of wood, ranges between 200 kg / m 3 and 1200 kg / m 3 . Fresh wood shows much higher values. The landing weight of fresh oak is around 1000 kg / m 3 , in the dried state (12% wood moisture) around 670 kg / m 3 . The bulk density is considered to be the key variable for most of the technical wood properties with which it is correlated . Density measurements are therefore often used to check the quality of the wood (example: Resistograph ). In contrast to the gross density, the real density of the kiln-dry , wooden cell wall is largely independent of the type of wood and is 1500 kg / m 3 .

Wood is a visco-elastic material and its elastomechanical properties are therefore subject to the influence of time. So both the duration of the load and the type of force ( static or dynamic ) must be taken into account. In addition to the density and the direction of load , the structure of the wood, its history and the wood moisture influence the elastomechanical properties. It should also be noted that the density and elastomechanical properties of individual types of wood can be subject to a natural variance of 10–22%.

Of all the strengths of wood, its tensile strength has the highest values, while the compressive strength of wood reaches around 50% and the shear strength (shear strength) only around 10% of the tensile strength values. The tensile strength of conventional structural steel (370 N / mm 2 ; 7800 kg / m 3 ) is five to six times as high as the tensile strength of construction timber (~ 80 N / mm 2 ; 450 kg / m 3 ), but the latter is about 16 times as easy; the strength value given here relates to the load along the fiber . Wood is therefore characterized by its favorable strength-to-weight ratio.

Acoustic properties

The sound velocity achieved in wood fiber parallel values 4000-6000 m / s, transverse to the fiber only 400 to 2000 m / s. Parameters influencing the speed of sound are density , elasticity , fiber length , fiber angle , wood moisture content , wood defects (knots, cracks). Because of its good acoustic properties, wood is used in musical instrument making. But it is also suitable as a material for sound insulation. Chipboard with a surface density of 15 to 20 kg / m 2 achieve a sound insulation of 24 to 26 dB.

Sound propagation time measurements are used to test the dynamic modulus of elasticity in the quality control of sawn timber and to diagnose the condition of trees ( sonic tomography ).

Thermal properties

Due to its porosity, wood is a poor conductor of heat and is therefore conditionally suitable as thermal insulation . Spruce wood has a thermal conductivity of 0.13 W / (m · K), for comparison reinforced concrete : 2.00 W / (m · K). In the case of chipboard, it is even lower at around 0.10 W / (m · K). Insulation boards made of soft wood fiber reach 0.04 W / (m · K). The thermal conductivity increases with the wood moisture and the bulk density of the material.

The specific heat capacity , i.e. H. the amount of heat that is necessary to heat 1 kg of a material by 1 Kelvin is almost twice as high for wood with 0.472 Wh / (kg · K) than with concrete with 0.244 Wh / (kg · K). In practice, the thermal expansion of wood can be neglected, as it is overcompensated for by the shrinkage behavior due to drying .

The thermal decomposition of wood starts at temperatures above 105 ° C, is strongly accelerated from 200 ° C and reaches its peak at 275 ° C. Thermal wood degradation can take place at temperatures below 100 ° C after longer exposure . The flash point of the wood is between 200 and 275 ° C. In the absence of oxygen , pyrolysis occurs . Central European timber has a calorific value between 3.9 and 4.0 kWh / kg with a usual water content of 20% .

Optical properties

The color and structure of the wood are perceived as aesthetically pleasing. Strong knots and irregular discoloration are considered to be wood defects. As a result of the effects of ultraviolet light, wood darkens. Ultraviolet radiation damages the wood's surface over a long period of time . Above all, the lignin is denatured and broken down and, in the case of direct weathering, is subsequently washed out by rainwater . The surface then looks dirty gray. If rainwater is not exposed, the UV effect gives the wood a silvery-white color. The effect of sunlight is limited to the surface. It can be countered with pigment-containing glazes or varnishing .

Biological properties

Wood is biodegradable , but it is also susceptible to biotic pests . So it can z. B. attacked by insects , fungi or bacteria and permanently destroyed in its substance. Fungi can attack wood with a moisture content of around 20%. Blue fungi ( Ascomycetes , Fungi imperfecti ) only cause a superficial discoloration, while wood-degrading stand fungi cause white rot to brown rot . Mold rot and degradation by bacteria is only possible with high humidity, especially in contact with the ground . The larvae of wood-destroying insects such as house billy beetles and rodent beetles can attack the wood even if the moisture content is low. More resistant heartwoods are only very slowly degraded biotically . Their resistance is divided into resistance classes 1–5 according to DIN EN 350-2.

The biotic wood decomposition can be largely constructive wood protection to avoid or diminish. The focus here is on preventing moistening and, if necessary, using suitable resistant heartwood. In just weathered wood in exterior as free-standing wooden structures and pylons one expert is chemical wood protection advised and supporting structures required by DIN 68 800th Wood modification as thermowood or acetylated wood is a new way of making wood less sensitive to dimensional changes and rot caused by moisture .

The biological properties of wood also include the permeability of the wood, which is due to its anatomical structure. Dot closure and verticalization reduce the permeability and thus the impregnability of the wood.

Processing and areas of application

Use of wood in construction
The largest self-supporting wooden roof of the world stands at the fair in Hannover and became the EXPO 2000 built
Millennium tower in Magdeburg
Tallest wooden structure: Gleiwitz transmitter

The logging as primary production counts as part or a downstream branch of the forestry and with this to the agricultural sector . This includes the first processing steps up to the sawmill or industrial wood and firewood . The following wood processing already belongs to the manufacturing industry .

Wood is one of the sustainable raw material and energy sources, provided that the amount used does not exceed the amount that has grown back. The ease of processing and the associated low energy requirement for extraction and processing also play an important role in the ecological assessment. In LCAs cut wood products from excellent.

Wood is processed either as sawn timber , as veneer , as wood-based material or as fiber material . Wood and plywood are wood drying and subsequent conditioning to the respective use of moisture brought. Nowadays this is done exclusively through industrial drying processes .

Historical use

Wood has been used intensively since the Paleolithic to generate energy ( fire ), for weapons and objects to be thrown, as a material for tools and simple devices and, since the Neolithic, increasingly as a building material.

Even in the course of the hominization , the skill in handling devices had increased (but this can only be proven with stone tools because of the chances of tradition being handed down), while other primates did not get beyond the simplest forms of using wood, e.g. for nest building and poking (see use of tools in animals ).

Wood as a building material

Wood is used in construction as construction timber and can be used there e.g. B. be used as solid wood , glued laminated timber or in the form of wood-based materials. It is used for structural , insulating and cladding . The wooden frame construction , the wooden skeleton construction and the traditional half-timbered construction are based on load-bearing wooden structures . The use of glued laminated timber and wood-based materials allows modern timber engineering to create unusual wooden structures, such as B. the EXPO roof in Hanover and the 190 m long wooden bridge near Essing over the Main-Danube Canal . The increasing use of glued laminated timber (glued timber beams) in hall constructions has come under discussion due to accidents. The damage was due to design flaws and a lack of control . The standard-compliant load-bearing capacity reserves of wooden structures are so high that there are no risks with regular inspection.

Wood as a load-bearing material is mostly used for smaller buildings or upper floors and roof structures of other buildings. The tallest wooden building in Germany is in Magdeburg . It is the millennium tower (opened in 1999 as part of the Federal Garden Show on the site of the Elbauenpark ). The tallest European commercial building with five floors is in Espoo , Finland. The construction was mainly led by the Finnish company Finnforest and completed in 2005.

In 2013, the Pyramidenkogel observation tower with a 70 m high platform was built in Carinthia from curved glued wood piles - stiffened and braced with steel elements.

In concrete construction , essential parts of formwork , namely the standard elements formwork beams , formwork panels (made of coated three-layer wood) and formwork elements (made of waterproof plywood in a metal frame) are made of wood. Forms for columns made of unfoldable cardboard are based on cellulose fibers made of wood. Part of the wooden formwork is lost as firewood , many elements are re-used - possibly after de- nailing .

Wood of low density can be used in raw or processed form for thermal insulation ( insulation materials ) (e.g. fiber insulation boards , balsa for the insulation of liquid gas tanks ). Wood fiber boards of higher density have good acoustic insulation properties. Chipboard ( flat pressed board , OSB ), as well as plywood panels, are used for formwork and for wall elements in timber frame construction.

In contrast to metals , wood is not electrically conductive . For this reason, numerous transmission towers for medium wave transmitters made of wood were built in the thirties , with the antenna wire being hung inside the tower.

With the exception of the transmitter tower in Gleiwitz , all of these structures were either destroyed at the end of World War II or have since been demolished. In addition, Deutsche Telekom AG in Brück uses two 54-meter-high wooden towers that were made without the use of metal parts. These are used to hold antennas to be measured . The metal-free construction of the towers enables the antenna diagrams to be measured without being disturbed .

Other applications: Wood is used as formwork in construction pits as well as for masts and wooden railway sleepers for structure-borne noise absorption on bridges and over tunnels . In the past, softwood was used in mining as a stamp to support the tunnels , as it emits cracking noises before breaking (the wood can warn). Wood is also used to make bins and silos to hold aggressive salts .

The combustibility of wood is initially a disadvantage when used as a building and construction material. It should be noted, however, that wood can also have advantages over steel structures in terms of fire protection . This is especially true when other flammable substances are added. With large cross-sections, wood is classified as fire-retardant because a heat-insulating carbon layer is created on its surface when exposed to fire , which protects the inner wood. By design and by fire-retardant paints the leaves resistance period a wooden structure increase. In the event of a fire, building stability only decreases slowly and can be assessed, whereas steel structures tend to suddenly and uncontrollably collapse due to the temperature- related loss of strength .

Wood as a construction material

Grown wood is a natural three-dimensional fiber composite material with a comparatively low density, but high rigidity and strength. The lightweight construction properties are approximately comparable to those of glass fiber reinforced plastic (GRP). Grown wood is usually very resistant to material fatigue, is easy to work with and has advantageous aesthetic and ergonomic properties. Depending on the wood and wood material, there are cost advantages compared to other construction materials . Wood and wood-based materials absorb good mechanical vibrations , comparable to plastics . The directional dependency of the material properties ( anisotropy ) and the interaction with water are often problematic in constructive use . The swelling and shrinking have an influence on the dimensional stability and is colloquially often referred to as the working of the wood.

Wood is divided into solid wood (solid wood) and wood-based materials. There are different classifications for wood-based materials. Often in:

distinguished. Wood-based materials always consist of individual wooden elements (e.g. wood fibers, veneers ) and binding agents . Furthermore, a classification according to:

  • Semi-finished goods in the form of solid wood such as boards , strips , rods , panels and veneers ,
  • Semi-finished products in the form of wood-based materials, such as chipboard , wood fiber boards of various densities or plywood
  • Blocks for turning and carving ,
  • Laminated beams as structural elements , formwork beams and laminated boards for concrete formwork,
  • Tonewood for musical instruments

respectively. Depending on the wood element and the binder used, the properties of wood-based materials are changed compared to natural wood . It is therefore very important to make a sensible selection of the wood-based material for a construction material. Areas of application for wood and wood-based materials are:

Wood ( bush hammered or iced)

Ballpoint pen with a housing made of bush hammered beech

A special way of giving grown wood an extraordinary structure is to infect it with a parasitic fungus by storing it in a damp environment ( sticking ). The fungus penetrates the layers of wood and changes the nature of the cells. This process creates individual patterns and shades of color. The treated wood is then suited to the production of design objects of all kinds. In order to stabilize the weakened by the fungus wood structure, are usually after the halt resins or plastics with special vacuum process is introduced into the material.

A special icing process applied to beech wood leads to similar results as sticking . After the wood has been moistened, it is frozen and then dried. The result is a very light wood that is almost black grained . This result, which occurs very rarely in nature, is known as ice beech .

Wood as a furnishing material

The aesthetic properties of wood are in the foreground when using wood as parquet and for ceiling and wall paneling . Come here partly tropical Edelhölzer or so-called non-ferrous hardwoods (z. B. Kirschbaum , Elsbeere ), which primarily as a veneer to be processed for use. Nowadays, sliced ​​face veneer is mainly used in furniture construction. Wooden floors must also be sufficiently resistant to abrasion , which is why hardwoods are usually used .

Also psychophysiological effects are known: in a comparative study of the Joanneum Institute at an Austrian school resulted in a significant stress-reducing , u. a. the heart rate lowering effect on those students who were taught in wood-paneled classrooms . Likewise, the social stress felt by the students by the students decreased.

Industrial wood

OSB panel

Wood is the most important raw material in the pulp and wood materials industry. The raw material is either only mechanically crushed or chemically digested as well . Primary products are wood chips (chopped up wood), shavings , wood fibers or veneers (wood sheets). Basically, only debarked wood is processed. Glued chips or wood fibers are pressed for the production of wood-based materials . Plywood, on the other hand, consists of cross- laminated veneers, which are mostly peeled from steamed blocks .

For the production of pulp, the lignin has to be removed as far as possible from the fiber base. Common digestion processes are the sulfate process and the sulfite process . The residual lignin is removed by bleaching the pulp. In the production of wood pulp or wood pulp as a base material for cardboard and low-quality paper , the lignin remains in the fiber mass. Paper made from cellulose used to be called wood-free . Cellulose and wood pulp are u. a. Paper, cardboard and cellulose products such as celluloid and viscose fibers are made.

Wood as a raw material for the manufacture of textiles

Chemical pulp is used to manufacture textiles "made of wood" (see also sulfite process ) and processed into yarns and fabrics made from viscose , cupro , cellulose acetate or other chemical fibers based on cellulose .

Recycling and energetic use

Piled wood, pile of firewood
Recycling code for wood

In its pure form, wood can easily be disposed of by composting or by incineration while generating energy at the same time. As a renewable raw material, firewood has a good ecological balance if it is grown and extracted sustainably. Old and waste wood is increasingly being used as fuel in biomass power plants for regenerative and CO 2 -neutral energy generation. Wood is also used as fuel in wood stoves . Thanks to the development of automated firing systems for wood pellets or wood chips , wood as a fuel is now not only economical, but also equivalent to burning oil or gas in terms of convenience . In 2006, around 2 percent of the primary energy supply in Germany was covered, which in view of the lack of subsidies can be regarded as an economic success.

Since March 2010, particularly low-emission wood gasification boilers have been subsidized by the state within the framework of the MAP (market incentive program for renewable energies).

Another recycling method is high-temperature carbonization . By this method can be made of wood and other organic materials chemical raw materials are produced, the fossil sources to replace. At the same time, it represents the material usability of wood and other renewable raw materials , which could become increasingly important with the decline in fossil fuels. Wood has the recycling code -50 (FOR).

Further material applications:

Economical meaning

The camel thorn tree (here in Sossusvlei ) produces an extremely hard wood

Wood is one of the oldest and most important raw materials and materials known to mankind. The annual wood production still exceeds the quantities of steel , aluminum and concrete . The total amount of wood mass accumulated in forests worldwide was estimated by the FAO to be around 422 gigatons in 2005 . Currently 3.2 billion m³ of raw wood is felled annually, almost half of it in the countries of the tropics. The round timber volume (2011) amounted to 1.578 billion m³ for the FAO. The highest annual felling intensity is found in Western Europe at 2.3 m³ / ha . Almost half of the global wood supply is used as firewood, mainly due to the countries in the tropical zone. Here, energy generation is still the most important type of wood use - the proportion of firewood in Western Europe, on the other hand, is just under a fifth of the log.

In 2000, only 2% of the timber felled worldwide was exported as raw timber; Consumption or processing into semi-finished goods (sawn timber, wood-based materials, fibrous materials for paper as well as paper and cardboard) therefore takes place almost exclusively in the countries of origin. The largest consumers of semi-finished wood products produced worldwide are the countries in the temperate zone with 73-87%. On the producer side, lumber production only accounted for 35% of total production in 1998, with wood-based materials and fibrous materials for paper accounting for 16% each, and paper and cardboard for 32%.

China developed into the largest timber importer in the world. Wood is mainly used for construction and furniture production. Much of China's furniture production goes abroad.

Europe without Russia

The most densely forested countries in Europe excluding Russia are Finland, Slovenia , Sweden and, with some distance, Austria . The largest forest areas in absolute terms are found in Sweden (around 28 million hectares), Finland, Spain , France and Germany . The highest mean stocks of wood per hectare of forest are available in Switzerland , Austria, the Czech Republic , Slovakia and Slovenia (more than 250 each), while Germany has the highest total wood stocks in Europe with over 3.4 billion cubic meters (followed by Sweden, France and Finland).

The wood shortage , an impending or existing shortage of wood, was perceived as a significant economic and social problem from the 16th century until the early 19th century. The debate about this led to the conversion to fossil fuels in the course of industrialization and to the systematic professionalization of forestry and forest science .

Germany

The Forest in Germany covering 11.4 million hectares, 32 percent of the country's total and has a growing stock of a total of 3.7 billion stock cubic meters .

Annual logging can fluctuate greatly due to weather events and changes in wood prices . In a long-term comparison, it has increased significantly: an average of 38.4 million cubic meters were felled annually between 1993 and 2002, and an average of 56.8 million cubic meters between 2003 and 2012. In 2007 the highest mark was reached: 76.7 million solid cubic meters were felled (mainly softwood). This was due to extreme wind and storm events such as Hurricane Kyrill .

In 2014, logging in Germany totaled 54.4 million cubic meters without bark . Of this, 40.1 million cubic meters were harvested from coniferous wood and 14.2 million harvested cubic meters from hardwood. In 2014, 44 percent of the nationwide logging was done in private forests, 20 percent in corporate forests , 34 percent in the state forests of the federal states and 2 percent in federal forests .

The most important types of timber are spruce , pine , beech and oak . The forestry and especially the timber industry (wood industry) contribute around 2% of gross value added in. Wood has as raw - and material acquired a strongly increasing importance, since it almost CO 2 -neutral can be generated, is readily compatible with environmental and sustainable economic manner, is to be processed with little energy and can be recovered fully material. Professionally manufactured and processed, wood is also a durable material. In 2011 the total turnover in the German wood industry was 14.95 billion euros.

Austria

Austria has a forest area of ​​3.92 million hectares (1998), that is over 46% of the national territory, with an upward trend. The productive forest comprises 83% of the forest area, tree species composition in the productive forest (for wood stock): Spruce 61.4%, beech 9.2%, pine 9.0% and larch 6.8%.

Norms and standards

  • DIN 68364 (2003-05): Characteristic values ​​of wood species - bulk density, modulus of elasticity and strength
  • DIN 4074–1 (2008-12): Sorting wood according to load-bearing capacity - Part 1: Softwood lumber
  • DIN 4074–2 (1958-12): Construction timber for wooden components; Quality conditions for construction timber (softwood)
  • DIN 4074-5 (2008-12): Sorting wood according to load-bearing capacity - Part 5: Hardwood lumber
  • DIN EN 13556 (2003-10): Round and sawn timber - nomenclature of commercial timber used in Europe
  • DIN EN 350–2 (1994-10): Durability of wood and wood products - Natural durability of solid wood

See also

literature

  • HH Bosshard: Wood Science Part I – III. Birkhäuser Verlag, Stuttgart 1982–1998, ISBN 3-7643-1630-6 .
  • M. Chudnoff: Tropical Timbers of the World. (= Agriculture handbook 607). Kessel, Remagen-Oberwinter 2007, ISBN 978-3-935638-82-1 .
  • D. Fengel, G. Wegener: Wood - Chemistry, Ultrastructure, Reactions. Reprint. Verlag N. Kessel, 2003, ISBN 3-935638-39-6 .
  • Dietger Grosser: The woods of Central Europe. A microphotographic wooden atlas. Verlag N. Kessel, Remagen 2003, ISBN 3-935638-22-1 .
  • Karl Hasel, Ekkehard Schwartz: Forest history. A floor plan for study and practice. 3. Edition. Kessel, Remagen 2002, ISBN 3-935638-26-4 .
  • R. Bruce Hoadley: Wood as a material. O. Meier Verlag, Ravensburg 1990, ISBN 3-473-42560-5 .
  • Thomas Königstein: Advice on energy-saving building. 4th edition. Blottner Verlag, Taunusstein 2009, ISBN 978-3-89367-117-5 .
  • Paul Lehfeldt: The art of wood construction. Reprint-Verlag, Leipzig / Holzminden 2001, ISBN 3-8262-1210-X .
  • Udo Mantau, Jörg Wagner, Janett Baumann: Material flow model WOOD: Determination of the occurrence, use and whereabouts of wood products. In: Garbage and Garbage. 37 (6), 2005, pp. 309-315, ISSN  0027-2957 .
  • Peter Niemz: Physics of wood and wood materials. DRW-Verlag, Stuttgart 1993, ISBN 3-87181-324-9 .
  • Alois Payer: Wood as a material: material science (architecture for the tropics). A compilation of other literature, last version dated February 15, 2010.
  • Joachim Radkau : Wood. How a natural substance makes history . oekom-Verlag, Munich 2007, ISBN 978-3-86581-049-6 .
  • JF Rijsjdijk, PB Laming: Physical and related properties of 145 timbers . Kluwer, Dordrecht / Boston / London 1994, ISBN 0-7923-2875-2 .
  • Erhard Schuster: Forest and Wood. Data from the history of the use and management of the forest, the use of wood and important peripheral areas. 2 volumes. 2nd Edition. Kessel Verlag, Remagen 2006, ISBN 3-935638-62-0 and ISBN 3-935638-63-9 .
  • FH Schweingruber, A. Börner, E.-D. Schulze: Atlas of Woody Plant Stems. Environment, Structure and Environmental Modifications. Springer, Heidelberg 2006, ISBN 3-540-32523-9 .
  • Anselm Spring, Maximilian Glas: wood. The fifth Element. Frederking & Thaler, Munich 2005, ISBN 3-89405-398-4 .
  • Rudi Wagenführ: wooden atlas. Fachbuchverlag Leipzig in Carl Hanser Verlag, Leipzig 2006, ISBN 3-446-40649-2 .
  • André Wagenführ, Frieder Scholz (Ed.): Pocket book of wood technology. Fachbuchverlag Leipzig in Carl Hanser Verlag, Munich 2012, ISBN 978-3-446-42605-4 .

Web links

Commons : Wooden  album with pictures, videos and audio files
Wiktionary: Wood  - explanations of meanings, word origins, synonyms, translations
Wikiquote: Wood  - Quotes

Individual evidence

  1. ^ Friedrich Kluge , Alfred Götze : Etymological dictionary of the German language . 20th ed., Ed. by Walther Mitzka , De Gruyter, Berlin / New York 1967; Reprint (“21st unchanged edition”) ibid 1975, ISBN 3-11-005709-3 , p. 315.
  2. ↑ See Joachim Radkau : Wood. How a natural substance makes history. oekom Verlag, 2007, ISBN 978-3-86581-049-6 .
  3. ↑ According to Holz-Lexikon.
  4. ↑ Johann Heinrich von Thünen Institute: The chemical composition of natural wood (PDF; 412 kB), Institute for Wood Technology and Wood Biology, winkelheide.de , accessed on August 2, 2019.
  5. ↑ Global Forest Ressources Assessment 2005. (= FAO Forestry Paper 147), ISBN 92-5-105481-9 , p. 21, ( online ).
  6. ↑ See introduction to the questions and answers on the subject of tropical wood, www.regenwald.org.
  7. ^ According to Niemz 1993 and Rijsdijk and Laming 1994. Source: treeland.de .
  8. ↑ Reinhard Peesch : Wooden device in its original forms. Academy Publishing House. Berlin 1966.
  9. ↑ The EXPO roof: data and images. In: wegezumholz.de .
  10. ↑ Nils Klawitter: Skyscrapers made of wood: Better than steel. In: Spiegel Online , April 11, 2014.
  11. ↑ Production facilities made of wood in the car factory. ( Memento from July 9, 2015 in the Internet Archive ) Press release from the specialist agency for renewable raw materials .
  12. ↑ https://mortalitas.eu/gestocktes-holz/
  13. ↑ https://www.eisbuche.de/
  14. ↑ https://www.bm-online.de/praxis-und-kollegentipps/materialtipps/mit-hilfe-von-vaeterchen-frost/
  15. ↑ Learning in the "wood class" makes you healthy. In: ORF .at , December 21, 2009.
  16. ↑ School without stress. In: humanresearch.at (PDF; 353 kB).
  17. ↑ FAOSTAT (2011) .
  18. ↑ Fighting in Siberia: China's hunger for wood triggers dispute with Moscow orf.at, June 8, 2019, accessed June 8, 2019.
  19. ↑ a b c Entry on forests in Austria in the Austria Forum  (in the AEIOU Austria Lexicon )
  20. ^ State of Europe's Forests 2007. The MCPFE Report on Sustainable Forest Management in Europe. MCPFE-LU, Warsaw, 2007, ISBN 978-83-922396-8-0 , p. 182 f.
  21. ↑ Summary of the results of the second national forest inventory ( Memento from January 17, 2009 in the Internet Archive ) (PDF; 91 kB).
  22. ↑ Third National Forest Inventory (2012). Retrieved September 2, 2015.
  23. ↑ Timber Market Report 2014 - Annex Total Felling. In: bmel.de . Retrieved August 25, 2015.
  24. ↑ Statistics on the forest in Germany; Data from the second national forest inventory (2001-2003) ( Memento from May 16, 2014 in the Internet Archive )
  25. ↑ Sales figures in the German wood industry are increasing. In: treppen-schmidt.de . Retrieved November 23, 2012.