Wood supply chains

Wood supply chains

Forestry as an industry is not intended for itself. It represents several parts in a complex forest-wood chain. Technologically speaking, forestry part of the forest wood supply chain forms a series of production processes that transform natural resources from forests into products and services. The production process of timber production takes place through the production stages. Production processes vary in different environments and have evolved over time in different directions. For example, the production processes of wood extraction from the northwestern part of Slovenia consist of technological procedures that are not acceptable in the north-eastern part of Slovenia. Different equipment and machines are required in the process of carrying out technological procedures, which enable the implementation of a certain procedure. Production processes also vary by raw material (maybe product or semi-finished products) in which they take place.

For the selection of the most appropriate technology in timber extraction, we need clear and comparable descriptions of possible technologies. Since 2013, Slovenian Forestry Institute uses the "funciograms" developed by prof. Joern Erler and offered for wider use. "Funciogram" is a graphic representation of the harvesting system model. The harvesting system is a simplified description of the production process. Below we present some (for the Slovenian space) common harvesting systems with accompanying technograms and costs calulations.



Traditional production of roundwood

The most common system of wood production is a technology implemented in a combination of traditional felling with a chainsaw and skidding with an adapted forest tractor, followed by transport of roundwood with forest transport composition (truck). Technological scheme shows the production chain of timber felling, skidding and transport. The process begins in a forest stand with felling, trimming, and cross-cutting with a chainsaw with 4kW engine power. After that collecting and hauling timber to the forest road follows with an adapted forestry tractor which has a complete forestry upgrade (safety frame), forestry chains for wheels, double drum built-in winch (5t) and a radio controller unit. Transport of round wood to the end user is done by a semi-truck equiped with a crane for transporting roundwood.

 

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Tradicionalna proizvodnja okroglega lesa

Non-professional production of firewood for own use

The example represents a production chain for the production of firewood (length 1 m). The manufacturing process begins in a forest stand with felling, delimbing, and crosscutting with a chainsaw with power of 4kW. This is followed by timber collecting and hauling to the forest road. This is done by an adapted agricultural tractor which has a complete forestry upgrade (safety chamber, forestry chains on tires) and radio-controlled double-drum built-in winch (5t). Assortments of roundwood are transported from forest road to the end user with three-axial truck for round wood with a crane and trailer. At the final destinantion firewood is produced using a standard tractor and a hydraulic vertical log splitter (up to 30t), 1m logs are split to the chunks (firewood logs) of 1 m.

 

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Tradicionalna proizvodnja okroglega lesa

Non-professional production of wood chips for own use

The example represents production of wood chips for own use in household. Production starts in the forest stand with cutting, delimbing, and crosscutting with a chainsaw with 4kW power. Collection and skidding of timber to skid road is done with an adapted agricultural tractor (e.g. light forestry safety frame, forest chains on tires) and electro-hydraulic single drum winch with radio control unit (6t). From the forest road to the end-user transport of roundwood (i.e. pulpwood and fuelwood) is carried out with a forestry transport composition (three-axle truck for round wood with a crane and trailer). At the end user wood chips are produced using a chipper that is powered by a tractor and equiped with a loading device.

 

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Neprofesionalna proizvodnja lesnih sekancev za domačo rabo

Production of green wood chips

The example represents cutting according to the whole-tree method (forest worker fells a tree, but does not finish it in full). Cutting is followed by haulage with a larger forest skidder, which is equipped with a (double drum) winch and permanent four-wheel drive. Haulage of whole trees (including crowns) from the stand takes place along the forest skid-road to the forest road, where trees are further processed into assortments and logging residues. In this case, the logging residues are gathered, without any further special procedures, along the forest road and are thus suitable for further processing into woodchips. In special cases, economy allowing, whole trees are recommended to be utilized into woodchips (e.g. coppice stands, attack by pinewood nematode, early 1st thinning…).

 

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Proizvodnja zelenih lesnih sekancev

Fully-mechanized cutting

The example represents the nowadays well established forms of fully-mechanized cutting. Selected example represents fully-mechanized cutting with the class of middle size harvesters, whose rated engine power is greater than 140 kW. Their weight is more than 21 tons, but does not exceed 50 tons. Fully-mechanized cutting requires skid trails with 30 metre spacing. In the event of thick trees in the intermediate zone, which is inaccessible by the machine's cranes (between skid trails), a combination with wood cutter is necessary, which fells trees towards skid trails. Cutting and assortment production (4m length) take place along skid trails and are carried out by a harvester. Cutting is followed by haulage to the forest road with a forwarder. The greatest problem in this technological system is the machine's weight and with it associated possibility of damages being caused to the soil. This technology is limited mainly to soils with good ground bearing capacity and not too wet grounds. Biggest advantage of this production chain is high productivity rates in case of boreal stands. Transport of assortments to end user is done by a truck.

 

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Strojna sečnja

Cable crane yarding

The example represents a modern way of forest production with the aid of the whole-tree method and cable yarding. Forest worker fells a tree with a chainsaw, but does not finish it in full (whole-tree method). This is followed by cable crane yarding, which means that a cable device with pivoting, rotating and tilt over tower is mounted to the truck chassis, which enables yarding along the cable line to the forest thoroughfare upwards, downwards or horizontally. Such devices have the carrying capacity of 30-40 kN and are suitable for yarding distances of up to 800 metres. Owing to the need of further treatment of trees, a loading crane equipped with processor aggregate for wood cutting, utilization and sorting is added. Part of the processor head with pickup rollers folds back so as not to impede the gripping of logs. After the hauling, the entire wood mass (roundwood and logging residues) is suitably disposed along the forest road. Further transport of roundwood from forest road to the end user takes place in a classical way with different versions of forestry transport compositions.

 

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