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Bio fuel thinning

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Specific performance functions for biofuel thinning with multi-tree handling are available. The functions are based on simulation studies (1)..

Biofuel thinning and conventional thinning (with or without logging residue extraction) differ in the cost functions used. In biofuel thinning it is assumed by default that multi-tree handling is applied. Biofuel can also be extracted in regular thinnings if Forest Fuel Extraction is enabled for thinning. If so, all biofuel extracted is assumed to be logging residues, not whole trees. The assortment extracted is controlled by the price list (see below), but the cost functions for bio fuel thinning assume that all harvested trees will be used for biofuel.

To simulate a pure biofuel thinning, in the Cost and Revenue and Treatment Model control tables you need to:

1.	Specify when a biofuel thinning will be applied.

2.	Select the cost function (or type in your own).

3.	Enter price for bio fuel.

Detailed instructions for each step are shown below.

Enter criteria for what defines a "young stand thinning" (ungskogsgallring) in the Treatment Model control table, heading 3.3 Young Stand Thinning (Figure 1). Enter the maximum relative age Max Relative Age (medelålder/(LÅF*1.1)), and the maximum absolute age. Min Height and Max Height refers to the mean tree height interval when a thinning is is considered a "young stand thinning" (ungskogsgallring), and consequently when a bio fuel thinning is a possible alternative (figure 1a). You can also tell the program to switch from ordinary to bio fuel thinning automatically if there are many understorey trees (figure 1b).

Ange kriterier för vad en ungskog är i kontrolltabellen Treatment Model, avsnitt 4.3 Young Stand Thinning (figur 1 a och b). Ange max relativ ålder Max Relative Age (medelålder/(LÅF*1.1)), max absolut ålder. Min Height och Max Height avser höjdintervall för när gallringen betraktas som en ungskogsgallring, utöver de andra villkoren, och följaktligen då biobränslegallring kan utföras (figur 1a). Alternativt kan du ange att biobränslegallring ska utföras om antal underväxt-träd är tillräckligt stort (figur 1b).

Sätt också Thinning Type = ForestFuel.

ControlTable_TreatmentModel_YoungStand

Figure 1a. With this setting (TreatmentModel control table), all young stand thinnings are done as bio fuel thinnings.

ControlTable_TreatmentModel_YoungStand_2

Figure 1b. With this setting (TreatmentModel control table), a thinning is carried out as a bio fuel thinning if the number of understorey trees is larger than 2000 per ha. The diameter limit for understorey trees is entered as "Max Diameter Understorey" in the same control table. I annat fall görs en vanlig gallring (enligt valet av "Thinning Type" (figur 1a).

For biofuel thinning, specific cost functions and settings are used (Figure 2).

Forest Fuel Harv Cost Function: For harvesters, several functions are pre-set (1), but you can also add new functions. Click on the right of Forest Fuel Thinning Cost Function and select “Configure Coefficients…” (Figure 3) to open the form (Figure 4).

HarvesterCostThinFF: Hourly cost (per G15-hour) for harvesters.

ForwarderCostThinFF: Hourly cost (per G15-hour) for forwarders.

Forest Fuel Thin. Corridor Width: Corridor width at multi-tree handling (1 or 2 m).

G15 Prod. Corr. Forest Fuel Harv: Conversion factor for productivity in G0-time (which the functions are based on in this case) to G15-time for harvesters.

G15 Prod. Corr. Forest Fuel Forw: Conversion factor for productivity in G0-time (which the functions are based on in this case) to G15-time for forwarders.

Forest Fuel Forw Cost Func: Cost function (coefficients) for forwarding.

ControlTable_Cost_Biobransle

Figur 2.

Figur 4.

Starting from version 2.11, you no longer have to enter a specific price list for bio fuel thinnings. Instead, the price for harvest residues is used (Harvest Residue Price). You can find this in the same price list that is used for ordinary thinning (. The cost is set in SEK/tonne before harvest cost (cost functions above are used for that, including harvester and forwarder). Possible transportation cost paid by the forest owner should be subtracted from the entered price. An alternative is to specify the net price and then set the harvest costs for bio fuel extraction to 0 (by setting the coefficient LogBias to 0 (see below).

PrislistaBiobransle

References

1) Sängstuvall et al., 2012, Simulation of harvester productivity in selective and boom-corridor thinning of young forests, Scand. J. of Forest Research 27(1):56-73.