Extraction of harvest residues

To simulate bio fuel extraction, it must be activated in the Treatment Program Generator (PlanWise) or Scenario Settings (RegWise) control table (Figure 1). StandWise includes a box where you can check if biofuel extraction should be included (Figure 2).

Figure 1. To activate biofuel extraction, Biofuel Extraction must be set to True for the activity in mind. This is done in PlanWise (and StandWise if you run all periods at once with the button “Last period”) in the Treatment Program Generator control table. In RegWise this setting is found in the Scenario Settings control table.

If you have specified Management System = Continuous cover forestry, the choice above is shown instead.

Figure 2. In StandWise, you check the box “Extraction of biofuel”

If you have specified that biofuel will be extracted (see above), it will be extracted according to the settings in the “Biofuel” section of the Treatment Model control table.

Biofuel is extracted, by default, only in spruce-dominated stands. The required proportion of spruce can be changed by changing the MinSpruce value (1). If stumps are to be extracted, their minimum or maximum diameters can be specified, MinDiamStump or MaxDiamStump (2), respectively. The extraction is only applied for tree species where Stump Extraction =  “True” (3). Under “Utilization”, you can specify the extraction percentages for different tree parts (4). In normal cases these will not be changed from their default values, except when stumps are not extracted per default, but instead are given a value showing that stumps will be extracted: Stump (5).

Utöver dessa inställningar påverkar även Min Diameter... i slutavverkning och gallring hur mycket biobränslen som tas ut (se under Utförande i avsnittenoch).

On top of these settings, there is also an effect of Min Diameter… in final cuttings and thinnings on how much biofuel is extracted (see under Execution in the Thinning and Final felling sections).

Figure 3.

According to the standard settings, no stumps are extracted. If they will be extracted, it is recommended that you specify the extraction percentage to 90 %, at most.

Cost functions for harvest residues and stumps

For biofuel thinning, you use other cost functions. The following are valid only for extraction of harvest residues in connection with conventional thinning, selective cutting and final felling.

In the “Cost” control table there are function parameters for extraction of harvest residues (“Harvest Residue Extract. Cost") and stumps (“Stump Harvest Cost”). Different functions are available for thinning and final felling, but the standard values are the same. For selective cutting (continuous cover forestry) the same function is used as for thinning. Note that stump extraction can only be applied at final felling.

The functions have the form:

C = A0 + A1*Dist, where

C = Cost per ton (dry matter)

Dist = terrain transport distance.

Biofuel revenues

The gross revenue for biofuel (free at roadside) is set in the Pricelist control table in the "Harvest residues" section. The price is given in SEK/ton dry matter. Possible price reductions arising from the supplier paying for transport to an industrial site are not handled separately, but assumed to be included. An alternative is to amend the road transport cost to industry in the optimisation model if optimisation will be used.

In the “Pricelist” control table, Top Diameter denotes the minimum diameter of cut logs (pulpwood and timber). If this is set to more than 5 cm, a larger proportion of each tree will be available for biofuel extraction. If the top diameter is set to a large value, e.g. 200 (cm), no pulpwood and timber will be cut in the bucking action.

In the Heureka simulation, extraction of harvest residues after thinning leads to a basal area growth reduction of 5% up to 15 years after extraction. Stumps cannot be extracted at thinning. In final fellings, it is estimated that biofuel extraction leads to a loss corresponding to one year’s growth. However, this is not yet implemented – in the current version no growth reduction is simulated after final felling.

The amount of carbon in the soil will be reduced when biofuel is extracted. This is because the input of litter from harvest residues will be lower. The program takes this into consideration (Q-model), read more about carbon analyses in Heureka Wiki.

Extraction of biofuel is presented under the results category “Financial Value”. When a simulation is run in PlanWise or RegWise you have to select the variables you want to be saved in the Results database. In StandWise, they are calculated automatically.

Harvest Residues Available and Stumps Available denote how much biofuel could be extracted if all harvest residues were extracted from the harvested trees, and all stumps that could be extracted (while meeting the stump extraction requirements, stated above). Stumps Available could also have been named Stumps Available for Harvesting.