Proceedings World Bioenergy 2010

Figure 1: The studied regions
2 MATERIAL AND METHODS
For the estimation of the potential harvestable
amount of slash and stumps from regeneration fellings
given a scenario according to which Swedish silvicultural
practices are not going to change ten years in the future
(2010-2019), NFI sample plots (more than 3000 sample
plots evenly spread over the complete forest area of
Sweden) were utilized. Each individual plot was used as
the unit for decision for different future silviculture and
felling measures and a growth prognosis for the trees of
each plot was produced.
In order to decide from which stands slash and
stumps will be extracted and the quantity that should
remain in the forest the following restrictions were taken
under consideration.
• no extraction was counted with for productive
forest areas that are situated in areas of nature
protection.
• wet areas as well as peat soils with low bearing
capacity as well as all areas that are located 25
meters from a lake, sea, waterline or any other
ownership category than forest were not
considered for extraction
• 40% of the logging residues were left at the
felling site
• no hardwood stumps were extracted
• areas that have an uneven ground structure
and/or a slope of more than 19.6 0 according to
the Swedish terrain classification scheme were
not considered for extraction.
• regeneration felling areas of a size of less than
1 ha were not included
The costs for harvesting the residues, transforming it
to chips and bringing it to the end user were also
calculated. For slash the machine systems that were used
were the following
Slash system 1: Slash forwarder, roadside
chipper, container truck.
Slash system 2: Slash forwarder, slash
truck, industry chipper
Concerning stump harvesting, stumps were
forwarded to the roadside, transported by truck to the
industry and crushed there. Productivity and machine
22 world bioenergy 2010
cost data employed in this study were obtained from
practical experience and scientific studies (Table I). All
calculations were made with the FLIS tool [5].
Table I: Compilation of machine costs (SEK/ODT) for
the slash and stump machine systems
Slash Stumps
System 1 System 2
Stump lifter - - 187
Forwarder
180 m (420 m)* 163(208) 163(208) 163(208)
Chipper 166 119 119
Truck
50 km (100 km) 108(191) 124(197) 218(364)
* Average forwarding distance(one-way), ** Average
transport distance
The moisture, dry matter and heat content for both
slash and stumps was assumed to be 50%, 0.82 MWh/m 3
loose raw chips and 0.17 ODT/m 3 loose raw chips,
respectively. Compensation to the land owner was set to
172 SEK/ODT (2.5 SEK/m 3 loose raw chips) while
administration costs were set to 73.5 SEK/ODT (13
SEK/m 3 loose raw chips). Cost for machine allocations
between production sites (2500 SEK/machine and
allocation) was related to the amount of the harvestable
amount (ODT) available in the production sites [6].
3 RESULTS
3.1 Potentials
In Table II an estimation of the harvestable potential
of slash and stumps in the different regions of Sweden is
given. A majority of the potential (55%) is located in the
south half of the country (Central and South Sweden).
Table I: Annual regional harvestable potential of stumps
and slash in Sweden
Slash Stumps Total
Million ODT/year
Upper Norrland 0.63 0.90 1.53
Central Norrland 0.78 1.08 1.86
Central Sweden 0.78 1.06 1.84
South Sweden 0.98 1.20 2.18
Whole Sweden 3.17 4.24 7.41
3.2 Marginal costs of slash and stump procurement for
the whole of Sweden
The potential annually harvestable amount of slash
and stumps is ca. 3.2 and 4.2 million ODT, respectively.
Slash can be harvested at a lower cost than stumps which
leads to that the marginal curve for slash starts at a lower
level than the curve for stumps. When the curves
approach the maximum harvestable potential they bend
strongly upwards. That is due to the fact that a part of the
logging residues is located in small production sites, far
away from the industry making transport costs very high.