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