Proceedings World Bioenergy 2010

HARVESTING FOR ENERGY OR PULPWOOD IN EARLY THINNINGS?
Dan Bergström & Fulvio Di Fulvio
Department of Forest Resource Management, Swedish University of Agriculture Sciences
SE-901 83 Umeå, Sweden
Dan.Bergstrom@srh.slu.se, Fulvio.Di.Fulvio@srh.slu.se
ABSTRACT: The objectives of the study were to compare the profitability between pulpwood and energy wood harvesting
systems in early thinnings. The availability of merchantable volumes of pulpwood and energy wood was calculated for three
different types of first thinning stands of pine, spruce and birch, i.e. nine different stands. The energy wood and pulpwood
prices were based on year 2009 market prices for Sweden and a system analysis was carried out including costs for
harvesting and forwarding to roadside. The tree volume of removal ranged from 15 to 84 dm 3 and was in average 38 dm 3 . In
average the biomass to pulpwood ratio of the gross income in the pine, spruce and birch stands was 2.1, 2.9 and 2.3,
respectively. The net income for the pulpwood system was negative (generating costs) in all stands. The net income for the
energy wood system was profitable in 67% of the stands; 133 €×ha -1 in pine stands, ranging from 37 to 145 €×ha -1 in spruce
stands, and 19 to 76 €×ha -1 in birch stands. If the market price for energy wood increases with 30% (compared to the current
level) harvesting for energy wood in early thinnings could generate a considerable income for the forest owner.
Keywords: bioenergy, forestry, thinnings, young forests, harvesting, wood chips.
1 INTRODUCTION
In Sweden there are large areas of young forests that
have not being subjected to a pre-commercial thinning
(PCT) and thus are dense and rich of biomass. However,
performing a late PCT in such stands is expensive and the
only alternative is to perform an early thinning. In early
thinnings about 20-30% of the cut trees are too small
sized for pulpwood and are left unutilized at the felling
site. However, in the energy wood system full trees are
merchantable and there are no restrictions of tree size and
therefore all tree biomass are commercial available.
Energy wood thinning can be a profitable alternative
compared to pulpwood thinning [1]; the biomass removal
can be 15-50% higher and the harvesting costs from
stump to road side can be reduced by 20-40% [2].
In early thinning operations for pulpwood multi-stem
processing heads are used which render higher efficiency
compared to using single-tree processing heads. In the
multiple-tree handling of whole trees in thinning for
energy wood accumulating felling heads (AFH) are used
which can be mounted on single-grip harvesters or
specially designed feller-bunchers [3] [4]. These multitree
handling system shown to increase productivity by as
much as 35-40 % when compared to single-tree handling
[5]. In energy wood harvesting the felling and bunching
operation still remains the largest cost component in the
system (forwarding and comminution included) [4] [6].
In 2009 the wood fuel (chips) costs for the thermal
industry in Sweden was in average 167 SEK×MWh -1 (~
317 SEK×(m 3 solid) -1 and the pulpwood price at road
side was in average 310 SEK×(m 3 solid under-bark) -1 [7].
The most profitable alternative depends on the relation
between merchantable volumes, biomass prizes and the
costs of respectively harvesting systems and supply
chains.
The objectives of the study were to compare the
profitability between pulpwood and energy wood
harvesting systems in early thinnings, from stump to road
side.
2 MATERIAL AND METHODS
The availability of merchantable volumes of
pulpwood and energy wood thinning in different types of
first thinning stands was estimated using pine, spruce and
birch type stands from Bredberg (1972). In the analysis
three stands per species aged from 22 to 42 years (age
classes: “young”, “middle” and “old”) were used. In each
of the stands the volume availability per treatment were
calculated at a 30% level of intensity of removal of the
basal area. Only trees with a dbh ≥ 5cm were used in
calculations and trees where thinned from below
according to a pre-suggested thinning “priority” [8]. The
minimum pulpwood stem diameter under-bark was set to
5 cm and the merchantable logs length range between 3.0
and 5.5 m. The oven-dry weight of stem, branches and
needles biomass was calculated using Marklund’s (1987)
[9] functions and was then converted into solid volume
by using stem basic densities and values for crown
biomass by Hakkila (1978) [10].
Stumpage prices were based on year 2009 market
prices for Sweden: the roadside price of pulpwood overbark
was 278 SEK×m -3 (340 SEK×m -3 u. b.) and the
energy wood price at roadside (tree parts) of 200
SEK×m - ³biomass -1 . Prices and costs were translated into
Euro (€), assuming an exchange rate of 1€=10SEK.
A system analysis was carried out including costs for
biomass harvesting and forwarding to roadside. The
harvesting productivity (productive work time; PW [11])
was set to 5.4 m 3 pulpwood×PW-hour -1 in pulpwood
treatment and 11.0 m 3 biomass×PW-hour -1 in energy
wood treatment, according to Kärhä et al. (2004) [12] and
Kärhä et al. (2006) [13] functions. The productivity of
pulpwood forwarding was based on Nurminen et al.
(2006) [14] study giving an average value of 13.8
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