Transcript 3. Forests - Important Energy Source

FORESTS –
IMPORTANT
ENERGY SOURCE
Forests in the EU
Apart from their importance for ecology and
environment conservation forests are one of the
Europe's major renewable resources which
provide multiple benefits to the society and
economy. In the EU, the forests and other
wooded land take up about 177 million ha (over
40% of the land area), of which 130 million ha
are available for wood supply.
With Sweden and Finland as the leaders,
forests cover a half of territory of the
following seven EU member states: Sweden,
Finland, Slovenia, Spain, Latvia, Estonia,
Greece
Forests in Sweden
Important facts :
70% of the country’s territory is
covered by forests;
total forest area is 28.4 million
hectares;
total standing volume on productive
forest land is about 2.9 billion m3;
total annual growth is about 111
million m3 (productive forest) and
around 117 million m3 (all land use
categories);
average standing volume per hectare
is 131m3;
average annual forest productivity is
5.3m3 of wood per hectare.
Conifers are the dominant tree species in
Sweden
Sustainable
management
Wood energy, if recovered from sustainably
managed resources with special regulations for
harvesting and collecting energy wood, is a
climate-neutral and socially viable source of
renewable energy.
In Sweden, the stands suitable for collecting
energy wood are:
spruce-dominated stands of no high
biological, cultural, or social values;
rot damaged stands;
forest plantations on agricultural lands.
Normally, logging residues are not collected
on the sites prone to ground damages
or having fine fraction soils, on
wetland forests, high elevation
sites and stands close to water
catchment.
To ensure sustainability it is recommended to leave at least
20% of logging residues in forest.
Special guidelines regulate stump harvesting
which is allowed in selected stands only with at
least 15% of stumps left in the cutover.
Amount of energy
In most cases thewood
estimates of the amount of
energy wood are based on the characteristics
of harvestable stands ripe for final fellings,
thinnings or cleanings. The exploitable volume of
energy wood depends on the amount of wood:
potentially available;
actually available;
technically or economically available.
In the stands where logging residues can be
collected the potential amount of energy wood
is estimated to be about 40% of the total timber
volume which is normally reduced to 35%
following the sustainability criteria and
environmental constraints.
In some cases, because of poor infrastructure,
transportation distances, or the forest owner’s
decision, the amount of energy wood to be
recovered decreases, and that actually available
is about 60% of the potential amount.
Forest residues energy
Woody biomass for energy is usually recovered
in forest operations, using for it mainly
residues from final felling and thinnings. In
Sweden, forest biomass is collected in about
60% of final-felled areas. This approach is still
seldom used in thinnings. There is a big potential
for using stump-wood and small-sized trees for
energy, but the methods of harvesting require
further development.
logging residues 20-30%
timber –
70-80%
stumpsup to 20%
Proportion of different fractions of the aboveground tree biomass
Wood fuel
Wood energy is produced from:
sawdust and other residues from
sawmills and wood-related industries;
other wood not demanded by the industry
or trees of no industrial value;
logging residues;
fuelwood.
Types of wood fuel :
firewood;
wood chips;
pellets, granules and
briquettes;
charcoal.
Wood fuel can be used for:
household needs;
heat supply (stoves, central heating
furnaces, boiler houses, central heating plants
(CHP), cogeneration stations);
fuelling steam engines and steam turbines
that generate electricity.
Outturn of energy
wood
To estimate the approximate outturn of energy
wood in forest operations some simple
calculation methods are worked out based on
long-term experience. Technological losses of
about 20-40% are accounted for.
In final felling
the average
outturn of energy
wood is about 2030m3 per each
100m³ of timber.
In mixed spruce
and broadleaved
stands it can reach
35-45% from the
total volume of
timber.
In average 1 ha of forestland yields about
80m³ of energy wood, including firewood.
The highest outturn of energy wood is in
spruce stands, reaching more than 130m³/ha.
Note: with increasing stand quality the
outturn of timber assortments is getting
higher compared to that of energy wood!
Amount of forest fuels
2009 figures for Sweden:
removals of forest fuels was 5,704,000m3
loose (87% from final felling and 13% from
thinnings);
tops and branches were collected from
115,095ha, and stumps from 5,010ha.
In 2010, logging residues were extracted from
150,000ha of forestlands. According to expert
estimates it is possible to increase the amount of
energy produced from forest residues 4 to 6
times. In such a case, too, only the smallest part
of the available volume will be used.
The annual amount of energy in TWh
generated from different types of wood
residues
Type of
Totally
Today
Estimates
residues
available
Forest
11
20-25
40
residues
Stumps
0
10-12
40
Small
trees
1
10-15
140