Potentiale zur energetischen Nutzung von Biomasse in der ... - EPFL

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Estimation of the biomass volume available for energy use
Having calculated the actual in-stand volume and annual increment of biomass at each pixel it is now
important to estimate the proportion of the total harvestable amount of biomass which could be used
for specific energy needs. According to the WSL classification (WSL 2003) the following types of trees or
parts thereof could be used for energy purposes (Table 47).
Species type Category Diameter
Availability
for energy use
Coniferous logwood 10 – 69 cm 13%
brushwood and wood residues < 10 cm 100%
Deciduous logwood 30 – 69 cm 19%
logwood 10 – 29 cm 100%
brushwood and wood residues < 10 cm 100%
Table 47 Availability of trees for energy use. Source: WSL 2003.
Knowing the characteristics of each forest stand as regards repartition of trees by species group and
diameter, one can estimate the proportion of annual biomass increment that could be used for energy
at each pixel. As a result of all methodological steps described above, each pixel containing the
exploitable forestry plantations should be assigned with a certain volume of fresh biomass that could be
harvested annually for energy use.
Generalised approach
In case the detailed data on individual forest stands are missing, a more generalised approach for
estimation of potentially available volume of energy biomass can be applied. According to this approach,
in the first instance, the predominant species group should be determined for each pixel belonging to
the exploitable forestry plantations. This can be done on the basis of the GEOSTAT dataset “Variety of
Swiss Forests” (SFSO 2001) which distinguishes four main types of forests subject to the percentage of
coniferous species (Table 48).
If possible, more precise data on respective percentage of coniferous/deciduous species should be
gathered. Otherwise, some averaged values should be chosen in order to decide about the repartition in
specific locations of trees of particular species groups.
Forest type Percentage of coniferous species
Coniferous forest 90–100%
Predominantly coniferous forest 50–90%
Predominantly deciduous forest 10–50%
Deciduous forest 0–10%
Table 48 Forest types in GEOSTAT dataset “Variety of Swiss Forests“. Source: GEOSTAT (OFS 2001).
Next the annual increment of biomass at each pixel should be calculated by multiplying the surface
occupied with specific tree species by the respective annual growth rates (Table 42). Finally an averaged
factor of biomass availability for energy needs for each species group should be specified. It could be
estimated from any representative sample dataset or basing on expert judgements. As a reference the
SFOS/SAEFL (2003) data could be taken, according to which the share of energy wood in total
indigenous timber production is estimated approximately at 20%.