Abschätzung von Substitutionspotentialen der Holznutzung und ihre Bedeutung im Kontext der Treibhausgas-Berichterstattung

The greenhouse gas (GHG) emissions associated with the use of the renewable raw material wood can be divided into three mechanisms of action. On the one hand, the biogenic CO2 emissions and their removal in the carbon pools "forest" and "harvested wood products" (HWP) as part of the biogenic carbon cycle, and on the other hand the other GHG emissions of the wood processing industry as part of the manufacturing sector as a third element.
The quantification of these climate relevant effects is carried out by means of various calculation methods on different scale levels with mostly different system boundaries (land or product system) and concerns temporally and spatially divergent dimensions (retro- and prospective effects). However, a sound and comprehensive analysis of the climate relevance of the forest-based sector must always take into account all effects and impacts. This applies in particular to the estimation of possible indirect GHG reduction effects (substitution potentials) associated with the use of wood.
According to the methodological requirements of the Intergovernmental Panel on Climate Change (IPCC), the biogenic CO2 emissions and their removal (carbon storage effect) are reported under the category land use, land use change and forestry (abbreviation LULUCF) as part of the National GHG reporting. All other GHG emissions related to the processing of raw materials in the manufacturing sector (including the timber industry) (including electricity consumption) are recorded and reported according to the source principle primarily under the categories “energy” and “industrial processes”, i.e. not assigned to any economic sector. In order to avoid double-counting with LULUCF, biogenic CO2 emissions from the thermal use of wood (energy) are carried in the category energy for information only ("carbon neutrality").
Since the non-biogenic GHG emissions of the wood processing industry cannot be determined with methods provided by IPCC, other approaches must be used. The life cycle assessment (LCA) method, which is internatio-nally standardised, provides a computational basis for this. Among other things, it is used to estimate the global warming potential (GWP) of a product system that fulfills a previously defined function (functional unit). At the same time, a material and/or energy substitution potential (here: reduction effect in relation of GHG emissions) merely describes a potential effect associated with the replacement or substitution of a defined product system with a functionally equivalent alternative. This conse-quently corresponds to the difference in the GWP results of two functionally equivalent product systems. The complex interrelationships of the biogenic carbon cycle along the forestry and timber chain, on the other hand, cannot, for methodological reasons, be plausibly quantified and mapped for wood-based products by means of LCA that are dimensionless in terms of time.
For a well-founded quantification of possible GHG substitution potentials through the use of wood, several sources of data must therefore be consistently combined in accordance with the relevant methodological requirements (IPCC and international standards). For the use of wood in buildings, corresponding analyses of the various system elements are available, which have been externally reviewed several times.