English Abstract At the moment three alternative approaches for
estimating emissions and removals of CO2 from forest harvesting and wood
products are under discussion. These are atmospheric flow approach, stock
change approach, and the production approach. Several methodologies are
being developed to deal with these approaches. In the present report we
test two of those The 'Forest Research Institute from New Zealand has
developed an Excel based model' (FR), and the FA model (Alterra supported by
FORM Ecology Consultants). The IPCC approaches themselves are not under
study here, only the models representing them. Above that, a sensitivity
analysis of the data input has been done, with a special focus on life
spans. The models are qualitatively and quantitatively compared , and a
sensitivity analysis on life spans was carried out. In principle both
models (FR & FA) are very comparable, and can in principle be used as a
basis for improved IPCC guidelines in this area. However, the current FR
model focuses on the carbon dynamics in the long life span products only (on
purpose), and thus lacks the following sources of CO2: actual burning of
fuelwood (in atmospheric flow and production approach), immediate
decomposition of wood residues (in atmospheric flow and production), and
harvest figures (in stock change approach), which are relevant for
determining the overall wood products carbon balance of a country. Thus the
results of a full quantitative comparison of the FR and FA model were not so
relevant. Finally, it is noted that the production approach can be
interpreted in different ways. A wide variety of life span estimates was
found in literature. Different shapes of decay functions are used. Also,
confusion can occur because the half lives, total lives, as well as in- or
excluding the disposed off phase, are used in literature. This contributes
a lot to the uncertainty regarding life spans. The carbon balance of wood
products showed the strongest sensitivity to life spans for New Zealand and
The Netherlands. Especially the production approach is sensitive for
changes in life spans. The overall effect of a decrease in life span is an
increase of the sources, or in the case of The Netherlands under the stock
change approach, a change from sink to source.
