Page 261 - Materials Chemistry, Second Edition

4.5 Impact Categories, Impact Indicators and Characterisation Factors 245

Thetime scale, infinite in theory, for a computation of ODP values according
to a flow equilibrium model of the World Meteorological Organization (WMO)
is different to the calculation of GWP. 200) There are, however, also ODP values
calculated for a relatively short period of time. 201) The objective of time dependence
has also been discussed by the WMO. 202) Accordingly, stationary ODP values of
relatively short-lived compounds (e.g. HCFC) are small because they are computed
in relation to CFC-11 whose flow equilibrium will only be reached in centuries
even presupposing releases. The brief impact of relatively short-lived compounds
is therefore underestimated. If ODPs are calculated for a short time horizon, the
values can be around an order of magnitude higher;however, because of smaller
persistence, the values are still below those of CFC-11 and CFC-12. In LCAs with
an expressly intended comparison of freons and substitution products in their goal
definition, the time dependence should be explicitly considered (computation loc.
cit. WMO, 1994). For LCAs not specifically concerned with this problem, stationary
ODP values should be used. In Table 4.10 an excerpt of available ODP values is
listed.
There has been a slight loss of importance for the assessment of ozone depletion
because it is presumed that the Protocol of Montreal and its supplements have
been adhered to. Even so, the effect will prevail for some decades and attention
is therefore required, in LCA also! In preparing the LCI it should therefore be
carefully investigated to what degree the process of substitution has occurred in
the reference time of the LCA study. Furthermore, N Oshouldbeincludedas
2
potentially ozone degrading gas. This is especially important since there seems to
be much more ‘laughing gas’ around in the atmosphere 203) and new sources in
addition to agriculture are sought and found (e.g. nitric acid production). As this
gas is equally important for the impact category ‘Climate change’, better LCI data
are to be expected in the near future.
4.5.2.3.4 Characterisation The quantification (characterisation) of the impact
category stratospheric ozone depletion results from ODP values as equivalence
factors similar to those of the GWP:

ODP = ∑ (m × ODP ) (4.16)
i
i
i
The load of the ozone-depleting gases per fU (m ) can be taken from the inventory
i
table and appropriate ODP values from respective charts of the WMO.
i
ODP is a typical mid-point characterisation factor, based on the precautionary
principle. There are other attempts to quantify the effects of stratospheric ozone
depletion within ‘endpoint’ models. Evidently, an increase of UV radiation at the
surface of the earth may damage both: human health and ecosystem quality.

200) Udo de Haes (1996).
201) Solomon and Albritton (1992).
202) WMO (1994).
203) Crutzen et al. (2007).