Page 210 - Materials Chemistry, Second Edition

194 4 Life Cycle Impact Assessment

The usefulness of such relative structuring is illustrated by a comparison of the
standardised value for CO -equivalents with those of R11-equivalents as category
2
indicator for stratospheric ozone depletion.
Because of international conventions, substances known by their stratospheric
reactions for the ozone depletion (persistent halogenated gases; see Section 4.5.2.3)
were only used in larger quantities in product systems with freons as propellant
or coolant or with methyl bromide as pesticide. The produced quantities have,
since the 1990s, substantially diminished (significance of N O see Section 4.5.2.3).
2
These substances will therefore rarely appear in recent primary data. However, in
generic data sets stored in data bases, these substances are often present in small
quantities, as a multiplicity of processes with all side processes were aggregated
into one data set.
Normalisation of the category indicator result ‘R11-equivalents’:
• Contrary to CO -equivalent, release data to R11-equivalents as reference for
2
standardisation are not available in Germany. If as approximation a total amount
of ozone layer-damaging substances produced in Germany in 2004 is used,
,
which corresponds to 9364 t, 36) R11-equivalents the following normalisation
result follows:

Category indicator results R11-equivalent Normalised value

Emissions caused by the Annual release in Germany Specific contribution
product system per functional unit

2.20E−06 kg 9.36E+06 kg 2.35E−13

The relative significance of the product system concerning the category indicator
‘CO -equivalent’ is thus about three orders of magnitude higher than that of
2
category indicator ‘R11-equivalent’. Because the result of the normalisation is
determined by the reference quantity, the relative significance of 2.2 × 10 −6 kg R11-
equivalents of the product system rises if the emitted amount as reference quantity
decreases. These influences must be critically discussed in the interpretation (see
Chapter 5).
Because of its global and regional significance, the impact category ‘stratospheric
ozone depletion’ is classified as very important, and hence, the estimated specific
contributions within comparative LCAs could strongly modify the final result. The
result could, for example, be: Product A has a 10 times larger specific contribution
concerning the impact category ‘stratospheric ozone depletion’ than product B.
Normalisation in these cases can show that the relative significance of this impact

36) Data to the environment at http://www.uba.de; in 1990s the corresponding value amounted to
10E+04 tonne R11-equivalents within Netherlands, which is substantially smaller Breedveld,
Lafleur and Blonk (1999).