Page 254 - Materials Chemistry, Second Edition

238 4 Life Cycle Impact Assessment

inventory, and the respective GWP :
i
GWP = ∑ (m × GWP ) (4.12)
i i
i
m = load of the respective substance i per fU.
i
The GWP mostly selected for LCAs is GWP 100 (see Table 4.9). If in an impact
assessment, several time horizons are used, it must be ensured that only GWPs of
the same time horizon are used in the summing up according to Equation 4.12.
GWPs of various time horizons of very long-lived GHGs only differ slightly;
therefore, the life times in Table 4.9 are to be considered.
GWP values should be adopted from the latest IPCC or WMO report or from
recent secondary literature.
4.5.2.2.4 ‘Carbon Footprint’ Carbon footprint (CF) is a popular name for the
GWP, especially if global warming is used as the one and only impact category in
a LCA-type study. Such studies can be used for estimating the contribution of a
product system, process, company or country with regard to CO -regulations such
2
as the Kyoto-protocol, CO -certificate trading, and so on. The name is catchy, but
2
clearly a misnomer, because carbon is a chemical element without which life would
not be possible (and thus cannot be bad in itself) and there are several strong GHGs
without carbon in the molecule (N O; SF ;NF ). A separate standardisation of CF 176)
2 6 3
is nevertheless meaningful, since the international standards ISO 14040 + 14044
do not describe in detail how the GWP = CF has to be determined.
Furthermore it has to be considered that a life cycle study with only one impact
category is not and never will be an (environmental) LCA and even less so a life cycle
sustainability assessment (LCSA). 177) A low CF per fU may be overcompensated
by other environmental and social risks and impacts, as clearly shown by nuclear
electricity production.
In addition to the cited pre-standard publicly available specification, PAS 2050
and ISO/TS 14067, private initiatives have also been developing CF guidelines
in order to enable enterprises to correctly measure, calculate and report the CF
of product systems or even companies ‘from cradle-to-grave’ or at least ‘from
cradle-to-factory gate’. The most advanced guidelines are those developed by the
World Business Council for Sustainable Development (WBCSD) together with
the World Resources Institute (WRI) 178) . The development of these guidelines has
been accompanied by international congresses, education and training in order
to gain experience by applying the draft guidelines to real-world studies on a
global scale. It is to be hoped that these life cycle initiatives will lead to correct
action for the reduction of the GHG emissions and help to reduce the – already
inevitable – increase in global warming to a tolerable limit. 179)

176) British Standards Institution (2008), Sinden (2009), Finkbeiner (2009) and ISO (2013).
177) Valdivia et al. (2011).
178) WBCSD and WRI (2010, 2011).
◦
179) Politically, this limit is presently set to an average increase of 2 (K) above the pre-industrial level.