Page 97 - Materials Chemistry, Second Edition

82 A. Bjørn et al.

The classification is based on the identification of the environmental issues that
each elementary flow can contribute to, such as water depletion, non-renewable
resource depletion, climate change or freshwater eutrophication. The purpose of the
next step, characterisation, is to translate the LCI results (quantities of elementary
flows aggregated across all unit processes of an LCI model) into indicator scores for
the different impact categories. This essentially reduces a list of hundreds of
quantified flows (the LCI results) to a manageable number of indicator scores
(typically around 10 or fewer) with a clear environmental meaning, which is
practical when comparing the environmental performance of two or more products.

Normalisation
Normalisation is an optional step under ISO 14044:2006 to support the interpre-
tation of the impact profile from the characterisation. Normalisation means that
indicator scores for all impact categories are expressed in a common metric, typi-
cally the annual contributions to total environmental impacts of an average person.
This serves mainly three purposes: (1) for decision-makers to better understand the
magnitude of characterised results by relating them to a common familiar and
external reference, (2) to check for errors in the assessment resulting in unrea-
sonably low or high normalised results and (3) to pave the road for weighting.
Weighting
Like normalisation, weighting is an optional step under ISO 14044:2006 to support
the interpretation of the impact profile. In weighting, the (typically normalised)
indicator scores for the different impact categories are made comparable by
assigning weights to each impact category that is intended to reflect their relative
importance. This relative importance is inherently subjective and can be based on
the opinion of experts, policymakers or the general public (or a combination of
these). Weighting allows calculating a single indicator score by summing all the
weighted impact scores. This is often considered useful by decision-makers wanting
to understand which product system performs best “overall” in a comparison.
The detailed choices on impact assessment methods and factors are made in the
impact assessment phase of the LCA but it is necessary to select the impact cate-
gories in the scoping phase to ensure that the inventory analysis collects data on all
elementary flows of potential relevance for the selected impact categories.

8.3 Deliverables

The types of deliverables should directly reflect the intended applications of results,
as defined in the goal definition. To be compatible with the ISO 14044 standard an
LCA study must include an impact assessment, and most LCA studies have two
deliverables, the LCI results and the LCIA results. Some LCA studies (e.g. col-
lection of data for unit process databases) only involve the construction of a life
cycle inventory (LCI), in which case the only deliverable is the LCI results. In any
case, LCI results should be documented with full transparency (see Sect. 9.7)to