Page 49 - Materials Chemistry, Second Edition

44 3. Life cycle thinking tools: Life cycle assessment, life cycle costing and social life cycle assessment

After data collection, a calculation procedure to validate the collected data has to be
implemented; data have to be connected to the unit process and to the reference flow of
the functional unit. These actions are necessary to generate the results of the inventory phase.
In this phase, a required item concerns allocation procedures. The main problem is which
flows and environmental interventions must be allocated to the functional unit, and which
should be allocated to other product systems. Within LCA studies, two different cases have
to be distinguished for the application of allocation procedures (Toniolo et al., 2017a). The first
case occurs when simultaneous products are manufactured and thus, different inputs and
outputs shall be allocated to different products, whereas the second case occurs when subse-
quent products are realized in recycling or reuse systems. In general, almost all of the indus-
trial processes produce more than one product or recycle a portion of the waste material
(Frischknecht et al., 2005, 2007; Frischknecht, 2010).
However, even if in general allocation procedures represent a critical point (Ardente and
Cellura, 2012), this distinction is not deeply investigated in ISO 14040 and ISO 14044. Any-
way, it is possible to appeal to ISO TR 14049 where some examples are described and some
considerations are added. Other considerations can be found in the ILCD (International
reference Life Cycle Data system) handbook. If the market value of the waste or end-of-life
product at its point of origin is above zero, in LCA perspective, it is a co-product and the
multifunctionality has to be solved by allocation. However, the case of recycling is insofar
different from the general case of multifunctionality, as the secondary good is not only a
co-function of the system, but is itself recycled again and again (while each time at lower
amounts and/or quality, considering losses of each loop) (EC-JRC, 2010).

3.1.3 Life cycle impact assessment

In this phase, the effects of the substances on the selected impact categories and the pro-
cesses that generated them are analyzed (Toniolo et al., 2017b). Inventory data are associated
with environmental impact categories and category indicators. The elements within this
phase are (ISO, 2006b):

– Classification. Classification assesses which global/local impact the input/output is
contributing to. There are input-relating categories and output-related categories. There
are several categories that are commonly used, such as climate change, ozone layer
depletion, eutrophication, acidification, particulate matter formation, and several impact
categories under development, such as acoustic impact.
– Characterization. Impacts are quantified within given categories with the general Eq. (3.1)
(Goedkoop et al., 2013):
EP jðÞi ¼ Q EQ jðÞI (3.1)
where EP( j)i is the environmental impact of substance i with reference to the impact cat-
egory j, Q is the quantity of substance I, and EQ( j)i is a factor representing the substance i
contribution to the impact j. Different substances contributing to an environmental impact
are aggregated considering their substance-specific effect. Scientific models are used, there-
fore characterization could be considered objective. Fig. 3.3 shows an example of character-
ized results of an LCA study.