Page 163 - Materials Chemistry, Second Edition

148 A. Bjørn et al.

being installed (increase in production capacity) or existing equipment being pre-
maturely taken out of use (decrease in production capacity). Yet the ecoinvent
centre argues that the consequential version of the database (which is based on the
long-term marginal technology) is “applicable to study the effect of small,
short-term decisions, since each individual short-term decision contributes to the
accumulated trend in the market volume, which is the basis for decisions on capital
investment” (Weidema et al. 2013). In relation to the ILCD-defined decision
context situations, the ecoinvent 3 database can, strictly speaking, only be used to
model consistently the parts of Situation B studies involving structural changes
(using the consequential database) and Situation C2 studies (using the allocation
default or cut-off database). However, as noted in Sect. 9.2.2, economic allocation
is often the only practical solution to multifunctionality, irrespective of decision
context. We therefore advise that one of the two allocation versions of ecoinvent is
used for Situation A, B (only non-structural changes), C1 and C2. However, the
LCA practitioner should check for any multifunctional processes that have high
contributions to early iteration LCA results and, where appropriate and technically
feasible, manually change the multifunctionality solution in accordance with the
scope definition of the study to test its influence on LCA results.
Whenever data is sourced by online searches or LCI databases it is important to
pay attention to the available metadata describing the characteristics and conditions
of the process to evaluate how representative the data is for the actual data needed.
Metadata usually specifies the exact technology (or mix of technologies, in the case
of average or generic data) involved in a process, the location (e.g. country) of the
unit process, the time during which the data applies and relevant operating con-
ditions (e.g. climate). The metadata allows distinguishing between medium and low
data specificity (see Table 9.4). Relevant metadata for foreground processes should
be reported by the LCA practitioner (see Sect. 9.7) and furthermore considered in
the later sensitivity analysis and uncertainty management (see Sect. 9.6).
When using a unit process from an LCI database in the foreground system it is
preferable to adapt it to make it more representative of the actual process to be
modelled to the extent that this is possible (see Sect. 8.7). One improvement of the
representativeness that is usually possible is to manually change the electricity grid
mix that fuels the process to a mix that matches the geographical and temporal
scope of the study. Note that such adaptation is not possible if a unit process is
‘aggregated’, meaning that the elementary flows of all processes upstream and
downstream have been aggregated, so the reference flow is the only output of the
aggregated process (or input, in the case of waste treatment processes) apart from
the elementary flows.
Aggregated unit processes are often preferred for constructing the background
system because the LCA practitioner only needs to include the aggregated pro-
cesses that link to the foreground processes of an LCI model.