Page 113 - Materials Chemistry, Second Edition

98 A. Bjørn et al.

8.5.4 Recommended Modelling Choices for the Identified
Decision Context

ILCD provides recommendations for model choices for each of decision contexts
(Situation A, B, C1 and C2) identified as part of the goal definition (see Chap. 7).
These recommendations are the outcome of a comprehensive consultation process
within the LCA community. Since different actors with different views have had a
saying in this consensus process leading up to the ILCD recommendations, they are
somewhat internally inconsistent, as pointed out by, for example, Ekvall et al.
(2016). Below we present the recommendations for each decision context and make
notes about the parts that are disputed. Table 8.4 summarises the recommendations.

Situation A
Situation A concerns micro-level decision support (see Chap. 7) and the conse-
quence of a decision (e.g. the introduction of a new product on the market) is
therefore of interest. Ideally, the marginal process should therefore be identified and
used for all background processes (such as electricity supply) and cases of multi-
functionality (e.g. of an incineration process) should be handled by system
expansion with marginal processes, provided that subdivision is not possible (see
Sect. 8.5.2). This ideal for Situation A is logically consistent with a consequential
modelling framework. Yet, ILCD recommends using an average market con-
sumption mix for background processes and in cases of system expansion in the
background system. ILCD terms this attributional modelling, although system
expansion was previously associated with consequential modelling, as mentioned
above. The main reason for diverging from the ideal is that for the small changes
studied under Situation A it can be very difficult to identify marginal processes, i.e.
to understand the long- and short-term consequences on the market of introducing a
small change in its composition of product systems. The actual market behaviour in
response to small changes may also not be well-represented by simple mathematical

Table 8.4 Summary of ILCD recommendations on LCI modelling choices
Decision LCI Handling of Modelling of background
context modelling multifunctional system
framework processes when
(ILCD subdivision is not
terminology) possible
Situation A Attributional System expansion Average processes
Situation B Mix of System expansion Mix of long-term marginal
attributional processes for processes
and structurally changed.
consequential Average processes in all
other cases
Situation C1 Attributional System expansion Average processes
Situation C2 Attributional Allocation Average processes