Page 124 - Materials Chemistry, Second Edition

8 Scope Definition 109

Disposal
Use
Manufacturing
Product development

2015 2020 2025 2040
Fig. 8.15 Example of time frames expressed for different life cycle stages

innovation (such as the pulp and paper industry); but it can have a low represen-
tativeness if it is part of a sector with rapid technological development, such as IT,
energy (with the growing focus on decarbonisation) and waste treatment (with the
focus on waste avoidance and recycling of materials).
In line with the requirements to define the geographical scope of processes, LCA
practitioners must in the scope definition define the time frame of the processes in
the different stages of the life cycle. Figure 8.15 gives an example of how time
frames can be represented.
These times are largely influenced by the expected lifetime of the studied pro-
duct(s). For example, in a study involving furniture the expected lifetime, from
consumer purchase to disposal, is decisive for the time at which waste treatment can
be expected to occur. In other cases, the lifetime of installed capacity in the fore-
ground system has a great influence on the time frames. For example, in a study
involving a decision to construct a new incineration plant, the number of years that
it is planned to operate (typically 20–30 years) is decisive for the timing of the
involved unit processes. In all cases, the intended application of results and reasons
for carrying out a study, as stated in the goal definition, can guide the time-related
requirements. In the illustrative case study on window frames, the time frame of the
manufacturing and use stage is estimated to be 5 and 20 years, respectively.
Following the formulation of the time-related requirements, the LCA practitioner
must attempt to obtain the highest overall possible time-related representativeness
when constructing the inventory model, within the time or budget constraints of the
LCA study. When comparing the time aspects of the obtained inventory data with
the time-related requirements it must be noted that the time at which a dataset was
published is usually not equivalent to the time for which its data is valid (several
years may pass between the first-hand collection of data and the publication of the
data). In the foreground system the focus should be on those processes taking place
in the future that the results of an initial iteration show to be important and that is
also expected to change relatively rapidly (see above). The available current or past
data for these processes can be used to project how they will evolve in the future.
For example, the electricity mix of the future might be projected from past trends
along with plans issued by public authorities that govern the electricity system. See
also Chap. 21 on prospective LCAs and technological foresight. Regarding the
background system, LCA practitioners usually have to make do with the most
recent process contained in the LCI database used, while considering any trade-offs