Page 134 - Materials Chemistry, Second Edition

9 Life Cycle Inventory Analysis 119

achieved in the sense that no processes need to be cut-off due to missing data or
budget constraints. The two main weaknesses of the EEIO approach are (1) that the
coverage of elementary flows is rather limited, compared to the process-based
approach and that (2) the resolution of many products and services is quite low due
to the heterogeneous nature of many sectors, as defined by national trade statistics.
Chapter 14 deals with IO-LCA and in particular how to use EEIO to complement
and guide process-based LCA. This chapter will make references to EEIO, when
the approach can complement the process-based approach.

9.2 Identifying Processes for the LCI Model

This first step of the LCI details the coarse initial system diagram made under the
scope item System boundaries (see Sect. 8.6) and draws upon the related com-
pleteness requirements. The outcome of the step is a detailed depiction of the
foreground system, i.e. all the processes it is composed of and their links, and the
processes of the background system ‘neighbouring’ the foreground system, i.e.
where links to LCI database processes will be established.

9.2.1 Detailing the Physical Value Chain

For all decision contexts (A, B, C1 and C2—see Sect. 7.4) the approach to iden-
tifying processes is to start with the reference flow and construct the entire fore-
ground system process by process:

0. The unit process having the reference flow, as product output, should first be
identified (or unit processes, in the case of more than one reference flow). This is
termed a ‘level 0’ process. In a study where a window is the reference flow, the
level 0 process is the assembly of the window.
1. The processes required to deliver flows that will be physically embodied in the
reference flow should then be identified. These are termed “level 1” processes.
In the window example, examples of level 1 processes are the production of
glass and the window frame.
2. The processes required to deliver flows that perform a supporting function to the
level 0 process (i.e. not becoming physically embodied in its output) should then
be identified. These are termed ‘level 2’ processes. In the window example,
examples of level 2 processes are the supply of electricity used in the assembly
of the window or the transportation needed to deliver the flows of the level 1
processes to the level 0 process.
3. The processes required to deliver services to the level 0 processes should then be
identified. These are termed ‘level 3’ processes. In the window example,
examples of level 3 processes are administration and marketing.