Page 135 - Materials Chemistry, Second Edition

120 A. Bjørn et al.
4. The processes required to produce and maintain the infrastructure that enables
the level 0 process should then be identified. These are termed ‘level 4’ pro-
cesses. In the window example, examples of level 4 processes are production and
maintenance (oiling, replacing and repairing parts) of the assembly machines.
After having identified level 1, 2, 3 and 4 processes belonging to the level 0
process (the reference flow), Step 1–4 is then repeated for each these processes.
This procedure is illustrated in Fig. 9.1 for the window example.

Upstream Downstream

1) Sand

1) Limestone

2) Heat 2) Electricity
2) Natural gas 1) Window supply
glass

3) Admin. 1) Window 2) Transp. 2) Cleaning 2) Transp.
frame
*
3) Business
travel 2) Electricity 0) Window Use Waste 3) Admin.
supply assembly management
4) Furnace
4) Furnace for
2) Transp.
glass
recycling
3) Admin.,
R&D 4) Incin. plant
for frame
3) Marketing

4) Assembly
machine

Fig. 9.1 Procedure for identifying processes of the foreground system, exemplified in the study of
the life cycle of a window. The starting point is the process that delivers the reference flow, ‘0)
Window assembly’. The foreground system is then populated process by process by proceeding
upstream and downstream from the reference flow. Unlinked arrows present on some processes
indicate the existence of other processes that were not included in the figure. Use and Waste
management are in italic, because they represent life cycle stages, rather than actual processes. The
star at ‘Waste management’ indicates the existence of multifunctional processes, i.e. glass
recycling and incineration of window frame. Abbreviations in the figure: Incin incineration, Transp
transportation, Admin administration, R&D research and development. Numbering and colour
code, identify the process level for the different foreground processes