Page 50 - Materials Chemistry, Second Edition

34 2 Goal and Scope Definition

chemical industry, but agriculture and its downstream industries are known for
their co-product problem as well. Thus, for example, with the production of grain,
straw is produced as a co-product that is transferred as ‘usable product’ to the system
surrounding. In this case, environmental loads of the processes must be allocated,
according to defined rules, both to the examined product and the co-product (see
also Section 3.3, ‘Allocation’, and particularly Section 3.3.2.5, ‘System Expansion’).
Co-products can play a role in different unit processes of a product tree.
2.2.2.2.2 Secondary Raw Material Non-directly usable by-products are usually
called residual material. Depending upon the recycling potential, distinction is
drawn between ‘secondary raw materials’ (after cleaning or other processing) and
‘wastes’. The ‘Closed Substance Cycle and Waste Management Act’ 18) in Germany
has resulted in different designations for the same issue: wastes for reutilisation
and wastes for disposal. Secondary raw materials that are gained from waste for
reutilisation leave the system and are used as input in other product systems.
Recycling of materials, which lead to new products, where the materials thus
become parts of other systems, is called open loop recycling. 19) The respective
secondary raw materials (e.g. scrap, waste paper, waste glass, plastic wastes, etc.)
leave the product system under study, of which where they are the residual material,
as respective wastes for reutilisation.
Within the system boundaries remain materials in those recycling processes that
lead back to the same product (the one under investigation), that is, it remains
in the product system (closed loop recycling). 20) Moreover, in the case of product
re-use, these materials remain in the investigated system (usually after cleaning).
Examples of closed loop recycling are the re-feed of plastic shreds, punching,
cutting-off, and so on, into the extruder. A good example of re-use is the refilling of
returnable bottles.
Rules to be applied for allocation (Allocation, see Section 3.3.4) shall already
be specified within the goal and scope definition; if not avoidance of allocation,
for example, by system expansion, becomes compulsory in a specific case 21) (see
Section 3.3.2.5).
The system boundary requires further explanations, the most important concern
being the geographical and temporal system boundary.

2.2.3
Geographical System Boundary

The geographical system boundary results from the economic context and from
the product definition:
• Is the concerned special product manufactured in factory A, at site B, and so on,
or a group of very similar products manufactured in multiple factories all over

18) German: ‘Kreislaufwirtschaftsgesetz’.
19) Kl¨ opffer (1996), Hunt, Sellers and Franklin (1992) and Boustead (1992).
20) SETAC Europe (1992), Curran (1996), Kl¨ opffer (1996) and Hunt, Sellers and Franklin (1992).
21) ISO (1998, 2006b).