Page 130 - Materials Chemistry, Second Edition

114 3 Life Cycle Inventory Analysis

plant with waste water and incineration gases of fuels or evaporated propellants
of sprays are released into the air. In these cases that are better classified with
consumption (rather than use) disposal does either not exist or will be delegated to
the waste water sewage plant. Environmental loads due to use and consumption
are within the system boundary. 117)
Two substantial questions need to be answered in the context of disposal in LCA.
1. Modelling of waste disposal of a product (Section 3.3.5.1). If a product becomes
waste, depending upon the country, waste flows enter a disposal system.
According to the determined average mass flows, the waste disposal is analysed
and modelled by an LCA.
2. Comparison of different waste disposal options (Section 3.3.5.2). Different possi-
bilities of waste disposal are to be compared with one another.
Both questions and their handling by system modelling are discussed in the
following example ‘Disposal of Cardboard Packaging’.

3.3.5.1 Modelling of Waste Disposal of a Product
Figure 3.22 presents schematically two disposal options for cardboard packaging:
In this example 80% of the cardboard packaging is assumed to be recycled and 20%
to be burnt in a waste incineration plant. In a specific LCA the different utilisation
pathways common to the country are to be determined in the inventory phase.
The primary benefit of both options is the disposal of waste cartons. Both variants
have, however, an added value. In the first case (recycling) the added value means a
saving of 70 kg cardboard production from raw materials, in the second case (waste
incineration) an extra 14 MJ electricity and 80 MJ heat are obtained.
Added values must be considered in the assessment. For example, in the
comparison of cardboard versus aluminium packaging different disposal pathways
exist and thus different added values.
Concerning the system modelling there are two variants to what can occur to the
70 kg secondary material, 14 MJ electricity and 80 MJ heat (Figure 3.22):

• They can be reused for carton production in the same system. In this case it is a
CLR (see Section 3.3.3).
• They can be used in other systems. Then it is an OLR (see Section 3.3.4). All
decisions concerning the allocation of environmental loads of the distributing
and the receiving system, which were discussed there, are to be made. If multiple
receiving systems are involved, the examined complete system might become
very large.
For a simplification of the examined system it is often treated as a closed-loop
system without the secondary material, electricity or heat being really used by the
same system. For a valuation of saved environmental loads equivalence systems
are assessed which are treated as credit entry in the examined system. Hereby the
technical equivalence has nevertheless to be verified carefully (see Figure 3.23).

117) Kl¨ opffer, 1996b.