Page 119 - Materials Chemistry, Second Edition

3.3 Allocation 103

System 1 System 2
Inputs Inputs

Production Production
system system
for product A for product C

Co-product B
Product C
Product A

System boundary

Figure 3.14 System expansion with product comparison – both systems do not have an
equal benefit.

System 1 System 2
Inputs Inputs Inputs

Production Production Production
system system system
for for + for
product A product C product B

y kg co-product B y kg product B
z kg product C
x kg product A

System boundary
Figure 3.15 Providing equal benefit by addition of an equivalent system.

assigned for A and C. If the full life cycle of A and C including use and disposal
has to be considered this is also true for the equivalent system B.
If several production routes exist for B, the most common route, which may
include some arbitrariness, should be applied for the assessment. If B can only be
produced as co-product of A: bad luck! Should other co-products be formed in those