Page 109 - Materials Chemistry, Second Edition

3.3 Allocation 93

…
I 1 I 2 I 3 I 4

700 kg product A

Pre-products
Unit process
"production"
I o
300 kg product B

O 1 O 2 O 3 O 4 …

Figure 3.10 Unit process with co-products.
Thesimplechain with i = 4 unit processes shows the principle of a procedure
in an LCI without co-production: The sum of the inputs (I)and outputs(O)of
the life cycle is the sum of individual amounts whereby inputs can also be side
chains (branches in the picture of the product tree) or partial LCIs as, for example,
the aggregated data by APME (Plastics Europe) or by ECOSOL (for surfactants).
According to Figure 3.9, for the conduction of this simplest LCI, only the following
additions have to be made in order to get the total input and the total output:
I = ∑ I
tot i
i
O tot = ∑ O i
i
It goes without saying that an adding of non matching inputs and outputs does
not make sense.
Co-production implies that at least two products are formed in one unit process
(Figure 3.10). This is particularly frequent in the chemical industry, 79) agriculture,
the mining industry, oil refining and extractive metallurgy, less frequent in machine
and tool-making. In chemistry the formation of several substances in one reaction
is more of a rule than an exception.

3.3.2.2 ‘Fair’ Allocation?
The major task is to fairly allocate the environmental load, that is, inputs and
outputs, to the products A and B (more generally A, B, C, … ). The choice of the
attribute ‘fair’ indicates that a strict scientific solution cannot be provided. In the
science of economics the problem of allocation has been known for over 150 a. It
concerns the allocation of fair costs to the individual products. Costs for individual
products must be derived from the total costs. The British political economist John

79) Riebel, 1955.