To make an easier interpretation of results an external normalisation
depicts the dimensionless outcomes in the Table S5/aec
and Fig. S1. The advantage of lightweight materials like carton or
aluminium leaves no doubt. The effect of bottle volume can be also
observed, bigger the volume smaller the potential environmental
effects of collection, although this reduction after the PET 1.5
seemed to be plateauing. It may be an effect of compressibility
assumed in the model.
At the waste collection, the density of waste becomes important,
for example the PET-bottles and carton show the significance of the
balancing between weight and volume, namely the effective
compression in the case of bigger PET-bottles or cartons might lead
lower impacts in smog creation category (cf. Fig. 4 or Fig. S1 POCP of
thermopress and coll. point PET 2.0).
3.3. One-way versus reuse systems
Fig. 5 shows the comparison of a one-way packaging and a
refillable packaging system regarding different numbers of refills.
The impact assessment covered the recycling and credits for the
production of secondary materials. The impact of the one-way
system was represented as a constant line, due to the missing
refilling. The lines of PET one-way and Al-can are overlapping. The
impact of refillable bottles was reducing with increasing number of
refill trips. This decrease arose from the reduced demand for primary
materials in bottle production. The relations between refill,
production of new bottles required, efficiency of collection and
ratio of rejected refillable bottles was calculated on the basis of
Equation (1) (see chapter “Limitations of the Model” and
Supplementary Material Equations S1eS4). Those bottles, which
were not refilled further, were recycled into secondary materials.
The GHG impact of refillable glass bottles was decreasing faster
than the PET due to the notable difference between the energy
demand of production of primary and secondary glasses. The cross
points of the lines define the break-even point between the oneway
and reuse system. Beyond the break-even point, the refill
system will provide more benefits considering the GHG impact.
This point was reached by the PET-bottle after the first refill, while