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 for the glass needed two refills to become environmentally sounder
than one-way bottles. Reduction of GHG emission became less
significant after 7e9 refills. This means that the reuse systems have
an asymptote where further increasing number of refills do not
generate significant environmental benefit. This plateau can be
caused by the effect that by the first few refill a significant part of
new bottle productionwas avoided, and after a certain point, where
the plateau begins, the system just needs to replace the discarded
or broken bottles.