Avoided material production and substitution ratio
The good environmental performance of recycling and pyrolysis that was highlighted previously is mostly
explained by the credits brought by the avoided material production. However, the choice of possible
assumptions around this issue is very broad and is possibly a source of disparities between the
different cases. For example, pyrolysis leads to the production of various products that can potentially replace
petrochemical products, such as naphtha and paraffin, or replace fuels such as diesel oils. In the case of open-
loop recycling, recycled products can also be used for a large range of applications. For example, in study no 1
(BIOIS, 2006), PET recyclate is assumed to replace resin and fibres.
Table 40 Overview of the assumptions regarding the avoided material production for recycling and pyrolysis
Study
number1 2 3 4 5 6 7 8 24 Atmospheric^ residues,^ C3/C4^ compounds,^ naphtaVirgin plastics similar to the ones being recycledVirgin plastics similar to the ones being recycledVirgin plastics similar to the ones being recycledVirgin plastics similar to the ones being recycledPyrolysisVirgin plastics similar to the ones being recycled for closed‐loop
recycling (case 8[PS2])Avoided material productionVirgin HDPE bottles for PE recycling
Virgin resin, virgin PET fibres and virgin PET flakes for PET recyclingRecyclingVirgin plastics similar to the ones being recycledVirgin plastics similar to the ones being recycledNaphta, paraffin and refinery gas OR diesel oilIn addition to the choice of the substituted material, the question that also arises is what is the ratio of
substitution. In most current LCAs it is assumed that recycled plastic will substitute directly for
virgin plastic on a 1:1 basis (i.e. 1 kg of recycled plastic is equivalent to 1 kg of virgin plastic). However, this
implies that high quality recycled products are obtained.
The sensitivity of the results with regard to the material that is substituted was looked at in study no 2 (Shonfield,
2008) for two recycling scenarios. The base scenario, for which a degree of virgin plastic displaced by recycled
plastic of 100% is assumed, is compared to a scenario in which only 20% of the recyclate replaces virgin plastic
(the remainder being evenly split between substituting for concrete and wood). The consequences of this
change on the global warming potential (see Table 41) are huge. The two recycling scenarios switch
from saving impacts to contributing to net emissions. This means that under the assumption of a degree
of virgin plastic substitution of 20%, the impacts from the recycling process are no longer offset by the benefits
from the avoided material production. Under this assumption, the ranking is (the best alternative being the one
on the left):
pyrolysis < landfill < recycling <incineration