Key parameters
There are many parameters and assumptions that affect the outcome of the LCAs in question. Moreover, those
parameters might function in combination and give more diverging results when trying to compare across studies.
However, there are some key parameters that have a decisive influence on the overall results:
Electricity mix
Technological efficiencies
Inclusion of carbon sequestration / storage
Other (material composition, substitution ratio)Electricity mix
The effect of the electricity mix can be seen in many steps of paper’s waste system. The upstream processes and
the waste management processes require electricity, but also the substituted electricity’s composition has an
impact on determining the overall LCA’s results.
Moreover, some studies (studies no 1, 3, 4 and 5) chose to work based on the attributional LCA
approach, using average mixes, while others opt for the consequential approach, using marginal
mixes (Ekvall and Weidema, 2004). The difference for a country with a high share of carbon-neutral
energy sources is quite substantial, when examining global warming as an impact category. Study no 2
refers to a geographical scope in Sweden, where the average mix is used for production of paper. Even though
the recovered electricity replaces hard coal, attributing more benefits to incineration and landfill, recycling is still
the most preferable option. The same study (although without a proper sensitivity analysis) claims that if an
average mix was substituted instead, the results would be quite different, probably even more in favour of
recycling.
Differences across studies can only be partly explained by the choice of electricity mix. Studies no 1, 3 and 5
substitute a less carbon intensive electricity mix, resulting in a decrease for the benefits of incineration and
landfill for climate change. Studies n°2 and 4 substitute fossil fuels exclusively, which results in reinforced
benefits from all energy recovery activities (mainly incineration). The expected outcome would be that studies
n°2 and 4 would rank incineration higher and recycling lower than in studies no 1, 3 and 5, however the LCA
results show the exact opposite. This paradox could be explained by the choice of different parameters that are
related to recycling itself; recycling is also related to electricity mixes, because the avoided paper production,
which is itself quite an energy demanding process (study no 1 assumes production of virgin paper in Sweden
where the electricity mix is much less carbon intensive than the Italian mix substituted for energy recovery).
Table 19 Substituted electricity mixes used in the reviewed studiesStudy
number
Substituted
electricity
Mix composition
1 Italian average 81% fossil ‐ 19% renewable
2 Hard coal 100% fossil
3 French average 10% fossil ‐ 78% nuclear ‐ 12% renewable
4 fossil mix 100% fossil
5 Scandinavian average 14% fossil ‐ 23% nuclear ‐ 63% renewable
Technological efficiencies
The effect of the chosen level of technology on the results is evident. However, some efficiencies within the paper
waste management system are more important than others.
A vital parameter when simulating a landfill is the extraction efficiency of the landfill gas. The losses
of this procedure determine the methane emissions from the landfill while the captured quantities are used for
electricity and/or heat production. Study no 1 uses a state-of-the-art landfill with both high extraction efficiency
(55%) and efficient electricity conversion. Study no 3 also presents a high extraction efficiency of 50%. On the
other hand, study no 5 reduces the efficiency to 25% and, consequently, the results are worse for the landfill
option in that study. In Table 20 below, the relation between the assumed methane recovery efficiency for each
study is compared to the relative preference for landfill over recycling. Although the overall climate change results
are dependent on many factors, there seems to be a relation between the level of preference for landfill and the