Application of LCA as a decision-making tool for waste management systems |
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Authors: | Nyland Cecilia Askham Modahl Ingunn Saur Raadal Hanne Lerche Hanssen Ole Jørgen |
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Institution: | 1.?stfold Research Foundation, P.O. box 276, 1601, Fredrikstad, Norway ; |
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Abstract: | Aim, Scope and Background When materials are recycled they are made available for use for several future life cycles and can therefore replace virgin
material more than just once. In order to analyse the optimal waste management system for a given material, the authors have
analysed the material flows in a life cycle perspective. It is important to distinguish this approach for material flow analysis
for a given material from life cycle analysis of products. A product life cycle analysis analyses the product system from
cradle to grave, but uses some form of allocation in order to separate the life cycle of one product from another in cases
where component materials are recycled. This paper does not address allocation of burdens between different product systems,
but rather focuses on methodology for decision making for waste management systems where the optimal waste management system
for a given material is analysed. The focus here is the flow of the given material from cradle (raw material extraction) to
grave (the material, or its inherent energy, is no longer available for use). The limitation on the number of times materials
can be recycled is set by either the recycling rate, or the technical properties of the recycled material.
Main Features This article describes a mathematical geometric progression approach that can be used to expand the system boundaries and
allow for recycling a given number of times. Case studies for polyethylene and paperboard are used to illustrate the importance
of including these aspects when part of the Goal and Scope for the LCA study is to identify which waste management treatment
options are best for a given material. The results and discussion examine the different conclusions that can be reached about
which waste management option is most environmentally beneficial when the higher burdens and benefits of recycling several
times are taken into account.
Results In order to assess the complete picture of the burdens and benefits arising from recycling the system boundaries must be expanded
to allow for recycling many times. A mathematical geometric progression approach manages to take into account the higher burdens
and benefits arising from recycling several times. If one compares different waste management systems, e.g. energy recovery
with recycling, without expanding the system to include the complete effects of material recycling one can reach a different
conclusion about which waste management option is preferred.
Conclusions When the purpose of the study is to compare different waste management options, it is important that the system boundaries
are expanded in order to include several recycling loops where this is a physical reality. The equations given in this article
can be used to include these recycling loops. The error introduced by not expanding the system boundaries can be significant.
This error can be large enough to change the conclusions of a comparative study, such that material recycling followed by
incineration is a much better option than waste incineration directly.
Recommendations and Outlook When comparing waste management solutions, where material recycling is a feasible option, it is important to include the relevant
number of recycling loops to ensure that the benefits of material recycling are not underestimated. The methodology presented
in this article should be used in future comparative studies for strategic decision-making for waste management. The approach
should not be used for LCAs for product systems without due care, as this could lead to double counting of the benefits of
recycling (depending on the goal and scope of the analysis). For materials where the material cycle is more of a closed loop
and one cannot truly say that recycled materials replace virgin materials, a more sophisticated approach will be required,
taking into account the fact that recycled materials will only replace a certain proportion of virgin materials. |
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Keywords: | Cardboard decision-making tool LCA methodology packaging plastics recycling waste management |
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