Approaches for end-of-life allocation
Modelling end-of-life (e-o-l) in LCA can be hard especially when recycling is involved. Which product system gets the benefits and which system gets the burdens of recycling? Like with many choices in LCA also with modelling end-of-life, it is important to know your starting points, as defined in the goal and scope section of your LCA or the standards and product category rules they refer to. These starting points include the system boundary and end-of-life allocation. This article describes the related important concepts in LCA. There some of the most common approaches for end-of-life allocation are mentioned:
Recycled content (or ‘Cut-off’) approach
Closed-loop scenarios
Circular Footprint Formula (CFF)
The recycled content approach is most used for LCA and is elaborated hereafter when discussing how to model recycling in SimaPro. The ecoinvent Cut-off system model is following this approach. In essence for recycling this system model means that wastes are the producer’s responsibility (“polluter pays”), and there is an incentive to use recyclable products, that are available burden-free (cut-off).
If waste is generated the waste treatment is fully modelled ignoring possible substitution of material or energy in case of recycling. This means that all burdens are allocated to the producing production system and that the resulting material or energy becomes available free of burden for a next application.
How to model the use of secondary material in SimaPro?
As mentioned before, modelling the use of secondary (recycled) material is relatively easy. With the cut-off system model the waste processing is completely allocated to the previous product system, and therefore the secondary material becomes available free of burden. Only additional dedicated processing (like sorting, washing, transportation, etc.) to make it suitable for your production system should be modelled.
To illustrate we take ecoinvent 3.9.1 polyethylene waste (under Processes/Material/Plastics/Recycling) processes:
“Waste polyethylene, for recycling, unsorted {GLO}| waste polyethylene, for recycling, unsorted, Recycled Content cut-off | Cut-off” is an empty process, meaning that all waste treatment has been taken place before this ‘for recycling’ process.
Based on that empty process, “Waste polyethylene, for recycling, unsorted {Europe without Switzerland}| market for waste polyethylene, for recycling, unsorted | Cut-off, U” contains the container and transportation for collection of this post-consumer waste.
“Waste polyethylene, for recycling, sorted {Europe without Switzerland}| treatment of waste polyethylene, for recycling, unsorted, sorting | Cut-off, U” includes all processes for sorting and includes a surplus of about 10,5% unsorted input as well as the treatment of the waste that arises (through “Waste plastic, mixture {Europe without Switzerland}| market group for waste plastic, mixture | Cut-off, U”).
How to model waste processing (before recycling) in SimaPro?
Processes where waste arises in SimaPro can all be under LCA Explorer/Inventory/Processes, except for waste scenario’s.
Modelling waste processing in SimaPro can be done directly, by including a waste treatment process in the process where the waste arises, or through waste scenario’s. As long as the material is considered waste, waste treatment is needed according to the cut-off system model. As soon as the material is considered material for recycling, waste processing stops. The exact location of this point is not always clear. It differs per material flow and may differ per region and often this point is already after collection. Because of this there aren’t many standard waste treatment processes for recycling in SimaPro database. As an exception such processes are available for crushing stony material under Waste treatment/Construction waste.
Please note that all processes under Waste treatment/Recycling/Transformation are empty processes. They are used in waste scenario’s for separated material from the waste stream, thereby assuming that after separation this part of the waste fraction is no longer waste and that all further processing needed for recycling can be allocated to the next application.
So, for your end-of-life modelling for recycling you need to assess what processes to include, if any. And model accordingly.