Consideration of processes prior to end of life

Question

Hello,

I am currently working on the life cycle assessment of different end of life options for plastic waste. In my analysis, I would like to choose the end of life option depending on the plastic type (for example: mechanical recycling for PET and incineration for PE). The analysis should also consider the processes required to sort the plastic waste into the single plastic type flows. In a separate forum post, I was recommended to split these two parts of the process into two different product systems. However, I would like to model this whole process in a single product system to be able to proceed to a sensitivity analysis of the overall process.

For this, I would expect a product system with the following chain of processes:

* Process 1:
          - Input: mixed plastic waste (PE + PET + PP + PS)
          - Output: sorted plastic waste (PE/PET/PP/PS)
* Process 2-a: (e.g. recycling)
          - Input: Plastic waste type (e.g. PET)
          - Output: Production of polyethylene terephthalate, granulate, recycled
* Process 2-b: (e.g. incineration)
          - Input: Plastic waste type (e.g. PE)
          - Output: Electricity/Heat

No matter how I tried, I was never able to create flows linking the sorting process to the end of life processes.

Do you have any recommendation on how to handle this kind of problem?

Thank you !

Answer 1

Hello,

Thank you both for your quick answers. I now understand that the output of the sorting process cannot be the single streams of each plastic type but has to be a generic flow representing the sorted waste. The definition of the single streams will be represented by their end of life in process 2-x.

However, even with this change in my project, I am still able to create the desired chain of processes for some reason. I have tried defining the flows of mixed plastic waste sorted and unsorted as product and waste but neither worked. (I would like to attach pictures of the processes that I created but for some reason, when I do, I get the error message that my message exceeds 12000 characters).

When I try to create a product system out of this chain of processes, I receive the following error: "No process with valid reference product output or waste input selected".

By reading some previous posts, I could see that processes need at least one output that is not an avoided product. When I add a random product to the process, it seems that I can create the desired product system. However, in the case of an end-of-life process, I would not expect any product.
What would you recommend in this case ?
Thank you!

Comments

You could use an output flow which is called "recycled plastic". Maybe have look in this tutorial https://www.openlca.org/wp-content/uploads/2020/06/GreenDelta-Bottle-Tutorial_1.10.pdf
It helped my dealing with the EoL issues. It is treated from chapter 9.

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RomanB,

This tutorial doesn't cover recycling
In fact i can't find a tutorial anywhere that covers how to model recycling

Answer 2

Hello Adrien.

You need to ensure that the plastic you want to choose as the input to your EoL process, is also in the output column of the sorting process. If you have a flow as an output in the one process, that process shows up as the provider for the flow in other processes. If you choose a process as a provider for a flow, you link that process, and everything that is inside it.

Answer 3

So, process 1 to 2a, and to 2b? If you consider 2a and 2b still mainly waste treatment processes, then P1 has output sorted plastic waste, P2a input sorted plastic waste and output of a product, and you need to apply allocation to consider that this process is multifunctional (as it treats waste and produces a product), and the same for 2b. That will work. Good luck, Andreas