Incineration of customisable plastic waste

Question

Hello,

I am novice in terms of working with OpenLCA and would like to get acquainted with the software by performing a simple analysis based on the incineration of 1kg of plastic waste. For this, I would like to vary the content of the plastic waste feedstock (PE, PET, PP, PS).

I use the ecoinvent database and I was able to find existing processes for the incineration of single plastic waste flows. I thought about creating a product system with 4 parallel processes corresponding to the 4 types of plastic waste present in the feedstock. However, the predefined processes of the ecoinvent database seem to work as standalones: they cannot be addressed with an exterior flow and therefore cannot communicate with other processes within a product system, is that right?

What would be the correct way to model the incineration of a customisable plastic waste feedstock using the ecoinvent database? The ecoinvent processes contain 232 inputs and 1857 outputs. If I cannot use the processes of the ecoinvent database, I would not know where to find the data to address all these variables.

Thank you in advance.

Kind regards,

Adrien

Answer 1

Hello Adrien,

In order to model the incineration of a plastic that is not in OpenLCA, you need to know the Life Cycle Inventory of that process, this can sometimes be found in research articles. 

However, with the given case, incineration of all four plastic types are available in EcoInvent. You need to:

1. Make a process with a reference flow. This flow is not important in this case. 

2. Add four outputs into the process, under the input/output tab in the process: 

 2.a Waste polyethylene

 2.b Waste polyethylene terephthalate

 2.c Waste polypropylene

 2.d Waste polystyrene

3. Choose the provider for each process to be incineration. It is important that you choose similar processes if you want to compare the processes. The process called treatment of waste PLASTIC TYPE, municipal incineration | waste PLASTIC TYPE | Cutoff, S - CH is available for all of them. 

4. Go to the overview of the process, and create a product system. Click finish to the pop-up.

5. Click calculate, and choose an appropriate LCIA method. If you are in doubt, CML-IA, ReCiPe 2016, or EF 3.0 or EF 3.1 are all generally recognized. The LCIA determines which impact categories are included in the analysis. Once you have chosen, click finish. 

6. Interpret the results that appear. Which plastic has the highest GWP when incinerated?

Good luck.

Comments

Hello again Adrien.

I do not remember this study specifically. Perhaps there other questions on the forum that answers this question? Alternatively, you can pose a new question on the main page. A hidden question like this is likely to go unnoticed. :)

Answer 2

Hello,

I am now trying to gradually increase the complexity of my system by adding a sorting process prior to the incineration process (for the case that we would want to recycle the PET bottles but still burn other plastic types for example). I have tried several methods but none of them gave satisfying results.

I created a sorting process that is fed with the waste input (that was previously directly used in the incineration process) and creates flows of sorted plastics as output. I then tried to feed these output flows to the incineration process but however I turned it around, the sorting process was never included in the product system.

What would be the right way to handle this additional process to make it effective?

Thank you.

Comments

Hello Adrien.
It sounds to me like you need to make two different product systems.
One product system consists of one process:
Input: Plastics
Output: Plastic wastes that are incinerated
The other product system consists of two processes:
Process one:
Input: PET (if you want to compare to the other system that includes plastic), electricity/transport (what is necessary for sorting)
Output: Sorted plastic ( lets say 1 kg. This will be a homemade flow, used as reference flow)
Process two:
Input: 1 kg of sorted plastic (from previous process. Remember to choose the provider to be the last process.). Furthermore, if you want to include recycling you should include the necessary flows here. For recycling of PET, i recommend the process called something along the lines of Production of polyethylene teraphthalate, granulate, recycled. If you use the cutoff approach, this process describes the production necessary to produce one kg of recycled PET, without any impacts from the previous lifetime of the plastics.

Furthermore, important to note. If you are comparing the end of life for two products, you might want to include displacement of energy and material after end of life. This is not in accordance with cut-off modelling, but it is interesting nonetheless. You can include the following in the two product systems:

System 1 output: Electricity medium voltage (Displaced product), District heating, natural gas (Displaced product). The amount should be equal to the net energy gain stated in the description of the incineration process, multiplied by the amount of incinerated material.

System 2: output: Polyethylene terephthalete (displaced product). Equal to the amount produced, (minus a waste in the recycling, if there is one).

These displaced products will show you how much energy production is avoided due to incineration, and how much impact from production of virgin granulate is avoided from recycling of PET.

Good luck!

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Hello Matias,
It starts to be very interesting and ever closer to the topic that I want to study.
Just one question to make sure that I understood it right. By creating two distinct product systems, there will be no physical link between the two processes, right ? Or is there a way to connect two product systems in the tool ? The impact assessment of the overall process will not be available directly in openLCA and will require the addition of the impacts of each product systems offline, or ?
The target would be to choose the end of life depending on the plastic type between recyclable plastic and non-recyclable plastic.
Therefore, I would have expected the following:
* Process 1:
          - Input: mixed plastic waste (PE + PET + PP + PS)
          - Output: sorted plastic waste (PE/PET/PP/PS)
* Process 2-x: (e.g. recycling)
          - Input: Plastic waste type (e.g. PET)
          - Output: Production of polyethylene terephthalate, granulate, recycled
* Process 2-y: (e.g. incineration)
          - Input: Plastic waste type (e.g. PE)
          - Output: Electricity/Heat
Thank you !