Hello,
I am conducting a LCA in accordance with the EN 15804 standard for construction products, and I have some questions regarding how to correctly model the end-of-life stage, specifically modules C3 and D (please see tables and attached screenshots).
The product consists of several materials: steel, aluminium, plastics, zinc, and glass. In module C3, I have included the energy consumption associated with product disassembly. Some amount of the materials are recycled, all plastics are incinerated, and the rest are landfilled.
For the modelling, I applied the “double negative” approach in module C3 (considering treatment processes in the inputs and waste plastic in the output as it is incinerated) and selected the “avoided product” option in module D for all the products.
The issue is that I’m getting negative impact values in module C3, which I understand should not be happening. I am unsure what I might be doing wrong or how to correct it.
Could anyone advise on how to correctly model this end-of-life scenario?
Additional assumptions I have used include a 90% recycling efficiency and 60% energy recovery efficiency for plastics.
I have checked the OpenLCA manual and reviewed related forum posts, but I haven’t found a clear answer.
Thank you for your support.
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MODULE C3
Inputs
| Flow | Provider |
| aluminium scrap, post-consumer | aluminium scrap, post-consumer, Recycled Content cut-off | aluminium scrap, post-consumer | Cutoff, U |
| electricity, low voltage | market for electricity, low voltage | electricity, low voltage | Cutoff, U |
| glass cullet, sorted | treatment of waste glass from unsorted public collection, sorting | glass cullet, sorted | Cutoff, U |
| iron scrap, sorted, pressed | treatment of metal scrap, mixed, for recycling, unsorted, sorting | iron scrap, sorted, pressed | Cutoff, U |
| zinc scrap, post-consumer | zinc scrap, post-consumer, Recycled Content cut-off | zinc scrap, post-consumer | Cutoff, U |
Outputs
| Flow | Provider |
| Product 1 (reference flow) | |
| waste plastic, mixture | treatment of waste plastic, mixture, municipal incineration | waste plastic, mixture | Cutoff, U |
MODULE D
Outputs
| Flow | Avoided product | Provider |
| Product 1 (reference flow) | | |
| aluminium scrap, post-consumer | ✓ | aluminium scrap, post-consumer, Recycled Content cut-off | aluminium scrap, post-consumer | Cutoff, U |
| electricity, low voltage | ✓ | market for electricity, low voltage | electricity, low voltage | Cutoff, U |
| glass cullet, sorted | ✓ | treatment of waste glass from unsorted public collection, sorting | glass cullet, sorted | Cutoff, U |
| iron scrap, sorted, pressed | ✓ | treatment of metal scrap, mixed, for recycling, unsorted, sorting | iron scrap, sorted, pressed | Cutoff, U |
| zinc scrap, post-consumer | ✓ | zinc scrap, post-consumer, Recycled Content cut-off | zinc scrap, post-consumer | Cutoff, U |
| heat, district or industrial, natural gas | ✓ | heat and power co-generation, natural gas, conventional power plant, 100MW electrical | heat, district or industrial, natural gas | Cutoff, U |
