Negative impact in result graphs, ELCD 3.2.

Question

Hi, I'm trying to understand how it's possible that I can be getting results of negative impact. My LCA is comparing different types of plastic, and it claims that for PVC-S, when the end of life process is incineration, there is a massive benefit to marine life ecotoxicity. The benefit is almost the same value as the impact of PC plastic (-1.635kg 1,4-DB eq and 1.625kg 1,4 DB eq respectively).

In the 'result contributions' section, I can see that it is the incineration stage that is generating the negative impact. Surely this is not right?

I've tried turning auto link processes off and building the model graph manually but that didn't change anything. 

My LCA also models the same plastics through the same processes but with end of life as landfill, the results for which are all positive.

Any help is greatly appreciated.

Answer 1

Check other posts here, I assume this is linked to the ELCD database and its ambigous, negative and positive product inputs for meant-to-be fully aggregated system processes. You need to create your product system manually with this database and must not use the direct calculation.

Edit: the pictures somehow did not survive, you can edit your post if you like to include them