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Recently, I downloaded and imported the latest version of USLCI from their Github website along with the three available LCIA methods.

However, when I created simple processes and product systems to evaluate the environmental impacts of two PET (Polyethylene terephthalate) pellets included, the project report showed all the environmental impacts as negative. I have tryied to import different format of USLCI (JSON-LD or zolca) and changing LCIA methods, but none of them worked.

Additionally, the environmental impacts of product systems were positive when calculated directly. Once calculated in the project, a large negative contribution appeared in the last row of result contribution. 

I am currently confused and unable to identify the cause of this issue. Any advice would be greatly appreciated. Thank you very much!

in openLCA by (120 points)

2 Answers

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by (2.5k points)
open up the results tree for that super negative process in the contribution tree. I bet their is some dummy process that has looping inputs and outputs. dummy proccesses can not be grad and dropped like normal flows, they require different editing.
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ago by (140 points)
Make sure that the allocation method in the project that you created is set to "As defined in process" instead of "None" which is often the default and can cause negative results.