Negative or Zero Impact Assessment Results During Calculation in openLCA

Question

I am currently trying to run a product system with a cradle-to-grave system boundary. I am using openLCA version 2.6.2 and the ecoinvent 3.12 database.

When I run the product system using the auto-linked connections from the upstream to downstream unit processes, the impact assessment results appear normally. However, when I try to run only the upstream unit processes, all of the impact results are negative.

I then tried to manually link the unit processes to each other, but the resulting impact assessment values were all 0. The impact assessment method I am using is IPCC.

Why could this happen? Is there possibly something wrong with the datasets I am using or the way I have linked the processes?

I am also attaching screenshots showing the negative impact results, as well as the input/output inventory data I used.

Any help or guidance would be greatly appreciated. Thank you very much.

Answer 1

Hi, thank you for your for question, it seems you combine unit and system processes, why? I do not understand 

the auto-linked connections from the upstream to downstream unit processes

vs 

when I try to run only the upstream unit processes

- what is the difference? Downstream is with end of life? Thank you. Ideally, update your question above.

Comments

Thank you for the explanation. Here I am sending the screenshots of the two models: the upstream-to-downstream model and the upstream-only model.

Thank you for your help.