Product system loops in contribution tree

Question

I’m modelling a multi‑stage textile system. When I run the LCIA for the full product system, the contribution tree shows repeated nested loops of the same foreground stages (P7→P1 appearing multiple times). The model graph looks correct and I don’t see any circular links in the inputs/outputs.A second issue is that T1 (a transportation stage), which is correctly set as the provider for P1, does not appear anywhere in the product system contribution tree. However, it does appear when I run a direct LCIA on P1 alone.Is this looping behaviour normal for openLCA’s contribution analysis? And why would a transport stage appear in direct LCIA but disappear in the product system LCIA?

Answer 1

The contribution tree turns the looped LCA system into branches of a tree that are not looped; as a consequence, processes in a loop can appear several times, every time they are "vistited" when following the links in the model graph. This is as expected.