I ran an impact analysis using TRACI 2.1 on a simple potato production product system within openLCA (reference process is "potato production | potato | Cutoff, U" from ecoinvent (cut-off, regionalized); 1000 kg as functional unit). I am having trouble accurately interpreting the results for eutrophication impact in the Sankey diagram, which lists the final process -- "potato production | potato | Cutoff, U" -- as having:
Direction contribution: 3.737 kg N eq (100.00%)
Upstream total: 4.422 kg N eq (100.00%)
The upstream total is accurate and adds up to 100% as anticipated both in the Sankey diagram and the contribution tree. The direct contribution value is correct at 3.737 kg N eq, however we are unclear of why the percentage is still at 100%.
Thank you in advance for any insight on why this might be the case!