openLCA archived user forum

Hi,
I have some doubts about the LCIA results I obtained. I calculate the environmental impacts of "P" product system with CML Baseline. I create a project of that product system "P" and I calculate again the results with the same impact assessment method (CML baseline). The results differ to each other and I do not know why.

for example:
Climate change- GWP100:
"P" product system: 9.596E5 kg CO2 eq
"P" project: 1.044E6 kg CO2 eq

Thanks in advance

Maite

Hi, Maite,
not totally sure whether I understand, you are comparing the system process results with the results of a product system? For which database? For ecoinvent, for example, you should then receive exactly the same results, for ProBas, your results might differ as the links for unit processes are not fully complete (the database does not contain everything that is included in the system processes). And if you have modifed the product system, then of course the differing result reflects your changes?
Best wishes,
Andreas

Yes, the results are not the same. The study incorporates many processes from various databases and It only occurs with the process Anode, at plant which I found in the case of study "pet vs alu empty". I calculate the GWP of the product system and I receive one value of kg CO2 eq, I create a Project and I select as a variant the product system Anode, at plant and with same impact assessment the result is totally different.

I attach the results I had. I checked with other processes of "pet vs alu empty" and the same occurs.
Thank you
Best,
Maite

Hi,
I checked more examples of the data collected in "case study pet vs alu empty" and the same occurs. Maybe I am doing something wrong but I have problems only with this database. Creating a Project and calculating any impact, the results received are different from the calculation of a Product System.

Best wishes,

Maite

It looks like you are using different functional units for both, is that possible? The relations between the different results seem about the same?

It could be, but I evaluated the same functional unit, 1 kg of material. I don't understand why because with other databases there is not any problem. I attached again the results received as an example.

Thank you very much!

Can you show a screenshot of the functional unit for the product systems and for the project - thank you!

Hi,

I had the same problem, the results of the project and the product system didn't match.
Setting the allocation method in the "Compared product systems" section of the project to "As defined in processes" solved it.

Hth,
Strifus