Difference in results

Question

Hello

I have a problem due to a big difference in results obtained by the same model.

In the file enclosed you can see the results one obtained by the model using Ecoinvent 3.12 (the higher results) and the lower one obtained using Ecoinvent 3.12 library.

I used the same method (IPCC 2021 ISO 14067) and the same allocation.

I create a new database and then I add the Ecoinvent 3.12 library created by a fresh Ecoinvent 3.12 one.

In the same database I import my model with its parameters and method and finally I perform calculation of product system.

Why there is the difference? Is something wrong in my flow?

Thank you

https://ask.openlca.org/?qa=blob&qa_blobid=9954992828345608931

Answer 1

Do you have no validation errors (right-click database "validate")? Are all your imported foreground processes correctly linked to the same provider from ecoinvent (please click "Check linking properties" and make sure that there is no processes without default provider set)? Is the required amount and the calculated inventory (the total elementary flow results) the same?

Comments

Database is validated.
Processes are linked but when I check the reply states there are some of them unlinked. I checked twice and there are the correct providers.
Yes required amount and inventory are correct

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What means "but when I check the reply states there are some of them unlinked"?

When you click check linking properties, there should be no processes without a default provider set. If there are, you should set them. Otherwise they will be set automatically to the first provider in the provider list of the exchange, which can of course lead to different results as when you set the default provider by yourself.

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All processes are linked and I checked the correct provider.
But the results are diferent

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Difficult to say where it is coming from without seeing the model. You can check the contribution tree and look at "C4: Manutenzione infrastruttura" to see why there is a 20% difference. We must know if it is due to a difference in inventory or due to a difference in characterization (factors for the environmental impacts).

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Checked again and infact there was a different link in provider, solved, but now the difference is around 14%.
It's the only value out of control (C4: Manutenzione infrastruttura) all the other are ok now.

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If this is the only one, and it is only for one sub-processes, but the other ones are fine, it is very likely that the provider are still not the same.

To be on the safe side, you can create a new product system and select "only link default provider". And make sure that all provider are the same and none is missing by using the "check provider linkings" feature.

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I did as you suggested, but nothing the difference is still evident.
Product system created from the original model gives the result of 6.97385E7 kgCO2e
Product system created from the parametric model + Ecoinvent 3.12 library gives 5.85276E7 kgCO2e.
Both product systems are created by the process C4: Manutenzione infrastruttura

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Just take a random ecoinvent process and do the same test. I'm sorry but I can't help for your own processes, where I don't know the details and where you first wrote  that you checked and the provider are correct and then later wrote that there was a different link in the provider.

You can also see in the contribution tree where the difference is coming from. You can see there if the difference is from a flow, from an amount value, from a characterization factor, from a different provider etc.

If nothing works and if the issue is not only with your own processes (that I don't know), you can send a mail with more details on the process. But because you said that "It's the only value out of control (C4: Manutenzione infrastruttura) all the other are ok now.", it is most likely an issue that is related to your own process that you created.