ecoinvent Forum Archive

Dear ecoinvnet,

I have a question about the difference in LCIA (Freshwater Eutrophication) between two silver production activities in different sites.

I am using ecoinvent 3.7.1 in openLCA 1.10.3, the LCIA method is ReCiPe 2016 Midpoint (E) provided by openLCA. System model: consequential.

The two processes I am looking into:

1. silver-gold mine operation with refinery, RoW (S)

2. silver mine operation with extraction, PE (S)

From ecoinvent's ecoQuery dataset, I found that the first silver production activity has a negative value for Freshwater Eutrophication, which implies that this silver production activity reduces the impact of Freshwater Eutrophication under the consequential system model approach. (please correct me if I am wrong)

However, the second activity which is also silver production, givesa positive Freshwater Eutrophication value.

I understand that the consequential system model is doing substitution for by-products. However, is it rational that for the same silver production activity (literal meaning, not the 'activity' in the database), they have different signs in the same impact indicator?

And how would you explain that the first silver production process has a positive impact on the environment?

Shouldn't silver extraction/production have a negative impact on Freshwater Eutrophication (this means a positive value)?

I also read it from a scientific paper Resource efficient recovery of critical and precious metals from waste silicon PV panel recycling that 'recycled silver has significant benefits for ADP and freshwater eutrophication.'

Could you help me to explain what is the reason for this difference, mainly why does the first activity have a negative value? (and if that's rational)

I attached the LCIA results I got from openLCA and also reading from ecoQuery dataset.

Thank you very much for your help!

Best regards

Dear user,

Thank you for your question. The difference in scores for the activities “silver-gold mine operation with refinery” and “silver mine operation with extraction” can be explained by the differences in by-products produced in these activities. The activity "silver-gold mine operation with refinery" for example produces gold as a by-product.

As you pointed out, the consequential system model uses substitution instead of an attributional approach. This means, that the activity “silver-gold mine operation with refinery” is credited with the avoidance of the production of gold. Due to the high impacts of gold production, this avoided production results in a negative score for Freshwater Eutrophication.

If you want to read more about the consequential system model, please take a look here. Please also note that we deleted the scores that you attached as those are not public. Please contact us via the support email in case you would like to include attachments in your question.

Kind regards,

Nora Minas, Junior Data Analyst, ecoinvent Association