LCIA - Result Intrepretation

[rehmanraheem]

Why am I getting negative values for Ecotoxicity, and Eutrophication?

[marc-vdm]

Hi,

That would be impossible to tell without looking at your system, but in general there are three causes for this:

• Negative flows (e.g. CO2 uptake in forestry),
• Negative characterization factors (e.g. atmospheric SO2 as a decreasing global warming effect),
• Negative flows due to substituted processes (avoided production).

You can see in your figure what processes have negative contributions and you could investigate from there.

If I see it correctly, the negative flows have to do with waste treatment, it could be that you've inverted a sign e.g. waste treatment in ecoinvent uses negative numbers.

[rehmanraheem]

Thank you for your comment. Yes my inventory has some wastes, especially polythene, that is causing these negative values.