EF 3.1 EoL modelling with ODA gives negative impact values

Question

Hi,

I’m using the EF 3.1 database and I am modelling the EoL of a product, which includes recycling of cardboard and plastic, and incineration of the percentage that’s not recycled of those components and of wood. I intent to use the opposite direction approach to model waste. I modelled the recycling processes as inputs with positive values and the incineration processes as outputs with positive values. I didn't use the auto-link function to create the product systems.

However, I think I did something wrong because the results of the impact analysis show negative values for acidification, ecotoxicity, EF-particular matter, etc.

The images show inputs/outputs of the process, the model graph of the product system, and the results of the impact analysis.

Should I have modelled the process differently (i.e. inputs and/or outputs and absolute values)? Or are the negative results okay?

I appreciate any help I can get.

Thank you. Regards,

Elli

Answer 1

If you (for whatever reason ;)) still want to use the opposite direction approach, you must not use waste flows. Use either waste flows or the opposite direction approach (which was basically the approach before we introduced waste flows in openLCA).

Best wishes,

Andreas

(I removed the formatting text at the beginning of your post)