Double negative or not?? Waste flows and product flows in ecoinvent APOS vs ecoinvent Cutoff

Question

Hi!

I am noticing that the same flows are sometimes defined as different flow types in ecoinvent. this is a problem since waste flows (if not defined as waste flows) need to be added to the output with a negative sign (as opposed to just having them in the output)

How i noticed this:
I wanted to see the differences in the results when using ecoinvent APOS and ecoinvent Cutoff for the same LCIA (same flows, same processes, same providers, same material and mass etc)

Waste flow in APOS: ("waste wood, post consumer")
You can see that this is a normal waste flow in APOS, so i can add it to the output

Cutoff:
But in Cutoff, the same flow is defined as a product flow. So i needed to add it to the input with a negative sign in front of it in order to follow the ecoinvent waste system.

From what i understand, waste flows do not follow the old "double negative" system from ecoinvent.
But... if a flow, that is clearly a waste flow... is not marked as a waste flow but as a product flow... then it needs to be implemented with the "double negative" system.

is that correct or am i on the wrong track here?
and if what i found an error in the ecoinvent database and i should notify them?

Thanks!

Comments

Matias has already replied but to your specific question (is that correct, modeling a product flow with double negatives) - yes, that is correct

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thank you! i cant seem to upvote the comment but thanks a lot!

Answer 1

Hello Berndk,

You will notice that in the Cut-off database, the process used for waste wood, post consumer has almost no impacts. That is because it is actually viewed as a co-product, that can be used in other productions. As such it follows the rule of cut-off, and all environmental impacts from the previous life has been cut off.

I suspect the waste treatment for the product flow for APOS represents a similar flow, but with some allocation.

If you are looking for a waste disposal process, i would recommend looking for the waste flow "waste wood" and choose either a market process for waste wood, or a treatment process for waste wood, such as "incineration of waste wood".

I hope this helps