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I want to look at the Impact of waste treatment and I have numbers on how many kg of wood, plastic, paper, etc. is disposed of. I am creating a process using the Opposite Direction Approach but am unsure where to put the input and output (waste flows or reference flows) and where to use a negative sign. I’m sending a screenshot as well. Looking forward to your help!

in openLCA by (120 points)

1 Answer

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by (90k points)
In the opposite direction approach, you must use product flows not waste flows (unless you are using a really old openLCA version). Then, simply set a negative sign for waste input (the process that has in reality waste output), and for waste output (the process that treats the waste) a negative sign as well. Hth, and I would rather recommend the waste flow modeling ;)

Best wishes,

by (120 points)
I see!

So I have the reference waste flow that I created manually  on the input side, which is the sum of the mass of all waste disposed by the company.

On the output side I have waste flows for each category of waste and their respective mass with the according provider.

Is that correct?