Difference in results between system model Cut-Off and APOS

Question

Hello, hope you doing well

I have a question regarding a difference in results verified for the same exercise/example in OpenLCA but built with different system model processes.

My main goal is to perform a system expansion and assess the envirnonmental benefits of the byproducts of electricity from incineration and biogas from anaerobic digestion.

These are the process, they are the same for each system model Cut-Off and APOS.

The thing is, the results with the model system APOS are within the expected, the electricity and biogas have a negative signal, translating in a positive environmental impact and an environmental benefit i believe.

But with the system model Cut-Off, the results are different. It doesnt account for the byproducts, the environmental impact is 0.

My question is, why doesnt the cut-off model account for the system expansion? Is there any allocation or method that i can do in order to also get results with the cut-off model?

Thank you for your help!

Answer 1

Hi, interesting question, I think contributions of the biowaste treatment are just much smaller in the cut-off than in the APOS over the supply chain, therefore you see 0.0000 for the total result but it is not 0 but something else, slightly above 0 (also since exactly 0 as total result would not be shown in the contribution tree). You can check in the impact analysis, if you set view all you should see a result for the system expansion waste treatment there that is not 0. Success!