I still don't understand the difference between unit and system process. Could anyone explain it to me again?

Question

Hello everyone,

here is my situation:

I imported the ecoinvent database in my openLCA software -> I copied two ident datasets in a now folder -> I changed one of the processes from unit to system -> I created two product systems (one with unit and one with system) and calculated both of them.

I can still not see any change anywhere and do not understand what the difference is or what a unit/system process would be useful for.

What am I missing?

Thank you very much in advance!

Answer 1

Also to add that marking a process as "system" or "unit" does not change anything about the process itself. One can incorrectly tag a unit process as a system process or vice versa. The main reason for this tag is that it is used when creating a product system if you ask openLCA to prefer system processes over unit processes

Comments

Awesome, this makes it so much clearer!
Thank you very much!

Answer 2

A system process only contains elementary flows, resulting from aggregating the background system.

A unit process contains process inputs/ouputs (besides also elementary flows) such as electricity, processed materials, ...

Comments

(and basically, the system process is an LCA calculation result, fully aggregated)