While using the EN15804+A2 method with the ecoinvent EN15804 add-on on a process with no inputs but only outputs (1 elementary flow + waste flows). The results I obtained were always negative for all indicators regardless of the treatment provider (municipal incineration ou sanitary landfill...) or the waste flow (waste paperboard, waste polypropylene...). This does'nt make any sense to me environmentaly speaking and as it is not the case for other flows than the waste ones. Is it a requirement of EN15804+A2 method ?Should I have put a negative sign before my parameters for example ?
Maybe you are using the system process version and you are not using the latest Nexus implementation? Which version are you using? In general, I always recommend to use the unit process database by default, especially for EN15804 where you want (and often need to) see the supply chain.
Some time ago there was a bug in the system process calculation engine that created negative inventories for waste treatment processes. The absolute values were correct, but the sign was opposite. This was corrected in August.
See also here: https://ask.openlca.org/7563/unit-vs-system-process-in-en15804-add-for-ecoinvent-problem
