+2 votes

I want to calculate the impacts of ABS plastic and when i press the calculate button,the results give me a negative sign. what is that mean? Why i have negative impact during the production mix of ABS? for example global warming potential should be positive because i have CO2 emissions during the production. Although it is negative

Thank you
in openLCA by (180 points)
edited by
by (740 points)
I get negative impact result of urban land occupation, using ReCiPe method. What does negative sign means?

1 Answer

+1 vote
by (13.6k points)
selected by
Best answer

There can be multiple reasons for negative results:

  • You modelled a loop in your product system, that consumes more of the circulating product(s) than it produces (e.g. steel production that needs more steel (e.g. 1.2 tons) than what it actually produces (e.g. 1 ton; which only should/could happen in a subsystem of a real LCA); currently, openLCA cannot handle such systems, but it could if we add some kind of sequential calculation in a future version)
  • Your elementary flows are not consistently on the same input or output side (e.g. CO2 emissions on the input and output side in your processes). openLCA currently tries to infer the `impact direction` of a flow from the inputs and outputs of the processes in the system. If an elementary flow is on both sides, openLCA infers this `impact direction` from the first occurrence of the flow in a process. We maybe add a direct field for this `impact direction` to the elementary flows or LCIA characterization factors (probably with a better term).
  • Other things like formula errors, negative amounts, etc…