Monte Carlo results are negative

Question

Hello openLCA team,

After running the Monte Carlo uncertainty analysis using logarithmic normal distribution, some of the impact categories produce negative results which don't match the base results. The waste flows are assigned a negative geometric mean, which I assume to be the problem. Is there a way to correct this issue without changing all values manually?

Comments

I ran into the same observation while crediting byproducts as 'avoided production' or waste flows in the input as 'avoided waste'. The log-normal distribution from Monte Carlo seems to be 'flipped' having the tail end into negative direction. I believe this is due to the substitution/system expansion/crediting the avoided impacts. I'm currently a bit confused about this myself (also, how to handle the negative log-normal values later on in e.g. Excel), and would appreciate if someone more knowledgeable could explain it better.