Hi- I am trying to model the emissions of feeding crickets. One of the byproducts is insect frass (which is basically insect excrement). In my project, the frass is generally used as fertilizer. I've expanded my system boundary to include it as an output in my process, and clicked the "Avoided Product" checkbox. As for the frass itself, I divided the mass being produced equally between nitrogen fertiliser, as N; potassium fertiliser, as K2O;phosphate fertilizer, as P2O5.
The database I used is ecoinvent 3.6 (cut-off), and the LCIA method I used was Recipe Midpoint (H) v 1.13.
When I ran my system, I was very surprised to see that I had negative emissions from my system, mainly from the avoided fertilizer production.The negative emissions from the fertilizer were much larger (on an absolute scale) than the positive emissions from the corn and soy that are being fed to the crickets. As a result, the total CO2 emissions turns out negative.
Just wanted a sanity check to see if this is correct. Does avoided fertilizer usually result in such a large credit?