I have some spoiled mayonnaise somewhat similar to in this picture. I was wondering whether it is possible to use it as an alternative for molasses in liquid fertilizer fermentation.
I wouldn’t recommend that.
Molasses is - simplified - liquid sugar with minerals, so a carbohydrate. It feeds a certain range of bacteria that need sugars. We know similar mechanisms from sourdough, yogurt and wine making, where carbohydrates are fermented.
Mayonnaise is mostly fat and a bit of protein. So it will also feed microorganisms (as evidenced by the spoilage), but those are not the same that you want to feed with the molasses.
And for your fertilizer, it means the mayonnaise will not help your fermentation process and possibly hinder it by giving unwanted microorganisms a boost.