I've seen locust pod bits still holding together after 30 day or 90 day
compost, but not big
enough that it bothered me. There's a lot of sugar in those pods! Makes them helpful to get a compost going. The big worry for me with locust (if you're talking Gleditsia triacanthus) is the thorns and the seeds. The seeds will happily sprout after a trip through the compost heap, and those thorns are wicked, wicked things. I use them as nails around the house, fun little conversation piece but they'll go straight through glove, shoe, hand, foot, tire, etc.