I use wood ash , grass thatch and 6 to 12 months to removed stumps.
Cover stump with 3 to 4 inches of hardwood ashes, then cover the wood ashes with 6 to 12 inches of wet grass clipping thatch to start the lye reaction on the stump and heat composting of the thatch. After the lye has leached into the stump and the thatch has gone through initial heating, the woodlice, beetles , termites , springtails, rollypolies, carpenter ants, etc. will begin building Stump City. In the spring the used to was stump can be turned with a hoe into mulch without a lot of effort and sweat.
"I didn't have time to slay the dragon. Its on my "To Do" list !"