Most compost mistakes are pretty easy to correct. A few, though, may haunt you for a while. I've made a mistake that I have to face again and again for the last 5 years.
I compost in various places around my place. I usually try to get one good hot pile going a year. The other piles are tucked along the pastures and in the woods where they slow compost for a year or two before harvesting.
September six years ago, I decided to hot compost right at the edge of the veggie garden. We also butchered chickens for the first time that year, and I added the by-products of that event to the pile. Once winter set in, the pile cooled, but we ate chicken all winter and I added the spent carcasses to the now cold pile.
Come spring planting time, I spread the pile on the garden, sifting out some still intact bones into my new cold pile. In the fall of that year, I spread the new pile into the garden before winter, figuring that those bones would HAVE to compost by spring.
I just planted my fourth vegetable garden since that cycle. I'm still finding intact chicken bones. Brittle, but still intact. By the scores, still.
I have learned my lesson. For the last 3 years, I now stew all my cooked chicken bones in the crockpot overnight. As a result I get both chicken stock for the freezer, and maleable bones much more suitable for the compost pile.
What's your most memorable compost mistake?