RHS advice is to dig it in in the autumn and the aminopyralid will be neutralised by spring. I’d try stacking it in a heap somewhere out of the way, sprinkling soil between the layers. Leave it at least a year and test it by planting a couple of spare tomato plants in the pile, if they are OK everything else should be.
It doesn’t affect grass so you could spread it over rough grass if you have any.
Hope that might be of some use
