If it was in powder form (and dry), most of it could be swept up for disposal. Any residues can be treated with an alkaline solution of sodium hypochlorite ("Chlorox")solution, pH 9. That converts cyanide to cyanate.
This is followed by adjustment of pH to 7.2 to 7.7, and decomposition occurs quickly.
If you can't run pH adjustment, or don't have facilities to perform it, it can be destroyed by treatment with the same material, but at pH 8.5 - it is completely destroyed in 1 to 2 hrs.
The results? Carbon dioxide and nitrogen.
And chlorox isn't that tough to get ahold of.
(I've done this before!)