Couldn't you just dry it and turn it into a meal? Most extracts are made from the roots but I don't see why you couldn't use the leaves as well. You probably don't need to use much.
I bought 2 bags a couple years ago to mix into my soil. If you make it or buy powder yucca keep it in the freezer. I wasted a bag leaving it in my garage it turned into a wax instead of powder