i don't live in cane toad country anymore, but I'd be stuffed if I would put a bagful of those things in my fridge or freezer where I keep food.
I have also noticed outright kills with a golf stick, its a solid blunt force trauma to the brain and very quick, no stress on the toad because there is no being caught by a human and handled and put into a plastic bags with your mates with no oxygen.
It may not be sanctioned by the animal rights activists who usually have their heads in the clouds anyway, but is it effective ?yes. If the first blow doesn't kill it then It is heavily stunned and doesn't feel the next one coming. I don't actually see anything wrong with that approach.