How do you throw away a kitchen knife (or for that matter, any knife)? It seems extremely dangerous to just throw it in the dumpster, even if it's wrapped up real well.
I agree that donating the knife to a thrift shop is a good idea. But it pains me to think of putting tape on a knife blade. Someone's going to have to clean it off, and that risks injuring them.
Instead, find a piece of cardboard that's longer than the blade of the knife, and more than twice the depth of the blade with an inch (~3 cm) or more to spare.
Fold the cardboard in half, so it's now roughly larger than the size of the blade, and then place the blade so the back of the knife is against the fold. (You can do it the other way, but you'll risk dulling the knife: cutting paper isn't good for knives.) Finally, tape it down.
You want to make sure it's well compressed, so the knife is being held in by friction. You could always sandwich something rubbery in there with it to provide more friction.
(This is how I used to transport my knives when moving between apartments.)
Another alternative, if you're really disposing of it, and don't mind dulling the blade, is to poke it into a piece of corrugated cardboard. Just find a piece that's longer and wider than the blade, set it on the edge of your counter, put a hand on top to hold it steady, and then slowly push the blade in.
First of all, consider donating it to Goodwill or another charitable organization. Even if it is barely usable by your standards, it might help someone else out. Whether giving your knife away or throwing it out, I think it is sufficient to put some duct tape over the edge and then wrap it in a couple layers of bubble wrap.
Check with your local recycling companies. We have a metal recycling facility that will accept kitchen items such as small appliances, utensils and dishes made of aluminum, tin, stainless steel, etc. It may be worthwhile to simply add the knife to their scrapheap where things will be melted down and recycled. Far better than disposal, in my opinion. (But consider the goodwill option as well.)
Since you're throwing the knife out, take a hammer to the edge. You don't need to hit hard -- the edge is obviously pretty thin, so it won't take much to roll the edge. Just place the back edge of the blade against something hard and heavy -- anvil, concrete block, etc. -- and tap firmly all along the sharp edge until sufficiently dull.
You're over thinking this. Just toss it in the bin.
There are plenty of other dangerous sharp things in bins already. Eg, broken glass, tin cans/lids, etc. Anyone going through bins (eg Freegans, garbage disposal workers, super spy's jumping out of buildings) knows to take precautions (or will learn quickly). Odds are that no one will go through your bin on that particular day anyway.
You can decrease that further by putting in in the bin the night before collection day.
If you must do something active, it's not worth the effort/waste to find something to wrap it, just stab it through anything plastic or cardboard you are throwing out (so I am seconding the news paper suggestion). Eg Milk Carton, empty plastic meat tray. It doesn't need to be perfect, you are just trying to add another chance on top of what is already fairly safe (just throwing it in the bin).
While performing on stage I adopted the "lob a full 360" approach but my juggling partner usually returned them.
Now I would take it to my dump, tip, recycling centre, and present it to a member of staff. This has three advantages:-
1/ No wrapping or unpleasant bending.
2/ It's a day out.
3/ It becomes an S.E.P. [Someone Else's Problem]
My brother, a chef, would have lodged it in a Kitchen Porter, thereby also creating an S.E.P.