It simply has to be washed no other way. Add Arm & Hammer baking soda (You'll need several large boxes) but it will work. The washing is the only way. Get a couple of friends and hit the laundromat. They have big tables for folding too.
Now, if you're donating it, they won't mind washing it if they know the story and expect it to reek. It's worth it to most of them and if not, find another recipient.
I just went through the same thing.