It depends where you dive. Nice bakeries and restaurants, you can actually go in there and ask and they'll give it to you.

Other places just throw it out in the same dumpster as everything else. Meaning you're gonna have to dig through the torn bags (no one seems to understand that dragging the bags across concrete will tear them) of rotting cabbage, that brown puke water that's a combination of veggie water, hog fat, animal guts and blood, and god knows what else is in there.

Not to mention the cost of food is severely offset by the cost of medical care when you get shanked by a 4" crack needle...