I’ve often wondered if thoroughly rinsing my recyclables makes sense or is just a waste of water. Apparently, I’m not the only one, as Slate’s Green Lantern recently looked into the issue. The author seems to play both sides, first insisting that rinsing is NOT necessary:
Recycling facilities are well equipped to handle dirty cans and bottles, so some caked-on tomato sauce and the occasional stray chickpea won't significantly hinder the process. (These facilities can even handle that lime wedge you left in your Corona bottle.) Residue left on plastic or glass containers generally gets flushed out with water at some point in the process; most of the gunk left behind on steel and aluminum cans is burned away when those containers get melted down. So there's no need to waste water by running the faucet over your recyclables—even if you were to get them squeaky clean, they'd probably end up getting washed again, anyhow.
Later, the author concedes that rinsing might be a good idea after all (especially in single-stream systems), given that food-encrusted recyclables attract vermin and gross-out recycling workers.
The debate rages on.