What should I look out for with the type of mulch I use?

[PunkRotten]

I am kind of afraid of the municipal mulch. I have used it before and found all kinds of foreign materials in it including, plastics, rubber, rocks and more. I found out the source of the mulch comes from the green recycling bins from homes. Given that information, those yard scraps could have pesticides and other toxic chemicals mixed in. I'd use it for an ornamental garden but not an edible one.

[Teddy12b]

I've been reassured that the mulch I'd be buying isn't going to be full of junk and trash.