Beans are legumes and legumes take Nitrogen from the air and store that in nodules on the roots so most bestest is the just chop the beans above ground growth right back into place.
I would think the Collard greens could be handled the same way since they grew there taking nutrients out of your soil that would be better put right back into that soil. Like any other "green manure" you may need to wait a couple of weeks after chopping this residue down but if you have a good, working Soil Food Web that residue should not take very long to be digested, and if it does that should tell you your soil needs more work to get that Soil Food Web active.