I pretty much do the same thing as
@Siska-Coda. I always list my decent quality animals on the market at the price which the game suggests. I have way more CC now than I could ever spend, but I want to help the community by making animals available. If an animal doesn't sell after the first time or two that I list it, however, I go ahead and release it.
The recycle bins never worked in Franchise mode. It's mentioned in the game help file under "Conservation Credits", as is the distinction between Franchise mode vs. other modes.
To be clear, what the help file mentions as working in non-franchise modes for earning CC is to "Improve your Zoo's conservation rating". Which is generic, but if you also read about the Zoo ratings in the help file, it specifically mentions recycling bins as one of the ways to increase that rating. Ergo, using recycle bins can help earn CC in non-franchise modes. You don't get the CC just for having the bins, you have to use them along with other methods to actually increase the zoo conservation rating.