I use a green bin that the city of Berkeley picks up and sends to a central composting facility in Modesto, CA. I’d considered driving down and picking up some free compost sometime until I found out that there is a lot of carelessness with what gets sent to composting facilities.
It isn’t widely publicized, but there are increasing amounts of compost that is contaminated with very long lasting herbicides that are manufactured by Dow Chemicals.
After finding this out, I ordered a 2nd composting bin for my yard. When compost comes from your own yard, you can control what goes into it and ensure that poisons don’t end up in your compost.
The chemicals in question are ending up in commercially sold products as well and are clopyralid and its close cousin, aminopyralid. Both can persist in compost, hay, & manure for years. Before you buy (or pick up free compost) you’d better ensure it is being tested by the producer for contaminants.