I have been using an Earth Machine composter for about 5 years now, and feed it regularly with vegetative kitchen waste and various yard scraps.
I am really very ignorant of rats (I did see one in an alley in downtown Detroit once, and it wasn't a pleasant sight!), but I find it hard to believe that rats would be able to get through the hard and comparatively thick plastic of which the Earth Machine is constructed.
Does anybody out there have any experience with rats and Earth Machine composters? I'd really like to know if a study exists that determines one way or the other how resistant they are to rats. Anecdotal evidence from hundreds of Earth Machine owners probably won't sway the city commission to rescind the ban (or change the ban to a ban on OPEN composting of food waste).