Because my plumber was over yesterday I asked him about this. He approved what I do and that is that oils and grease of 1/3 cup or so and less get run down the drain with cold water, anything more than that goes in a can, frozen and discarded.
I suspect that most fats disposed of down the residential kitchen sink never make it to the sewage treatment plants. The quantities are so small that the fat congeals and sticks to something long before it gets there. That's why the pipes plug up locally in the first place.
Here in San Francisco we have a City recycle/compost program and that's where my waste grease goes (what little there is of it.)
coffee can in the fridge, when it's full its outta here. some little bit goes on
the doggies food, too...keeps their fur nice.
can you imagine the days when you had to save it all- pig, cow, chicken, game, whatever- without refrigeration and then use it to
grease wagons, to make lye soaps, candles, lamp oils, etc? fonkay.