We've had them for ages. They are collected separately and go to a composting facility. Food waste cannot be fed to pigs any more as it used to be.
The larger bin we have holds 21 litres, and if anyone is throwing away that amount of food every week I think they really need to look at how much food they are wasting. We usually only fill one of the bags each week and that is mostly vegetable peelings and the like.
The bags supplied are made from compostable starch derivatives, and ordinary plastic bags should not be used as they contaminate the compost.
The trial scheme was very successful and cost effective in our area and has now been extended indefinitely.