These have numbers corresponding to each Flat. They indicate that the residents of each flat should use their’s and only their bin.
This means that every time bins are collected, all of the bins have to be taken out, regardless of whether they are full or contain only a single empty tin of beans.
These bins, on the other hand, don’t have numbers. The residents put their rubbish in the first bin until it is full up, and then they go onto the next bin.
This means, that when bin day comes around its very clear which bins need to be taken out for emptying and which don’t.
So, why do the recycling bins have numbers and the rubbish bins not? I don’t know for sure. The numbers are hand-painted so they don’t seem to have been added as part of any official process, but perhaps someone’s attempt to make individuals take more responsibility, either for recycling or for putting the bins out on bin day (or even perhaps because they were fed up with ‘their’ bin being filled up by others). It seems those numbers have had unintended consequences in the resident’s behaviour and created a bit of a divide, and reduced efficency.