In theory people can separate waste much better than a machine, since they have more knowledge about the waste itself.
In practice, with all my good will, I find that following the directions for separating is very difficult, since (just one example) paper can be recycled, but not if it is coated, which is not easy to judge sometimes.
Also, many people do not follow the rules, it's life.
Anyway, mechanical separation does exist. While it cannot (I think) surpass manual sorting, it brings reliable results, which it could also be that they surpass not the theoretical, but the actual quality of manual sorting.
My question is: are there studies about the real effectiveness of manual vs mechanical sorting of household waste? I assume in this case only a humid/food vs everything else manual separation, since it's easy enough to do and to understand.