Abstract: The invention concerns a method for treating a mixture of wastes (2), the latter being with heterogeneous sizes, shapes and consistencies, the treatment method being characterized in that it includes the following successive steps: Step E1 during which the mixture of wastes (2) is separated into a first fraction of wastes (13) the size of which is smaller than about 180 mm, preferably smaller than 140 mm, via a first series of separation orifices (7, 8) and into a residual second fraction of wastes (14), said first series of separation orifices (7, 8) comprising primary orifices (7) and secondary orifices (8) the size of which is larger than the size of the primary orifices (7) so that the mixture of wastes (2) is first brought into contact with the secondary orifices and then with the primary orifices (7), Step E2 during which the first fraction of wastes (13) is subjected to a composting process so as to compost, at least partially, the contained biodegradable wastes. Wastes sorting.