Which aspects should one consider in order to select the right digestor? First of all, the type of matrices that will be treated, whether there are pollutants and in which form they will reach the plant. In California, in fact, with the introduction of the AB 1826 (requiring businesses to recycle organic waste), the collection of food waste is at the centre of a lively discussion to determine the most economic and efficient ways to separate these matrices and ship them to the treatment sites.