Abstract
The legislation on the payment of the urban hygiene services has been, in the last years, subject to several variations (i.e. Tarsu, Tia,Tares, and Tari) and has always defended the possibility to apply exact system of charge, following the EU principle: "Pay as you throw". The number of Comuni involved in such change is gradually increased, notwithstanding the normative doubts that delayed the application of the "pay as you throw" norm. We get the exact charge by quantifying the waste produced by each user either "per piece" (for instance counting the number of cumbersome pieces of garbage taken away) or "by weight" ( for instance weighting the content of the bins), another possibility is to procede "by volume". In Marnate, a Comune with more than 15.000 inhabitans in the Provincia of Varese, it has been succesfully applied for over one year a charge system based on containers with Rfid transponders able to recognise the code and the volume of the user's bin. The user does expose the bin in order to be picked up and the bin's content is weighted and the result is transmitted to a central server. These data are then processed to determinate the variable price. The progresses in the construction of UHF transponders and the resulting costs reduction have allowed to even employ them on disposable plastic bags. The link plastic bag/user does happen at the moment of the plastic bags delivery (it's indeed possible to have more readings at the same time thank to the UHF system, potentially even all the plastic bags codes together). The results show that this system allow to comply the EU directions and it increases the efficiency of the differentiated gathering, valuing the correct behaviour of the citizens.