I. Introduction
According to the latest report of the International Solid Waste Association (ISWA, the global association representing operators in waste processing and disposal) [1], currently in the world are produced about 4 billion tons of waste each year. Half is represented by urban waste (those produced by households), while the other half concerns the so-called special waste, coming from industrial and productive activities. Although there are no unambiguous estimates, in the next 10-15 years this production could even increase by 50% due to the growth of the world population and economic development. The situation is worrying, especially because, according to ISWA estimates, around half of the world population (3.5 billion people) does not have access to the most basic waste management services. This is why every year mountains of waste are produced and abandoned, with often irreparable environmental and health damage. Urban waste is a huge expense for municipal administrations as well as a damage for the environment. According to the World Bank [2], in fact, the disposal of urban waste currently costs about 205 billion dollars a year and this cost could even double within 10-15 years. Then, waste management is one of the heaviest costs in the budgets of public administrations and continues to grow as the population increases. Furthermore, the environmental aspect must be assessed: according to the World Bank survey, urban solid waste accounts for 12% of global methane emissions and 5% of total greenhouse gases production. In light of all these considerations, it is normal to think that modern smart cities must implement serious plans for reduction, recycling and recovery of waste, favoring separate collection and charging higher taxes to citizens who do not adopt it. In particular, smart cities can exploit the Information and Communication technology (ICT) to integrate a plethora of physical devices connected to the network, the so-called Internet of Things (IoT) [3], [4], [5], [6], to optimize the efficiency of city operations and services.