Selective collection and recycling of glass from MSW: a pilot experience in the city of Rome

In recent European directives, waste recycling is generally assumed to be environmentally advantageous, although collection, sorting and processing of waste materials involves significant environmental impacts (European Commission, 2001). Therefore, it is essential to properly design each stage of a waste management system. The Municipal Solid Waste (MSW) management in Rome is organised on selective collection of paper waste (in white containers) and of multi-material waste, composed by plastic, metal and glass waste (in blue containers). All the other typologies of undifferentiated MSW are collected in green containers. The selective collection based on multi-material waste is certainly user-friendly, but determine high costs and low efficiency in the successive phase of materials recovery and recycling. The environmental department of the Municipality of Rome carried on a pilot experience of selective collection, aimed to collect separately plastic and metal waste from glass waste and, in particular, to improve the glass collection by colour. In particular the aim of this experience is glass separation by colour, adopting a special container, the so-called Dual Box, for selective collection of white and coloured glass. In fact, the economic value of waste glass is strictly linked either to contaminant grade or to colour purity, particularly in the case of white glass. After the choice of a representative district, suitable for socio-economical characteristics, the project included different steps: • a campaign aimed to inform and make aware of the project the involved citizens; • four sampling cycles on collected waste and relative waste composition analysis; • an imaging-based procedure aimed to automatically recognize the different typologies of materials. The project involved different administrative and technical subjects: • the AMA (Azienda Municipale Ambiente), the municipal agency in charge for waste collection in the area of the city of Rome; • the COREVE (Consorzio Recupero Vetro), the Italian Consortium for glass recovery that supported project; • the CTR (Compagnia Tecnologie e Recupero), a company operating in the field of waste recovery and recycling that designed and realized to this purpose, a special container, called Dual Box; • the Department of Chemical, Materials, Raw Materials and Metallurgical Engineering of the University of Rome “La Sapienza” that has the responsibility to direct the executive technical committee, composed by members of AMA, COREVE and CTR, with the aim to control the campaign and to validate data and results. In this work, the pilot experience of selective collection of glass from municipal waste in the city of Rome has been analysed. Samples of the collected glass, coming both from traditional waste containers and from Dual Box, have been analysed to find out the composition and to determine the selectivity of the collection process. To this aim, different classes have been defined (white and coloured glass, plastics, metals and other materials). An imaging-based procedure has been applied to recognize the different typologies of materials, with special attention to glass materials.